Framing against block wall (1 Viewer)

[Patrick.C]

My basement (and future site of my home theater) is mostly underground with a door in one corner where the lot slopes down. The inner part of the space is already framed around the stairs and I will be framing against the perimeter block walls. Most of the HT contruction photos that I've come across on the web have had conventional framing done against block or poured walls. But the friends and family that I've consulted with on this project have all suggested nailing the studs directly to the block "face down" as opposed to normal framing where only the edge of the stud is against the wall. When I inquired about insulation, the reply was "What insulation? You have the best insulation going - you're underground.". Nailing the studs directly to the wall would certainly be easier, but I want to do it right if that isn't the proper way.

Opinions?

 

[DaveHo]

Even though you live in a warm climate I wouldn't recommend that. There will still be a temperature differential between the finished and unfinished sides of the wall. Moisture will move from the warmer finished side to the colder unfinished. The lack of a vapor barrier and the lack of airflow over the block wall caused by nailing directly to it could spur mold growth. Not to mention the fact that it will be a pain to do any wiring on those walls as you'll be forced to use the shallow electrical boxes. That is how basements used to be framed out in the old days...

-Dave

 

[Nick P]

I concur with Dave. Go with traditional framing held off the foundation by 1 inch and insulate the new stud wall.

 

[Patrick.C]

Why 1 inch from the floor? And how is this done? Stacked soles?

 

[MarkMel]

He means build the wall 1" from the block wall. Leave a 1" space between the bloc wall and the conventionally framed wall.

 

[Aaron Gould]

I put in Roxul rock-wool in place of standard insulation. According to the Roxul's specs, it resists moisture, thus greatly reducing the possibility of mold/mildew.

 

[Nick P]

What MarkMel said. You want the airspace to prevent moisture transfer to the wood studs. For the bottom 2x4 plate you should use a pressure treated stud.

 

[Patrick.C]

Ok - got it. Is there a need for an extra layer of insulation then to fill the extra depth?

 

[PhilBoy]

When I framed my basement, I built the walls on the floor (I think 1/4" shorter than the lowest ceiling height), so that when the wall is finished you simply 'flip' it up into place.

Before lifting the wall into place, I backed the framed wall with black construction (roofing) paper, thus giving an additional moisture barrier against the block wall and a back to hold the insulation in place.

 

[David WS]

I used a paint/concrete sealer on my block walls first, then I framed with 2x4 studs, insulation, vaporbarrior (8 mil poly) and finally drywall. My basement is noticably more comfortable. I've read that as much as 1/5 of your heating costs can escape through cinderblock basement walls. Do what others above mention. You'll never regret doing the extra work to make it right, you will regret doing it on the cheap or lazy.

Just my $.02

Dave

 

[Patrick.C]

Dave - is your framing an inch away from the wall and is the poly vapor barrier between the drywall and the studs or the studs and the block?

 

[David WS]

The studs are right up against the wall. The vapor barrier is between the studs and the drywall.

bloack Wall -> paint/sealer - > studs -> insulation(between studs) -> vapor barrier - > drywall.

I didn't leave a space between the blocks and the studs for two reasons. 1) I didn't want to lose the space. 2) I kept thinking that it would give a mouse or other creature a perfect place to live.

I don't have a mouse problem or anything but it just seemed like a bad idea. I could see a whole mouse society living in that space. Maybe I'm just parinoid.

Dave

 

[Patrick.C]

I was thinking the exact same thing.

One more question if you don't mind - what kind of paint/sealer did you use? A friend in the water proofing biz recommened a product called ProKote. I have him trying to get me a 5 gal. bucket of it.

 

[David WS]

I used a product from Menards call UGL (?) dry-lock. (I think that was the name) It comes in a 5 gal bucket and goes on real thick. It is designed to soak in a 1/8 inch or so and then seal up. It really did the job.

 

[SteveFred]

Hi everyone,

Yes always do standard framing even when in the basement with block/poured walls.

I bought a house in 98 (house was built in 56 and the basement was probably done in the 70's)and they had all the framing with 1x2's bolted to the walls and actually carved out the block to get the electrical boxes in.

I ripped out every last board in the basement and re did it, the basement went from being cold to very comfortable.

I am about to embark on a new HT project in less than 4 week. My new house will be complete on Aug 12th.

Home pics and future HT pics on my www button above my post

Steve

 

[KenA]

From everything I read, you shouldn't use a vapor barier or fiber insulation. They both cause all kinds of problems with mildew and trapped air. Check out this document from Buildingscience.com. I'm using their advice and installing 1" XPS against the wall with studs holding it in place. You can go with firing strips if you want to save room.

 

[David WS]

In my city you are required to have a vapor barrier. XPS is a insulator and vapor barrier in one. Hence the need for foil tape to seal the joints between sheets. I can see the issue with mold growing inside of fiberglass insulation. The thing that I don't understand is why mold won't grow BEHIND the XPS as well. If moisture seeps into the concrete wall and finds its way to the inside surface, it will be a cool damp surface. Mold will grow there just as easily.

I spoke to a rep from a insulation company at a building show last winter. He sells the spray-in/expanding insulation systems. He told me that he was pushing the state to allow his system to be used without a separate vapor barrier. He is working with a building group that claims allowing moisture to freely move in and out of basement walls will reduce problems. He said that so far they had not gotten approval. He also added that instead of a poly vapor barrier, they would require the use of a paint that has a higher ability to retard moisture penetration into the drywall.

I don't think anybody would say that a vapor barrier is not needed in a basement. The key is to keep moisture as far away from the line where cold and warm air will meet. That's why I sealed my concrete wall and used a vapor barrier on the inside of the 2x4's.

BTW. The picture of all the mold in that PDF is quite dubious. The mold is growing under a WINDOW. I'd bet that window leaks like a seive. Of course mold will grow in that situation.