Concrete Stem Wall Foundation
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- Опубликовано: 11 июн 2016
- Master builder Dave Osland gives a brief overview of the excavation, forming, pouring and stripping of stem wall foundation.
This type of foundation accommodates a raised wood floor, as opposed to a slab-on-grade. Both are common in residential home construction..
If people read the comments before commenting, just think of all the time saved! Thanks for another educational video. I got a foundation coming up.
Dave Osland you and your crew work very clean and the concrete looks clean the pour was fantastically good
Thanks Dave for another awesome video!
Interesting video Dave, thanks for sharing
That foundation looks sturdy.
Excellent video.. thanks. I'm looking to do this myself to save a significant amount of money. Great info brother!!!
Glad it was helpful!
Here in Washington we build the stem wall with MDO form panels. No need for stakes to hold lumber together The panels have snap ties, no need for too may stakes. The panels are set on top of removeable 2 by 8 form lumber resting on wood spreaders and spreader cleats. After poring the low footing boards are removed as well as the upper form boards. Then it is backfilled. Often we need to lay perf drain pipe in the ground along side the footing which is covered with drain rock..
Thanks for the reply!
There are different methods for different job sites, etc.
After using reusable ply forms for several years, I switched to the 2x forms, as I immediately put the forms back into the framing (usually the floor), saving the pain of moving and storing the forms between jobs.. Dave
He could throw those screws in a bucket just as quickly as throwing them on the ground. Efficiency can always be refined.
What's it cost to sort, haul and store about $10 worth of dirty screws? After about a 100 foundations, you kind of weed out what's worth doing and what's not. I used to save and bundle the wood form stakes, too, but no more. It's less time (money) to just buy new ones, which are less prone to splitting when hammered and screwed. The WT wedges are reused, as well as the 2x forms, which are incorporated as the floor joists-
Dave
great video thanks for the work
Neat looking job. But as an ACI Field tech and project manager, I point out somethings where house builders are typically more lax: The small rebar size (No.4) is too small to serve as a structural reinforcement. Should be a No.5 minimum. And "wetting up" concrete means adding water to increase the slump. This weakens the compressive strength dramatically. You're using a 2500psi mix which should have been 4000, and then souping it with water and undersizing the primary reinforcement. It's a recipe for movement and failure. If the home subgrade experiences the slightest differential movement, the stem wall/footing element will crack.
Contractors and Homeowners: I can't stress enough the importance of getting a soils report before placing a foundation. Soil preparation for a foundation is the most important step in foundation construction. If your soil strength is low, it won't matter on hoe well the concrete foundation is constructed; the house will experience differential settlement - a costly mistake.
My foundation is to be a slab on piers and beams, with a low corner correction.
I'm dealing with a wall for supporting the addition of select fill (60/40 sand clay) that is being used to vertically to lift a corner up 4 ft. from original soil over a 35 foot spanse at the junction of a 90 deg. corner for a pier and beam foundation and want to install a chain wall to support the corner properly.
What device is used (seen in your video) to support the rebar that is placed horizontally inside the wood walls (corners included) in the forms? Is it somehow removed after the concrete is poured before the concrete is set?
Please discuss the horizontal placement of rebar and how it may be incorporated to meet with a 8 rebar stems in an 8' vertical BB pier. How many stems are needed vertical in a 24" beam on a per foot basis, over 35 ft.in form a corner pier 8' deep 36 BB 18" diameter?
Thank you!
You Bet-
Next time I hope to be able to do a more in-depth video!
dave
I love doing this
Very nice video. Well explained. Makes me feel confident that I could do it. One question: when do you install the wt8 ties? Are they installed as you work your way up the forms with rebar?
The WT's are placed after both inside and outside forms are in place. We place them and set a horizontal course of rebar on them(as required) and generally wire them, centered, to the wt's as necessary to keep them in place. Remember to use a spacer (chisel, 16d nail, etc.), so the wt can be slipped into place between the 2x forms.
If the form wall is high/tall, the wt's are spaced closer together (toward the bottom of the stem wall) to withstand the pressure. They are also placed within a foot of each end of a form, corners or intersection- anyplace you suspect the form will spread or move from the immense pressure of the wet concrete-
Dave
Makes me think the owner is going to keep his car collection down there. Two large overhead bays, no windows, high ceiling for 4-post car lift. Nice that the floor is going to drop onto the stem wall on that pour.
I find that my crew and I are quicker with common nails rather than screws. Once a screw head is filled with concrete, you're using a nail puller regardless. Plus typical screw have no sheer value.
We also rather use steel stakes rather then wood. The steel ones last for multiple jobs rather then just one. We also will use a chipping gun with a 1" impact bit to really drive the stakes home.
I like the screws, as they provide easy, quick adjustability in the form work.
I also wash/spray down the forms soon after pouring, revealing the screw heads, and pull the vertical stakes before they're locked into hard concrete.
I like the wood stakes, as I can trim them flush to the tops of the forms, providing easy, unobstructed screeding of the concrete. The trimmed pieces are used as speeders and anchor bolt locaters...Dave
Hey Dave, thanks for this very informative and helpful video. I saw that you stubbed up what looked like your DWV and incoming water lines through the garage stem. I've been trying to find a detail for how to do that for the shop/ADU I'm building on my own place. I thought you had to sleeve anything that went through concrete. Am I mistaken? Did you just ell them into the stem above the footing and run them up between the rebar, then wrap in foam?
Good question. The risers you see are for electrical and communications. They are NOT wrapped, as would be the case with plumbing. They were brought in from below the stem wall and have 12-36" radius sweeps, depending on diameter of the pipe. They are located to (hopefully) to come straight up into a panel without having to offset the risers.
When you pull out the verticals wood supports, doesn't it leave a void in the footer? I see the comment about removing them 1 hour after pouring. Is that 1 hour after topping off the footers or 1 hour after topping off the stem wall forms?
Yep- any form stake will leave a small void in the concrete. It doesn't affect the structural strength of the foundation.
I try to pull the stakes soon after the stem wall is topped off, generally about 1-2hrs after the footings have been poured. Any longer than that, you've got a miserable task ahead of you....
your video shows a continuous pour of the ftg and stem wall - this seems to make sense over a two pour process. Are there positives to framing up the footing first and then laying the stem wall on top? Also if I was going to use the form boards for framing material and want to go with 2x4 walls; is it okay to use 2x4's for the stem wall forms? Thanks
Good question!
There are times the footing is poured first and then the stem wall is placed on top-
If you're stacking CMU's (concrete block) on top, foam (ICF's) block wall or some other type of formed wall.
This requires vertical rebar stubbed up to tie the above concrete to the footing. I've been on jobs that require sand blasting the lower concrete to assure a clean adhesion between the joints (commercial work) and between "lifts" (successive pours) that are going up many feet in the air!
I prefer the continuous poured footing/stem wall where I can use it for strength here in earthquake country....
Dave
great idea with the foil on the j bolts. Hard to find a clear simple video on stem walls. Did you coat the vertical stakes to remove them easy? What was the width of the stem wall?
The foil was one of my son's ideas!! We don't coat the stakes, sometimes we spray down the forms with diesel (poor man's form oil) or water down just before pouring.
About an hour after the pour, we gang up and pull the stakes while the concrete is green.
8" stem wall (two story)
dave
Pulling the stakes while the concrete is still green is the proper course of action. Using diesel as a form oil is a bad idea, it can lead to spalding and any inspector worth his salt will bust you if he notices it.
Great informative video Dave, I see you a flat job site, did any rough and fine grading took place before you start digging your foundation trenches?
You didn't mention anything about grading the lot.
Good observation-
The lot is very gently sloped.
It required only "grubbing"- scrapping the top few inches of organic material away before
exacvation. Usually necessary on any lot- slopped or flat.
Planning to Build in SW Florida and here CMU construction is a standard. The foundations in flood areas are typically built using a poured footing then 3 courses of CMU then a slab on top that also fills the block up. I’m thinking about using cast in place concrete for everything. The footing and the stem wall first then pour the slab over after the plumbing. Any suggestions are appreciated. Great videos by the way
just added a video showing my method of using the CMU w/ slab on top connection...
@@daveosland3199 good video. Florida seems to have some specific reinforcements requirements. I just feel that if I were going to spend oa ton of money on building this house, I would want to make the stem wall cast in place instead of CMU. I'm concerned about the cold joints though
@@drchamp1902 I have poured many more cast-in-place (solid concrete) stem walls than CMU's.
There's a time and place for each... Dave
I noticed from your video that your form stakes become surrounded by the footer concrete. Any concern with leaving holes in the footers? I am considering the use of U-Posts so they can be pulled out afterwards. The U-Post would support the compressive load of the form wood and the shear load of the lower board(s). I plan on using form ties or strapping between the forms to maintain the wall width. (my walls will be ~3-1/2' tall)
The holes are small and don't affect the strength or integrity of the foundation.
Just pull em' out before the concrete sets up too much!!!
I like the wood stakes because I like to trim them off flush to the top of the forms so there are less obstructions while sticking off the mud. I also don't like the cleaning, moving and storage of expense stakes. It's the same reason I try to plan on the immediate reuse of 2x forms in the construction of the house, rather than cleaning, moving, storing, etc.. of other types of forms. Dave
Oh man I wish we could build shallow foundation like that in Canada !
Yea, we ain't got much frost down yonder here in California ( though I've done some 8' deep footing/stem walls for basements!
+Dave Osland that's how we commonly build our houses where I live. The local frost depth is only 36 inches but basements are common and 8 foot+ poured walls at times.
Actually Trevor, you can! You can use "Wing Insulation" to protect the footings from frost and that is really, the only difference.
Those vertical stakes are enough to keep the forms from blowing out?
Good question-
The 1x2's are for the vertical support of the forms.
They're only part of the solution.
The steel form ties go between the forms to keep the form structure from blowing apart under the tremendous strain of the wet concrete
Look up Simpson WT8 form tie...Dave
Dave - Awesome demonstration of how to form and pour. I am a DIYer currently building a "little house" 10'X12" for a backyard office. I am setting forms as you did in this video with a foundation in a trench and the stem wall formed over the trench. Seeing your details helps me understand that you can never reinforce and support the forms too much (I have done that on all of my previous concrete and steel projects because I am old school) and that I am going in the correct direction. Thank you.
I understand that you pour the footer and then have to wait a while before pouring the stem wall. How long do you need to wait between pouring the footer and then pouring the stem? And when you pour the stem, do you vibrate the stem?
You mentioned "wetting the concrete" before you pump the stem wall. Could you explain how the process of wetting the concrete is done? I imagine that water would be added to the concrete in the delivery truck. Is it a second delivery with a different slump? Or is the wetting done in the original truck? I am only pouring about 6 yards (foundation and stem wall) so will only have one delivery.
Sorry for the late reply.
You maybe already done.
Usually the stem is poured about 30 minutes after the footings.
Absolutely vibrate, tap the forms with a hammer or even plunge a 1x2" up and down into the stem wall to help the concrete settle and fill voids.
The concrete is wet up just enough to help it flow into the stem wall, by the driver while on the truck.
Dave
Why am I so fascinated with foundations? Perhaps an analogy for life. Hmmm...
Yep!
Even Jesus talked about foundations! "cornerstones"- the first block set in a foundation...
buenos videos
que amable!
Nice video. I wish you had time to video the early part of the process instead of the still images. Thank you.
Those form ties are in-available in my area. I wish they would market them here in The Northwest.
Weird, because Simpson makes them.
I would assume anyone selling Simpson would stock them....
Thanks Dave, That helps.
I am also having trouble finding those ties here in the nw. White cap had some that would work for plywood forms, but they looked at me like I grew a second head when I asked about the wedge bolts
Simpson makes em'. Even Home Depot carries Simpson- Dave
Were the 1x2s holding up the stem wall formwork pulled out of the concrete immediately after pouring?
Within a couple of hrs, max. Any later, it'll be a bear. Too soon and you risk the forms moving. With concrete, timing is everything! Leave the kickers in place to hold the forms in place....
Awesome- Thanks Dave!
thanks and what about using 2x4 for form boards and then using them for stud's?
That's a lotta extra labor hanging all those form boards.....And there's the cleaning aspect of it....
Dave
then again you can use 2 x 8 for form boards and use them for roof trussing
The crawl space looks tight on this job. Maybe it is an optical illusion. Will there be at least 24" between the grade and the joists? Nice video!
Good question! Probably not 24", but definately the 12" to girders and 18" to joist clearance required by code.
@Dave Osland I’m really impressed by this instructional video, it’s the best thing on the internet I’ve found.
When you set string lines for building line, can you suggest a way one man can do this alone or am I going to have to get a mate out to help me?
Good question!
- String lines can be set and measured by yourself to a point. After initially setting up string lines and double checking measurements, I pull diagonal measurements from corner to corner to verify everything's square.
This requires a second body to hold a tape over the intersecting corner strings. I imagine one could set up something to hod the tape for you in a pinch....
Dave
what happens to the voids in the footer's from the vertical 1x2's when they are removed?
as with all form stakes in concrete, there is a small void in the footing. the soil surrounding the footing eventually fills them in.....It doesn't affect the strength or integrity of the footing/stem wall.
Dave
Do you drive the vertical stakes first and arachnid each 2x8 from there? Thanks
Yep-
Tight string lines are put up at exactly the building lines. Stakes are driven in 1.5" back from the string to accommodate the 2x form boards. This sets the form boards at exactly the building line. We hang the boards w/ screws for easy adjustment and disassembly after the pour...
Dave
Good
What’s the dept of that footing and how many stories your going???????
use HBT wall products 36 square meters floor area 3days installations
How do you grade with the walls poured
As in finish grading? with a small tractor/by hand. Garage slab prior to pouring- small tractor/by hand-
Dave
Good call on throwing away the screws. Once they get concrete in the head they are useless!
Yea, spending an hour gathering up $12 worth of dirty screws?? Duplex nails or screws are part of the cost of doing a job. Screws make adjusting easier than nails. I'll reuse anything I can that makes sense, like the WT wedges or plastic bolt holders....
A lot of cathedrals get built from bar stools
how far apart are the J-Bolts
Generally 48"' o.c.. It used to be 6' on single story, 4' on 2 story, but I haven't seen 6' called out for some time. Some shear wall areas require tighter spacing per engineering.
Code requires a bolt within 12" of corners and end butts (splices).
I use 5/8x12" bolts for good (extra) embedment (min. 7") and because I use 3x, not 2x mud sills...I like the 3x3x.229" HD washers- Burly!
Dave
What Does stem “ S T E M “ stand for
Thanks
stem- as in the stem a plant or trunk of a tree
Idk if Is it just me but that's allot wasted screws. Dont throw them away re use what you can but great vid
A lot of potential flat tires too
We throw them down next to the foundation and they're buried in backfill. You chalk it up to a $15 expense on a $15,000
foundation. Years ago "duplex" nails were used and bent /thrown away when pulled after pouring....
The screws get weakened after use, and concrete in them too. Nothing worse than struggling with stripped screws after re-using them.
whats the name of that type of snaptie?
Jackie Kemp wt8
WT8 (for an 8" wide stem wall)
Where are the foundation vents?
Good question!
The vents will be cut in the subfloor frame rim board.
See the subfloor frame video- ruclips.net/video/4xMSep0uiRs/видео.html
Dave
W
What’s the the slump?
it's been awhile on that pour but probably a 6 or so as to get down in the forms and avoid any voids...
You can go to woodprix if you would like to make it yourself guys.
Is he just throwing the screws hes taking out on the ground???
Yep- Right into the void between the footing and excavated trench wall, well below grade and the finish grading. Untreated screws will rust away in a few years. Several people have commentated how wasteful, etc.. it is, but there's maybe $10 worth of screws on a $20k foundation. Far cheaper than to paying someone to take the time to recycle them.
We do gather loose ones up that might pose a problem... Dave
He also wasting time throwing down the stakes. He can put them on top of the footing and then collect them( that will save his back too).
And he throws screws too... Should have save them for future re use...
He's young, he doesn't thimk about that. Nothing hurts him yet, the lucky duck.
You say you used 2500 PSI concrete, but doesn’t code require “concrete shall be 3000 PSI minimum for foundation and retaining walls(including stem walls)? Section R404.1.2.3.1; table R402.2
I’d make sure you are using the right material before you have to redo all that
Good question! When 3000 PSI or greater is used,( here in Calif.) "special inspections" ($$$) are required in many jurisdictions.. Until recent upgrades in the code, I've avoided it when possible.
so nobody is gonna comment about all that concrete leaking from the bottom of the forms?
You may be seeing the transition from the the 8' stem wall flowing into the 18" wide footing.....
By filling the lower footing first and then come back a while later and fill the stem wall, there is actually little or no "blow out"....
It's not leaking, it's actually pouring into the spread footer below which is formed by the dug out trenches
Easy way to set anchor bolts ruclips.net/video/PZx8b8eNvZo/видео.html
May I ask what state you are in?
All those screws all over the jobsite. Whether it's getting back filled or not that sucks
not enough rebar
2 runs top and bottom, horizontal runs in the stem wall @ 16" o.c., vertical hooks from top to bottm @ 18" o.c.. #4 Grd 60 bar. All per engineer. Dave
@@daveosland3199 Then you must have a weak code on your side. On my side, "quantity"-wise we put about 5 times more rebar in foundations; for vertical and side support (not just for horizontal support). But it's ok, as long as you're building by code. Dan
@@PeacefulCountryLife Seriously? 10 #4s in the foundation bottom, and 10 #4s in the stem wall? What are you building? A bomb shelter? A nuclear reactor? With all that steel there is hardly any room for the concrete.
Why this guy throwing away the screws? Can't he re- use them?. Is not unsafe ? Can he use a empty bucket and put them in ?
Wasted all the screws
part of the cost of doing a job....
seing "the Machine" throwing away those good screws is the reflection of how sick the American building society is.
And I bet this house will be touted as "sustainable" and "energy efficient".
I caught that too. I like all screws policed up and not just buried on site. But that's just me.
W