Please advise on this new type of basement construction
I’d like to get some feedback on a new type of basement construction I came across recently.
Background: I signed up for a GBA account two or three years ago as I began planning my eventual retirement home. I don’t participate much but I am a regular reader. I originally was interested in ICF due to being in west Texas and the chance of tornadoes. Technically I’m in zone 3B but just a stone’s throw from 4B. I will assume 4B for winter and 3B for summer when planning the house. I will still consider ICF but after discussions with the only local builder I’ve found who uses it, it looks like the cost premium will be too much. So, I am also considering a wood frame / brick house built to Florida type hurricane standards along with a basement. While checking out homes being built in the area, I came across a new type of basement construction I had not seen before.
They start the home construction by trenching walls for the basement. The trenches for the walls appear to be about 6” wide. After the trenches are dug, they insert rebar in the outer third of the trench leaving enough room for a 2” x 4” top plate to sit on the wall flush with the interior side. The concrete walls are then poured. Then the basement is dug out and a concrete floor is poured. The rebar is then bent 90 degrees so it can be integrated with the slab when poured. A treated 2” x 4” top plate is installed on top of the basement walls. Next, 16” trusses are installed on top of the basement and the opening for the stairs is framed up to be flush with the slab when poured. The tops and sides of the trusses are then covered with ¾” plywood. The plywood is covered with tar paper. The slab is then poured (including over the basement ceiling). I’m not sure of the construction details beyond what I’ve shared but the basement ends up fully finished.
The size of these types of basements is restricted such that the exterior wall of the basement must be at least 5’ to the inside of the exterior wall of the house. Apparently, this mitigates moisture issues. We only get around 15” of rain a year. The joke is that you ought to be here the day we get it.
1) Overall impression of this type of basement construction? Do you see any particular issues?
2) Would you use Drylok on the interior wall before finishing?
3) In my climate, should insulation be installed under the basement floor before pouring?
4) How would you finish this type of basement? Wood frame walls? What type of insulation? Would you insulate the ceiling of the basement?
Thanks for your time.