Footings - rocket science?

[5030tinkerer]

All this talk about foundations getting dug and setup has me wondering. Everyone I talk to says to hire a pro to dig the footings for the ICF house that I am building this spring - that way it is their responsibility is something goes amuck. If a guy has a laser level, a backhoe, and a tape measure, and feels comfortable with using these tools, is it so far out of line to dig, form up, and pour his own footings?

Ed

 

[Bird]

Ed, I think it just depends on how confident you are and whether you want a "warranty" from someone else. When we built my brother's house, we did everything ourselves except installing the HVAC system, the garage floor, and the carpet. But my brothers had experience as building contractors. A fellow who worked for me built his own house, with the help of his sons. They did a beautiful job; really nice place, but in less than a year a part of the foundation settled and the fireplace chimney pulled about 3" away from the rest of the house. He said he'd never do a foundation again himself.

 

[Paddy]

Footers are easy if you know what your doing. They need to be on soild ground ( not muddy back wash), wide enough( tables will help you over engineer it) and deep enough( same tables as before). Level is more critical with CIFs. You don't have mortor joints to make up as you go. I use a watter level. OK, a garden hose with clear tube at the end.

Oh, and square, don't forget that one!

 

[Highbeam]

On the short list of things not to half-a$$ on a home construction project is the foundation. Level, solid, square, and substantial cannot really be compromised. If not completely confident, hire this one out.

 

[keeney]

The foundation digging shouldn't be that big of a deal with a couple of things to pay attention to:

1. Don't over-dig. If you do an inch or two, you can make up for it with more concrete, but I wouldn't mess with trying to fill it back in.

2. The "level and square" part comes when you setup the actual forms. It takes a surprising amount of wood and stakes to form up the foundation. Triple check your transit. Square the corners by measuring the diagonal.

3. You have some additional ability to re-square things when you set the wall forms (ICF) , but it would be really nice to not have to mess around re-leveling things.

4. Be sure to leave plenty of room in the trench to work safely. Not sure how deep you are going, but with a 9' deep hole typical here in MN, its nice to have it be a good 10' wide.

 

[wilkesland]

Well it depends. If I am going to build the wall that rests on the footing, then I will build it every time - as I am about to do on the wrap around porches for the house we are building. On the other hand if I am contracting out the wall construction, as I did for the basement of the house, then I put the footing construction in their scope of responsibility. My life is too short to argue with contractors about level, finish, width yada yada yada. Oh by the way, I'm a registered professional engineer, so I'm perfectly capable of designing an adequate footing and I'm a pretty fair at building stuff myself. In my case, my basement walls have a warranty against leakage and I wanted to do nothing that would give the contractor a chance to void the warranty if anything goes wrong.

 

[Egon]

Chances are if you have to ask questions about footings its best to have them designed and placed by those that know and are familiar with your area.

Egon

 

[5030tinkerer]

Excellent points, all. It sounds like I should maybe bite the bullet and pay someone else to do this. I have no concept of how much money we are talking about here, but the one thing that I am relatively confident of is that I will be kicking myself if it is messed up. I had already decided to have the excavation done by someone else. Then again, I haven't had exactly stellar success in having contractors do good work. /forums/images/graemlins/mad.gif

The issue with ICF's is that they are SO easy to put up and don't leave much possibility for screw up - so long as it starts out right. Integraspec (the ICF manufacturer) tells me that they recommend just digging a few INCHES beneath the excavation that was done for the basement for the perimeter footer. While that concept can hold readily true for the portion of the basement that is dug well beneath the 42" frost line, I do have a concern as the basement gets closer and closer to the walkout portion as that will obviously have to be dug deeper.

As far as the width of the footing, the documentation that I have read on that topic is fairly consistent. For a two story home with concrete walls, go with an 8" thick 31" wide footing if your soil only has 1500psi of load bearing capability (the ICF dealer says that 24" is plenty, but for the difference in concrete cost, I figure why not go the 31" and give myself some extra insurance against not having the separation issues noted in the post above).

 

[CurlyDave]

go with an 8" thick 31" wide footing if your soil only has 1500psi of load bearing capability

I think you mean 1500 pounds/sq ft for soil load bearing capacity.

When I built my house, I had a soil engineer look at the foundation, and 2000 pounds/sq ft was the lowest he said we had and it went up to 8000 for some of the places.

IMHO, it doesn't really matter. I am going to end up owning the house I build, and I would much raqther pay for $1000 worth of extra steel and concrete than pay an engineer $1000 to calculate that I don't need the extra steel & concrete.

I put the foundations in with lots of overkill 16 years ago, and there has been no cracking, no settling, an no problems.

There is no excuse for having an underdesigned foundation. The cost and effort of doing it right is peanuts compared to the pain and frustration of fixing a settling problem.

 

[flusher]

Check Kurt Casper's website for info on ICF house construction

ICF info

He used the Amvic system. Lotsa photos and construction adventures on Kurt's website.