I've been drafting a house for a couple years now and through many iterations I discovered one of the biggest flaws in how I was drafting was in not knowing what I would be building the house out of.
After looking up the differences between Concrete and Lumber construction I settled on the idea of drafting a concrete house. I found some nice ICF designs and have since been designing the house with ICFs in mind. However, recently I've been doubting the information I've been given. See I keep getting conflicting information on how thick ICFs should be.
How thick should an ICF Exterior and Interior Wall be in my drafting document?
Bonus: What parts take up what amount of space? How thick is the Core Concrete, insulation, etc.? And what tolerances should I have for drywall to go over the walls?
Best Answer
ICF block comes in core sizes of 4, 6 and 8 inches, and the insulation is 2.5 inches per side. Most of the ICF houses I've worked on were exterior and load bearing only. In Ontario, other jurisdictions may be different; any time you're dealing with load bearing walls you need to have an engineer certify it and submit it to your local building authority. I've never heard of any engineer putting their stamp on someone else's drawing (I'm sure it does occasionally happen) because they are absorbing the liability for someone else's work.
From my experience, foundation walls are always 8" + 5" for the insulation and I've seen 6" on upper levels. The 4" blocks, I would imagine, are for partition walls. They are very comfortable houses to live in. The rated insulation is pretty much what you get, as opposed to a wooden structure. With lots of extra framing and pack points, along with poor insulators and difficult spots to insulate, the actual R-value of your typical wooden structure is far less than the R-value listed on the bags of insulation or what the spray foam guy is telling you. Wood is a poor insulator.
ICF is also very tight so a HRV or ERV in a warmer climate is a necessity. Also, consider concrete floors over corrugated metal with radiant floor heating, if you are in the north. The drywall can go on a stud wall directly on the face of the block. Most seem to use steel studs. Hope this answers at least some of your questions.