Suspended Concrete Floors?

[RobertBrown]

I can't wait for Transit to chime in here!
Seems like CMU block and compacted fill (stem wall) is the way to go, but I must have missed something?

 

[Builder]

I can't wait for Transit to chime in here!
Seems like CMU block and compacted fill (stem wall) is the way to go, but I must have missed something?

I agree. I said that in my last post as you can read here:

Might be better if you just built perimeter block walls with 8" block and fill with compacted crushed concrete around both sides (like a garage is built). Then just build your metal framing and walls on the top course of solid block with anchor bolts. Then when the roof is on, open the shop doors and pour your floor.

I would build it like a raised garage. You just have to make sure you use compacted fill around the walls. He'll also need a driveway that is "ramped" up to the door.

 

[boxygen]

I think the key part of his question was when he said that it was in a flood plain. I think He wanted it on piers so when the water level comes up it washes underneath the structure without putting any pressure on the foundation or building. When we build houses on the coast of Maine, they are required to be on piers within a certain distance of the high water line as required by the DEP. We are about to start one that the front of the house is on piers and the rear of the house has a typical concrete frost wall since it is in out the the required setback. And I think he wants concrete so he can weld. Those were my assumptions, I may have misinterpreted though.

 

[tallyho8]

I just installed a new concrete porch 30' x 7' on my son's house 4' above ground level. The previous porch was concrete poured on 26 gauge corrugated metal and from 2 to 3' thick and in perfect condition after 74 years.

We had to tear the old porch out to replace termite eaten sills and joists in the house that had no termite shields on the piers.

We replaced the porch with a 2 1/2 to 3" thickness of 4000 psi concrete set on 26 gauge galvalume R panels. We asked the concrete company to bring some cardboard test cylinders to insure that they did not short the cement in the mix.

I prefer using metal instead of wood for the form decking because the wood will rot out and attract insects.

There will be no heavy loads in a 12 x 24 tool shed and there is no reason a concrete floor 3' high can not be used with sufficient support. My reasoning goes that the thinner and lighter you make the floor the easier it is to support and 5000psi test concrete that is the same thing that the highway department uses in bridges can be reinforced and still be very strong in 3" thicknesses.

 

[Builder]

I think the key part of his question was when he said that it was in a flood plain. I think He wanted it on piers so when the water level comes up it washes underneath the structure without putting any pressure on the foundation or building. When we build houses on the coast of Maine, they are required to be on piers within a certain distance of the high water line as required by the DEP. We are about to start one that the front of the house is on piers and the rear of the house has a typical concrete frost wall since it is in out the the required setback. And I think he wants concrete so he can weld. Those were my assumptions, I may have misinterpreted though.

Ahh, flooding, then go back to my "piers" idea. lol

 

[RobertBrown]

I agree. I said that in my last post as you can read here:


Indeed you did, as did gpflepson. I'm not at all sure why that type of construction is unsatisfactory, but it seems much easier and less expensive. Building techniques vary greatly in different locations. I'm sure there is a reason why it won't work.

 

[cdhd2001]

Bingo! We have a Winner!

I think the key part of his question was when he said that it was in a flood plain. I think He wanted it on piers so when the water level comes up it washes underneath the structure without putting any pressure on the foundation or building. When we build houses on the coast of Maine, they are required to be on piers within a certain distance of the high water line as required by the DEP. We are about to start one that the front of the house is on piers and the rear of the house has a typical concrete frost wall since it is in out the the required setback. And I think he wants concrete so he can weld. Those were my assumptions, I may have misinterpreted though.

 

[mjncad]

mjncad, Fair enough, I'm not discrediting you or engineers in general. Many engineers simply reference published charts that are available to everyone that knows they exist. The good engineers will save you money by not over engineering a project. MikeD74t

Agreed!

 

[MarkV]

Maybe I am missing something but all the suspended slabs I have been around on jobs required a lot of support under them until the concrete cured. I don't see how you are going to easily do that in a 3' high space unless you plan to leave all that material down there. It sure would be easier in my mind to build a block wall and add compacted fill. It is done all the time and I'll bet it would end up cheaper.

Does the flood issue really affect the building if it is set on a block wall or is it a matter of building restrictions because of the flood plain?

MarkV

 

[Builder]

I think the concrete piers are the most prevalent form of flood plain construction near me at the jersey shore along the coast. However, there's still wood floor structure sitting on them.

I wonder if the OP couldn't use treated lumber underneath for structural floor framing, apply a gypcrete layer on the subfloor, then install some kind of tile, flagstone veneer, etc. to get the "fireproof finish" he needs????

We do this for radiant heated floors with about 2" gypcrete, then porcelain tile