Single-Pour Footer and Stemwall
joenorm
| Posted in General Questions on
I’m about to pour my footer and stemwall all in one shot. I am wondering if I should “cap” the top of the footer form so the concrete does not ooze out with the weight of the concrete in the footer?
Or is concrete viscous enough that it won’t want to do this?
Thanks
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Replies
Joe,
How are your wall forms held up now?
We pour most walls monolithically. The footing is 2"x8"s tied together by 1"x3" every four feet top and bottom. This gets staked to keep things where they should be. 2"x4" bottom plates for the wall forms get nailed to the 1"x3"s. This keeps the concrete from overflowing.
You can try to do without tops on the footings. Pour in two rounds. the first filling the footings, and a second right after for the walls. That takes some judgement as it needs to set a bit, but you risk getting a cold joint if left too long. It also means having just the right slump - and it's not something I'd do on my first time p0uring a foundation. There are enough other things to be concentrating on. Vibrating the mix, levelling the pour, setting the bolts...
Thank you for the reply, Malcom.
This is how I have my pour set up right now with the 1x3 as you describe but without the 2x4, just a lot of metal spreaders. I'm trying to eliminate as many variables as possible so I may take the time to cap off the footer, Doesn't seem worth the gamble if we got a wetter mix for some reason and had concrete overflowing the footer.
I've poured scores of foundations, and I still don't like it. The less variables the better.
Malcolm, would you say a 6” slump is about right for pouring in two rounds?
Adam
Adam,
It depends. If that slump was achieved entirely by water, then it is too high. If it was caused by admixtures then it's fine, but a 6" slump is still right on the edge of being too soupy.
Malcom,
Running your 2x4 on top of the 1x3 as a "cap" leaves a 3/4" gap for the concrete to escape. Is this not enough of a gap to worry about? Or do you address this another way. Thanks
No it is fine. I your mix flows through that it is is too wet.
Hi Malcolm.
I am about to form up a monolithic footer and foundation wall myself. When you say: "footing is 2"x8"s tied together by 1"x3" every four feet top and bottom. This gets staked to keep things where they should be. 2"x4" bottom plates for the wall forms get nailed to the 1"x3"s. This keeps the concrete from overflowing." Malcolm, does it look like the attached image? If yes, do you just leave the 1x material that is embedded in concrete in place?
Thank you.
-Mike
Mike,
The only things that get left in the concrete are the 1"x3" that fasten the 2"x8" footing forms together - and the concrete ties.
The sketch I've attached shows the footing formed that way, the 2"x4" plates, on which sit 2"x4" uprights every three feet, a 1"x2" pour strip for levelling, and a 2"x4" whaler attached to the outside of those uprights which get props as needed staked into the surrounding ground. The sketch doesn't show the stakes on the outside of the footing used to keep it in place.
Malcolm, thank you for your response. I labeled a few items on your image and attached it. Do I have the outside/inside correct or backwards
1. I assume #1 is to hold #2 in "precisely" as any slight bulging of exterior wall will have a bad effect on plumb and square; whereas inside wall could be off a 1/4" and it would not e an issue, thus no "whaler"? on the inside wall??
2. I assume #2 is to give a ridgid straight edge so the outside wall is dead on (no bulges)?
3. What is #3 for? Is it the thickness of exterior sheathing in order to make a smooth surface to seal exterior wall sheathing to concrete?
4. What is a 1x2 pouring stick? Is it #3? It seams the top edge of the form boards would be for leveling?
Thank you.
-Mike
Mike,
Correct on #s 1 and 2.
#3 is a level strip. You can form up the walls so the top isn't level and instead use the 1"x2" as a guide for your trowel to smooth the top of the pour. It also allows you to run your siding down over the foundation 1 1/2" while leaving the sheathing covered. If you are using a level-strip you need to make your foundation longer to compensate.
In terms of sequence: Form the footing and add rebar. Form the outside wall, brace corners (running diagonal 2"x4's from bottom plate to corner uprights), attach the level strip, then form the inside adding ties and rebar as you go.
I'm going to leave a late reply here on the off-chance that you see it, Malcolm. Do you use 1/2" or 3/4" plywood to form the stem wall? Many thanks.
Jack,
I still use 1"x8"s, and slide the ties in between the rows. The boards get used as diagonal sheathing once the forms are stripped. If you are using plywood, ideally you use 3/4" form-ply. It has a smooth surface and is easier to strip.
Hi, this is very interesting. I hope not to have to use the 2x4 lids on the footing part, seems like a lot of work and I have over 200' of footing/wall to pour.
if i do in 2 pours in the same day, spaced say 4 hrs apart, what do you recommend for sump on the footing part and then on the wall part?
also do you know if the pump truck typically charges by the hour or by the day?
thanks
Steve,
The 2"x4"s aren't there just to keep the concrete in the footings. They are the bottom plates which align your foundation walls and what you attach the studs to that hold the 1"x8" wall forms.
All this is designed for a monolithic pour. If you aren't pouring at the same time, there isn't much point forming this way. Just do things as they usually are done. Form and pour the footings, then form and pour the walls later.
A four hour gap between p0urs is a bad idea. The footings will be partially cured. Hard, but not hard enough to support the weight of the walls and may crack.
Actually i just calculated how much concrete for my 70x22' foundation (house+garage) and its a lot, 16 yards for footing part and 24 for stem walls, so 5 full trucks. based on that, i think i'll be pumping pretty much none stop all day anyhow
thinking about it, since its just me and the wife plus the pump truck guy who probably doesn't help, maybe its better to do separate pours
but i really like the idea of a monolithic foundation. not sure what to do, go safe with 2 separate pours or try for monolithic? I have a lot of concrete experience but usually with a team of 10 guys, this is the first time i'll be doing a DIY job for myself.
i read this 'The concrete company usually allows 10 minutes per yard. IF your pumping the concrete,' https://www.quora.com/How-long-can-it-take-to-pour-10-yards-of-concrete. so 1.5hrs per truck. the more i think about it, the more i think 5 truck loads for 2 people in a day is too much.
Steve,
We use a minimum three person crew. One on the pump, one to vibrate the forms, and a third who levels the top and sets the anchor bolts.
That's a fair-sized pour. You will have to be careful of cold-joints, but it shouldn't take more than three hours.
what about I do in 2 pours, probably about a week or 2 apart since it will take at least that to do the wall forms? should i do anything to avoid a cold joint problem?
something else that complicates things is the land/footing are sloping and stepped so its not a simple foundation.
thx for the help
"should I do anything to avoid a cold joint problem?"
Keep moving, try and fill your forms right to the top, rather than doing two passes. And Joe said: get more help.
so you are saying don't do 2 separate pours weeks apart, do one continuous pour and keep the concrete coming all day right.
that was my original plan, i'll see if i can get some help
Steve,
No, cold joints are only a problem within a single pour. Usually they occur if the batch plant sends the trucks out too slowly, or you go around the foundation in lifts, and the concrete has time to begin hardening before you get back to it. If it is going to take you all day to pour your foundation, they would be a real possibility. The solution is to speed up.
Hardly anyone pours monolithically. Most foundations have a cold joint between footings and the stem-walls above. That's not a problem, and is why the two are joined by rebar or a reglet in the top of the footing.
If you're going to do two pours I think the first thing that would go would be the monopour footer/stemwall. Pour the footer in one pour and the wall in the other.
Find a couple friends to help you.
sorry to beat this subject to death but i worry about pouring a 4-5' high wall the same day as the footing, i know by experience how concrete forms like to move under the weight of that much concrete.
so i got to thinking, i have about 2-3' of wall below grade (after backfill) and about 1-3' above grade, so i'm thinking, do pored concrete for the below grade part, and stop just below finished grade. then use block walls, perhaps the ones with the decorative face (Split Face) , above ground.
this way i get the lateral strength of poured concrete below grade and don't have to panic if my forms move by a bit underground, since i can fix that with the blocks above ground. also save some money on formwork and get to do the backbreaking part of block laying a couple of feet off the ground.
what do you all think?
Steve, It can certainly be done. Just needs to be formed well. Also, it is common to pour in lifts of a foot or two at a time to avoid blowouts and allow the lift to setup a little while you travel around the form. HOWEVER, I have read your comments on this thread, and I would HIGHLY recommmend you form it all up, but get someone to handle the pour. I am gthe most DIY guy around, but after being part of a few concrete pours going south, I only handle very simple concrete work. If you decide to do it, I would get atleast two additional friends. This way you can have your hands free during the stress of the pour. Have one person (well versed in his duty of running the concrete vibration tool. You do not want him doing too much or too little. One error will settle your agregate too much and weaken the top of you wall where house attaches. Too little and you will have unsightly craters all over your wall, Everything is easy if you know what too do and do it propelry. Next I would have one person directing the pump hose. Then I would have one person finishing the top, Also, the hose operator will gett some experience and confidence as he does the pour, so hopefully he does not waste too much from overpouring at the end. The last pour I helped on was an ICF wall about 16ft tall. My buddy did it and he had over 20 of us helping and it was very high stress. He did have a little bulging and one partial blowout. He did a lot of meticulous detail, but failed in one small point. That was his shop building. For his house he did nit ask us all to help. He hired a crew EXPERIENCED in ICF pours. I have built my last 3 houses and I am doing one now. I would do everything, and I mean everything, except a concrete pour. Not trying to discourage you, but you cannot undo a concrete mistake realistically. Also, note how I put in ALL capital letters the word EXPERIENCED. There are con men abounding who think they know their trade because they worked with a second rate crew for a couple years. They might even show you fancy photos that they may or maynot have been part of. They may have expereince with pouring slabs and not know how to pour a basement wall or in this case a stem wall, and it will show when the form boards are pulled or it won't show, but your aggregate will be below your j-bolts. There are plenty of pros, but there are plenty of cavalier people who know you will never see or have a claim on their shoddy work.
thanks for the advice, i am certainly not underestimating how things can go wrong in a big pour. i've supervised a number of concrete swimming pool pours where i live now in Thailand and know how tricky pours can be. that's why I'm planning to keep the wall height on my project under 3'
thanks and i will definitely get some help on the day, but i'm confident i can build a 3' high concrete form ok, 6', i wouldn't be so confident.
Steve,
It's a terrible idea. Unfortunately most building tasks that require a set of skills - some basic, some more advanced. It makes no sense to compromise your foundation because you don't have them. Get some help - with the forms and the pour.