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Finishing A Basement

I live in the southeast and have a basement that I am about to frame around the concrete walls. I am going to use 2x4 wood. 

Do I need to use PT (pressure treated) wood other than the bottom? Or do I use it all the way around. I read somewhere that I frame it up like normal (PT on the bottom and white wood elsewhere), but line the concrete with foam sheets and don't use a vapor barrier on the insulation. What are your thoughts on this.

John C.

There are many different methods of finishing basements. Using Pressure Treated lumber for the sole plate (the bottom board) is necessary because the concrete will wick moisture out of the soil and into the wood. It wouldn't hurt to use treated lumber for the entire wall... if the basement ever floods, there will be less repair work.

About 10 years ago I did a little research on basement finishing methods for my own house, which had a damp basement. I concluded that the best method was this approach:

- Wash the walls (and floor) with Muriatic acid, diluted 50/50 in water. This is hazardous! Wear eye protection, or a face shield. The acid cleaning is necessary to remove lime from the surface of the concrete. My old house had little white puffs of lime that formed as moisture passed through the walls and evaporated. I rinsed the walls with a garden hose, and I used a shop vac to suck up the rinse water. This was a lot of work, but a very necessary step. Without this acid wash, nothing will stick to the concrete.

- Paint the walls with a quality basement paint. In 1991 Consumers Reports had just done a study of basement paints. I don't recall the specifics, but their guide books may still have the info. I used Glidden oil-based basement paint, which had a high content of Portland cement in it. This stuff really stunk, so ventilation is required.

- Paint the concrete floor with oil-based concrete floor paint.

- Attach a sheet of ordinary 4 mil polyethylene plastic to the wall. The trick was finding a glue that would stick to polyethylene. I tried many different glues on some samples, and 3M super 77 spray adhesive was the best. It costs about 10 bucks a can and only covers maybe 100 to 200 square feet.

- Build an ordinary stud wall. I just built the wall laying on the floor and tilted it into place. But watch out for uneven heights in your floor-to-ceiling dimension.

- Install wiring as normal. If you use UF (outdoor rated) wiring, you may not have to replace everything in the event of a flood. It's just a pain to strip the cable jacket.

- Insulate with regular fiberglass insulation. I couldn't find anything other than kraft-faced insulation, so that's what I used. Here in the north, they recommend only one vapor barrier, and on the inner-most part of the wall. But a basement is a little different. The kraft facing is really just a vapor retarder, not a true barrier. The polyethylene is a true vapor barrier.

- Install a finish wall surface. I used T1-11 plywood with grooves at 4 inch spacing. It looked okay, kinda rustic. Good for a basement, and very durable. If I used drywall, I would only use MR (moisture resistant) wallboard, at least on the lower half.

- Finish trim with colonial casing and rough-sawn 1x2's.

I noticed right away that the humidity in the basement was much improved, because the dehumidifier no longer ran continuously.

I visited my old house recently. The basement remodel is holding up pretty good, but I did notice that the quality of my work has really improved over the last decade!

There are more ways to finish a basement, more than I have time for. A lot depends on the age of your house and any moisture problems you may have. My old house (built in 1950) had no damp-proofing on the outside of the concrete, so moisture entered readily. Newer houses always have some form of damp-proofing, at least around here. You may not need the basement paint, the acid wash, and the plastic sheet. But if you are experiencing a lot of dampness in your basement, these steps should help.


Bruce W. Maki, Editor.

John Replies:

I checked with the local building codes on this, and with people who do this in my area, and this is what they suggested:

The wall is going against a poured wall (8" thick)

Use " sheets of insulating foam board and glue on the concrete wall, seal all seams with tape. Build the wall as normal, and use UNFACED insulation. Install sheetrock as normal.

The house is 9years old and has the normal waterproofing stuff on the outside when it was built. The area I live in is NOT known for floods (not in a flood plan or anything like that) and the basement does not have any moisture problems to begin with...

Thanks again



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Copyright 2001

Compiled September 2, 2001