Foundation Experts look here!!

[Novadiecast]

I have been planning this garage and all my zoning is all done etc.....
The Garage will be 32 x 54 with 2' of block above grade. It will have a heated floor.

I sent the plan to a concrete guy to get the foundation quote. I don't have it back yet. He tells me that they don't use foam anymore they use a blanket to insulate the concrete under the slab and then you can staple the Pex right to the blanket. He also said he didn't like to do 12" blocks below and 8" blocks above grade. As you know this would give me a shelf to support the slab. Hea said he would rather the whole slab drop a little than have the perimiter support and have it crack in the middle. I requested a 4' apron also

The area this will go in in my back yard will have some fill. About 1' at the front and 2 ' at the rear or the garage.

Please advise how you would do this foundation/insulation and slab.

Pictures are at this link.

http://s27.photobucket.com/albums/c153/novadiecast/Garage/

Thanks in advance guys.

 

[Novadiecast]

I know we have some experts here... please help!!!!!!

 

[Franz©]

You really need a Concrete Placement contractor who is concerned about giving you a good slab that will last, and not somebody who is looking to slam another job and maximize his profits.
""He tells me that they don't use foam anymore they use a blanket to insulate the concrete under the slab and then you can staple the Pex right to the blanket.""
Hell yes, any dunce can unroll a blanket, it takes some level of skill to properly install foam. He doesn't give a damn about the insulation value once he's gone.

""you can staple the Pex right to the blanket""
Well that'll work well. Of course the PEX is mislocated in the slab, and it's probably against PEX manufacturer's recommendations, but it makes for a quicker SLAM job, and you'll never find out.

""Hea said he would rather the whole slab drop a little than have the perimiter support and have it crack in the middle. ""
I'm absolutely certain he knows exactly what he's talking about here.
Of course, he also knows you don't have a clue. The statement loosely translated to "I have no intention of doing proper compaction, it cuts profit".
The size of your slab on fill pretty much dictates some support going to undisturbed mineral soil will be necessary to prevent settling in the middle. That can be either bullnoses or ground beams, but it needs to be there or the slab will fail. Having the slab inboard of the wall rather than monolythic to the foundation wall eliminates this problem for the so called contractor.

The short version is you are dealing with a halfassed immitation of a concrete placement contractor, and you should be learning about PEX, Insulation, and concrete placement and slab values.

Does this begin to help?

 

[flesburg]

I would get a second concrete guy involved for his opinion, because I disagree with your guy. Dig deep enough to get to good compaction. Have a foundation poured at that depth. Have it tested. Lay up 12 inch blocks, fill with gravel that is a mix of fines and course grades (that will compact). Set 8 inch blocks on top flush on the outside, unless you want a brick ledge, and pour the floor so it sets on the wall. If the concrete guy is still skeptical, have piers set to support the floor, or make additional support walls through the middle. You do NOT EVER want your floor to settle, because it will not settle level, and it will crack. Also REBAR, and cross rebar the floor every foot. No more than 2 foot and cross tie the rebar. Make sure the rebar is in the middle of the pour and that the concrete guys do not tramp it down to the bottom with their feet. Rebar at the bottom of your floor does no good.

Watch the concrete guys like a hawk!!!!!!!!

I'll have to post some pictures of my new garage soon. It is 1 1/2 stories too. And so far I am pleased with it.

Watch out for your concrete contractor. And do not necessarily go with the low price. Check out references, and take the time to look at their work. Even visit a pour sight and watch his crew in action.

 

[Novadiecast]

Ok this is the feedback I am looking for. I have contacted a couple others for an estimate. One does poured walls, for a comparison.

Thanks guys and keep the information rolling in. I have waited a long time for my shop and I want it to be done right!

 

[flesburg]

Additional. I would do poured walls if I were you. with lots of rebar. I had 8" walls poured with a 1.5" "brick ledge" on the inside. Rebar came up out of the walls every 2' at the edge of the "brick ledge". The floor rests on the "brick ledge" on all four sides, and the rebar in the walls was bent over and tied into the rebar in the floor. The structural engineer called for two "piers" to be poured into my floor where load bearing posts were going to be. The posts were hidden in walls, but were used to support the "beams" which hold up the second story room. The "piers" are 2' x 2'. My walls are 4' high, and the inside was excavated 4' because of "poor soil" and filled with about $5000 worth of gravel. We let the gravel set and compact for about a month, and mechanically compacted it twice before we poured the floor. The gravel was so hard they had to use a jack-hammer to dig for the two piers. My structural engineer thinks it will never move.

I put some extra money in the concrete, and encourage you to do the same, because I have found out in the past how expensive it is to dig up a bad concrete job. Skimp on anything you have to, but do not skimp on concrete, because it is not plesant to fix a building which has a bad foundation.

PS. Hire a structural engineer to go over your plans, and most especially review your foundation work. Might be the best $1000 you ever spent.

 

[flesburg]

PS: Have the structural engineer inspect the form work and be there on the pour days and check that the concrete is up to specification. Ready mix companies are or can be as
"crooked" as a professional gambler. There is something called a "hot load" that will totally screw you, and you will not know it for months, and they will not even kiss you.

 

[Franz©]

Well hell, if you want to do pours correctly, insist the pour be properly vibrated to eliminate air pockets, and NO a dipstick plunging a 2 x 4 into the pour doesn't do the same thing.

A while back I posted a link here to a multipart piece Don Solomon did on shopfloortalk. Don is a concrete placement contractor in Texas, and wrote a damn fine piece. They do things just a bit diffrent in Texas than we do up in the Great White North because they don't have much frost, but 90% of what he wrote is dead on the money.

Spans are killers in floor pours, and if the edges of the pour rest on a solid foundation, you damn well need support in the center, because whatever is under the concrete will eventually settle. When it does, the concrete deck is a bridge, and if it can't carry the weight it breaks. There is onehell of a lot more to pouring concrete than just letting it fall out of the truck.

 

[Novadiecast]

I have called the best poured wall guys in the county (not noted to be cheap) and will be discussing all of the above with them on Thursday. So I will keep you posted. I would, like you said spend a little bit more here and skim somewhere else. My father in law has a busted floor in his garage that totally *****.

 

[jklingel]

Right. "Hot pour" is snot pour. My son's basement got "hot poured" because the driver lost his way. The guys had to work their butts off to push the "mud" down the chute w/ their feet. He should have sued the contractor for not dumping that **** over the bank and ordering a new truck. The floor cracked like hell in no time, and the contractor refused to do anything. Needless to say, anyone who asks gets his name and the whole story. I hope he goes out of business soon. Mistakes in concrete are permanent.

 

[Cave Man]

I am a structural concrete estimator and project manager in MO. I just built my garage and will tell you how I did it. I am not into telling people how to do things so take this as you will.

I excavated 2'-6" wide by 1' thick footings around the perimeter to below frost depth, reinforced with four #5 rebars in the long direction and #5 rebars at 18" on center across the footings. I was going with concrete walls so I also tied vertical dowels extending out of the footing at 18" centers to tie the wall and footing together the I poured the footing. The walls were 8" thick with #4 rebar at 12" centers horizontal and vertical. I then installed 2" rigid foam insulation full height on the perimeter walls. I then drilled and epoxied dowels into the walls at 18" centers at the center elevation of the slab. This will tie your walls and slab together just as good as having a slab seat. Next I brought the subgrade up to elevation with compacted minus rock. I reinforced the slab with heavy wire mesh and poured the slab 5" thick. Make sure that you use a spray on cure imediately after the surface is finished and cover with concrete blankets if necessary to keep it from freezing. I have been in concrete for 15 years and know the three rules of concrete - it is gray, it gets hard and it cracks. The key is to controling where it cracks. Within 24 hours of pouring your slab you will want to sawcut 1/2 inch deep control joints on 12 to 15 foot centers in both directions. This will cause the cracks to be located under the joints so that they will never be seen or noticed. I used 3,500 psi concrete for footing, walls and slabs.

Recap - the most important things for keeping your slab from cracking - dowels into walls, saw-cut control joints, curing, wire mesh.


I hope this helps. I would be glad to send you some drawings if you would like.

 

[Mr.N]

A while back I posted a link here to a multipart piece Don Solomon did on shopfloortalk.

Thanks for the info!

link --> http://www.shopfloortalk.com/forums/showthread.php?t=8678