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Old 01-10-2010, 04:25 PM   #31
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Concrete Footings for a Detached Garage???


One thing to keep in mind on these little drawings is that there is normally rebar running all the way from the footing, on up through the stem wall, through the slab, on through the full height walls... right up to tie in with the bond beam at the top extent of your building walls. I'm not showing any of it because it is a pain to draw, and it clutters up the drawing.

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Old 01-10-2010, 05:55 PM   #32
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Concrete Footings for a Detached Garage???


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Originally Posted by canyonbc View Post
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.

Most definately. Done all the time here. You simply use 2x4 forms (plenty big for a garage this size) parellel to the outside forms @ 4-6" wide in the same direction as the slab pitches. You will also need short forms at the garage door size. No forms on the back side (side opposite the OH door), as this will be where the floor is at the same level as the walls.

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

I tried a search to no avail, but I'm fairly sure it's been discussed before along with a few diagrams.

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.

The way we do it is by using longer (30-36") steel stakes every 4' or so as well as 1"x2" props (~12" long so they don't split as easy) screwed between the outside form & the 2x4" curb form to prevent spreading. The stakes don't hold the greatest when it comes to spreading, but are more in place for the height.

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.

Trial & error and/or experience. For a 16 x20 slab, I think if you had some help, you could handle this part. If you were to go this direction, I would suggest getting an "inside corner tool" to help finish the inside cove. The $10-15 tool can make your life much easier.

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???

We normally nail thru teh steel stakes but screw the 1x2's in place on top. Just make sure to choose slightly longer screws than necessary so that you can let the screws stick out a 1/2" as they will be less likely to get filled with concrete when pouring. A little drip of oil in the screw heads helps as well.

Thanks all again for the advice??
I'll try to explain this a little better & hopefully it makes sense:

- Set-up the exterior forms as shown in the earlier pics & sketch put up by vsheetz?

- Do all grading, compacting, placement of vapor barrier (if applicable), etc.

- Depending on if the 16' or 20' direction is going to be pitched: Use either a 16' 2x4 or scab 2- 2x4's together to acheive at least 20' long.

- Set bottom of 2x4 on top of back exterior form at back of garage.

- In the front, you have to hang the 2x4 in mid air with a steel stake. In the front, you'll want the TOP of the 2x4 level with the exterior form. This will give you 3.5" of pitch across the floor if you do it this way. By raising the 2x4 at the front of the garage, you can achieve less pitch if so desired. There is a common misconception among DIYer's that these curb forms have to be ripped down on a long angle, but that is not the case. If you do it the way I wrote, you will use the exterior form for your curb height & the BOTTOM of the curb 2x4 form as the height of the floor.

I hope that makes at least a little sense.
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Old 01-10-2010, 06:18 PM   #33
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Concrete Footings for a Detached Garage???


Willie T, you are a master with Sketchup! Thanks for all of the great insight. Two final questions from my end:

1. Is there any bracing of the blocks horizontally (i.e., anything comparable to the horizontal runs of rebar you'd use for a poured concrete stem wall)? Maybe it's not necessary. I only ask, since that support seems to be lacking with this approach

2. Would you have any concerns using blocks like these for stem walls in an earthquake zone? I live in Seattle, and while we don't get many earthquakes (the last one of any significance happened in 2001), we are technically in an earthquake area. I hardly ever see block foundations around here, but have no idea if there's a good reason for that, or if it's just that builders aren't used to this technique.

Thanks again. You guys are awesome.
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Old 01-10-2010, 07:19 PM   #34
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Concrete Footings for a Detached Garage???


Quote:
Originally Posted by Willie T View Post
Answers are in quoted text.
Great Information

I will be going to play with sketchup right now.

Yes, lots of rebar especially here in California.

Thank you for clairifiying that you do want to tie the slab and foundation together.
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Old 01-10-2010, 07:22 PM   #35
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Concrete Footings for a Detached Garage???


Quote:
Originally Posted by jomama45 View Post
I'll try to explain this a little better & hopefully it makes sense:

- Set-up the exterior forms as shown in the earlier pics & sketch put up by vsheetz?

- Do all grading, compacting, placement of vapor barrier (if applicable), etc.

- Depending on if the 16' or 20' direction is going to be pitched: Use either a 16' 2x4 or scab 2- 2x4's together to acheive at least 20' long.

- Set bottom of 2x4 on top of back exterior form at back of garage.

- In the front, you have to hang the 2x4 in mid air with a steel stake. In the front, you'll want the TOP of the 2x4 level with the exterior form. This will give you 3.5" of pitch across the floor if you do it this way. By raising the 2x4 at the front of the garage, you can achieve less pitch if so desired. There is a common misconception among DIYer's that these curb forms have to be ripped down on a long angle, but that is not the case. If you do it the way I wrote, you will use the exterior form for your curb height & the BOTTOM of the curb 2x4 form as the height of the floor.

I hope that makes at least a little sense.
Thanks,

I definetly think I can depict a picture from everything you wrote.

So many ways to do the foundation, glad to take in all the information to make the best decision.
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Old 01-10-2010, 08:41 PM   #36
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Concrete Footings for a Detached Garage???


Going off the premise that I were to do my foundation with a 8 x 8 x 16 normal weight block, is there any tricks or calculations you guys would recommend in figuring out many blocks would be needed???
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Old 01-10-2010, 09:05 PM   #37
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Concrete Footings for a Detached Garage???


Sounds like it is about 113 - 8 x 8 x 16 block per 100 sq feet of wall? Can anyone confirm this.

I have also found that you want about 7.5 cubic feet or mortar per 100 blocks used - can someone confirm this too???

If i were to get the mortar bagged should I be looking at Type S Mortar in a foundation setting?

Can anyone elaborate on what a grout mix is and why you would not use normal 2500 psi concrete???
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Old 01-10-2010, 09:39 PM   #38
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Concrete Footings for a Detached Garage???


Right on, on the blocks. I'd say a little light on the mortar.

With grout vs concrete, it's a water content and mixture ratio thing. Concrete, as it cures, tends to actually shrink a little. This leaves you with a less than desirable tight bracing inside the blocks. Sounds nuts, but that tiny, tiny space left between the blocks and the hardened concrete core costs you a lot in reinforcing column strength. I don't know the details right off the top of my head, but I learned many years ago from commercial work that you really don't want to pour the wrong stuff in the wrong place.

Simply put, concrete loses strength when it's made soupy enough to flow as it needs to in "grouting" work. Grout, on the other hand is mixed to account for and to anticipate the water absorbing properties of masonry units (blocks), and it hardens the way it is supposed to inside block cells.

Unfortunately, most of today's concrete guys would give you a vacant stare if you asked them about this sort of thing. Kind of like the way they will also tell you "Concrete will get cracks... nuttin ya kin do about it." But ask them why the sixty year old slab in your father's garage has never cracked, and they will again get the stare. A lot of skill and quality has been lost in many of the trades over the decades. But I guess that's progress.
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Old 01-10-2010, 09:41 PM   #39
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Concrete Footings for a Detached Garage???


Quote:
Originally Posted by TitaniumVT View Post
Willie T, you are a master with Sketchup! Thanks for all of the great insight. Two final questions from my end:

1. Is there any bracing of the blocks horizontally (i.e., anything comparable to the horizontal runs of rebar you'd use for a poured concrete stem wall)? Maybe it's not necessary. I only ask, since that support seems to be lacking with this approach

2. Would you have any concerns using blocks like these for stem walls in an earthquake zone? I live in Seattle, and while we don't get many earthquakes (the last one of any significance happened in 2001), we are technically in an earthquake area. I hardly ever see block foundations around here, but have no idea if there's a good reason for that, or if it's just that builders aren't used to this technique.

Thanks again. You guys are awesome.
Most of this will come down to a local building department decision. They are your definitive and final answer for things structural.
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Old 01-10-2010, 09:49 PM   #40
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Concrete Footings for a Detached Garage???


Yes, Type S is suitable for below grade work.

HERE is some good information about mortar.
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Old 01-10-2010, 10:15 PM   #41
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Originally Posted by Willie T View Post
Right on on the blocks. I'd say a little light on the mortar.

With grout vs concrete, it's a water content and mixture ratio thing. Concrete, as it cures, tends to actually shrink a little. This leaves you with a less than desirable tight bracing inside the blocks. Sounds nuts, but that tiny, tiny space left between the blocks and the hardened concrete core costs you a lot in reinforcing column strength. I don't know the details right off the top of my head, but I learned many years ago from commercial work that you really don't want to pour the wrong stuff in the wrong place.

Of course, most of today's concrete guys would give you a vacant stare if you asked them about this sort of thing. Kind of like the way they will also tell you "Concrete will get cracks... nuttin ya kin do about it." But ask them why the sixty year old slab in your father's garage has never cracked, and they will again get the stare. A lot of skill and quality has been lost in many of the trades over the decades. But I guess that's progress.
Well hopefully with sights like this knowledge and I mean good knowledge can transpond through out the generations and us (younger folks) can learn.

Thanks for the site about mortar wanted to ask one other question to ya about the block foundation, what size or dimension do you guys use down in Florida, to give some reference to what I would should be doing out here. Like you said though the building dept. of my county will be making the final call.

Anyone else with there footing sizes too, please shoot them out.
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Old 01-10-2010, 10:30 PM   #42
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Concrete Footings for a Detached Garage???


We usually run a 12" high by 16" wide footing for a garage like you're talking about. We go down around two to three feet because we have no frost line to worry about.

It's working on midnight here, and I still have to walk the dog.

Catch ya later.
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Old 01-10-2010, 11:12 PM   #43
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Originally Posted by Willie T View Post
We usually run a 12" high by 16" wide footing for a garage like you're talking about. We go down around two to three feet because we have no frost line to worry about.

It's working on midnight here, and I still have to walk the dog.

Catch ya later.
thanks for the knowledge, looking to keep the footings about like you described.

enjoy walking the dog

thanks again mike
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Old 01-11-2010, 05:37 AM   #44
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Concrete Footings for a Detached Garage???


Just a thought as I didn't see it mentioned, the height of a block wall will allow you to use 2x4x8 wall studs (if they apply in your height requirement) Vs longer studs.

Here in the mid-west we need to go below frost line so it's footer, then block, then floor.

Willie T, Very good info.
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Old 01-11-2010, 08:35 AM   #45
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Concrete Footings for a Detached Garage???


I thought I'd introduce the first step in laying out your garage. (Well, it's actually the third step, but more about that later.)

The small triangle measurements help you get the lines started in more or less the correct orientation.

The cross measurements on the large rectangle are what you will use to check for accuracy. Slight increases in one measurement will be echoed by reductions in the dimension for the other diagonal. Playing with the relative measurements is how you get the rectangle square.

And it HAS to be EXACTLY square. An eighth of an inch off is NOT acceptable.

The second picture is how you locate your "Batter Boards". These are what you will attach your string lines to for the really accurate layout.
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Concrete Footings for a Detached Garage???-lay-out-rectangle-1.jpg   Concrete Footings for a Detached Garage???-lay-out-rectangle-2.jpg  

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