I am designing an ICF home and among other goals one of them is simplicity in execution. Coming from stick built homes I find it a bit challenging as to what the exact unfinished floor / ceiling height should be. In this case the floors will be done with insuldeck and may end up being finished as polished concrete for the most part. The bathroom floors may end up being tiled while bedrooms will have carpet. I am planning to have the ceiling height at 8ft 1/2" so standard 8ft drywall can fit right in. Does that sound right or should I leave more gap beyond 8ft?

To accommodate 8 foot drywall sounds like good reasoning. But drywall usually goes in horizontally, so you want to stick at least with easy multiples of 2 or 4. So 8, 10, or 12 feet leaves less waste (9 or 11 feet would create more waste).

In my region however residences are being built with taller ceilings. It's more common to see 10 foot ceilings at least on ground level, but that's personal preference.

They make drywall in 9 and 10 foot lengths to accomidate easier installation in taller ceiling rooms... So if you want taller ceilings, a little more/different engineering analysis, a little more block and a little more concrete, but not a whole lot of additional labor...

Oops, Doubletap:)

Sheet rock is also available 54" wide for 2x horizontal for 9' ceiling. As I remember I went 9' 1" to allow for the ceiling rock (you want that on top of the wall rock) and a so-you-don't-have-to-fight-things gap at the floor. Baseboard will easily cover a gap up to 1/2" between rock and flooring so there's no need to make it a tight fit. 9' ceilings are nice, not too high but give the room a more 'open' feel.

Thanks for all the replies. In this case I have a total building height restriction so I need to fight for every inch so I can't go over 8ft ...

Posted By pacificstart on 21 Sep 2015 12:49 PM
... I am planning to have the ceiling height at 8ft 1/2" so standard 8ft drywall can fit right in. Does that sound right or should I leave more gap beyond 8ft?

If you are shooting for nominal 8' walls, then make the exterior ICF wall height match that of a standard 8' pre-cut wood stud with top and bottom plates.  An 8' pre-cut wood stud is 92-5/8" long.  With one bottom plate and two top plates, that is an additional 4-1/2" or 97-1/8" or 8' 1-1/8" (accommodates 5/8" sheetrock for the ceiling plus 8' of sheetrock on the wall, plus a 1/2" gap at the bottom).  But if you plan on anchoring a 2x or 1-1/2" thick wood top plate to the top of the ICF wall to provide attachment for the rafters/trusses, then you need to subtract 1-1/2" from that 97-1/8" total wall measurement for an actual finished height of the ICF wall of 95-5/8" above the floor deck.  Otherwise, you will have to custom cut every stud, or if the exterior wall is slightly higher than standard 8' stud walls, you will have to shim all of the interior walls up to meet the trusses or shim the trusses down to meet the interior wall top plates. 

If you are using trusses on 2' centers and plan on lots of heavy loose fill insulation above, it is not uncommon to install 1x (3/4") cross lath on 16" centers under the truss bottom chords to provide additional support for the ceiling sheetrock, so that additional 3/4" height would need to be considered as well.

Arkie - good catch here.

I was totally missing the fact the interior walls will be made with 2x4s. Which leads to the next question that deserves probably it's own thread.
What are the pros and cons of steel studs vs wood studs for the interior walls when floor is concrete and ceiling is foam with Z metal furring?

I used steel studs, and even using the heavier gage ones, they were slightly cheaper than wood. That, coupled with the lousy quality of wood prompted my decision. My walls came out dead straight, and have stayed that way. I did find the steel studs to be more labor intensive. There are holes punched for plumbing and electric, but you need to drill and grommet holes through the top or bottom. You need to line openings with wood to mount doors and trim. I also beefed up areas that would have cabinets and other heavy objects attached, such as TV brackets and bathroom grab rails. Hanging crown molding and baseboard requires the use of trim screws- slower than shooting finish nails.

Steel does not rot or grow mold, does not promote flame spread, and termites cannot eat it (don't know if the original poster is in California?). It's also lighter and easier to build in place.

I am in BC - termites is not an issue. Since all the framed walls will be indoors and contained within the ICF structure I am not sure to how much mold these walls can be subject to. All the framing will be behind drywall so the occasional fire risk is close to zero I would say. So these kind of issue are not really a concern in my case. The difference in cost over wood is about $2-3k for the whole house so that is not an issue either. Labor cost and ease of installation is more of an issue. The additional reinforcement for hanging heavy objects is more of an issue.

Also I'm thinking the better thermal conductivity of metal vs wood will make the internal walls catch more of the temperature of concrete structure propagated via the slab they are sitting on.
That can be either good or bad depending on how well the overall concrete structure is insulated from the earth and from the outside.

If I decide to go with steel how sturdy or solid these walls feel? For example how are they different when slamming a door or how do they propagate vibration along the wall? Do temperature variations cause any dilatation or contraction popping noises?

Mold spores are present on the lumber before it even arrives to the job site. Moisture from the concrete, in the slab and in the ICF forms, can elevate humidity levels in the house. Are you near the coast? Will your HVAC handle the latent load? Do you have shoulder seasons where you won't mechanically condition the air? Leaks, even slow ones, are another possible source. Of course you want to design properly and prevent any issues, but steel is impervious to most all of them when they do happen.

Reinforcement for hanging heavy objects isn't necessary in terms of pullout, but more for convenience. For example when hanging cabinets and you want to be able to put the screws anywhere, you might put plywood blocking in (but this is done in lumber houses too). The important places where you really need reinforcement are areas like stair railings that are subject to a lot of turning and pulling forces, and the hinge side of a door frame, or disability fixtures in the bathroom.

Steel framing seems flimsy when it's going in, but it stiffens up when the sheetrock is added (and there won't be any cracking, buckling, or pops in the sheetrock). I have worked with wood and steel framing, and I would call steel much less labor intensive. But if you ask a carpenter whether steel adds labor then his opinion may be "yes" because lumber is all he knows. And if residential carpenters are the only labor force in your area, then you'll probably choose lumber.

You found steel to be more expensive by 2-3K? Here in SC, it was cheaper than wood. You have to get a price from a real supplier, not a big box store. That being said, lumber is probably pretty cheap in BC. I can't tell any difference in noise/vibration from wood framed houses I've lived in. As jelly said, the steel will feel flimsy until you get the drywall on it. After using steel, I would never use wood again.

A 3 5/8 x 8 steel stud is $4.79 while a 2x4x8 fir stud is $2.55 at the local HD.


While I still find the moisture concerns in a properly managed building (no leaks and excessive moisture in the air or walls) a bit exagerated I am thinking going with steel will avoid something nobody seems to mention and that is the smell of the wood over time.

Mounting the base plates over a plastic sheet or building paper to avoid direct contact with the concrete should pretty much address the issue of moisture coming from the floor. I event thought of spray painting or coating the wood framing so to make it more impervious to moisture. But none of these will address the normal wood smell which becomes even stronger as the wood ages.
I like the smell of fresh wood and I don't mind the smell of the wood in an old house, it even brings old memories, however not everyone likes the smell of the old wood in a house. It will probably won't be a concern in my lifetime anyway but since a concrete building has a chance of being up for a long time why not build it that way...

Posted By pacificstart on 25 Sep 2015 03:31 PM
A 3 5/8 x 8 steel stud is $4.79 while a 2x4x8 fir stud is $2.55 at the local HD.

Like jdebree said, you're not going to get a good price on steel framing at the big box store. Check with the drywall and building material supplier.