GARAGE PROJECT

[B964]

I plan on a 32x 36 building. It took 24 15 yard trucks of fill,because of slope. The top soil was scraped off and it was vibratory rolled on each layer. The fill is like concrete now, I barely could pound in some stakes. The code here requires either a 4 foot frost wall or a monolithic pour. I will most likely go monolithic. I know it is a little small but only needs are for two trucks and near future tractor. I have a 12x24 shed for ATV's and other lawn stuff. Any opinions on the concrete are welcome. Having trouble with camera so no pics yet.

 

[Junkman]

I have never liked the monolithic pours and I feel that you would be better off with the 4' foundation wall in the long run. Just because a building code allows it, doesn't mean that it is the best method. Personally, I would have rather seen you build on the slope with a full basement and saved the money that the fill cost and put that into the foundation. Then used pre cast concrete slabs for the second story floor. That way, you would have the best of both worlds. An entrance in the rear and one at grade level. Double the square footage without double the costs.

 

[B964]

I am not sold on the mono idea yet either. I like your two story idea but did not have enough slope for it. Alot of the fill is driveway to build site to be level with road, house and to have proper drainage.

 

[texbaylea]

I have a monolithic pour of 48' x 60' without problems for 7 years now. I don't have the freeze problems you have but the primary requirement for such a slab is using #3 rebar 12" or 16" o.c. each way instead of mesh. Good Luck

 

[dltimmons]

B964,

There is nothing wrong with a monolithic foundation, provided you take into account, all of the factors of your situation.
No matter what type of foundation you use, you need to have the footing, (bottom of the outside portion of a mono slab, or spread footing under a foundation wall), bearing on undisturbed soil. Since I don't know how much of a slope your site is on, I can't say how much you will need to excavate, at any of the four sides, to achieve this.
You may, or may not, be required to provide a soils test, and an engineered foundation plan, in order to get a building permit. Around here, on an accessory building, (not for residential occupation, and less than X # of sq. ft.), an engineered foundation is not required. In your case, it would be cheap insurance.
A soils test, at the depth of your foundation, would tell you the size of the footing surface needed, and could save you a lot of future problems. An alternative to excavating down deep enough to get a good bearing surface for the foundation, is to have piers/caisons drilled to get down to adequate bearing. Usually less costly than excavating the entire foundation, if you have to go very deep.
It is common to pour floors/flatwork, over structural, compacted fill. With adequate reinforcing, and since the dead load is spread over such a large area, when done right, there are few problems. Since a foundation must support all of its' own weight, plus that of the entire building, and with a monolithic, anything sitting close to the outside of the building, on the floor, snow loads, wind forces, etc.
Pouring over fill is not a good idea, and in most jurisdictions, will not be acceptable to the building dept.
Check with your local inspector, and go from there.
I have a similar site that I have begun excavation on, for a future 30' X 40' garage shop. Into the hill I am on very firm soft rocky soil, but the other two sides have 4 to 5 feet of fill. So I am planning on having caisons poured under the two sides where all of the fill is.
Hope this long rambling bunch of noise, helps you in some way.
Good luck with your project,

DT

 

[B964]

I was thinking of some type of modified mono. Maybe a little deeper edge and thicker floor. You don't have a freeze problem down there, but why if you search web for foundation repair info it comes up with 100's in TX area?

 

[jpr62902]

I have zip, zero, zilcho experience pouring foundations. What are the problems you typically see with a monolithic pour versus other foundation types? My neighbor and I are planning a garage for his back yard and we were thinking monolithic was the way to go. Can y'all educate me on this one? In my area, code rquires a 30" depth to get below the frost line. Thanks everyone.

 

[Junkman]

about 2/3 of the way down on this web site, you will see a good drawing of the monolithic design. web page

 

[jpr62902]

In response to this question I PM'd to Junkman:

"Junkman, thanks for the info. I know what a monolithic foundation looks like (guess I shouldn't have said I knew zero). I'm just wondering why some people don't like 'em. What kind of problems do you typically experience with monolithic that you wouldn't with poured or block walls and a floating slab? Thanks again for letting me tap into that vast wealth of information we all know as the Junkman!"

He said:

"I have seen monolithic pours go bad when the ground below is "porous". By this, I mean that the ground is disturbed and when it settles, it will leave voids under the concrete. I think that if you were to do a monolithic pour, that it would be best to scrape off the topsoil and then dig the perimeter and pour on top of the ground. Most people tend to disturb the earth too much and this leads to problems. You might say that it is a personal choice. With a foundation wall, your building wall is above grade and with a monolithic pour, the side wall is usually attached to the slab at grade. This leads to problems of walls rotting at the bottom. I don't believe that you save any costs of materials in the end, but just a small time savings by having the floor poured first instead of last."

Couldn't you avoid the problem of rotting sill plates by just pouring\forming a higher and/or a thicker slab?

 

[texbaylea]

The slabs that have a lot of problems are on the Texas coastal gumbo. It has a high clay content that expands greatly with hydration. They dont build, and they should, self supporting slabs such as a post tension one. My soil here is deep sand and very stable. When we lived on the gulf coast, the house we built was on bell bottom piers footed down 16'. 42 piers and it did not move even through a flood.

 

[texbaylea]

The major problem with a monolithic slab is that the contractors use metal mesh then walk on it as they pour and it ends up on the bottom rather than in the middle of the concrete. When I built my current shop building, I specified #3 rebar 12" o.c. supported on chairs so that it could not get walked down. The bid was a little higher but worth it.

 

[Junkman]

</font><font color="blue" class="small">( ..........Couldn't you avoid the problem of rotting sill plates by just pouring\forming a higher and/or a thicker slab? )</font>

You would still be close to the ground unless the slab was say 12" thick and that wouldn't be economical. Some people will use concrete blocks on the outer edge to get the hight needed to keep the moisture from the wall, but the blocks themselves aren't well anchored to the slab usually. Just mortar keeping them in place. I like to see at least 12" above the surrounding ground before the woods starts and 18" is actually better. My old garage had a 6" concrete wall above ground and the lower portion of the walls started to rot from water splashing on them. Many times builders skimp on costs because they won't be around when the problems start 10 years later. I believe in doing it correctly the first time even if it costs more. In the end, it will save you money. Spend a little more now and save a lot later on because you will have to remove the old (wasted) and rebuild with new. A building is only as good as its foundation. In Florida, monolithic slabs are good, because there is no frost and the ground usually drains well. Termites are the problem down there though. /forums/images/graemlins/frown.gif