[Rszimm]

OK, So I'm forming for my footers right now. The footer is only 18" below the finished floor. 5" pad, 4" A-B under that. So I had the excavator level everything at -9" and then dig the footer trenches another 9" below that. The footers are 12" deep, so I have to form up the extra 3".

So here's my questions. I've got about 140' of footer. Forming on both sides, that's about 280' of length. I only have about 50 of the steel stakes (about 25 2' and 25 3').
1. Am I going to be OK with 50 stakes?
2. If not, are wooden stakes acceptable?
3. What's a reasonable spacing for stakes on the forms?
4. I only need 3" of height in the forms. Can I use 2x4s or should I use 2x6 and dig out the edges a bit?

 

[Nealtw]

OK, So I'm forming for my footers right now. The footer is only 18" below the finished floor. 5" pad, 4" A-B under that. So I had the excavator level everything at -9" and then dig the footer trenches another 9" below that. The footers are 12" deep, so I have to form up the extra 3".

So here's my questions. I've got about 140' of footer. Forming on both sides, that's about 280' of length. I only have about 50 of the steel stakes (about 25 2' and 25 3').
1. Am I going to be OK with 50 stakes?
2. If not, are wooden stakes acceptable?
3. What's a reasonable spacing for stakes on the forms?
4. I only need 3" of height in the forms. Can I use 2x4s or should I use 2x6 and dig out the edges a bit?

We make stakes out cheap grade 1x4 or we can buy them already sharp made out of 1x2,.


So you are thinking two pours footing and then slab?

I would do it different than you are thinking.

I will draw you a picture.

 

[Rszimm]

Three pours:
1. Footers
2. ICF walls
3. Slab inside walls

I considered a mono slab, but the ICF guys cautioned against that as it would provide an easier path for water to get under the walls (it’s a walk out basement).

So using wood stakes sounds fantastic. I didn’t think those would work because there’s a 9” deep trench just the thickness of the forms from where the stake needs to be driven (plus it’s very sandy soil). I figured the wooden stakes would just cave in the footer trench, but if you think it would work, I’ll give that a shot.

 

[Nealtw]

the outside of the footing needs to be a smooth finish so the frost doesn't catch it and lift it. So on that side, use a 2x12 or 2 2x6s and on the inside a 2x3 would be the right height and a 1x4 across the the top to hold them together.
When we do an 8 in footing we build the forms out of 2x6, we find the highest spot in the hole and lift it up and stake that spot at 8"and level and stake them all around some times we have great spaces below.
Only if it get close to 3 inches off the ground to we add more lumber to the bottom.

 

[stadry]

having built several icf bldgs, we found the better method is standard footing ( foundation ) & lay icf's on top,,, WATERPROOF the seam on 1st course using sealant ( we use slm5000 by sonneborn ),,, place traditional conc floor inside.
i'll leave staking method to neal,,, we used std steel pins rather'n wood but placed larger sized steel reinforced size footings

 

[Rszimm]

Thanks. Really helpful. A few follow ups:
1. How frequently do you put the 1x4 on the top?
2. How frequently do you place your stakes? (Maybe the same spacing as #1?
3. What’s a good length for form boards? I was thinking 12’ but I’m amenable to your advice.

I’m in Tucson, so frost is unlikely to be a concern. However I’ll probably still flatten that face so I can run my waterproofing membrane down the ICF wall and around the top and the outside edge of the footer.

As for doing a mono slab, I think you may have missed my previous message right before yours. Plus the engineer wants the slab doweled into the wall which can only really happen if I pour the wall before the slab.

 

[Nealtw]

You will want that extra space beside the footing later for the drain system.

 

[Marson]

Wood stakes are fine and maybe even preferable depending on the soil type. A three inch height is pretty minor so a stake every three or even four feet should be enough.

I would use 2x4’s and if there are areas where there are gaps underneath, just bank some dirt there.

If your footings are buried below frost then I don’t think you need to worry about frost grabbing the side. You do have to consider where your drain tile goes. Hopefully below the slab.

We also used to put in cross connectors between the inside and the outside footing drains. That would be tough with your setup. I believe that was a local code though.

 

[Rszimm]

I believe we’re doing just want you suggest stadry. Only difference is we’re probably going with poly wall for the waterproofing.

BTW, is it really that important to hold off on backfilling until the slab and basement ceiling are installed? The back wall would be SOOOOO much easier to backfill if I could dump over the wall with my skidsteer, but that’s not going to work if there’s a ceiling installed.

 

[Nealtw]

Thanks. Really helpful. A few follow ups:
1. How frequently do you put the 1x4 on the top?
2. How frequently do you place your stakes? (Maybe the same spacing as #1?
3. What’s a good length for form boards? I was thinking 12’ but I’m amenable to your advice.

I’m in Tucson, so frost is unlikely to be a concern. However I’ll probably still flatten that face so I can run my waterproofing membrane down the ICF wall and around the top and the outside edge of the footer.

As for doing a mono slab, I think you may have missed my previous message right before yours. Plus the engineer wants the slab doweled into the wall which can only really happen if I pour the wall before the slab.

So there are different types of slab on grade and I was think if what we call a pan slab. I missed the basement part. :biggrin2:
12s are pretty good, we often got 16 footers which are nice for long walls.

Stakes and ties every 4 ft should work I wouldn't go more than that.

How wide are the footings and how high will the walls be.

Are you building on a sloped lot, front or back high.

 

[Rszimm]

Footers vary from 18” wide in the front (the walkout part) to 3’ wide in the back (retaining 8’ of fill behind the back wall). The walls are 9’ high.

 

[Nealtw]

Footers vary from 18” wide in the front (the walkout part) to 3’ wide in the back (retaining 8’ of fill behind the back wall). The walls are 9’ high.

So the footing at the walk out has to be at frost depth the back footing where you have depth the footing can step up to right below the slab.

If you have a center bearing wall we usually put that in just below the slab too.
When you use the foam forms do they have different heights or are they all the same height. If you have choices what are they.

 

[Marson]

I can’t answer whether you can backfill before framing the floor. We used to always pour the floor first so we could use a pumper. Then backfill. You have to allow plenty of time for the concrete to cure. But local condo can vary so much that who knows what your situation is.

Back in the day we used to build on block foundations and there we’d frame the floor first and brace the walls with lumber. So there’s more than one way to skin a cat.

 

[Nealtw]

I can’t answer whether you can backfill before framing the floor. We used to always pour the floor first so we could use a pumper. Then backfill. You have to allow plenty of time for the concrete to cure. But local condo can vary so much that who knows what your situation is.

Back in the day we used to build on block foundations and there we’d frame the floor first and brace the walls with lumber. So there’s more than one way to skin a cat.

I think I have only built 2 or 3 houses after the slab is poured. We weren't used to it' my son broke a vertebra falling off a ladder, there was sand on the slab. Opps. Right after the roof is done they bring the plumber and then do the slab. No rain screwing it up and no shrinkage in the summer.

 

[3onthetree]

BTW, is it really that important to hold off on backfilling until the slab and basement ceiling are installed? The back wall would be SOOOOO much easier to backfill if I could dump over the wall with my skidsteer, but that’s not going to work if there’s a ceiling installed.

Yes, very important. In reality, I've seen very few framers starting without backfill, well, because workman's comp and OSHA. They will shore with a 2x8 long ledger and a few kickers. Some will run a couple horizontal 2x's until the steel arrives. All are inadequate. I could make a peace sign with the number of times I've seen better shoring - like every 4'-6' and not staked in the ground but pushing opposite kickers. Unfortunately ICF will hide any cracks.

You're going to backfill the 9' high wall blind from the inside? Aren't most hinge points on skid steers around 10', and you'll have shoring in the way anyway?

 

[Rszimm]

Yes, very important. In reality, I've seen very few framers starting without backfill, well, because workman's comp and OSHA. They will shore with a 2x8 long ledger and a few kickers. Some will run a couple horizontal 2x's until the steel arrives. All are inadequate. I could make a peace sign with the number of times I've seen better shoring - like every 4'-6' and not staked in the ground but pushing opposite kickers. Unfortunately ICF will hide any cracks.

You're going to backfill the 9' high wall blind from the inside? Aren't most hinge points on skid steers around 10', and you'll have shoring in the way anyway?

OK. I’ll wait and do it the right way. Unfortunately that means I’ll be backfilling with wheelbarrows rolling uphill as it’s not possible to get equipment behind the structure once it’s built. 8’ of fill, 2’ cut 60’ long is going to make for a miserable few days.

 

[Nealtw]

@Marson @3onthetree


You guys have missed one line in the discussion, so let's not jump the gun.

Maybe some more questions could be asked but the line was " the rear footing is 3 ft wide because it is a retaining wall." By description that is self supporting.



We spent 20 years on the mountains so almost every house is a walk out basement.

Most foundations that have a tight grid of rebar can be back filled within a week.

The times you don't are related to the slope of the land behind the house and how much water is retained in the fill that will be used for back fill.

Usually the on site engineer after looking at the slope and the fill dirt will decide if it can be back filled or it should supported with steel angle braces or just build the floor first.
If it is already a retaining wall the engineer likely has considered the hill to be less stable than he would like.

 

[Rszimm]

It’s built as a restraining wall, not a retaining wall. The wall is centered on that footer. There’s a lot of rebar in the wall (16” x 16” #5), but the wall is only 6” thick.

Soil here is basically gravelly sand with rocks. Very little silt and almost no organic matter.

I was hoping I could at least backfill the first 4’ over the top, that would save me a few hundred wheelbarrow trips. But ultimately it’s my house and I don’t want to harm the wall so I’ll do it right.

 

[Nealtw]

It’s built as a restraining wall, not a retaining wall. The wall is centered on that footer. There’s a lot of rebar in the wall (16” x 16” #5), but the wall is only 6” thick.

Soil here is basically gravelly sand with rocks. Very little silt and almost no organic matter.

I was hoping I could at least backfill the first 4’ over the top, that would save me a few hundred wheelbarrow trips. But ultimately it’s my house and I don’t want to harm the wall so I’ll do it right.

You can rent these or build similar out of wood.

 

[3onthetree]

Thx Neal.

Rszimm, not saying you can't backfill first, its done everyday. Just minimize risk. Food for thought maybe helpful in staging your construction:
- Restraining wall means the floor diaphragm prevents the overturning at the top, but the engineer can account for a retaining wall (cantilever) when the backfill occurs before the 1st floor diaphrapm is in. Here it's not designed that way, so for a 60' wall better to overthink your shoring without the 1st floor in.
- Also he's using the slab for the bottom lateral loads ("sliding"), so the full height kicker is better than just at the top 1/3 (like Neals pic ^^).
- A single curtain of rebar for a 6" wall 9' high means a full-height gravel backfill is needed to alleviate some hydrostatic pressure. I was picturing a good 5' or 6' overdig, so from the inside dumping the gravel vs. spoils would be challenging unless you like paying for a lot of gravel. That's why I mentioned the height of the bucket, as you'd be bouncing the bucket to try and throw the spoils beyond the gravel to fill the overdig.
- But you have a 2' cut all the way up? You're going to be back there installing the drainage and membrane waterproofing?

OK. I’ll wait and do it the right way. Unfortunately that means I’ll be backfilling with wheelbarrows rolling uphill as it’s not possible to get equipment behind the structure once it’s built. 8’ of fill, 2’ cut 60’ long is going to make for a miserable few days.