basement finishing

[pearllakebulls]

I'd appreciate it if anyone can help me with a couple questions.

First, about framing out block walls. Is it advisable to put some foam insulation between the block and the eventual 2x4 studs? if so, how thick? Then, should I put poly over that, or should the poly be the first layer next to the block? I will be putting some kind of insulation in the frame cavity for sure. Along with that, is it generally ok to do framing before obtaining permits and having an inspector visit. The load bearing wall is in of course, but I need to put in one wall to make two bedrooms, frame up closets, and frame out the block walls. Thanks for any insight.

[My_Key]

When we frame in the basement walls in new homes, we hang a layer of poly to act as a barrier between the foundation and the wood walls. We also try to leave a minimum of 1/2" between the foundation and the framing. Then go ahead and insulate the wall, put some poly on and then your drywall.

[My_Key]

Part 2 of your question.............You'd have to check with local ordinances to see what you need permits for. Adding them as "bedrooms" you will most likely need to pull one. Because to be considered a bedroom, it needs to have an egress window and a closet.

[Bear55]

I would seal your block with drylock or something similar just to have a little extra protection and then glue on some rigid foam insulation, 1/2 or 3/4 should be enough. Then build and insulate your walls.

My builder had insulation right up against the cement blocks with a vapor barrier on the inside. After a couple of heavy rains or condensation from warmer temps my insulation was soaked. I tore everything out and started over. It was a pain but I sleep better knowing I won't have problems down the road.

[BobT]

Does adding a sealer on the inside really last? With the way foundations are pushed around by frost and stuff it seems to be common to eventually have cracks, especially with older structures. I'm just wondering if a sealer helps long enough to be worth the cost and bother.

[BoxMN]

FWIW, here is an older thread where I described what our builder did for ours...

http://www.hotspotoutdoors.com/forum/ubb...ent#Post1840277

[Bear55]

We had some heavy rains this summer and I had some water seeping through, even more heavy rain this fall after I added the sealer and everything was bone dry. Not 100% sure how it will hold up over the years but its just one of a few things I plan on doing to make sure I don't have any moisture in my basement. I tend to lean to the overkill side of doing things so the extra $50-100 and time to slap on two coats is worth it to me.

[Tom7227]

I helped my brother with his project last year and what I learned is that each building inspector has his/her own standards they want followed. I suggest you contact the locals and get their input before you start to do anything. You may be out in the toolies and not think it's an issue but you may end up getting burned when you try to sell or mortgage the place. Egress windows, electric nuances, plumbing - frankly I doubt most contractors can just walk in a 'get it right' without talking to the local inspectors.

[Surface Tension]

Things are different depending on where you live but one thing is for sure. You need to have the permits before you get started.

Electrical and Building permits in this case. As said bedrooms will need egress windows. I'll go on to say that any room that COULD be used as a bedroom whether that is your intention or not will need to have egress windows.

In this case finishing off a basement ceiling height could be an issue for you. That and the windows are the two bigges.

I have my own opinions on insulating the interior walls of a basement. For that matter covering an interior wall.

Stop the water from getting down there in the first place with a proper slope away from the house. Once water gets below your grade the hydrolic pressure is something you can't stop for long. The waterproof coating IMO are good for a dampness barrier at best. Any wood that touches concrete needs to be treated so you'll have a treated plate. I'd leave an air space between the stud wall and block then use a closed cell foam for insulation. Or a stud wall with no insulation on the interior and insulate the exterior. The later I feel more comfortable with.

The electrical, when you get your permit you'll be asked what your doing as the permit is priced accordingly. You'll get some of the codes with that permit. Now you can then get started roughing in.

I'm not an electrician and won't or shouldn't offer much more there.

[SkunkedAgain]

I'm working on a similar basement remodel. From what I've read, seen, and heard, you do as ST mentioned above (frame with rolled insulation, rigid foam on the back, space between frame and the foundation wall). The main difference is that some cities require a vapor barrier between the rigid foam and the concrete wall. Go to your local building department. They should tell you everything there is to know.

[311Hemi]

I am just finishing my basement, I went with 2" rigid XPS directly on the foundation wall mechanically fastened using Z-channel to save space. Firing strips are usually whats recommended. You would build the 2x4 on the inside of that if you wanted. No additional vapor barrier installed. The XPS is sealed to the block wall on the top and the floor on the bottom using a non-hardening acoustical sealant, all seams are sealed with tape.

BTW...I followed the recommendations given on the buildingscience web site. They have some good material to read on moisture and finishing basements.

[Bear55]

Hemi after a good bit of research I did the same thing in my basement minus the Z channel and plus the firing strips.

pearllakebulls if you really want to do it right build your walls, leave an inch or so space behind them and have someone spray foam everything. Only downside is $$$ because those spray guys aren't cheap.

[pearllakebulls]

Thanks for all the replies, fellas. If I can get over this procrastination soon I will start the project!

[SkunkedAgain]

I see that 311Hemi used a non-hardening acoustical sealant on the XPS rigid foam. I went to the big DIY center this weekend and none of the three people that I talked to had any clue what to use to seal the edges of the XPS rigid foam. The building science HSOforum just says to use a sealant.

Any recommendations?

[311Hemi]

The stuff I used was OSI Acoustical Sealant and Menards carries it. It's in the large size tubes for a large caulking gun.

Quote:

OSI® SC-170 Acoustical Sound Sealant OSI® SC-170 Acoustical Sound Sealant is specifically designed for reducing sound transmission in all types of wall partitions to maintain specified STC values. This sealant is non-hardening, non-staining and very tacky. It adheres to drywall, wood, metal, masonry, polyethylene and other building materials. SC-170 provides an air tight vapor barrier when used with polyethylene sheeting to help prevent air infiltration and the formation of condensation.

[Bear55]

I just used the PL300 that glued the rigid foam to the walls to glue the seams together. I also taped the seam in case the glue didn't seal the vapor out.

[SkunkedAgain]

Thanks for all of the advice!

My initial concern about the PL-300 adhesive was that it didn't say anything on the tube about providing an air/vapor barrier. When asked, the guy at the big box store said, "I don't know - read the label." Thanks a lot buddy...