Overbuilding?

Started by cbrian, May 15, 2012, 01:27:40 AM

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BADB0Y

I'm also in TX and going post and I beam as well, but going all wood. The only advise I want to lend is to not scrimp one cent on your foundation if you want you building to last. This is the basis for all that comes later, the so make it count, but however you have to do it.
Please excuse my typos, I post from my cell phone 90% of the time!

cbrian

Finally got a chance to speak to an architect, was wanting an engineer, but an architect is who called me back. The architect I spoke with told me that at 3' or so I will hit solid rock. He says that there are many options, but that if I was dead set on piers to dig down to the rock, drill holes in the rock, and epoxy 3/4" re-bar. After that pour a 12" thick x 24" square footer reinforced with re-bar w/ some re-bar exposed to tie in a pier 12" in diameter. He says after tying into the solid rock that the pier would be stronger than going a foot down with a perimeter. The ideal situation would be to excavate to rock and pour a perimeter, but that leads back to the issues of not disturbing the area and cost.

Matthew 7:24
"Therefore everyone who hears these words of mine and puts them into practice is like a wise man who built his house on the rock."  8)


BADB0Y

Quote from: cbrian on May 16, 2012, 01:18:46 AM
The architect I spoke with told me that at 3' or so I will hit solid rock. He says that there are many options, but that if I was dead set on piers to dig down to the rock"

Where in central TX are you? When I was looking for someone to drill for my piers I found a guy who was very good cheap with good references, but he was too far away to be cost effective. He has a skid loader with a rock auger, and which will punch those holes in no time.
Please excuse my typos, I post from my cell phone 90% of the time!

Squirl

Rebar epoxied into bedrock adds a lot of stability to a footing.  It is a common recommendation I have heard of over the years on shallower piers.  If the Architect is sure you have bedrock at 3 ft then it sounds like he has some experience in the area.

I cannot comment on the lateral load of the piers.  I can give points on the rest of the design for that route.  Since most big box stores carry SPF No. 2 lumber, I use that as a default in most of my calculations.  At 40 psf, according to published joist sizing charts a 2x8 SPF No. 2 can span 12'-3".   So you should be good on those.
For the girders on the outside load bearing walls on a 24 wide building with 2 center bearing floors 3-2x10s can span 6'-4".  If going with 7'-6.5" span (8ft minus the 2.75 inches of half of each 6x6) then I would consider a larger size girder.
http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_5_sec002_par021.htm

For the center girder, because it has to hold half the weight of the floor it has to be larger than the outside girders 3-2x10's on a 24 ft wide building can span 5'-9" (bottom chart in the last link).
Girder sizing is not a well published and a commonly misunderstood topic. I did a short guide on how to read the charts. 
http://countryplans.com/smf/index.php?topic=10511.0
There was a recent topic that broke down the beam calculation math to prove out some of the charts.
http://countryplans.com/smf/index.php?topic=12159.msg156872#msg156872
The solutions are to upsize the girders or down size the spans (more posts).  I'll leave the second floor calculations to you.  Now you can see all the work that goes into designing a structure for a pier foundation system vs. a traditional full perimeter foundation.  This is a lot of the value you get when buying a plan, like the ones sold on this site.

Squirl

On the perimeter foundation, you can pour it by hand.  I assume you will still be using a mixer to mix.  I'm not sure about getting a great footing if actually hand mixing the concrete too.  Since you are in central Texas you have certain difficulties in pouring concrete in general.  My understanding is it hot and dry.  You want to keep your concrete moist and not to dry out to quickly.  To slow set time, try to use cooled water.  Whether you are pouring pads and columns or a perimeter footing you will want to get a wet bond between mixes, slowing down set times will help you achieve that.  You will almost assuredly have cold joint somewhere.  They make concrete bonding adhesive and sell it at the big box stores for $20 a gallon. It has a greater shear strength than the concrete itself and is pretty cheap, so you should probably give it a try.  It a common way pros bond a column to a base.  The instructions should be on the bottle.


Squirl

Quote from: cbrian on May 15, 2012, 12:32:07 PM
And next time your on the Texas Coast, take a look at the rows and rows of bay houses sitting on 6x6 piers 12' in the air.
Sorry, I couldn't pass on this one.  It lets me point out my favorite example of the Texas coast.



This house was built exactly to modern building codes on the Texas coast.  The neighbors weren't.

alex trent

1. If you pour piers of normal size for a house...say 12"x12" (with 18"x18" in the lower foot) x 5' there is no reason to have any problems with cold joints because of long times between pours for a single pier.  You can hand mix all you need in one throw and do the whole thing in an hour.

2.  You won't need cold water..a most unnecessary complication, but do keep the piers wet for a week or so.   Just spray water on them morning, noon and night...wrap with a bit of burlap. Wet the hole well before the pour and use wet sand and gravel if it is hot and dry.

3. If you do footings or piers, you can certainly mix by hand and get a good mix.  It is done all over all the time.  Get you some good help to turn it and work it and shovel it in.  Cheap labor...but a mixer is nice too.

Central TX is not hot and dry all the time.  Can be cold and wet too. Nothing to worry about with concrete pours of this magnitude in any case, even in the dry season.  Just a little water on it as cures is all you need.

cbrian

Thank all of you for all your valuable input. I have a ton to go over, and looks like a lot of re planning to do. To your question where in Central Texas, I purchased a couple acres on Stillhouse Lake, about half an hour from Fort Hood. I was also told when pouring piers or a perimeter to not use fine sand. Some in an earlier post pointed out that it sounds like I have caliche and they where right. I was told the fine sand would turn the caliche to concrete? ??? Now I am wondering why that would be a bad thing? I have been building for years, but being from Texas everything I have ever done has been on grade slab, I never would have thought this to be so involved. Feel like I am new to the show. I can only imagine moving North and trying to build! d* I gaurantee my first basement would not be waterproof. ;D

BADB0Y

Let me know if you want the info for the bobcat guy I mentioned. I found him on Craigslist. I had to throw a pretty wide net to find someone. He's out of Kempner, so he should be close enough.
Please excuse my typos, I post from my cell phone 90% of the time!


MountainDon

#34
Quote from:  link=topic=12174.msg157096#msg157096 date=1337117383
The constant naysayer barrage is getting old and in my opinion is and boring and counterproductive.

Sometimes it takes me a while to formulate a response to some things.

IMO, the only reason that discussion on piers might seem "boring and counterproductive" is that the subject keeps returning as new members come and ask questions about the subject. Therefore the same type of response is supplied, again.  In a similar vein, every time I post the graphic that defines and illustrates the proper placement of collar ties and rafter ties in a rafter assembly, I think to myself, "Here we go again".  I can think of a few other questions and responses that get old and tiring as well as they are repeated in some slightly variable form. If a person is reading all the new messages that get posted under all new and existing topics that will occur time and again, and possibly be just as boring. That's the nature of a forum. Ask a question; get an answer. Repeat.

Therefore, I'm going to continue to respond to these type of questions in the same manner I have for some time. It may be "boring" to some readers; heaven knows at times I am bored with supplying more or less the same answers to more or less the same questions. Hopefully though the information, opinions and facts supplied will benefit someone. If not today, perhaps someone who will read the messages next week, next month or next year.


[soapbox:on]
Foundations are unexciting and a lot of work when done in a manner recognized by engineers. You do all that digging, pour a bunch of concrete in the ground and then hide it. What's the sense in that? No wonder so many like to sweep it under the rug, so to speak. {anyone get the subtle attempt at levity?} Who wants to put a lot of time and money into something that no visitor can see, let alone get excited about? Better to put the time, effort and money into some nifty T&G wood walls or floor, isn't it. That brings out the oooh and aaahs, gets the slaps on the back. So if anyone does not like the civil attempts to discuss the pros and cons as something as fundamental as the foundation, please skip over that sort of thing.
[soapbox:off]

sorry for the hijack and rant.
Just because something has been done and has not failed, doesn't mean it is good design.

cbrian

Yeah I would love the phone number, if you know a guy that can dig that hard ground would sure save my back. As far as the picture of the coast, I only used that as an example, and understand the extreme conditions requiring deeper piers. I have been repairing houses for over 15 years in Central and South Texas. Many of the homes do sit on a perimeter footing with piers inside the perimeter (pier and beam). But many of those houses where built in the 1950's and are now in the lower middle class areas of most small towns. When you travel into the lower income areas you run into the homes from the 1920's -1930's then you get into houses sitting on everything from old rocks, tree trunks, and blocks right on the ground. I understand a 50k foundation is better than a 1k foundation. I understand the resell value of the better foundation house is higher, and that foundation will more than likely last longer. With that said, for those that cannot afford that type foundation, there are other options that last for years. To say that for everyone of those right on the ground houses you see 1,000 failed, is based on opinion and nothing more. Entire neighborhoods of what would be considered poorly constructed homes are still standing, and providing shelter for family's decades later. A little tender care some of those look better than the new 150k houses with their press wood moldings, and paper laminated wanna be hardwood floors all mass stacked in a row with a few feet of grass and no tree in site. The point is for those that cannot afford the best, like everything else in life there are other options, and sometimes those other options can give you a more superior finished product, if nothing else the money saved will leave more budget for other parts of the house. In a part of the country with no frost line, and mother nature as tame as a newborn baby, tons of concrete are not always needed, and you will always have someone tell you it can't be done. Best advise research, ask opinions, use your brain, move forward, and hold your head high at your accomplishment.

hhbartlett

Not to throw more fuel on the fire, but have you considered a wood foundation? (pressure treated) Sort of a hybrid of the step wall & block foundation, except instead of blocks, use PT wood. You'd still have to pour a cement footing, but I think you'd be able to do that yourself with an inexpensive mixer. Just thinking it might be easier to get lumber to your location than cement blocks.

And I'd agree with your comments about old neighbourhoods and crappy foundations. We lived in a place that was an old coal mining town (in Nova Scotia), there were lots of 80 year old houses made with big creosote treated sills sitting right in the mud. Others, like ours, sat on whatever rocks and crap they could find. In fact, our house had rough 2 x 8 floor joists, 32" o.c., and 3" x 3" wall studs in some parts. Doing renovations, I found most of the interior walls had wallpaper on the inside, facing the studs - meaning it came from another house when built. Some of the wood had fire damage where there was no fire. Yet, that house sat in a severe climate (by the ocean) for 80 years, and at least a couple of those it went unheated and vacant. Mind you, it wasn't exactly "level", and it creaked and groaned in the wind (boy, did we get wind there), but it goes to show you just how much a structure can take. And yes, all the other houses around were in similar state, still standing, with people living in them.

Squirl

Quote from: cbrian on May 17, 2012, 02:08:13 AM
I have been repairing houses for over 15 years in Central and South Texas.

Exactly.
The better a house is built up front, the less repair and maintenance it needs over the years.  A little bit of work and a small percentage of extra dollars or maybe even less dollars can get a better longer lasting result.  It is more of a case of knowledge and understanding of the why and how materials work over time.

Say the 3-2x10s vs. 3-2x12s for girders.  The house will not fall down with the difference of the two.  The house may flex over time and have the floors creak, loosen floor boards and nails, possibly crack plaster, or loosen windows.  The difference upfront is $72.  But you have the knowledge of books on carpentry, publicly published building codes, and trade organizations that state it will definitely work and be the strength needed to last over the lifetime of the structure.  I posted a link to the previous topics of with all the calculations of carpenters, who have built on the thousands of years of carpentry knowledge passed down through the generations as to sizing and spans.

So it is more of a question of building knowledge than cost.  This is also a large premium built into the cost of hiring a contractor. I have been rehashing the same basics and topics here for the past four years.  Many people are fully willing to go over the math and physics of the why and how things are done a certain way because we have received that help from others and want to pay it forward.

Although post and pier foundations may seem simpler and cheaper from the pictures. There is a lot more physics and engineering that goes into them than a picture can provide.  Not all of us are willing to wing it and guess when there are easier, better researched, and more published alternatives.

cbrian, I am glad you have been patient with many of us in our ability to explain the why and how behind building things a certain way.

Squirl

hhbartlett

I thought about that too.  Since cost is such an issue for cbrian, I did not suggest it. But let us explore some of the advantages.  If he does go with the perimeter footing he can certainly do PWF attached to it.  Since it would all be above grade and there would be no unbalanced fill on each side so he wouldn't need to worry about bracing the interior with a slab.

But since the PWF wood costs so much more per square foot than concrete I did not suggest it. It can also be difficult to source PWF lumber.  Regular PT lumber (much cheaper) can be used as long as it is above grade.  All lumber touching concrete (because it holds moisture) or within 18" of the ground is supposed to be PT.  Although the stepped concrete footing with 2 layers of block and a double 2x4 sill plate would probably be greater than 18" above the soil.  He could build a wall out of regular lumber, almost identically metolent's picture.  It would save on hauling a lot of blocks, and probably would be close to comparable in cost.


MountainDon

PWF does not require concrete at all. There are methods laid out using compacted crushed rock under the PWF wall structure. LINK near bottom of this page
Just because something has been done and has not failed, doesn't mean it is good design.

AdironDoc

Quote from: MountainDon on May 17, 2012, 10:06:59 AM
PWF does not require concrete at all. There are methods laid out using compacted crushed rock under the PWF wall structure. LINK near bottom of this page

As was used in my 20 x 40 at less cost than poured.

cbrian

So with a PWF you can actually make a basement? This is new to me, but sounds promising. Any figures on the longevity? I see that they pour a foundation inside the perimeter. I am guessing you could do a joist floor system w/ crushed gravel underneath, just raise the height of the PWF to compensate, and there would be no concrete involved at all. Only thing that worries me, and mind you I haven't read all the way threw the document that was linked, is how is the structure pinned to the ground? Is it bearing weight alone that holds the structure down?

cbrian

Quote from: AdironDoc on May 17, 2012, 01:04:26 PM
As was used in my 20 x 40 at less cost than poured.


Do you have any more pictures of the structure. Would love to see more details and the overall build also.

MountainDon

I should have put a footnote on my post.... Like pier fpoundations, PWF don't work in all soils.  PWF works best in type 1 soils. Read the entire document.

There's a chance the Web Soil Survey will have info on the soils in your area.  Or ask locally.
Just because something has been done and has not failed, doesn't mean it is good design.

AdironDoc

#44
Quote from: cbrian on May 17, 2012, 01:57:59 PM
Do you have any more pictures of the structure. Would love to see more details and the overall build also.

More photos of the PWF and overall structure on this thread:
http://countryplans.com/smf/index.php?topic=10791.0

A french drain runs around the perimeter of the PWF base, enters a length of PVC which diverts any possible ground water or seepage downslope. Diagonal supports were for support during construction and were left on for extra support against frost heave against the middle sections of the 2x's that make up the wall. Note that as the first floor pushes down with added weight, the diagonals actually create lateral force. Leaving them in was considered overbuilding, but this mechanical advantage was recommended and there was no reason to remove them once in.


flyingvan

Just wanted to add to the pile of stuf to look at----my two O/B projects were built on slopes with bedrock under thin soil.  This was my solution---high labor, low cost, should last forever since there are no cold joints and it's one massive piece
http://countryplans.com/smf/index.php?topic=11812.msg151774#msg151774
http://countryplans.com/smf/index.php?topic=11821.msg151922#msg151922

   Read all Don's warnings carefully----I went a minimum 30" deep where I could, and epoxied rebar into bedrock where I couldn't.  3 sticks of #5 rebar too

  I'm taking the chance you hadn't already looked at this but if you had my apologies
Find what you love and let it kill you.

cbrian

Quote from: flyingvan on May 17, 2012, 07:40:10 PM
Just wanted to add to the pile of stuf to look at----my two O/B projects were built on slopes with bedrock under thin soil.  This was my solution---high labor, low cost, should last forever since there are no cold joints and it's one massive piece
http://countryplans.com/smf/index.php?topic=11812.msg151774#msg151774
http://countryplans.com/smf/index.php?topic=11821.msg151922#msg151922

   Read all Don's warnings carefully----I went a minimum 30" deep where I could, and epoxied rebar into bedrock where I couldn't.  3 sticks of #5 rebar too

  I'm taking the chance you hadn't already looked at this but if you had my apologies


Thank you for the info, I did alittle digging the other day and found rock 6" in some areas, this looks like what I will have to do also.

cbrian

Quote from: AdironDoc on May 17, 2012, 05:24:40 PM
More photos of the PWF and overall structure on this thread:
http://countryplans.com/smf/index.php?topic=10791.0


Cool place you have! Nice views, and you did a great job on your build. Did you saw and draw your own logs?

AdironDoc

Quote from: cbrian on May 18, 2012, 12:38:09 PM
Cool place you have! Nice views, and you did a great job on your build. Did you saw and draw your own logs?

Thanks! I had my neighbor who owns logging equipment and a mill prepare them for me. I have yet to clean them up and poly them. Every project I'm at takes 4 times longer than I figured. At this rate the cabin will finished by the time I'm put out to pasture.