Insulating interior basement walls
I’m getting ready to finish off my basement. When it is finished it will be aprox 1000sq ft of the 1600sq basement area and will function as the primary “Hang out space” in the house, which is a 1600sqft ranch.
Areas will be: Entertainment/bar room with small office area seperated by 1/2 wall, kids play room and 1/2 bath. Other unfinished/partially finished areas will be storeage, mech room and my work shop.
I have no problems with the framing,electrical,plumbing or mechanical. My question is on the insulation for the interior fondation walls, which are 8ft poured concrete. House is 3.5 years old.
Being that this will become the most higly used area of the house, i want to make it extremely comfortable and moisture/mold free I can.
What I am thinking of doing is to put up 2in/10R rigid on the basement walls, build and stand the stud walls, insulate the stud cavities with 13R FG insulation and then drywall. I know this may be a little overkill, with a total of 23R in insulation alone, but is there any problems with doing this?
I am not plaining on any vapor barrier in the wall so that any moisture can evaporate out. I am using an article from the 3/05 issue(#169) FHB on rigid foam for the basement walls for some guidance.
Only deviation would be that the rigid would be the Extruded Poly not the expanded kind and I would be using the extra FG in the stud bays.
Any direction/comments/advice/ideas would be greatly appreciated. Happy Holidays,
J-
Replies
Concrete walls below grade are considered a "wet" location. This ought to be kept in mind as you make your walls.
I'd first put up a layer of the plastic mesh masons use to screen walls behind brick veneer. This will allow water seepage to drain.
Next, I'd use furring strips to attach the wall sheathing. Between the furring strips, I'd use foil-faced foam. Where moisture is an issue, foam simply cannot be beat.
Finally, I'd cover with ordinary drywall. I'd take care to space the drywall at least 1/2" off the floor, and leave a slight gap at the top as well. The gaps are to allow water to drain, and air to circulate.
I advise against any fiberglass insulation. It simply isn't much of an insulator when damp, and too easily becomes a nest for vermin.
I'd also look for some way to insulate the floor. Some products, intended for garages, look promising. You know ... the knobby rubber tiles that are also raised somewhat off the floor? You could always lay carpet atop them if you wished; and, with the raised base, you could likely get away with covering the floor over the drains (making it all nice and level).
Sounds like you have it nailed. This is the Building Science Corp recommended system.
1) Make sure the wall/floor system, wiring/plumbing penetrations and main floor system perimeter are airtight with a truly continuous air barrier system- drywall, expanding foam, foam board, caulking, maybe adhesive foam tape
2) Consider cutting a small interior drain along the interior concrete floor/wall intersection that will catch any future small nuisance foundation water leakage and let it drain down to the crushed stone under the slab. In a small city I used to work in, many foundations had this drain cast into the slab edge during the slab pour. Someone in western Canada patented a system to make this step very easy. (I have a re-usable system designed in my head but seem always too busy to put a prototype together. Maybe in retirement!)
3) Put down dimpled plastic water drainage membrane (Platon, Delta, etc.) under any subfloor, insulated or not. (I would do an insulated floor) It comes in rolls or on 2'x2' OSB sections that are T&G'd for a seamless fit (I find these a bit overpriced though).
These should make for a longterm dry basement. Good luck.
Edited 12/24/2006 10:12 am ET by experienced
I like the ideas presented here, particularly the mesh mason screen and perimeter floor drain. Instead of a continuous perimeter drain at the base of the mesh to take care of any incidental water, would drilling holes right through the floor into the gravel work? I am thinking 1/2" or 3/4" holes all the way around the perimeter, every few inches. This would be easy, albiet monotonous and hard on my back, to install in a retrofit situation like mine. Any problems with this because it would also hopefully adrress another issue I have?My basement walls are 100 year old stone, but nice and straight and all things considered quite dry. The basement was finished by the previous owners 8 years ago and so far so good. However, allowing water to escape through the bottom would alleviate moisture trapped in the walls (currrently FG batts, vapour barrier, and drywall) from wicking up under hydrostatic pressure into the structural brick walls and then spalling during freeze/thaw cycling.Thanks