Hi Everyone. I'm going to be building a 20x30 single story cabin in the wyoming grasslands. we've got a 40" frost line and I'm stuck on what to do for foundation. The plans I've purchased do not include any foundation work (they assume screw piles). I've got a quote for $8900 for a standard foundation with crawl space but am thinking I can do concrete piers myself for less than half of that if I can figure it out. I'm having a hard time determining size - the county planners don't care, there's no inspection and they say "ranchers hate it when we tell them what to do, so we don't." maybe some of you can help.
for a basic 20x30 building I'm hoping to run three rows of piers. I'm not sure how far apart each should be or what diameter. can you suggest? the cabin will be basic stick construction, no bricks.
How does one typically connect to the piers, J bolts or more of a traditional deck post holder? Our cabin will be subject to regular gusty winds, does this change my approach?
When using piers to get a crawl space will I be better raising the pier up above ground and building right on top, or having the pier only come up to the top of soil and using a post to elevate up to the joists for crawlspace?
is there a link anyone can point me to for putting a cabin on piers? everything I find is decks and such.
thanks!
Mark
With that frost depth and high winds, my first thought would be a full, connected, basement. Concrete or block perimeter walls, rigid foam exterior insulation under shoveled earth backfill. Well drained footings. Would that work?
... and welcome!
I will give you my experience building a 22x27 cabin on a slope using piers and posts. Been up almost year and everything looks good. Got a lot of the advice on how to do it (well) on here.
You will get a lot of opinions on piers vs, crawl space, slabs, etc. and most of them will be negative about piers. There are some very good points in those arguments, so do not discount Them. I built june on piers mainly because of the slope and while I could have done a "walk out" with a foundation, and even gained some advantages with that, I do not like them...so personal preference plays a part as much as construction details. Also, this was a lot easier on the environment than digging up the land to level it for the building. That also is important to me. Piers and posts are sound building and millions own them existb for various reasons. That they are not in the perceptive code is not a good reason not to do it...but there may be others.
Spacing of the piers depends on two main things 1) the support you need in the soil 2) the support you need for the structure above.
#2 is easy...size and weight which are interrelated and easy to calculate determine what you need to hold it all up. I'd venture a guess that with three rows and 30 feet, a pier every 6 feet is fine. That is three rows of six..18 total. You will need to size your beams to support the building and something on the order of three 2x10's will likely be plenty for each beam. I used two, but I have a lightweight cabin and no snow load at all.
#1...depends on the load bearing capacity of the soil. Lower bearing soil means a bigger base on the pier and maybe more piers. Try to find out what your is. Lots of reference to that and maybe you can get a local who can tell you what kind of soil it is. My guess is you are 1,500 psf or a bit better. You could be 1,000 or 3,000. If you have 18 piers and each one is 2 sq.ft at base, you have 36 sq ft. and at 1,500 lbs/sq ft have the ability to support 54,000 lbs total. or 90 lbs per sq foot which is within the typical figures for loading on a house your size.
You just have to make sure you site has good drainage and you are not sitting on a spring or other anomaly.
Concrete all the way up or post on top.
Concrete all the way up is much simpler to make strong..especially since you have wind. The connection between the bier (concrete) and the post is a vulnerable one and is subject to "bending' in the wind. You can deal with this, but if you do concrete all the way you do not have to.
The lower to the ground you make the tops of your piers, the more stable the structure will be. at a couple of feet, you have no problem.
My build is on here..Mtn Cabin in Nicaragua. Deal with a lot of this stuff with advice from people on here.
my build is 16x24 and here is how mine is laid out. Now I am not sure on the engineering with the spanning distances vs the size lumber but there is a lot of threads on this site if you are willing to research I think in my thread Don_P or MountainDon talk about the reference on page 2 of my thread I think.
(https://i1156.photobucket.com/albums/p566/ColchesterCabin/Foundation.jpg)
Hope I was helpful. Good luck!
thanks for that! what diameter piers did you use? how are you attaching to them?
JRR, I'd LOVE a basement, but it pushes us up and up. crawl space foundation looks to be $8900, full basement would be closer to $12k. I would love the storage and it's not that much deeper, but the excavation and extra concrete work are just not in the budget. I have high hopes of getting the foundation and shell done for $20k. if I can get the foundation done under $5k that gives me a lot more room to work toward finishing the inside.
My concrete piers were 12x12 inches square. Tapered out to 18x18 at the bottom for a 2.25 sq ft footprint.. 4 feet deep. My soil is a lot of clay so I dug and did not need a form in the ground. Built a small form for the one foot that came above ground. Dug by hand so cost is concrete and rebar and a bit of wood for the forms.
My 6x6 posts were attached to the piers with Simpson connectors....ABU types ..you can see them on their site and a lot of other stuff too.
http://www.strongtie.com/products/category_list.html?source=home
This way is definitely less than 5K
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Piers and posts ...... That they are not in the perceptive code is not a good reason not to do it...
If one subscribes to conspiracy theory's then I suppose one would believe that. There are those who believe that everything in the codes stems from the basis of somebody making money on some product. If one believes that the building codes have lots of good structural theory and practice behind the rules, then one will believe that there are sound reasons that codes do not recognize pier foundations.
If one has spoken with a very experienced licensed structural engineer as I have, then they may also be believers in the basic structural "advice" that can be found in the codes (BTW, the most commonly used code is the IRC and there is a thread on it in a board under the General board. ) There are many users of piers who do not understand all the implications inherent in such things and forge ahead simply because they see many examples of piers here and there.
I do not believe a building as large as a 20 x 30 should be built on a pier foundation, unless one has the blessings of a structural engineer. Soils vary too much to base the decision of what to use as a foundation strictly on the price tag.
For anyone insisting on using piers for a large building I would suggest that the best such foundation is likely one based on the use of the Bigfoot Footing System. Google it. As impressive as it looks in the larger diameter columns the company will not, can not, issue certification to a user that the system would be passed by an engineer. Why? Local conditions vary widely.
(I have had correspondence with one of the principles of Bigfoot and once summer is over and I'm back to a regular schedule, I plan on posting some of what I learned.) Some of the opinions that will show up on this sunject are from DIY builders who have built but one structure. Some voices will have years of experience behind them. In the end it is the DIY'er who makes the decisions that may later affect the stability and safety of what they build. Nobody else will care much after the topic is buried under new musings.
I asked this once before and never got an answer.
What does getting a local engineer or a soils guy (or both) cost? If someone has local experience and training, that would seem to solve the problem of having expert advice. Is it really that much, or do those guys not readily exist.
There are many users of piers who do not understand all the implications such things and forge ahead simply because they see many examples of piers here and there.
Empirical evidence is really useful. I knew smoking was bad for me before they put the warnings on the packs. Many of those that waited died.
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What does getting a local engineer or a soils guy (or both) cost?
Like soils, that can vary a lot from location to location. Does the engineer have to travel a distance to the site? Is he going to be asked to approve a entire plan set? Is it a simple plan or does it involve complexities? It could cost into the thousands or perhaps $300 -$500. ??? The thing about the IRC is that it contains engineered solutions to many of the problems that are encountered in design and construction. And they are free for the reading. Add to that the use of engineered trusses and joists where the engineering comes with the purchase of the product and it seems to me that most DIY builders can avoid the cost of hiring their own engineer. I have searched for a one size fits all solution to the question of using piers and have yet to find one. Many of us who build on piers have success because we have been issued some good luck.
Seems to me that $500, or even $1,000 is a small price topaz for the peace of mind this brings. And not a big investment in a 30K dwelling. If you do not need for permitting and you really want a site/soils review and not a full sign off in writing on a plan you have done, should be a lot cheaper then the full boat treatment, but just as useful.
I sure would have done it. You never know when your issue of good luck will run out.
mountaindon. for someone who is so set against piers like i have seen you say in MANY threads. why is your place on wood posts?
Because I am more knowledgable today than I was when I started out on our adventure. Someplace here there is an "explanation". Right now I'm out the door to the cabin; no time to find it.
EDIT: corrected spelling error
btw. my 20x32 is on three beams, each beam has 5piers. 8" tube wherr it comes out of the ground, 3' deep. they bell out to 18"-24" round and about 10" thick footings on compacted sand mostly. three pieces of #3 rebar in each tube and footing. then i used the asjustable post brackets that use a J bolt.
i have been thinking after its dried in and instead of simply skirting the bottom i may dig a trench around it and pour a footing and frame up a wall from it to the rim joists
This is a very common topic. I personally don't mind piers on smaller, or thinner structures. I've seen enough of the math posted by people more knowledgeable than I, and I was uncomfortable with the risk on my 20x30. Sure it is very low risk of failure in comparison to other methods, but it wasn't worth it to me. I am in a slightly different boat, I consider my 20x30 a house. I want it to last and hold value over my lifetime, which will hopefully be a long time. I will likely be dependent on this structure many years down the road, maybe when I am no longer physically able to make many repairs. A few hundred dollars extra and an extra week or two of work, on something that I was going to spend 30k and a year building was well worth it in my analysis.
It is unfortunate that the other set of plans did not include various foundation options, the 20x30 plans I purchased from countryplans included what you are looking for.
Cost is the primary argument I have read from most, but not all, people over the years. When all the factors are weighed in, there is very little cost difference between it and other foundation options. Most of the price you have been quoted is labor and knowledge. Information is power, power is money. The materials are cheap. Concrete is one of the cheapest building materials. Sure setting up forms and pouring a concrete foundation can be difficult and intimidating for the average DIY, but concrete blocks are a lot easier. If you are not able to reuse the forms on a pour, a block wall comes out a few hundred dollars cheaper.
I built a full crawlspace out of block with a 5 ft depth on a 20x30. Cost about $3100. Fully code compliant. The only thing stronger would have been a solid concrete pour.
Weekend Mini-excavator rental $600 delivered. Really easy to learn. Took about 10 minutes. If you grew up with video games it is just two joysticks.
Footing Forms and rebar $150.
3 yards of concrete delivered $300.
Concrete block and Mortar delivered $1500.
Sill plates and J bolts $150.
Center beam $150
Weekend rental of walk behind loader to backfill inside and out $250.
By the time you add in the piers themselves, the girders, the connectors, and the skirting, the costs come pretty close. A full foundation is a bit more work though.
There are also Permanent Wood Foundations, which cost a slight amount more in materials, but come together like framing a wall. It is a fast way to put in a full crawlspace foundation. I suspect it would be very functional in the cold arid grasslands of the west.
There are also frost protected shallow foundations, as long as the structure will have a small amount of heat through the winter (passive solar?), they can be fast, the same cost, and less work.
In addition to piers, there are a whole lot of options open the average do it yourselfer. Most have very similar costs, don't be intimidated by the quoted cost from a contractor.
BTW w*
Quote from: alextrent on August 01, 2012, 09:28:42 PM
I asked this once before and never got an answer.
What does getting a local engineer or a soils guy (or both) cost? If someone has local experience and training, that would seem to solve the problem of having expert advice. Is it really that much, or do those guys not readily exist.
It depends. Some county extensions or services may have low cost soil testing. My recollection was the soil and water extension in my county charged $150 a few years ago when I checked. Septic is highly dependent upon soils, and in my state an engineer is usually required to do the approval. Soil analysis was simply included with my septic testing.
My soil report with two off 10ft test holes was 1375 usd- required by county
I designed the foundation including rebar etc alongside the builder and months of study- the foundation is a crawl space 4ft interior height ridgid slab fully rebarred and in a single poor - basicly my mountain can move and my house will stay in one peice
It cost 2700usd for the engineer to get him to sign off on the design.
Mind you he had to drive 5 hrs to get to the plot and that includes an inspection of the rebar before the poor, so another long day and fuel
I think I have the most expencive built on here so far and I have'nt even dug a hole yet !
Here's my take on foundations, you can't just look at whats simple and cheap- you have to concider your plot and your conditions- what works in one place does not mean it will work with yours
Find out what your soils are- min supporting load
If you are in a large flat valley - maybe just from this site will work, if your on a mountainside like me, then maybe a site specific soil report is advisable
http://websoilsurvey.nrcs.usda.gov/app/HomePage.htm
Their report gave me a pretty good representation to what the soil guy gave me.
The site specifc soil report outlined specific requirements for a few suitable foundations..............
Look at your snow load
Look at your frost depth
Work out the weight of your house then the loading on the beams/walls
I have 90# snow load- even on a 10/12 slippy metal roof I get 76#
This adds up weight fast.............I have a worked example somewhere, that I need to post. as for my area by the time I've used 36" diameter BIGfoots at 6 ft spacing - its going to be easier and cheaper to do a foundation like Squirls.
Start from the roof down- know your loads and conditions then look at a foundation thats suitable
[quote\]
There are also Permanent Wood Foundations, which cost a slight amount more in materials, but come together like framing a wall. It is a fast way to put in a full crawlspace foundation. I suspect it would be very functional in the cold arid grasslands of the west.
[/quote]
Can you give some details what this is and how it works? Maybe ballpark cost as well?
Permanent Wood Foundations are, like the name implies, made of wood. They are pressure treated to the level of fresh water dock pilings.
There are two main types. The first are those with evenly backfilled soil on both sides.
(http://publicecodes.cyberregs.com/icod/irc/2009/images/ICODA2009061607395903345.jpg)
The second are ones with a poured slab on the interior.
(http://publicecodes.cyberregs.com/icod/irc/2009/images/ICODA2009061607395903344.jpg)
The purpose of both of these is to keep the weight of the outside soil from kicking in the bottom of the wood wall.
The charts and specs of the requirements can be found here.
http://publicecodes.cyberregs.com/icod/irc/2009/icod_irc_2009_4_par082.htm
I was going to do it for my foundation and looked into it over a year ago. The prices are based purely on memory. You would have to call around to local lumber yards and they would probably have to order the lumber stamped PWF.
Since there is an 18" minimum requirement for a crawl space, I wanted my studs to extend at least 2 ft above grade. So I asked for a 2x6x12 and I would cut them in half with the cut end up out of the soil. Since I planned on just trenching and evenly back filling, unbalanced fill height was unimportant. My recollection was that each plywood sheet was $50 and the 2x6s were $25. So for the wood it would have cost around $1900. The stone and equipment would all have cost the same, but I wouldn't have needed to order the 3 yards of concrete. So it would have cost almost the same as my block foundation but would have been a bit faster.
The reason I didn't go with it was because drainage is important with a wood foundation. Although additional drainage it is not required by code, it is still highly recommended. Below 12-24", my land doesn't drain. It is a "fragipan layer of shale clay". So when I say doesn't drain, I mean almost at all. It failed for conventional septic. Since there is almost no slope to my land, the is no way to install a french drain to daylight, and since my land doesn't drain a drywell would be useless. I had to scrap the idea of a PWF for concrete because it can sit in water better, and I am in the wet northeast.
If you do research it locally, would you please post the prices they quote you for PWF lumber?
I think the biggest factor on whether or not piers would be a viable choice is the ability of the ground to support the weight of the house. Piers are only a fraction of the square footage of a perimeter footing.
Take my house for example; it sits on 36 piers. The piers are 10" in diameter but tapered outward at the bottom to around 16" to 18" diameter. That's approx. 1.5 sq.ft. per pier or 54 sq. ft. for the entire house.
If I had used a typical stem wall with center support on a 16" wide footing for my 24' x 48' house, the footage would be approx. 245 sq. ft. or more than 4 times the piers footage.
I didn't have any qualms about the soil under my house supporting the weight, however, since it was on a mountain ridge and is basically nearly solid rock.
I went 18" to 20" deep (frost level is 6") and after the first 3 or 4 inches of dirt, I pretty much had to bust out the rest of the hole with a rock bar.
Here's a picture of how it looked before setting the end sills and floor joists.
(The posts are cedar, the rest is SYP; all milled with a chainsaw. Everything is tied together with 1/2" bolts and 1/4" angle iron.)
http://www.diychatroom.com/members/arky217-86953/albums/all-pictures/5437-1-18-12-031-600-x-450/ (http://www.diychatroom.com/members/arky217-86953/albums/all-pictures/5437-1-18-12-031-600-x-450/)
Arky
This is why we have prescriptive codes. The reason pier foundations require competent design is only partly with their decreased ability to resist vertical loads. Lateral loads must also be resisted, this is where the walls and continuous footing of conventional foundations come into play.
Construction is all about figuring out the loads and providing adequate resistance. If you cannot do this, then stick to prescriptive solutions, or hire an engineer. A fine house on an inferior foundation is only as good as that foundation. With all the respect it is due, if you get advice from the internet that cannot do more than blow sunshine up your backside, it is incompetent design. Incompetent people overestimate their abilities and do not understand the nature of what they are doing. We are getting a number of one house builders giving expert advice here, go carefully.
I would agree to go carefully, not only on this but on other stuff as well. Carefully is not the same as do not do it. This seems to be one area where small investment in an engineer is well worth it. Im am one of those one home builders, but I did my homework and have a sound build.
Soil bearing capacity being the #1 concern...and I believe it is a great part of it, should be easy to figure if you get a reliable soil test...which it seems you can do at a reasonable cost. A good investment for a pier build.
I could not do that down here.
The estimating guides for soils list from 2,000 to 5,000 psf for 'typical" soils. Assuming you have good drainage and no seasonal spring underneath. Mine is sandy clay..supposed to be 2,000 psf.
My 21 piers @2,25 sq ft/ pier are 47 sq. feet. At 2,000 psf, that is 94,000 lbs. soil bearing support capacity.
My house is about 20,000 lbs. dead weight (calculated from materials) and the allowance (mostly wind) for live load is 30 psf (90 mph wind) or another 18,000 lbs. Total is 38,000 lbs. So even at 1,000 psf soil bearing capacity (half of what we determine it is) this is OK, ....a good margin.
Given not having a soil test, had I not had this margin, i would have done more piers or bigger footings, given the fact that this is based on estimation, not a test.
A point to consider is that not all your piers near the same mount of weight. Ones at the ends bear quite a bit more...figures are published and on here I think. So you do need some margin for that. Fifty percent comes to mind, but that may not be accurate.
A little extra footing makes a lot of difference. My piers, if carried down at 12x12 would have only been 1 total of 21 sq. ft...not 47 sq. ft. as was done by tapering them to 18x18 at the bottom.EZ to do.
Alex, go to the link on postframe design I posted last week. Read the section on unconstrained posts. You overguessed the windward load, totally neglected the leeward load and applied the resulting horizontal load to the vertical load bearing capacity of the soil. That 18,000 lb horizontal load, or whatever it actually is, is trying to slide the posts off the piers or tip the posts or piers over... laterally.
Steve gave an important caveat, subject to frequent gusty winds. This should be designed by an engineer or it needs to follow the methods known to work outlined in the building codes. Personally, I do it prescriptively and put that money into structure. If you build conventionally we can give sound advice and back it up by referring back to the codebook and standard references.
Provide those for pier and beam and you'll have something to offer.
Provide those for pier and beam and you'll have something to offer.
I do offer something...how to calculate the required pier size for soil bearing capacity for pier foundations. Yes, there are a lot of other items in the "pier equation", but this is the one at hand in this post.
You are talking about something quite differen in your last response...lateral loads As a matter of fact, I did not neglect anything in the wind calculations....at least nothing of critical importance on either lateral or downward loads. I researched this a lot and there is a lot of information available . I posted a couple of links on the site and you commented on how valuable one was. I followed the basic tenants of this for lateral load. This is in addition to the empirical evidence I see in dozens of buildings built this way and withstanding the elements for decades.
Here is what I was referencing in he post in question....it is directly relevant to the original subject.
There is a vertical component of wind (puts downward load on the structure). This is what the 18,000 lbs in my calculations is. It is likely high....but that is OK. It is actually the highest i could find for my roof type..most a quite a bit lower. We are talking about soil bearing capacity here, so that is what I addressed.
As you know, wind loads on roofs is a complicated subject..but it does not differ on pier or full foundation buildings. On the opposite side of the side of the gable roof from the side with the load is a suction...that also can be calculated and varies with lot of factors. That is all boiled down in the tables (code, if you will) for roof construction and securing the roof. This is a roof issue, not a soil load bearing issue..as the force is up. The roof will go, way before the building is lifted (as least in my case).
The figure I used is for the max downward force of a 90 mile an hour wind 90 degrees to my 4/12 roof. There is some leeway in that, as if it is exceeded momentarily it puts load on the piers which can be tolerated. In my case, this is a very unlikely occurrence...plus i have an about double to that as a safety factor.
As for lateral loads...windward and leeward, I did not neglect them in my calculations (remember, the above is just for downward loads). Once you get above the posts, the lateral forces are essentially the same a in a full foundation building, so the issue is to be sure the pier and post and post and beam connections hold up to the vertical and lateral forces. Those also exceed the calculated forces for my building...most by a factor of two.
No, I cannot take you to a "perscriptive" chart for the connections...but there is a lot of other information to use. Yes be nice if there were a chart. I will say this...if a person is not willing to do a lot of homework and is not able to synthesize a lot of information, get an engineer. Or maybe get one anyway...I looked but could not down here. For a $2,000 fee (maybe a lot less0 and a $40,000 house seems like a good investment.
I have two people who are going to build houses based on my design. Both in the immediate area. They like the design as it fits into the topography and the environment. They also really like the idea that it does not require big machinery and excavation. I have discussed the concerns about this type of structure with them...both will do somewhat bigger ones. I am not sure if they fully get the issues but i will be sure they do before starting. They have a lot of money and connections in NICA so i believe we can likely get an engineer to look at all this and give us an opinion and specs. I will post what i find out. should be interesting and maybe a start at some type of reference.
We do both recognize that was incomplete. My posts have related to lateral design and yours sandwiched in between was not. We're getting into why Steve should have an engineer design his foundation rather than bits and pieces from us. If it is conventional those issues fall away.
I am all for getting an engineer. I do realize that without one there is a certain reliance on luck that may not be wise. My comments are not to imply otherwise and as I have said if I could have, it would have. All you anti-pier guys still gave me the advice I needed to do the piers...at least in a sane, if non-engineered manner...and I appreciate that a lot. My point here is that if you are going to do piers without an engineer, do extra homework and overbuild.
We're almost there Alex. If you do piers without an engineer... well, look at what we've seen here. One part is overbuilt and another part is totally ignored. The failure will not be the overbuilt part, it'll be what you neglected. I readily admitted this is not something I'm competent at, my advice to you was to keep you from hurting yourself, you're now using that little bit of knowledge to encourage others into the same predicament. You've taken a little bit of information and decided to champion a cause. I'm not at all comfortable with this approach. These foundations were common in the past, built by carpenters' best efforts according to their knowledge, much like those here. After many failures they are now an engineered foundation type, that is the empirical knowledge we have gained.
I'm actually not anti-pier I'm pro rational design. You have not solved the bracing problems as these houses are being built. You have more bracing than you were first inclined to do. My current thoughts on how to do this type of foundation revolve around a rigid moment resisting connection between a one piece pier and a stiff girder. This would probably not be a cheaper foundation but would provide for a smaller footprint on the land without requiring the digging that I think is part of the turn off for many of you. One engineer described what he saw typically done here as a collapse mechanism. My comments about competency are a pretty direct quote of another when we were discussing these foundations on the inspectors forum.
We are attempting to build a braced foundation under a braced frame. You can build the house stout but if the foundation fails that doesn't much matter. You've mentioned that the connections between support and bracing members need to be done correctly. With a typical foundation there are many connections and much soil interaction, the forces per unit area are relatively low. When those same loads are concentrated on less area and fewer connections the force per unit area and per connection is far greater. Although the loads may be the same, the stresses within the materials are indeed higher with this foundation. Getting things right becomes much more critical because those members and their connections are loaded much more heavily vertically and horizontally. We touched on that recently talking about timberframes, the members are quite large but there are fewer of them, they collect and concentrate loads. All of us that are used to conventional construction have been used to uniformly distributed loads, modern framing spreads and distributes the loads out to lower stresses on any one part. In conventional construction spreading out the loads over larger areas and the greater number of smaller members provides a level of redundancy, if one member or connection fails the members around it can probably handle the load that is thrown on them. If a member or connection that is collecting and supporting a large area fails, can the surrounding members handle a significant overload? It takes a good bit more thought.
What have I neglected, or ignored, as you put it?
You also seem to have a problem with overbuilding..not sure what that causes you concern, a to of what we see done on here is "overbuilt".
Last, and it is my last comment on this, as this now has become a silly exchange, is that I am not championing any cause. I simply posted some information, considerations and examples of calculating the pier size needed for a person already decided on the type of build they will do.
Alex, you may want to go back and re read what Don has posted.
You seem to have missed a few critical points. Namely the bracing
in your structure needs to be re examined. It's your house and you
are free to do what you want where you are, but if it was my house
and someone was alerting me to a potential problem, I would really
try hard to understand what he was trying to tell me. I still might do
it my way, but I'd at least be aware of the potential problems.
Bruce
I have reread and must be missing a post or two as I see nothing about my bracing in any recent post.
Earlier ones, as I asked for advice were great fully accepted and followed and nothing there either.
I'd be the first one who wants to hear any critique...if I choose to work on it, you are correct, that is my choice, but I have not seen. Coming from DonP I would likely give it very serious consideration.
What I have seen is another round "of piers are bad an will kill you" posts in response to my posting some advice on how to calculate solid capacity and relationship to piers and footings. That is my point about "enough already'...it's been said and said again and not that repetitive advice on something someone feels is so important is out of place, but now it spills over to those who give advice about it. As I said, enough already..be specific so I (we) can judge the reality of what is said.
I can point out what I see Alex and I am not critiquing your build. Since I don't do this and make no pretenses about it I doubt I'll get it all right. I realize it will hone your banter but that will not create a good design. You should develop a relationship with a good engineer as this seems to be something you will do more of. You can come back and prove that I'm full of cookies, but then you'll be doing it from a solid basis. I think I want to see the stamp if it's all the same.
We should probably start with the building code. This is the latest version, read R404.1.9.3. It has moved from engineering implied in previous versions to engineering required.
http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_4_sec004.htm?bu2=undefined
The RDP requirement should be the end of this discussion and in most jurisdictions by law it is. Continue with that line of thought. Assuming the house is insured, will they pay out on a claim if the house wasn't built to code? Code doesn't say you can't do this, it says there ought to be a stamp in the file backing it up. When you go to sell it and the home inspector spots this will he report it and ding the potential marketability, more than likely.
Now read that section structurally
Do you see "Sure go ahead and break the support column in half and put a hinge in the middle" anywhere in there or in the surrounding language? Not even for an interior pier with full perimeter walls taking the lateral loads. Notice the max pier heights under exterior walls but do recognize that we are actually talking about foundations under the braced walls.
Notice the minimum pier dimensions, have you been seeing those dimensions here? That is minimum acceptable engineering.
A piece of rebar stabbed into a shallow footing does not develop much tensile strength, look at lap requirements for the hint. A hook bent in the end will develop much better resistance. How many and placement?... engineering. You guessed 2, could be right but it was a guess wasn't it? Stability begins with three members most of the time doesn't it?
The girders need bracing to prevent rolling.
It might be worth thinking about how many of these foundations you are seeing going in professionally. In the industry we're having a hard time getting decks to take their lateral loads when attached to a braced house on one side. People here are putting the entire house on poorly braced legs that hinge on piers that sit on shallow footings, the rest seem to favor unbraced piers. And the code has moved towards requiring professional design. Yeah they're picking on you and its a conspiracy ::)... cause and effect. People have shut alot of doors that used to be open, do I sound happy?
QuoteThe reason pier foundations require competent design is only partly with their decreased ability to resist vertical loads. Lateral loads must also be resisted, this is where the walls and continuous footing of conventional foundations come into play.
This is the achille's heel of a pier or column foundation. The Main Wind Force Resisting System is comprised of the roof diaphragm, the braceed walls and the floor diaphragms all delivering the lateral wind load to a foundation capable of delivering those loads to the soil. The 5 pictures I can bring to mind posted here of failing pier foundations were all bracing problems rather than vertical load problems.
There has not been a situation or a lack of bracing that I've seen give you pause. This time there was wind in the equation, last time it was a soil type that really needed an engineer. This in the face of knowing what those who are registered design professionals have said about what they see here.
This foundation is a last option not the first. We do not have a set of approved methods to build one. What I've asked for you to post is some form of standard or details that could be approved. Find that hinged post in a drawing from a reputable source. It keeps coming back to, the real way to do it is to hire an engineer. If after many people do this and the engineers keep saying pretty much the same thing, we compare notes, then you have a prescriptive solution capable of petitioning for. Is that such an onerous task? You have admitted the engineering is really needed anyway, is this not the path forward?
I have no problem with overbuilding but it is a tipoff word. When the phrase is used by DIY'ers it invariably means just what I said, one part is overbuilt but another critical area has almost certainly been neglected. They've thrown a bunch of lumber and nails at a problem that is over their head and prayed. The term overbuilt and this foundation cannot really be used in the same sentence, by its nature it is not one an overbuilder would use. Last time we had a dustup you said I lived on a level mountain, this time that I have something against overbuilding. We have over 200 tons of native fieldstone in the current foundation, full perimeter footings, topped by heavy timber oak posts and beams from trees I logged off the property. The connections and braces are fully housed mortise and tennon. This makes something upwards of 50 log and timber homes, don't really know how many conventional and remuddles. I've repaired pier foundations more than a few times. So now we know my topography and resume for whatever that's worth. I guess to say, you've gotten personal with me as well, there is what is staring back across the table.
Truthfully, I do not know what your post is about. Not sure if you are telling me I should not have built on piers, should immediately shore up my build, stop giving advice to those who are building on piers, change insurance companies???
The only thing I got for sure is a suggestion that I initiate a perceptive code writing process for piers. Kidding, right? Or was it a dig about my inexperience? No matter.
Contrary to what you say, a lot of things I see and hear "give me pause'....likely have made 20 changes of some significance because of them and probably half of where from comments by you...which made this house a lot better.
If you or the other site honchos do not want me to post my experience because it fosters bad building, I will not do so. Having to wade through this piers are bad crap each time is irksome...and I stay away from irksome as much as I can...we have enough of natural irksome day to day here.
I don't have a dog in this hunt, but I couldn't help but be reminded of this thread about a 20x30 1.5 story house built on piers about 4 years ago that failed in a big way. http://countryplans.com/smf/index.php?topic=4952.200
The link is to page 9 of this thread and shows what happens when a foundation is not properly designed.
Unfortunately Don_P was not registered on this site until the house had already racked from a variety of causes and the discussion was centered on how to fix the problem. Some here had recommended bracing and the builder did have a couple sets installed, but was just a start and he was more concerned about getting the house done, installing heat and power and talking about chickens and other stuff.
The DIYer even put the insulation in backwards as I recall. He finally decided to abandon the build and the thread was closed. A very sad 6 month tale. This guy made more mistakes than I want to list, and he would have had problems with any type foundation because he failed to properly assess the site conditions.
The post pier foundation just failed sooner than other designs would have. Site conditions are critical in foundation design. Don't get me started about the rehab project I abandoned and that house has a full perimeter foundation or the house I grew up in that we added a basement to and had massive problems.
I saw that about two weeks after I got on here to ask about my cabin.. Made a believer out of me real quick. Hard to believe this happened on such a big build in such a big way. I think there was really no fixing it and he dismantled and built elsewhere.
This did not start with poor bracing or even the type of pier and post construction. He built it in a poorly drained area and when it go wet, it turned to soup. Nothing, not even a continous foundation would have been right in that place. That is why I always stress that this (soil/drainage) is the place to start when looking at how you will do piers.
The problem DonP has (or one, if not the main ones) is the "hinge" connecting the pier to the post. I agree with him. If you look at the three back piers in my build you will see that I have eliminated those by mounting beams right on the pier. A bit of insurance. But there are other ways to deal with that connection as well as eliminate it. I considered a one piece pier and after careful analysis and thought decided against it (keeping the picture of the house in question in mind)..
In the house in question, there were no such connections, so that was not the problem...it was built with posts in the ground and terminating at the girder (although I think his method of filling around the post is suspect). The house did not fail because of the connections or the type of pier/post, but because of the substrate. Additionally, the builder had little (or maybe no) bracing until it started to tilt. I looked back on the comments about that build as it took place and did not see any red flag warning about bracing it. Maybe a mention or two,
As it turns out, the ground he built it on was so poor, bracing in the best way would have been of little use, as it likely would have sank.
In my house, not only is my footing overbuilt by a factor of two (which is pretty easy to calculate), but my bracing is likely at least that much (harder to do). I do not rely on the Simpson connectors for lateral resistance, just use them to prevent uplift and sliding off the piers. I have calculated the force necessary to tilt my piers (this would happen if all else held and the piers took all the brunt) and it is 3x what the calculations of 90 mile and hour wind velocity would cause. If they turn at that point, not match I can do at that. We just has 4.2 quake here and cracked the concrete and block road. Mine did not quiver, shift or die. Footings still there is monsoon rains...several inched per hour and a couple a week.
Alex, rather than designing and teaching engineering from your level of expertise, which is what you are doing, find a paper, reliable engineering source or hire an engineer to walk us through the entire design process for this specific type of foundation, post it, and refer back to that. You are not an engineer and provide no way for anyone to check your assumptions against an example or standard for this specific foundation. Clear enough?
I do not agree with the lessons you took away from that failed house, choose to believe what you will. Reality plugs along uncaring of what we believe, houses behave the way we force them to behave. These are the costs of the methods you are choosing. I've mentioned before, the prescriptive path is a whole lot simpler... and better. Do you reckon Jim Walters or Beezer homes would be using this foundation if it was one dime cheaper than conventional methods, you wouldn't see a crawlspace in a bottom end production house. I'm not a honcho here, feel free to foster bad building if that is how you want to spend your time but don't be suprised if others spend their time trying to steer folks clear of potholes.
The way to check that this works is to look at the 100s of thousands of homes (millions I guess) built like this and doing very nicely....including many on here. Most of us have the ability to look at what is done, compare to our conditions and replicate with adjustments as necessary. If you can't that's OK, just don't presume that when others do it it is all wrong or that we rely on voodoo to make it work.
I am not designing or teaching anything, I am relating my own experience and viewpoint. I was under the impression that this site was to share experiences and not do engineering consulting, and that one did not have to be licensed builder, or whatever piece of paper you have that says you know more than another person, to share on here. People can use the info, compare it to what others say and what they see and observe and come to their own conclusions. If anyone built on what one or even a half dozen people say on one site, they should have their head examined.
Get a grip...it is all not that important and people are really smarter than you give them credit for. Your rants on this are really tedious...and now are not so much about building as they are about me. Don't worry, none is trying to take your spot on the totem pole...but others will have useful information too. And, unlike you, if someone differs with my advice, that doesn't disturb me. So why don't you get back to the thread and tell this guy what you think he should do with his foundation? You have not done that yet, but have concentrated on making a point about not believing anyone but you.
You'll have to excuse me if I am a bit terse. i am on my way up to tear my house down before it hurts somebody. Tomorrow I will start mo my neighbor's. I am sure your post will convince him to do that. No dynamite here, so it will be a lot of work.
Sorry you feel that way Alex. I can assure you, the honchos place you higher on the pole than me. I'm simply presenting my viewpoint as well. It would be nothing to climb higher on the pole, I could easily have you singing my praises rather than whining about me right now couldn't I. The reason you feel picked on is you keep coming back with the same thing, "Take my word for it", I'm simply asking for a cite. What I asked for, what the law asks for, what responds to the natural order of things, is rational design. Leave your emotions behind and look up the term. Any of the prescriptive foundations provide that, just follow the cookbook. You keep extolling the virtues of this foundation, why is it non code? Why is it not used anymore?
The piece of paper in my state does come from study, testing, experience and references from professionals. Something is bound to have sunk in. You've been studying this for something less than a year. I think that's worth consideration but you can dismiss it if it suits you. You've been allowed to present your point of view, no one has silenced you. That would take gorilla tape not paperwork. You keep telling me to shut up. You've made noises but thus far blessed relief has eluded us. I'm not going to stop someone from making their own decision now am I? We are free to weigh the responses and draw our own conclusions. Where is the problem? I actually thought you might spend at least a little time looking for a resource to satisfy both the op and me but waste your time pounding sand if you see fit.
To the op, no we have not found a reliable resource for this type of foundation, the code reference provides the information on how to do this properly, engineering required. I would spend the money on a crawlspace rather than an engineer myself. Even a subpar DIY block job is going to be a good bit stronger than piers. I would not put a post on a pier if you do go that route.
I can't really make out what Alex is suggesting, he seems to say that an engineer is needed but when push comes to shove the truth comes out. I chafe under the bit myself, I understand the frustration.
Does anyone else wonder if Alex can ever allow himself not to have the last word :D
I'd reply in detail, but I cannot. Going out to blow up some more post and pier buildings.
As to the last word...yeah when it comes to rebutting nonsense and misstatements it is important or the locos get it and that can mislead the found and fragile minded.
Got to go..booom there goes another sin against mankind...a post and pier. Watch out posties, we are coming your way!
What the heck ;D
I don't believe I've been talking about your house.
I googled "rational design of reidential shallow pier foundations", I suspect there is something there. This is your puppy.
I've freely admitted I'm not competent to be designing these. You've whispered in my ear that a good bit of what you know came from me. I think I congratulated you on having the best braced foundation I've seen on here. You're now using that information as if it were worth using wholesale. We've all been right here, we've watched this evolve. I'm calling BS. You've got to throw us a bone if you want some kind of credibility at disseminating this type of information repeatedly. What you are telling us is that I can take the kid in the window at burger king and make him an engineer in under 6 months... I'm a carpenter :-\
I would not usually think of using a pier foundation, if other foundation designs will work. But there are cases to be made for piers: steep hillsides and beach fronts come to mind. Pier foundations use to be very popular at beaches, I think the idea was to let occassional ocean ''swells" pass underneath the main structure. But that same foundation probably is weaker if the water is higher ... a direct hurricane wave for example. And if the hit is large enough, almost nothing works anyway.
And that brings us to "piles", much more expensive... more effective...than piers. Think of a large nail driven into the earth. Vertical support ... up and down, and horizontal shear ...if the pile is steel or reinforced concrete. More of the large buildings are now using piles. And I bet the pile is "extended" structurally upward thru the building.
Makes me wonder: if a pier foundation turns out to be the correct choice for the homebuilder, should the piers always end underneath a beam ... or, would it make sense to have some of the piers, perhaps in corners and outside wall-lines, extend upward into the wall structure ....becoming a part of the wall underneath the sheathing. More "balloon" and less "platform"
Just a thought.
I have never understood why so many people elect to put wooden piers on a concrete footing. Just seems to me that this approach creates a week point (or two) in the foundation. Call me old fashion but I prefer mason foundations. It is not much more labor intensive to erect block or concrete piers, j-bolt or appropriate fasteners to the support beam. The biggest down side is in remote areas where materials would have to be transporated that these concrete/block require. But in the same token the same or similar materials are already transported and used when you pour footings, sono-tubes and the like. Just a little more is all that is needed to eliminate the hinge points that post require. Don't get me wrong there may be a place for post foundations but I would feel better living in a house that did not have them. Am I missing something? Is it the cost difference?
"Pile foundations consist of deeply placed vertical piles installed under the elevated structure. The piles support the elevated structure by remaining solidly placed in the soil. Because pile foundations are set deeply, they are inherently more tolerant to erosion and scour. Piles rely primarily on the friction forces that develop between the pile and the surrounding soils (to resist gravity and uplift forces) and the compressive strength of the soils (to resist lateral movement). The soils at the ends of the piles also contribute to resist gravity loads." p.39
http://www.fema.gov/library/file?type=publishedFile&file=fema_p550_rev3.pdf&fileid=07d77b40-46ed-11df-b111-001cc4568fb6
There are full diagrams and load calculations on what it takes to build an approved pier foundation. As much as I like math and calculations, I don't have the time to work through them all for atomicskier. I am also not an engineer, so take that for what it is worth.
Again, I don't have a dog in this hunt, but the OP seems to have been forgotten in all the bantering on things not related to the original question.
Admittedly, I haven't been very active for several months, but as much as I respect all of the folks weighing in on this thread, we collectively haven't helped the OP very much.
The original question about help related to a pier foundation on a 20x30 single story in the grasslands of Wyoming is a question worth answering, but as usual, more info is needed. We have the frost depth, but we don't know soil type, snow loads, wind loads, site topography, etc.
Whether a pier foundation makes sense for the OP is greatly dependent on conditions we haven't asked about. So to the OP, I apologize for the collective here, some who seem to be grinding axes for some reason. :-[ If you are still out there, give us some more info and we will give you advice which will be worth exactly what you are paying for it. :P
1. Poppy...I think we did get the information in his first post. We lacked slope and soil type. By now he has enough to know what he needs for soil type to do it. Where he is should not be a limiting factor to piers (but, yes there may be others). As for concrete all the way up or post on top, we have also hashed that over well. I think if you have no real aesthetic preference (or if you will skirt, as he likely will out there) concrete all the way up, which gets rid of the pier/post hinge is the way to go. Harder to brace with concrete all the way up but can be done. There is advice on here. Use J bolts and good connectors to hold beams on. That too is on here...i got advice on beam mounting and itv in in my build..about midway in.
2. Piers and post vs concrete piers only. Not so much cost for me, but would have been more. Also I could cop out on problem getting the material in, which would have been a hassle (but at a buck an hour you can hire a lot of people to push wheelbarrows). Fact is, while there is not real inspection process there is a permitting process, which is very arbitrary. I am agains the forest preserve and I could not build a typical block and concrete house (or at least not get the go ahead very easily)....so I pitched this as a wood deck with a cover. Passed and now inspector in enamored with it. Even my back piers whci do not have posts, caused some concern as they start to look like a concrete house.
3. Be sure to keep piles and piers separate. Very different. The beach houses are built on piles...driven way into sand (like 20-30 feet). Piers are not the same.
4. DonP..I was going to ask a coupe of times if you had my build and me confused with someone else. I guess you did. I been going over my bracing the last day and wondering "how the heck am I going to ad more"? LOL Another topic on that... If you go back in this thread , i think you will see that I never offer blanket advice on piers/post...my contribution here was just on soil bearing calculations...which may be the most straightforward part of the pier process. If you cannot get past that then piers are definitely not for you, so that is the place to look first. I would not design one and certainly not on line. I still look at mine and wonder from time to time. It will fall off in a real quake.
FWIW: Somewhere above a comment was made that the end pier of a per foundation has a much greater load than the others. Not necessarily true. With a line of piers under a side wall the second pier in from the end often has the highest static load of all the piers. When loads from wind are added in things change. Lots of factors to be considered.
It seems to me that the issue of lateral loads (piers to soil and the lateral loads of the building on the piers) is the least understood component by DIY "designers". I do trust the opinions of a person who has built many structures over many years and who has repaired the work of many others over many years. Those of us with less building experience would do well to listen and take to heart what the voice of experience has to relate.
JRR, what you are describing is post frame construction. This is an engineered method but has a good bit of info online. There is some good info on the nfba.org site. This is deep in the meat and taters section;
http://www.postframeadvantage.com/pub/Design-Assistance
Google Dr. Harvey Manbeck and you should be able to find his powerpoint presentation slides.
I've posted these pics before, just clarifying what I mean when I'm talking about lateral forces acting on the foundation and how different foundations react.
Unbraced piers... Anyone that thinks the soil is going to brace a pier laterally without serious reservations needs to go pull on a few 20 year old fenceposts. That farmer owned a tamping bar and had thousands of posts of experience. That is the foundation Alex designed for speedfunk yesterday. Now think about them with a 25' tall house in a 100 mph wind on top. An old test was to measure the force required to move an identical test pier 1" at the top. Half of that amount is the allowable stress. That is still optimistic as moisture changes and time works on them. One form manufacturer is giving the lateral strength of a pier at 13" deflection. Design the foundation as if it were sitting on a parking lot.
(https://i180.photobucket.com/albums/x109/windyhilll/unbracedpiers.jpg)
Full perimeter foundation walls... there is no comparison
(https://i180.photobucket.com/albums/x109/windyhilll/crawlspace.jpg)
Pier and curtain wall construction is the lightest prescriptive masonry wall, you'll find it in the foundation chapter of the IRC. It's our version of the latino wall Alex described yesterday on the cmu thread. The piers take the vertical loads and the curtain walls take the lateral shear.
You can brace the piers. The members, placement, and connections become critical. Those loads that are so nicely distributed and dissipated along a full perimeter wall are concentrated through the relatively smaller members to the fewer connections. The pier should not have a joint in it, the braces need to go down as low as possible to the footing, the connections need to be well considered. Peoples intuition about force runs out after a few hundred pounds, this is not gut instinct stuff. Attach short braces well to a post and rotate, the braces then jack the girder off the post.
(https://i180.photobucket.com/albums/x109/windyhilll/bracedpiers.jpg)
Quoteif you have no real aesthetic preference
We still have a thinking problem.
Atomicskier, has described a site exposure of C, unobstructed, and mentioned 100 mph winds, the lateral loads are not trivial. We have 90-110 mph design windspeeds here. The unnamed windstorm last month hit 95 mph in places.
Aesthetics have little if anything to do with sound engineering. Engineering is required to make some aesthetically pleasing designs practical.
Every time I go to my optometrists office I see that in action: the building has a front wall that appears to be nothing but glass, very eye catching. Inside we see the steel beams and bars that make it possible, but most people probably don't even really see the steel, if you know what I mean.
I find it amazing the amount of either sketicism or negativity and depending on where you are on the issue will define which of the words I used to describe the scenaio you will choose. I don't think that anyone is denying the fact that a solid foundation poured is the best followed by a block foundation followed by piers. People have to stop and realize that building on peirs is not the issue or the problem here. Building on peirs then elevating your structure 3+ feet off the pier then in lies the problem. the laws of phyics and gravity and even murphy's law then have to get factored.
I personally see no problem building on peirs if done appropriately with common sense. I have seen houses/cabins built here on patio stones with the most redimentary leveling last 50+ years, not to say it is correct. My dad built a smal 12x12 cabin 15+ years ago using patio stones and the concrete blocks with the holes for the 2x6 slots groved in the top. That structured hasn't moved an inch over that time frame.
I can appreciate everyones opinion on this matter cause God knows I have one. But let's start doing more in a positive light. I feel everytime someone brings up piers they get tromped on and it doesn't do anything to help anybody. Yes there is a fine line between highlighting potential problems and beating people over the head with the IBC.
Lets just work smart and get er done!
Well said CC,
Enough has been said about the terrors of the pier foundation. At any rate, buildings seldom fail from foundation problems. Fire, moisture intrusion, lack of maintenance and several others are much more of a threat to long-term survival.
I agree with MTNDon in the fact that those of us with little experience are better off listening sometimes, but I still want to point out my experience with my pier foundation. Living about a mile off the road, off a fourwheeler trail, and building out of pocket I would have to say I had little choice but to use a pier foundation (dug by hand). I could have saved for a year or so and exanded my trail, etc. but once I get my mind made up there is little that is going to change it. With the help of MTNDon, rwanders, and Don_P I was able to beef up the cabin enough, provide lots of cross bracing, and, hopefully, shore it up so it can withstand Alaska's next great quake.
That being said, just about every day the foundation is on my mind. How's it looking? Are any piers leaning? Have any lag screws snapped? Heaving? I don't know how much peace of mind is worth to you. Enough to put in a full foundation?
Now with ALL that being said, if I were to do it all again, yeah, I would probably choose a pier foundation. Location, cost and time are all too important to me. If I were on the road, had a comfortable place to live while building and could save a bit longer, maybe then we have a different story.
Good report Comanche. MntDon, Don_P, rwanders and others have been a great help to many folks on this forum.