Hello, I'm wanting to build a concrete home and I've set on having concrete floors.  But the more I read up on them I get more confused.  It may just be there are 100 ways to skin a cat, but could someone shed some light on the subject for me?

I assumed that if you are building a home on a concrete slab, that that would be your the floor of your home (assuming it's a single story home) and you would just polish, stain, etc that.  But now I read about all these floor systems and using joists 12" on center, etc.  Am I wrong to think that you would insulate this slab from underneath, rough in your plumbing, electrical, etc that goes into the slab, then pour the concrete and there are your floors to do with as you wish?

Is the way I was planning on doing it very expensive or foolish for some reason? 

Thank you.

It is common for commercial buildings to be built just as you described. The electrical and plumbing chases and conduit are inside the concrete slab.

There are many options. What kind of floor do you want? Are you sure that the soil can support the load, etc.

If you want the concrete to be your floor, you need to take extra care in reinforcement and crack control.

With allergies, 2 dogs, 2 kids and living in the country, I've decided I want to go low maintenance with this build.  So I say yes, I am set on using concrete for my floors, but as with any build, nothing is set in stone until it's done.  When you say "can the soil support the load" I don't follow.  Would you need to do something other than gravel and power tamp and then rebar and fiberglass additive to solve those problems? 

I want a floor like I see in commercial buildings.  One that may need to be mopped once and a while, and that is acid stained NOT polished.  I assumed that this route would be cheaper since the slab has to be poured anyways, and no more floor products like tile or hardwood would need to be installed.  Is that not a safe assumption?  Thanks.

Well you're probably just reading about floors that are for a second story, or over a crawl space for one reason or another. If your area would allow you to use slab on grade I don't see why you couldn't use the method you describe.

Hi; how would I find out if my area would allow for what the method I mentioned?  I just moved to northern arkansas by oklahoma. I assume the main issue is frost is it not? Thanks.

Visit your local building codes office. I'm not aware of any codes that do not allow for concrete floors. However, be cautious of pouring 'slab on grade'. In some areas, that is literally what is done. Level out the site, set up forms and pour 4" of concrete. I do not consider this to be acceptable for a home, but especially not in areas with poor drainage. A slab that is raised 6-8" above your finished grade on a properly prepared foundation and fill, with vapor barriers and insulation in place, will provide a much more stable and comfortable floor.

And one more thing I forgot to mention. This may seem overly simplistic, but do not allow anyone to talk you into setting your walls on top of your floor slab. This is a common practice for commerical wood and steel frame construction, and I have seen it done on concrete basement walls where the footers and slab are poured as one (monolithic) pour, and then the walls are built on top. This is absolutely not an acceptable practice.

wes, could you elaborate on what is not acceptable about building on top of a slab?

Not simplistic at all thank you for mentioning that. Even with what little I know I knew that shouldn't be.  I've been considering the insulated concrete form type walls with this slab.  I did speak with a friend of mine that builds back home and he said that my idea is acceptable, but he did state to have the footings for the walls lower than the slab by 2-4 inches to prevent any water infiltration from seaking under the exterior wall and then into the home since it would then have to go up as well as in. 

It made sense to me, is he correct? 

Sorry for bending your thread:

I'd been considering a concrete floor depending on the site that I end up with, but my impression had been that they ran from 1950s terrazzo (blah) to stained grey concrete (not quite butt ugly).  Then I came across this white concrete site and its images really changed my perception to WOW:

http://www.cement.org/decorative/images.asp

Good luck,
Larry

Ryker, what your discribbing is the only way to build as far as I'm concerened. Even in a predominate ICF basement state that I live (MI) I would still build my home ICF slab on foundation just as you want. Yes you will still need stem walls even there in your warmer climate, but this is the most economical way to build new construction today.

Dave

Jelly,
I see two main problems with setting masonry walls (ICF or otherwise) on top of a floor slab. First, it creates a horizontal cold joint which will eventually leak, unless you take extraordinary measures to waterproof this area, and get very, very lucky that your efforts are perfect. Second, the slab and the walls will react differently to various internal and external factors such as humidity, temperature, seismic shifting, etc. This will lead to cracking of the slab, at the least. The slab and the walls and their footers, need to work as two separate systems, reacting to such factors independently.
Rykertest,
I generally raise the floor slabs, 12+" above the footers. This allows for installation of drain tile, and a drainage plane (clean rock), vapor barrier, 2" of EPS insulation board(yes, even in the warmer climates) under the slab.

wes, I'm not clear on what you mean would be the preferred method. Are you saying that first the footers should be placed, then the walls should be placed on the footers, then the slab should be poured within the perimeter to a level higher than the horizontal joint of the wall and it's footer?

Jelly,
Yes.
Actually, I prefer the cold joint between the footers and wallls be at or below the drainage plane, with vapor barrier, insulation, and slab above that. This allows any water that might enter through the cold joint to be drained away from the slab. Remember, we are also not just worried about surface water draining down the exterior of walls and seeping in through the cold joints, but also ground water that will come up under the slab throughout the footprint of the house. Without the drainage plane, which provides a capillary break in the hydrostatic pressure exerted by this ground water, your slab is exposed this pressure which will cause floor cracking, shifting of the slab, and water intrusion.

Wes, I'll be the first to admit that I am chemical engineer and not a civil engineer, and I can understand some of the thoughts you have, but I have also seen a LOT of homes built with walls directly in contact with the slab. In Houston standard building practice as been to use a floating slab for many years. Monolithic pours have a long history as well. A simple method of breaking the hydrostatic pressure if that's a concern, is to build a french drain underneath the inside perimeter of the footer.

Larry,
I also have seen many commerical structures built monolithic slabs. I've done a few myself. But in our area, basements or crawlspace construction is the norm for residential. My comments are directed by my experiences in the field. Rykertest was questioning the construction of a concrete house. I would not recommend the use of a monolithic slab under any type of poured concrete wall (ICF or otherwise). While monolithic slabs are cheap, fast, and easy (the reason they show up in commerical and production housing), I would not normally recommend it use in any habitable structure.

I really appreciate the input from experienced pros like wes, and I have no doubt that he's right. I have never seen it done that way, but that doesn't mean anything because I'm in Louisiana and things don't often get done the best way 'round here! Of course there are no basements here, and I am planning an elevated slab (a 2 or 3 foot perimeter wall with concrete block, fill the space inside with compacted sand and gravel, place a plastic barrier and pour a slab over the entire affair). Wes, in this case would I still be better off with separate footers and slab? I'm assuming that's more crucial in a basement or crawlspace? And if I didn't end up using concrete walls would it make a difference? Do you ever use a barrier under the footer to prevent rising damp?

I do not think there is a single "right" way to do this and I have seen a lot of regional differences, but it really depends on your particular drainage and subsurface conditions. 

Jelly, in your case, I would be hesitant to build a slab that is supported by both 2 or 3' of compacted fill AND stem walls/footings, unless you design your slab to be a structural element (expen$ive).   There WILL be differential settlement and there will be cracks (which are not the end of the world, either), but I would pour your slab inside the stem walls.  

I say this primarily because of the amount of fill.   This amount of fill means doing it in lifts, paying attention to the moisture content of the soil, etc.  Getting the compaction right in the normal residential construction world will be hard.  I do not know what your specific drainage and subsurface conditions are, but I see no downside to a vapor barrier under the footing.

While this is not a significant problem in Louisiana or Houston, the edge of a slab poured to the exterior must be well insulated to prevent cold bridging.

Bruce

Jelly,
In our market, we have a lot of duplex and quadplex rentals built in the exact manner you describe. These units are of conventional light frame construction, and trussed roof systems. The overall loading is not huge, and most is transferred to the exterior walls. This system seems to work OK. However, Bruce is correct in stating that the fill compaction is critical in your case. Where your fill goes, so goes your slab. Also, no load bearing interior walls on just fill. Use interior stem walls.
And vapor barriers are always necessary. even elevated slabs are subject to ground water penetration, and moisture in the fill will migrate thru the slab without a vapor barrier. And a little insulation under the slab will help stabilize the slab temperature during the colder months.

There really are no colder months, honestly. We are truly a semi-tropical climate. You could call them cooler months I suppose! The way I understood it was that the connection with the ground was more valuable in the summer to help cool the structure, than insulating it for the winter. I do understand the point about insulating the outside edge of the slab or perimeter stem wall though - I would think this would be important in both winter and summer.

My plans don't have any load bearing interior walls, so I'm good there. If I go with steel SIPS the overall loading wouldn't be significant. Concrete walls are still an option though, so that would be a different story. My biggest problem would be finding a local foundation contractor to do it this way. You know how it goes - old dog, new tricks. And I don't even want to think about the code official.

I know the vapor barrier under the slab is crucial, but I mean under the footers. How far up the side of the footer does the barrier go - all the way up to grade? Is it necessary to tie it in to the barrier under the slab?