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Old 01-08-2010, 12:32 PM   #1
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Concrete Footings for a Detached Garage???


Hello Everyone,

Would first like to say, I am hoping I posted this in the correct forum. I did not find a forum specific to concrete or foundations so made the judgment call that this would be the best one.

My question at the moment is hypothetical, well I should be saying I am not building my self a garage. Would like to in the next year or so for some family.

I was wondering about footings, I know you want the garage to drain and therefore there is a slope on the concrete slab.

In respects to the footings and stem walls.

Do you have to pour these foundations in two or three pours or can you pour a garage foundation with a 6'' sill wall Monolithically??

To explain:

In my experience two ways to do a foundation.

1. Footings with a stem wall and then pour the concrete slab

2. Monolithically - Footings and Slab all in one shot

For the future that garage I am hoping to work on and build will be 16 x 20 if that makes a difference

Thanks everyone in advance hope to learn a ton.

Mike

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Old 01-08-2010, 02:28 PM   #2
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Concrete Footings for a Detached Garage???


I poured a monolithic slab for my 24x30 workshop/garage in SoCal. No sill wall. Footing is ~12-18" wide and ~18-24" deep.
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Concrete Footings for a Detached Garage???-1-escavation-forms-underway.jpg   Concrete Footings for a Detached Garage???-2-forms-sand-base-spread.jpg   Concrete Footings for a Detached Garage???-3-rebar-installed-ready-pour-concrete.jpg   Concrete Footings for a Detached Garage???-4-day-concrete-pour.jpg   Concrete Footings for a Detached Garage???-5-concrete-poured-finished-.jpg  



Last edited by vsheetz; 01-08-2010 at 06:23 PM.
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Old 01-08-2010, 02:35 PM   #3
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Concrete Footings for a Detached Garage???


I am not sure what you mean by a sill wall. The foundation wall is usually called a frost wall in New England, however in other parts of the country a slab is often placed with a turned down edge which might be as little as 12 or 18 inches deep. The other design, specifically a footing with a stem wall, is generally used for the basement, not often used for a detached garage.

As for the pour, well you can pour the entire combination of footing, wall and slab monolithically if you choose, but more often the slab is poured separately, since the slab for a garage typically has no structural function, it is just there to provide a suitable surface to park your car on. The slab is normally designed with crack control joints, and in my experience is usually not tied to the frost wall at all.
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Old 01-08-2010, 06:20 PM   #4
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Concrete Footings for a Detached Garage???


Depicted below is a monolithic slab - and is how my slab in the pictures was poured. I have done both monolithic slabs and stem walls with the floor poured inside the stem walls.

I think what the OP is referring to as a sill wall would be the portion of a stem wall construct that would extend above the garage floor level - and the walls are built upon (OP, please correct me if am wrong). I have never seen a monolithic slab with an integrated "sill" wall, but I guess it could be done with the appropriate form work.

A height advantage can be had using the stem wall construction - in that the walls are thus higher from sitting on the stem wall and allowing more overall overhead clearance and room for a taller garage door. With 8' and taller garage doors becoming more the norm this can be a factor. Of course wood framed 9' or taller walls could be erected on a monolithic slab to accomplish this.
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Old 01-09-2010, 10:08 AM   #5
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Concrete Footings for a Detached Garage???


Quote:
Originally Posted by vsheetz View Post
I think what the OP is referring to as a sill wall would be the portion of a stem wall construct that would extend above the garage floor level - and the walls are built upon (OP, please correct me if am wrong). I have never seen a monolithic slab with an integrated "sill" wall, but I guess it could be done with the appropriate form work.

Most every garage slab we do has a concrete curb poured with the slab for two main reasons: It keeps the plate higher & away from potential water & allows the slab to be pitched to the OH doors while the curb is tapered to allow the wall to be built on a level surface. It does involve mor ecomplex forming & finishing, but it's still fairly easy to do. I believe this was covered a while ago, a few pics may even be in that thread.

BTW vsheetz, is that colored concrete or is it just decieving in the pic where your pouring it?
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Old 01-09-2010, 12:32 PM   #6
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Concrete Footings for a Detached Garage???


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Originally Posted by jomama45 View Post
BTW vsheetz, is that colored concrete or is it just decieving in the pic where your pouring it?
Good eye - yes, a terra cotta coloring in the concrete.

Last edited by vsheetz; 01-09-2010 at 12:35 PM.
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Old 01-09-2010, 02:26 PM   #7
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Concrete Footings for a Detached Garage???


Quote:
Originally Posted by vsheetz View Post
Depicted below is a monolithic slab - and is how my slab in the pictures was poured. I have done both monolithic slabs and stem walls with the floor poured inside the stem walls.

I think what the OP is referring to as a sill wall would be the portion of a stem wall construct that would extend above the garage floor level - and the walls are built upon (OP, please correct me if am wrong). I have never seen a monolithic slab with an integrated "sill" wall, but I guess it could be done with the appropriate form work.

A height advantage can be had using the stem wall construction - in that the walls are thus higher from sitting on the stem wall and allowing more overall overhead clearance and room for a taller garage door. With 8' and taller garage doors becoming more the norm this can be a factor. Of course wood framed 9' or taller walls could be erected on a monolithic slab to accomplish this.

That is exactly what I am talking about the short wall that extends higher then the garage floor.

It sounds like by this post and others that there is a way to form up the wall to achieve this with a monolithic poor.

Does anyone have some suggestions on how to this, maybe another thread where it has been discussed? Diagram anyone have to share???

My main question, is when you make a curb with a monolithic poor how do you support or hold up the form board of the curb on the slab side.

Do you put a stake in and then remove it once the curb has set up a little bit? - If so how would you really know it has set up enough to achieve that.

Can you build the form board up, screw it together and do not need a stake on the slab side because it is not enough weight???

Thanks all again for the advice??
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Old 01-09-2010, 03:06 PM   #8
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Concrete Footings for a Detached Garage???


Slab dimensions we use around here:



Rebar mat in the middle of the slab extends to within an inch of the outer perimeter. Two bars centred in the thickened footing and a single bar in the curb. Add Fibermesh and you should be good to go.

Typicial method for hanging the inside form without pins to support it.

Notice that for the drawing purposes that the gusset is shown at the top of the curb. Leave enough space there to slip a trowel under it. Anchor bolts are placed as per usual layout for your area, although you might want to use longer ones so they sit down into the footing at the thickened edge.


Last edited by jlhaslip; 01-09-2010 at 03:16 PM. Reason: add verbage
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Old 01-09-2010, 03:30 PM   #9
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Concrete Footings for a Detached Garage???


Quote:
Originally Posted by jlhaslip View Post
Slab dimensions we use around here:



Rebar mat in the middle of the slab extends to within an inch of the outer perimeter. Two bars centred in the thickened footing and a single bar in the curb. Add Fibermesh and you should be good to go.

Typicial method for hanging the inside form without pins to support it.

Notice that for the drawing purposes that the gusset is shown at the top of the curb. Leave enough space there to slip a trowel under it. Anchor bolts are placed as per usual layout for your area, although you might want to use longer ones so they sit down into the footing at the thickened edge.

Thank you so much for the drawing, I am printing it out and going in my notes.

great design, I see you have the plywood guesset on the back side and I assume you use gussets on top of the 2 x material to hold it together.

I like the angled design so you can get a trowel in there to finish as normal.

You have never had problems with the 2 x material that is cut an angle ever pushing out towards the slab? with not takes or anything holding it up???

Thanks again,
Mike
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Old 01-09-2010, 03:35 PM   #10
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Concrete Footings for a Detached Garage???


The concrete for my 24' x 36' shop was poured in '96 and the concrete man used the form which "jlhaslip" has shown. He used bolts to hold the forms in place for the 6" high wall he was pouring on mine, with the bolt being easily removed after the pour had set most of the day. I asked for this at the time as I had plans to just "wash out" my garage floor with a garden hose. Well, after it became more of a "storage building" for my wife and son I haven't washed it out since. As a matter of fact, I haven't been able to use it for it's intended purpose much. If anyone come up with a design for a garage/shop which will deter family members from using it as a storage building--please advise me of these plans. Thanks, David
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Old 01-09-2010, 03:43 PM   #11
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Concrete Footings for a Detached Garage???


Nope.

Make them out of 3/4 ply and leave about 6 inches of meat on the top and sides seems to work. Place one about every 3 or 4 feet on the outside wall. If in doubt, or using plywood for the inside form, add extras and reduce the spacing of them.

Use 2 x 2's to nail them to the inner/outer forms.

You can also look at additional support by using blocks across the top of the 2 x material.

As for bulging and wall deformation, that is why the wall is 5" wide only. With 1/2 " ply outside and 1/2" drywall inside of a 2 x 6 frame wall, the concrete can move a little and the wall can still sit where it needs to.

Of course, we don't need any earthquake or termite protection around here, so I am not familiar with any implications those conditions might bring into the equation.

I've built 30 ' x 40 ' shop slabs using this method and it was all good.
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Old 01-09-2010, 03:45 PM   #12
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Concrete Footings for a Detached Garage???


Quote:
If anyone come up with a design for a garage/shop which will deter family members from using it as a storage building--please advise me of these plans.
Hang an overhead door on the thing, but don't wind the springs. Works for me. :P
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Old 01-09-2010, 03:54 PM   #13
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Concrete Footings for a Detached Garage???


Quote:
Originally Posted by jlhaslip View Post
Nope.

Make them out of 3/4 ply and leave about 6 inches of meat on the top and sides seems to work. Place one about every 3 or 4 feet on the outside wall. If in doubt, or using plywood for the inside form, add extras and reduce the spacing of them.

Use 2 x 2's to nail them to the inner/outer forms.

You can also look at additional support by using blocks across the top of the 2 x material.

As for bulging and wall deformation, that is why the wall is 5" wide only. With 1/2 " ply outside and 1/2" drywall inside of a 2 x 6 frame wall, the concrete can move a little and the wall can still sit where it needs to.

Of course, we don't need any earthquake or termite protection around here, so I am not familiar with any implications those conditions might bring into the equation.

I've built 30 ' x 40 ' shop slabs using this method and it was all good.
Great thanks again for the advice. I am excited to give it a shot. I will keep everyone informed once the project starts....Gonna be a while though I think at this point
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Old 01-09-2010, 03:54 PM   #14
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Concrete Footings for a Detached Garage???


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Hang an overhead door on the thing, but don't wind the springs. Works for me. :P
Haha...I will second this.
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Old 01-09-2010, 04:57 PM   #15
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Concrete Footings for a Detached Garage???


Everyone new to concrete work thinks 'monolithic'. Be smart, and break this rather overwhelming (for a beginner) task into several stages. You will be glad if you do... and you will regret it if you don't.

The 'exploded' picture shows the most realistic way to tackle the job.

BTW...... Keep ALL rebar at least 2" away from the forms and the edges of the slab.... everywhere.
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