My Neverending Basement Project.........(long)

[thefed]

The guy said once they break up the floor, and replace the drain tile, they have to repour the floor 1/2 inch thinner.

The framing is top to footer board, all 2X4, They would have to all be cut off on the bottom and then spliced together........he was pretty adamant about it.........

yeah, that sucks. to make it really effective, you should be going all the way to the ceiling with some sort of plastic....so if those verticals are touching the wall they need to come out entirely...if theres even 1 cm of room behind, which there should be, you can run the plastic up....but you'd still need to remove that bottom sill plate. although, there should be a vapor barrier behind the studs already...what did they use?




ive seen too many basements...NICE basements....moldy due to not taking this step. *i* didnt take this step and wish i did....6 years ago i had no clue. now i'm in the mold industry it makes me sick! all basements leak...its just a matter of when. you kill 2 birds here...vapor barrier and leak prevention....never a worry. even condensation behind those studs/drywall will cause issues/damp smells over time...thus the need for a proper vapor barrier.

'll pm you some pics/links

 

[samclem]

There's a lot of debate concerning the advisability of using plastic against a below-grade masonry wall. I agree that it seems a good way to get liquid water that comes through the wall down to your drainage system. On the other hand, adding the plastic assures that there will be virtually no drying to the inside of the room, that any water vapor that comes through the wall will remain stuck behind that plastic. That can become a mold colony--I don't know what the mold is eating, but it can happen.

Insulation is another big issue--fiberglass is not the best answer usually, unless an inch or so of rigid foam insulation is placed against the masonry first. Given typical inside and outside temperatures, the foam assures that air inside the room does not encounter a "condensing surface"--a surface below the dew point of the inside air. If the foam isn't there, water vapor from inside the room easily flows through the fiberglass insulation, reaches the cold concrete wall and/or plastic, condenses, and forms a mold colony inside the fiberglass. Adding another vapor barrier on the inside of the wall is doomed to failure--two vapor barriers is always a no-no. The second link below has a few pictures of the mold that results with two vapor barriers. Bad.

With the foam against the wall and proper detailing, you've got a barrier that stops liquid water that leaks in from the outside from reaching your wood and fiberglass (if you use fiberglass). If you have an inside perimeter drain, the water will go into it if you've left a way for the water to get tot he pipe. The foam "breathes" a limited amount--mass air (with H20 vapor) can't pass through it, but it does allow water vapor to permeate. So, a wet wall can dry. Expanded polystyrene foam ("beadboard") has a perm rating of above 1.0 per inch of thickness, which will allow limited drying to the inside. That's what we want.

Here's a good site explaining everything briefly.
More, with more detailed explanations.

When I do my basement I'm going with 2" of rigid foam and furring strips to hold it to the wall and to which I will affix the drywall. I'm using the type of drywall without any paper on it to help avoid mold. I'll keep the drywall at least 1" above the floor (covered by a plastic baseboard) in case the water finds it's way in (or a burst pipe in the basement pumps it in). I spent a lot of time last year digging an external drain below the level of the footers and another to take care of ground water higher up, so I think I've done all I can on the outside of the house.

 

[thefed]

There's a lot of debate concerning the advisability of using plastic against a below-grade masonry wall. I agree that it seems a good way to get liquid water that comes through the wall down to your drainage system. On the other hand, adding the plastic assures that there will be virtually no drying to the inside of the room, that any water vapor that comes through the wall will remain stuck behind that plastic. That can become a mold colony--I don't know what the mold is eating, but it can happen.

Insulation is another big issue--fiberglass is not the best answer usually, unless an inch or so of rigid foam insulation is placed against the masonry first. Given typical inside and outside temperatures, the foam assures that air inside the room does not encounter a "condensing surface"--a surface below the dew point of the inside air. If the foam isn't there, water vapor from inside the room easily flows through the fiberglass insulation, reaches the cold concrete wall and/or plastic, condenses, and forms a mold colony inside the fiberglass. Adding another vapor barrier on the inside of the wall is doomed to failure--two vapor barriers is always a no-no. The second link below has a few pictures of the mold that results with two vapor barriers. Bad.

With the foam against the wall and proper detailing, you've got a barrier that stops liquid water that leaks in from the outside from reaching your wood and fiberglass (if you use fiberglass). If you have an inside perimeter drain, the water will go into it if you've left a way for the water to get tot he pipe. The foam "breathes" a limited amount--mass air (with H20 vapor) can't pass through it, but it does allow water vapor to permeate. So, a wet wall can dry. Expanded polystyrene foam ("beadboard") has a perm rating of above 1.0 per inch of thickness, which will allow limited drying to the inside. That's what we want.

Here's a good site explaining everything briefly.
More, with more detailed explanations.

When I do my basement I'm going with 2" of rigid foam and furring strips to hold it to the wall and to which I will affix the drywall. I'm using the type of drywall without any paper on it to help avoid mold. I'll keep the drywall at least 1" above the floor (covered by a plastic baseboard) in case the water finds it's way in (or a burst pipe in the basement pumps it in). I spent a lot of time last year digging an external drain below the level of the footers and another to take care of ground water higher up, so I think I've done all I can on the outside of the house.

How will you be attaching the furring strips to the xps? once you penetrate a vapor barrier of any sort, you are diminishing its effectiveness

I do like the xps vs plastic because you get the added benefit of a thermal break....the process i was explaining above is the most cost effective....and you're right to wonder what exactly mold would feed off of in a cinder block and plastic sandwich

 

[samclem]

How will you be attaching the furring strips to the xps? once you penetrate a vapor barrier of any sort, you are diminishing its effectiveness

I'll be using expanded polystyrene (EPS) (it has a higher perm rate than XPS). I bought some with borate in it to help reduce potential problems with mold and termites. It's not a guarantee, but it's better than nuthin. The EPS has a slightly lower R-rating than EPS, but I was most worried about keeping the wall dry.
I'm going to Tapcon the furring strips through the foam to the wall. Drill, inject caulk into the hole, drive the screw. In addition, I'll put a bead of EPS-compatible expanding foam adhesive on the foam before putting it against the block wall. More of the same at the joints where the panels meet. Nothing is perfect, but keeping inside air away from the cold block wall is the key to avoiding condensation moisture. With this, plus allowing drying through the foam, I'm fairly sure I can avoid any nasty surprises.

I'm still trying to decide what to do about the rim joist (at the top of the block wall). The pros advise insulating it with spray insulation--it is expensive, but it does a good job and prevents room air from condensing against the wood and causing mold. I'd go for it, but I wonder about termites. They tend to come up through the cracks in the blocks and it is very handy to be able to see or test for their presence in the rim joist or to see their mud tunnels to know if you've got a problem. If I cover that rim jost I won't be able to detect the little devils before they eat my house. Some folks leave 1-2" inspection strip exposed, I might do that.

 

[FinanceDude]

Everyone I talked to about this says DO NOT put a vapor barrier between the block and studs, or the block and insulation, and I mean everyone.

Would not the plastic sheeting cause other problemsl? I always thought you want walls to "breathe" some. ALL the basement guys I am dealing with are AGAINST putting insulation AND a vapor barrier on the wall. They say you want some inside air to get to the block on the inside of the foundation, particularly from the ground to the frostline. Seems you guys are saying the exact opposite??

 

[Keim]

Everyone I talked to about this says DO NOT put a vapor barrier between the block and studs, or the block and insulation, and I mean everyone.

Would not the plastic sheeting cause other problemsl? I always thought you want walls to "breathe" some. ALL the basement guys I am dealing with are AGAINST putting insulation AND a vapor barrier on the wall. They say you want some inside air to get to the block on the inside of the foundation, particularly from the ground to the frostline. Seems you guys are saying the exact opposite??

That matches what we were told, and did, when we finished our basement.

 

[Martha]

Everyone I talked to about this says DO NOT put a vapor barrier between the block and studs, or the block and insulation, and I mean everyone.

Would not the plastic sheeting cause other problemsl? I always thought you want walls to "breathe" some. ALL the basement guys I am dealing with are AGAINST putting insulation AND a vapor barrier on the wall. They say you want some inside air to get to the block on the inside of the foundation, particularly from the ground to the frostline. Seems you guys are saying the exact opposite??

Does it depend on what part of the county you are from?

 

[FinanceDude]

Does it depend on what part of the county you are from?

Yeah, I doubt Florida has a lot of frostline problems........

 

[samclem]

Everyone I talked to about this says DO NOT put a vapor barrier between the block and studs, or the block and insulation, and I mean everyone.

Would not the plastic sheeting cause other problemsl? I always thought you want walls to "breathe" some. ALL the basement guys I am dealing with are AGAINST putting insulation AND a vapor barrier on the wall. They say you want some inside air to get to the block on the inside of the foundation, particularly from the ground to the frostline. Seems you guys are saying the exact opposite??

Where you live does make a difference regarding placement of insulation and vapor barriers. You can pick one one of the 18 house profiles on this page and match the basement insulation approach.

"Vapor barriers" come in various "strengths", and this makes a big difference in what they do. I don't know what type your experts are objecting to.
- Vapor impermeable: =< 0.1 perm. Example: Plastic sheeting
- Vapor semi-impermeable: .1 perm to 1.0 perm. Example: Extruded polystyrene ("XPS," usually blue or pink) (unfaced) 1" thick
- Vapor semi-permeable: > 1.0 perm. Example: Expanded Polysterene ("EPS", unfaced, less than 3" thick).

More examples of perm ratings are at the pdf file on this page (pages 7-8).

What you want is an air barrier to prevent the warmer inside air from coming in contact with the cold block wall. Foam does this.

From Building Science Corp Info Sheet 511: Basement Insulation

Walls

Basement walls should be insulated with non-water sensitive insulation that prevents interior air from contacting cold basement surfaces—the concrete structural elements and the rim joist framing. Allowing interior air (that is usually full of moisture, especially in the humid summer months) to touch cold surfaces will cause condensation and wetting, rather than the desired drying. The structural elements of below grade walls are cold (concrete is in direct contact with the ground)—especially when insulated on the interior. Of particular concern are rim joist areas—which are cold not only during the summer but also during the winter. This is why it is important that interior insulation assemblies be constructed as airtight as possible.
The best insulations to use are foam based and should allow the foundation wall assembly to dry inwards. The foam insulation layer should generally be vapor semi impermeable (greater than 0.1 perm), vapor semi permeable (greater than 1.0 perm) or vapor permeable (greater than 10 perm) (Lstiburek, 2004). The greater the permeance the greater the inward drying and therefore the lower the risk of excessive moisture accumulation.
Up to two inches of unfaced extruded polystyrene (R-10), four inches of unfaced expanded polystyrene (R-15), three inches of closed cell medium density spray polyurethane foam (R-18) and ten inches of open cell low density spray foam (R-35) meet these permeability requirements.

Fiberglass is not the best insulation to use below grade because basements tend to be damp and fiberglass (esp the binders in it) can grow mold. It also does not block air movement, and can allow warm inside air to move to the colder surfaces (e.g. your block wall) where the wate rin it condenses. Liquid water can breed mold. Yuck. It is possible to use fiberglass successfully, but this is best done by first putting rigid foam against the wall to assure the air inside the air can't reach a cold condensing surface. I'll just use slightly thicker foam.

If you or your tradesmen want to read more:
-- Page with a link to a presentation on Renovating Existing Basements

Basement water management and insulation is tricky business. To make matters worse, in many parts of the country for many years buildings codes were flat out wrong (e.g. directing installation of "impermeable" vapor barriers on the innermost surfaces of walls, which has led to a huge mold problem in the affected areas.)

Good luck!