Acceptable alternatives to continuous concrete footings

Started by kinshollow, June 18, 2013, 03:15:14 PM

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kinshollow

The site I'm building on is difficult to access for a cement truck (an old road that was used previously is no longer available, and the current driveway is inadequate). I'm attempting to find alternatives that can be done by hand without large, heavy trucks.

For a two story, hollow CMU, house I need the minimum 12" deep foundation with 21" wide footings according to the IRC and IBC. Two options that seem feasible are masonry footings or to have a masonry foundation wall bear directly on the soil (without a spread footing). There is a picture of the latter on page 75 of the 2012 IRC, but I couldn't find any further information on this. 

For masonry footings I found a little bit of information in the IBC on page 408 section 1809.9. But I'm confused on exactly the right way to do this. I was hoping to use CMUs but the offsets described (1.5-3") would be impossible with those. I've spent a lot of time searching for information on the internet, but have only found very old diagrams of footings built with regular small bricks or companies selling precast footing systems. Any ideas on where to find better information would be very much appreciated.

The site does have an existing concrete foundation that was for a mobile home, but it's larger than the area I want to build on and is only comprised of a series of runners. I'm not sure if parts of it could be incorporated into a new foundation or not. I suspect it won't be particularly useful.

I am paying for everything as I go to avoid a mortgage, so am trying to keep the costs low.

Any alternative ideas would be appreciated, as would any suggestions for further learning.

flyingvan

http://countryplans.com/smf/index.php?topic=11812.msg151774#msg151774
http://countryplans.com/smf/index.php?topic=11821.msg151922#msg151922

   Here is my solution for similar issues.  It worked so well on the first build I did it again for the second.  Both footings were hand dug then formed up. I was able to get a concrete pumper fairly close but if you just form it up and mix and pour concrete as time and money allows, you'll have some cold joints but a masonry wall is all cold joints. 
   Advantages are, you only have to get the top of the forms level.  I had massive boulders to deal with so I could just drill them out and epoxy rebar in to them
Find what you love and let it kill you.


Don_P

Fix the road  ??? I've poured footings using bag mix and a wheelbarrow or small mixer. I've seen precast footing blocks used but have no experience. The theory is that as long as you support the house on the soil with enough footprint to bear the load in that soil strength without sinking, you're good. Typically the footing cannot project out further than its' thickness, or another way, the load travels through the masonry at a 45 degree angle at most, otherwise "punch through" is a possibility, snapping the extending sides off the footing.

The pic that I assume you are talking about fig R403.1(1) ((tip, page numbers vary, use the reference numbers like I just did so we can all keep straight)) works if the soil compressive strength is high enough to bear the load.  Then there's the engineer option.

kinshollow

Quote from: flyingvan on June 18, 2013, 03:30:40 PM
http://countryplans.com/smf/index.php?topic=11812.msg151774#msg151774
http://countryplans.com/smf/index.php?topic=11821.msg151922#msg151922

   Here is my solution for similar issues.  It worked so well on the first build I did it again for the second.  Both footings were hand dug then formed up. I was able to get a concrete pumper fairly close but if you just form it up and mix and pour concrete as time and money allows, you'll have some cold joints but a masonry wall is all cold joints. 
   Advantages are, you only have to get the top of the forms level.  I had massive boulders to deal with so I could just drill them out and epoxy rebar in to them

Thanks for the links and ideas. The masonry books I've read stress the importance of pouring the footings all at once, but that never made a lot of sense to me when foundations can be added onto for additions and such. I just read a post on the general forum about pouring a foundation in stages and how to reinforce cold joints. That may be the way to go.

Your solution would definitely help with working around the existing foundation (as opposed to removing large strips of concrete over a 28x60' area just to build a smaller house).

Squirl

Are you governed by the IBC or IRC?

I never saw 12" deep footing requirement in the IRC.  Where did you find it?

IRC
QuoteR403.1 General. All exterior walls shall be supported on continuous solid or fully grouted masonry or concrete footings, crushed stone footings, wood foundations, or other approved structural systems which shall be of sufficient design to accommodate all loads according to Section R301 and to transmit the resulting loads to the soil within the limitations as determined from the character of the soil. Footings shall be supported on undisturbed natural soils or engineered fill. Concrete footing shall be designed and constructed in accordance with the provisions of Section R403 or in accordance with ACI 332.
http://publicecodes.cyberregs.com/icod/irc/2009/icod_irc_2009_4_sec003.htm


First I can tell you if a concrete truck can't get to the site, getting enough block in for a 2 story house will be a pain.  I had access to my site and had a truck drop of six pallets to the front of my property.  That truck was just as big as the concrete truck.  I think speedfunk has pictures of the truck dropping off pallets of blocks for his house.   I don't know how far you are from the store, but delivery cost 1/3 what it would have cost me in gas and the time of all the trips to move the blocks and mortar myself.

With a good tamper you may get away with:
R403.4 Footings for precast concrete foundations. Footings for precast concrete foundations shall comply with Section R403.4.

TABLE R403.4 MINIMUM DEPTH OF CRUSHED STONE FOOTINGS (D), (inches)

Or 14" of crushed stone.  I've not seen many excavators with buckets less than 24" wide, so I would assume you would need 24" wide worth of stone.


I personally would prefer mortared blocks.

I've seen it done two different ways.

The first was to use bond beam or knock out blocks.  People would run rebar in these and fill them with grout.



The other was to build up progressive layers of masonry to get to the desired width.



If I were in an area with no rebar requirements and low seismic activity, I would probably prefer the built up method for that kind of footing span.

The code is occasionally vague.  To fill in the gaps or to help with interpretations, many inspectors turn to the associations that publish the language where the code is developed from.
For concrete American Concrete Institute.
http://www.concrete.org/general/home.asp?HP=h_home
For Masonry
National Concrete Masonry Association, Eteks
http://www.ncma.org/ETEK/Pages/TEKKeywords.aspx?KeywordID=167#kd
The Brick Industry Association, Technical Notes
http://www.gobrick.com/TechnicalNotes/LinkstoTechnicalNotes/tabid/11294/Default.aspx

These will probably be helpful in constructing a 2 story masonry structure.  I did not see masonry footings in the publications, but I didn't look very hard.


kinshollow

Quote from: Don_P on June 18, 2013, 03:36:14 PM
Fix the road  ??? I've poured footings using bag mix and a wheelbarrow or small mixer. I've seen precast footing blocks used but have no experience. The theory is that as long as you support the house on the soil with enough footprint to bear the load in that soil strength without sinking, you're good. Typically the footing cannot project out further than its' thickness, or another way, the load travels through the masonry at a 45 degree angle at most, otherwise "punch through" is a possibility, snapping the extending sides off the footing.

The pic that I assume you are talking about fig R403.1(1) ((tip, page numbers vary, use the reference numbers like I just did so we can all keep straight)) works if the soil compressive strength is high enough to bear the load.  Then there's the engineer option.

Before I do anything I do intend to crunch the numbers of fixing the road (which involves moving water pipes and building retaining walls) and ordering a concrete truck, versus the cost of buying smaller amounts of concrete and a mixer. The convenience of the truck is appealing, but the desire to build  now while the weather is good for concrete work is strong too. It's hard not to get over excited about each stage.

R403.1(1) is the same image I was referring to (thanks for the tip). My soil is poor so I don't think that would work. Thank you for explaining that.

It seems like 8x16" CMUs could be use for footings in a row of 24", then a row of 16", then 8", but I'm not sure how the building official would feel about that. Building codes were only just recently adopted here, and so the attitude seems to be very hesitant for anything out of the ordinary.   

The engineer is a last resort. I'm definitely glad the option is there though. I don't want to build a house that has a crack in the middle of it. The kids would probably have an issue with that... 

Squirl

In most older masonry books and guides, what you propose of 3 blocks, then 1 run length wise, then 1, is not out of the ordinary.  It is well covered in wall construction. You could even rebar the layers together.  If the masonry is done in a running bond pattern, it should be plenty strong enough.

QuoteR606.2.3 Change in thickness. Where walls of masonry of hollow units or masonry-bonded hollow walls are decreased in thickness, a course of solid masonry shall be constructed between the wall below and the thinner wall above, or special units or construction shall be used to transmit the loads from face shells or wythes above to those below.

http://publicecodes.cyberregs.com/icod/irc/2009/icod_irc_2009_6_sec006.htm

It may depend on the background of your inspector or department.  My inspector is also a licensed engineer.  I can discuss finer points of technical manuals and guides with him.  He understands the basis and intent of the code.  The requirements for being a building inspector can vary vastly.  A few I have talked with were framers before becoming inspectors.  They were not as technical in understanding the code when it was vague in masonry and concrete. At the end of the day, I had more worry than I needed to before I dealt with my inspector. 

kinshollow

Squirl:

Thank you for all the great info!

My county follows the IRC. The "12" footing" you asked about was just me not explaining what I meant to say well. I was referring to the minimum depth of the foundation for the frost line, not the thickness of the footing.   

The usual method of getting heavy objects onto the property involves having it delivered to the bottom of the driveway and then hauling it up in carts. I did this recently with 17 tons of gravel. Not fun, but doable. I also plan to buy the blocks in stages, and am luck enough to have access to a small truck that can make it to the site. Neither the site nor the store are far away, so that's not much of an issue. That being said, fixing the road is on the List, and it is true that if I can manage to get trucks onto the property it would save a lot of time I could put into other aspects of the job.

The bond beam masonry suggestion is not something I had seen before. Thank you for posting that picture.

Crushed rock is something I had looked into, but precast footings seemed to either be expensive or require a crane.

I may be making this harder than in needs to be.

Thanks again for all the great info and links. It's much appreciated.

 

kinshollow

Thanks for the feedback on this. I haven't gotten a chance to talk to the codes inspector yet, only his staff. The meeting hopefully will go better than I worry it might, but I'm trying to be as knowledgeable/prepared as possible to improve the odds. I've done construction work on a number of projects over the years, but I was never the person in charge.  :o 

Quote from: Squirl on June 18, 2013, 05:19:34 PM
In most older masonry books and guides, what you propose of 3 blocks, then 1 run length wise, then 1, is not out of the ordinary.  It is well covered in wall construction. You could even rebar the layers together.  If the masonry is done in a running bond pattern, it should be plenty strong enough.

http://publicecodes.cyberregs.com/icod/irc/2009/icod_irc_2009_6_sec006.htm

It may depend on the background of your inspector or department.  My inspector is also a licensed engineer.  I can discuss finer points of technical manuals and guides with him.  He understands the basis and intent of the code.  The requirements for being a building inspector can vary vastly.  A few I have talked with were framers before becoming inspectors.  They were not as technical in understanding the code when it was vague in masonry and concrete. At the end of the day, I had more worry than I needed to before I dealt with my inspector.


flyingvan

  If you buy the mixer, don't buy concrete---the prepackaged mix is pretty thin, I believe a 6 1/2 sack mix (Every yard of concrete has 6 1/2 sacks of cement)... You will save lots of money by making your own, and get a better mix. 

   Here's my formula, I'd be very interested to hear other people's....
   For one day's work (yesterday you had your forms set up and got the materials, carbo-loaded, skipped the drink and got a good night's rest)

--Deliver a yard of 3/4 gravel, dump it onto a clean tarp.
--Deliver a yard of sand, dump it right next to the gravel.
--Deliver 14 bags of portland cement; stack them next to the gravel and sand.

    Get your hose ready, do a dry-run with the wheelbarrow so you know it's a level and bump free run.
    Squirt water in the now running mixer.  You're going to measure your ingredients with your round bladed shovel, 3:2:1.
    3 shovels of gravel.  (You'll notice gravel doesn't pile very high onto a shovel; that's why it's 3)  Toss it in the barrel.
    2 shovels of sand.  This WILL pile high on your shovel  Toss it in.
    Chop an 'X' in a bag of cement and peel it back (caustic.  Wear gloves.) 1 shovel of cement.
    Add water until your mix is the consistency of oatmeal.  You want as little water as possible, just enough so it's workable, no more. 
    You can sort of tip the barrel a little to help it slosh around some.  Dump it in your wheelbarrow and repeat---you can get two drums-  worth in each wheelbarrow.
    Back off your weelbarrow a few feet---don't try to throw stuff in the barrel with it in the way.  Don't ask why I know this.
    Spray some water in the barrel, shovel in your gravel.  Let the water and gravel scour the drum while you go dump the wheelbarrow load.
     Go back and add the other ingredients.  While it's mixing, go back to your forms and push the concrete into the forms well---a 2x2 works well.  Really work it so you don't get any honeycomb voids.  (There are other little tasks to fit in while things are mixing, like lifting the corners of the tarp to keep your piles neat, drink some water, etc)
      This makes 2 yards of concrete.  Seems like with the water and cement it would be more, but they just fill the voids between the aggregate.

Concrete, delivered, 7  sack mix, with waiting time                          ---     $214/yard (maybe more with delivery)
Concrete, mixed yourself, from pre-mix   6 1/2 sack (?)                    ---     $163/yard
Concrete, from scratch                                                                      ---     $53.30/yard

   (San Diego prices 6/13)
Find what you love and let it kill you.

Squirl

Wow, prices can vary greatly.

Central NY.

$110 a yard delivered 3500 psi concrete.
$170 premix (45 80lb bags *$3.75) + $40 delivery, free if getting other things delivered.
$70 for just the cement 7 bags X $10. I have to order 11 yards to get delivery at $300 a load for each sand and gravel, or I could spend an entire day traveling back and forth between three locations trucking back the material plus gas at $4.00 a gallon.

Under almost no circumstances did it make sense to mix my own.

For difficult locations, such as when a septic field is in the way, or in dense residential neighborhoods, I see people use concrete buggies.



They can usually be found at equipment rental places.  They are $150 a day around me.

12" deep?  Please hold while I scream in envy.  (4 ft)


You are right, precast concrete walls are usually put in by a crane and bolted together.  Sometimes they can be tilted up by a tractor or backhoe. I saw them on this old house once.  Because the walls are simply bolted together, I would be willing to make a guess that a concrete block wall in running bond is as strong or better.  As long the bottom block is a solid block it should distribute the weight as good if not better to the crushed gravel.  This is where it helps to have a person who understands the basic theory behind the code.

The jagged edges of crushed stone generally lock together as it is compacted reducing shift and further compaction.  As a load is applied to the top it is distributed in a pyramid shape through the stone.  So the engineers got together and figured out how deep the gravel has for that pyramid to distribute the weight to the soil.  Then because they are engineers, they add in a nice big safety factor and put that in chart, TABLE R403.4 MINIMUM DEPTH OF CRUSHED STONE FOOTINGS (D), (inches) .  As you can see from the chart, the wider the wall, the shorter the pyramid (depth of gravel) has to be to get to the width of soil to hold the weight.  I also made a mistake earlier.  I used the 6" wall and got 14" deep, you would be using an 8" wall for 12" deep.


I don't trust gravel that much and would prefer a 12" wide grouted block as a footing even on top of it, but that is just my own fear, and is not based on anything scientific.

rick91351

Quote from: kinshollow on June 18, 2013, 05:21:34 PM
Squirl:

snip.........

My county follows the IRC. The "12" footing" you asked about was just me not explaining what I meant to say well. I was referring to the minimum depth of the foundation for the frost line, not the thickness of the footing.   

snip..............


Same here for the location here in this country.  Low elevations get 10".  Here its a full 12" deep - 2' 6" wide with 3 bars of #5 rebar.  Strip footings for foundation pony walls.  show at 12" X 12" with two bars of #4 rebar.  In this higher elevation it does cost more to build.

Concrete is charged at the yard price.  Then total truck time, from the plant - pour and return.  Then the mileage or zone component, then as of two years ago a diesel surcharge.  We are some where there between Squirl and flyingvan.  I still think we are at the five bag requirement here. 

Proverbs 24:3-5 Through wisdom is an house builded; an by understanding it is established.  4 And by knowledge shall the chambers be filled with all precious and pleasant riches.  5 A wise man is strong; yea, a man of knowledge increaseth strength.

Don_P

Our prices are similar to Squirl's, no advantage to mixing your own on a cost basis. I usually do a 1:2:3 mix similar to flyingvan when I do mix onsite but I use 5 gallon buckets to measure each ingredient as I charge the mixer. You can lean the portland out for a footing, a 4000 psI mix on 2000 psF soil isn't strictly necessary.

jsahara24

I just got 8 yards of 3500 psi delivered in NY for 860$  I can't believe how much it costs in California.  Amazing. 

Sent from my XT907 using Tapatalk 2



rick91351

I like Flyingvan's instructions on hand mixing cement.  As well as Don-P's five gallon bucket measure.   

Way way way back when I was working for a Ready Mix Company and gravel pit.  A number of people wanted sand and gravel mixed and delivered for the purpose of making it into cement.  The owner discouraged it or refused to do it because it never remained mixed in to the proper ratio.  Of course the customers were thinking he was wanting the additional truck charge.  Funny how looking out for someone sometimes equals hard feelings and insults and name calling.   
Proverbs 24:3-5 Through wisdom is an house builded; an by understanding it is established.  4 And by knowledge shall the chambers be filled with all precious and pleasant riches.  5 A wise man is strong; yea, a man of knowledge increaseth strength.

tmcmurran

Quote from: jsahara24 on June 19, 2013, 01:15:43 PM
I just got 8 yards of 3500 psi delivered in NY for 860$  I can't believe how much it costs in California.  Amazing. 

Sent from my XT907 using Tapatalk 2

Talk about a deal for 8 yards!!!.  $290.00 a cubic metre here for 30mpa mix, plus $1200 for a pump truck, plus tack on the 13% in taxes.  Just finished pouring 12 cubic meters and am dreading the bill once it comes in the mail. :(

umtallguy

If you cant get a concrete truck in how will they get a firetruck or ambulance in if you need one...

Don_P

Bingo.
The argument so often forwarded "I can't get a concrete truck in" is a clear indication that either the road needs improving or the lot is unbuildable. There are multiple large vehicles that will likely need to service the home over the course of construction and its' life. The materials delivery trucks, the septic tank and later pumper, propane and on and on. On our house we truly could not get the truck in, I hooked it to a dozer and there was my sign. When we did scramble the fire dept the only trucks that could come up were the little brush truck and the ambulance and they would not make it in bad weather.

kinshollow

Quote from: umtallguy on August 09, 2013, 12:24:36 AM
If you cant get a concrete truck in how will they get a firetruck or ambulance in if you need one...

I apologize, I missed this question from so long ago! The area isn't actually remote. It's just typical rural Tennessee. The building site is at the beginning of an old logging road, so it's not that far from the connecting road. Once we repair the front part it will become more of a driveway. It's still possible that many vehicles won't be able (or willing) to enter the driveway, but that's very common here and there are work-arounds.

kinshollow

Quote from: Don_P on August 09, 2013, 07:01:56 AM
Bingo.
The argument so often forwarded "I can't get a concrete truck in" is a clear indication that either the road needs improving or the lot is unbuildable. There are multiple large vehicles that will likely need to service the home over the course of construction and its' life. The materials delivery trucks, the septic tank and later pumper, propane and on and on. On our house we truly could not get the truck in, I hooked it to a dozer and there was my sign. When we did scramble the fire dept the only trucks that could come up were the little brush truck and the ambulance and they would not make it in bad weather.

I've been a steady lurker for several years now and still managed to somehow miss this reply. I apologize for that!

That's good that you did manage to get everything onto your property. I'm lucky in that the septic tank, electricity and water are already in place--the only thing missing is the house and (of course, the one section of road/driveway). At this point the plan is to repair the road and then have a truck come in as soon as it's warm enough to pour the foundation.

I hope it never becomes too much of an issue for you with emergency vehicles and bad weather! I currently live about 20 minutes from the building site in a small town where most of the houses were built rapidly in the 1940s. The way electrical lines and such are positioned many larger vehicles cannot enter the properties. The one time we had to call an ambulance, they parked in the street and wheeled the injured person out on a stretcher. It didn't seem to cause a delay, they seemed pretty used to it.