Insulating and finishing basement

[Art]

I need to insulate and finish the walls of an old basement. In this section of the basement a new foundation was constructed several feet below the old foundation which results in a ledge, the old foundation protruding into the room about 6 inches, so simply furring and insulating would not create a suitable wall. While moisture is not a problem, termites have been..

My first thought was to use steel studs on top of a pressure treated sole plate for total termite resistance and put fiberglass between them. Not a good idea given that seel would provide a bypass around the insulation. Also, I was surprised to find that fiberglass seems somewhat more expensive than foam. Finally, it may not be cost effective to insulate more than a foot or so below the ground level, which would be the top of the old foundation. A future project will be insulating the 1/4th of the basement that will remain a crawl space

While it would be easiest to install the foam on the inside of the studs, installing it on the outside would create two separate air cavities and thus a higher R value. It would also eliminate the problem of electric sockets piercing the insulation. If the foam has a foil side, does it matter which way it faces? If someone makes foam with foil on both sides, would it make sense to use it as there will be air spaces on both sides of the insulation? Is there a better way of doing this?

[JRam]

Art, I use steel studs all the time to finish basements. They are great where there is no load to bear. I usually use 1" to 2" white "poly" foam (expanded bead foam) because it is cheaper than rigid foam ( w/ or w/o foil) for the same r-value and there is no need for the foam rigidity as it will be sandwiched between the concrete wall and the steel studs. I apply the foam right to the concrete walls using a foam adhesive to stick it and to seal the edges and seams for a moisture barrier. Of course this all assumes a relatively straight, even and sound concrete wall.

***If there is ANY water infiltration, it must be taken care of first. The foam is not enough to keep water out. It will only insulate the concrete wall from the interior air, thus preventing moisture collecting on the inside surface of the cool concrete (sweating). If there is any water coming in from the outside the foam will keep the wall wet and provide a breeding ground for mold and bacteria.*** The steel studs are installed against the foam leaving the dead air space you mentioned as well as leaving room for wiring and plumbing. As a side note, I use 1-5/8" steel studs on the perimeter. Being installed against the foam, they have plenty of strength and the foam and studs finish out to the same thickness of a standard stud wall (or less if you just use 1" foam). One other caution... Steel studs require special handling for electrical wiring. Make sure you use plastic bushings anywhere electrical cable passes through them. Check you local codes and/or ask the advice of an electrician if you plan to do your own wiring. Good luck! Jeff Creative Home Services Muskegon, MI

[Jay Chan]

How much head room in your basement? I have a feeling that finishing a basement may not worth the effort if the ceiling height will become low (after you raise the floor and put in a drop ceiling). I don't know about the average market value of a finished low ceiling basement. But I will not want to pay extra to buy a house that has a finished low ceiling basement.

Just try to warn you before you have spent a lot of effort in your basement project.

Jay Chan

[Art]

Thanks for the replies. Unfortunately, glueing to the old walls is not an option-way too rough a surface not to mention the problem with the old foundation protruding 6" into the space. Water is not a problem, in fact the only time in 20 years I have had water come into the basement is when the neighbor got a little careless with a 1 cubic foot per second flow of irrigation water. I assume that since the foam has no structural strength, I will need to use washers, strips of wood or gypsum board to hold the foam against the studs. As for the economics of finishing a basement in a house built c 1918, the area right now is usable for it's expected purpose-a workroom. Finishing the walls should raise the value because it would cover the work done to stabilize a major foundation crack in a 12" thick unreinforced concrete wall. Finally I compute that close to 20% of my heat escapes though the basement walls. Gypsum board is merely the easiest way to protect the insulation from a cat that has learned the joy of shredding foam.

In fact, I expect THAT will be my biggest problem, protecting the work in progress from the Claws".

Art Utah