Hi all,
I’ve read the other posts, www.buildingscience.com articles, etc., and I still have some questions about foam panel walls in a basement.
The basement is below grade, ceramic block walls, with two stories of brick over 2×4 framing above. Although the walls occasionally feel moist, there are no leaks even during big rainstorms and all of the grading, gutter, & downspouts are fine. It looks like the walls have had some leaks in the past – I’ve been in the house 4 years and did the grading, gutters, etc. The house was built around 1938 and the location is in Maryland.
I plan to install foam panels directly against the interior walls and strap them with 1×4 for the wall covering.
Here are the questions:
- Should I use expanded foam or extruded foam? Expanded foam is more “porous†and more permeable to water vapor, thereby allowing the walls to “dry to the inside.†But does this make it the better choice? Which is the better product for basement walls?
- What brands of foam come with the borate? Is it recommended?
- I like to use the PL polyurethane adhesive for general construction. Should I use it to attach the foam panels to the wall and to each other?
- Do the expanding foam sealants work as gap fillers with the foam board, or will they melt it?
- Should I use some kind of tape on the foam board joints?
- There is no paint on the walls. Is it worthwhile to paint them with Drylok before covering with foam?
- At the top of the wall but below the ceiling joists are the 2x wood plates for the first story wall. They are set on cement – no sill seal in those days – so they may wick moisture. Should I cover them with the foam board? I worry that they will stay wet and not dry out if I cover them with foam, but if I don’t cover them then moisture will condense on them because of the cooler surface and no vapor barrier.
- Do you have any suggestions for attaching the 1×4 strapping to the hollow ceramic block wall? The ceramic block is too hard and brittle for Tapcons or ramset fasteners, and I can’t locate the mortar joints through the foam. In the past I have drilled for expanding anchors. Any other ideas?
- I understand that ½ inch sheetrock is recommended as a heat barrier for the foam board. Will code generally allow 7/8 inch wood T&G boards instead of the drywall? Or should the T&G go over the drywall? I hate to have the mold-loving drywall sandwiched in the wall but I’ll do it if required for fire protection.
- How do you run the electric cabling in the walls? Will code generally allow BX armored cabling to be run between the foam and the sheetrock, and hollowing out the foam for the boxes? (An electrician will do the work but I want to know for planning purposes.)
Thanks in advance.
Billy
Replies
I really can't answer any of those questions, but have had the exact same my questions myself. There seems to be no concensus, so you need to digest whatever feedback you get back and decide for yourself.
In my case, we have a similiar wall (concrete block, no big leaks now, but clearly there was at one point, brick above on stick-framing). I'm going to be putting 4x8 sheets of EPS foam along the upper 4 ft. of the wall, leaving the lower 4' uncovered. I'm not using a VB, nor taping/sealing the foam. Then 2x4 (or 2x2) metal studs, upper 4' sheetrocked (probably blue-board), lower 4' a removable wainscotting. The idea is that the walls will be 'breathable' so any moisture won't be trapped on either side. The removeable wainscotting is in case there ever is a major water problem (doubtful) and more for just having easy access (we may add HW heat later, as well as additional wiring potentially).
I'm curious as to the answer to #1 as well. We're going with the pink stuff just because it is thinner per r-value. Saves some space.
The Drylock, AFAIK, is only useful as a pseudo VB. It doesn't actually stop leaks (as the previous owners so eloquently proved in their attempts).
I also have the same question re: #7. Our joist 'holes' are filled with cement and then the same 2x plate. I didn't want to cover them for the same reasons (didn't want to trap moisture) yet I assume that's a big area of heat loss. I also think that's where some of our basement creepy crawlies come in (namely house centipedes)...so I'm tempted to at least spray the edges with foam to seal off air movement.
Again, though, this is just my final decision based on asking the same questions numerous times and reading various articles.
My plant/ tree guy told me to spray my concrete walls with a mild hydrated lime solution before installing the foam. He says that mold doesn't like an alkaline environment.
I believe the ( bug resistant) borate impregnated foam is designed for exterior applications.
http://oikos.com/esb/43/afm.html
I would probably cover that 2X4 plate with a good dose of low expansion spray foam.
I too am considering expanded foam on the interior of my unfinished basement and have alot of the same questions. I don't envy you, attaching to ceramic is going to suck!
1) Exstruded foam is a better choice. More durable and less porous
2)Check with manufacturer.
3)Use only an adhesive that specifically says it is safe for polystyrene.
4)To my knowledge exp. foams will not melt polystyrene but see #2
5)Only if you like wearing a belt and suspenders!
6)That would be your call
7)Insulate them
8)Build a wall out of 2x2's, fasten at top and bottom and use some of the adhesive from #3 to bond the middle to the foam to stiffen it up.
9) check with local builing code dude
10)Another reason to build a wall out of 2x2 or 2x3, spaced out fro the faom so cable can be run behind w/o drilling.
Mr T
Do not try this at home!
I am an Experienced Professional!
Thanks Mr. T,
You busted me on reply #5. ;-)
I like your idea with the 2x2s -- much easier to build a plumb wall and it will eliminate most of the holes that I would have had to drill into the ceramic block.
On #7, the plates have masonry underneath and brick outside, so the plates will wick moisture from the structure -- although insulation will prevent condensation it may also largely prevent drying of the wood? Or not? Is it still better to insulate?
Thanks again for your quick on-target reply.
Billy
I posted a similar question, but with must different details the otherday, but have not responses.
http://forums.prospero.com/tp-breaktime/messages?msg=38726.1
"5)Only if you like wearing a belt and suspenders!" (about sealing and taping the foam joints).
It problably won't matter in this case since he will have a tight fit agains the wall. But in my case the foam will stand out 1-2" from the wall and I am going to seal it because I don't want a way for humid summer air to move behind it and condense on the cool foundation wall.
AFAIK borated treated foam is only available in the expanded foam.
But I see little need for it.
"At the top of the wall but below the ceiling joists are the 2x wood plates for the first story wall. They are set on cement – no sill seal in those days – so they may wick moisture. "
Now I am not a pro and have limited experience, but lets look at the possibilities, both moisture and termits.
Termites - the only place that I can see that termites can get into this structure would be from the the outside via the mud sill. Which then can do know. The only difference would be that this area will be closed and not open to inspection. But termites now can go directly from that plate to the joist and not bee seen. I see that is something to control from the outside.
Moisture - how does it dry now. Some through the 2" edge, which will be covered with foam now. Some through the joist, but my guess is that most of it would be my air circulating on the top of the sill between the joist. I don' know know exactly what all he is doing, but I suspect that area will either befilled with insulation or at the least the flow will be blocked/reduced.
The question is how much moisture is there. How about a test. Cover the top of the plate in joist bay with plastic during a wet period and wait a week and then check for moisture. Even better if he has a moisture test available he can use that and compare it with sill plate in an area that was not covered and with the joist.
Something that might help would be to go ahead and treat the area with borate surface coatings.
Also the plate could be extened with some 2by material (maybe even PT) so that form the top plate to the new wall and the DW would directly attach to it.
Hi. I was reading a thread the other day and it had some of what you may be looking for. Also use the search function and there are more discussions on it.
The thread I was in started with #38507.1
It also has some good pictures for review.
Clay
Clay & all,
I saw that thread and it was good, but I still had questions.
Building Sciences has some good articles on basement insulation problems and systems here:
http://www.buildingscience.com/resources/foundations/default.htm
and a short article on best practices for basements here:
http://www.buildingscience.com/resources/foundations/renovating_your_basement.pdf
BTW, the basement walls previously had 7/8 inch pine T&G boards over 1x6 furring strips. No insulation -- just an airspace between the paneling and the block walls. Most leaks would not touch the finished wall (floor was a different story) and the T&G wall could dry from both sides. It worked pretty well for probably 50 years, but the dust and critters sure enjoyed the space between the T&G and masonry.
Wood or some other wall material seems to be a better choice than drywall for basements. Are there good alternatives to paper-backed gypsum or concrete backerboard?
Interesting thought on the removable wainscoating just in case there's a leak.
The floors will be ceramic tile set over self-leveling cement and underfloor heat over Wedi insulating/backerboard.
Billy
Edited 1/13/2004 11:22:50 AM ET by Billy
I'll go and look at the site tomorrow, just got done working.
The other approach is to stop the moisture at the starting point. hickory backhoe and water proof the foundation from the outside with perimeter drains Ug I know. But that's one solution if your real energetic.
Clay
Just happened across this while searching for something else. Have no idea if it is actually any good:
http://oikos.com/esb/45/truewall.html
billy.. try this thread..
http://forums.prospero.com/tp-breaktime/messages?msg=38726.1
Mike Smith Rhode Island : Design / Build / Repair / Restore
Thanks...
Does anyone attach the foam panels with non-expanding spray foam as opposed to construction adhesive? It seems that it would be easier to get good contact with the wall using the spray foam. And it would dry more quickly. The stuff sticks to everything so it seems that it would be a good adhesive for foam, but I don't know.
On the other hand, the slight expansion of the foam as it dries could push the boards away from the wall.
I am sure someone has tried this -- how well does it work?
Billy
Yeah, the stuff sticks to everything it shouldn't. But does it have any strength beyond what it needs to support it's own weight?
Well now that you ask, yes it does have strength to support more than its own weight. That's part of the reason people say that foamed in place insulation reduces house creaks, improves structural rigidity, etc.
The question was whether anyone has used it adhere foam panels to masonry walls, and how well does it work for this application. Furring or sticks will provide additional mechanical support.
Billy
Hi Billy.
I've got a personel project going right now that is on the interior wall of a 90 year old hse. The exterior is brick and it has a liner course of Adobe, then 3 coat plaster. Plus I need to save any framing space possible. There are no water problems known. Lets see if I can get these pictures to this page. If you work with the foam after it's out and you work it it colapses. Also roofing systems have used foam to apply sheathing for quite a while.The process is slow but seems to do a nice job.
Plus if your wife needs to wax for hair removal, just use crazy foam and .
Clay
Edited 1/14/2004 10:26:45 AM ET by Clay
I'm trying to get a picture of the back of the foam, and I see that 2 of the files of the picture are actually video. So let's see if the 3rd is a charm.
Clay
Ok Last one I promise, I need to figure out how to keep the picture to a small amount of pdf bits.
This one shows a full panel with some sticks to keep pressure on it while it cures. This is the same thing that is going to hold the sheet rock on.
Clay
Hi Clay,
Nice work, and thanks for the pics.
Did you use non-expanding foam?
On the walls, did you use any clamps or screws to hold the foamboard in place until the foam dried? Did the foamboard stay flat after you pressed it down?
Attached is a photo of my walls -- the lower wall is wider than the upper wall, so it makes it easy to use thicker foam above and thinner foam at the bottom which is well below grade.
Billy
Off topic -- the house is generally very well built -- 3 inch wide joists, etc., but it has always bothered me that the stairs creaked badly. When it came time to do the basement one of the first things I did was to knock out the plaster and wire mesh ceiling in the stairwell to the basement so I could get access underneath the stairs above.
Check out the gaps between the stringer cuts and the stair treads and risers. The damn stairs were floating in air! Apparently they let jacklegs on construction jobs even back in 1938. I glued and screwed blocks in place and the steps are rock solid now.
Billy
If you look at the last picture the 2xs are wedged to hold it flat while it cures. I used both minimal and 3x expanding only cause I ran out, so far from what I can tell it's all working good. If you do a test piece of flat anything,piece of sheet rock or foam or plywood and run a bead of foam, and press it then pull it apart after a little while it kind of collapses most of the expansion.
Plus the deal with what I'm working with is behind the plaster is adobe liner brick which is useless for any holding power. Once its cured it is exactly where you hold it to with the jacks it doesn't move and it's feels better then you would have thought.
Have a little slack for me on the E front, I'm still trying to get all the fancy E tools to work. I'm still learn'n there language.
The stair pictures look like the carpenter cut the stringers but left the job and let the handicapped helper finish them off. plus in those days they didn't have construction adhesive.
Clay
Edited 1/14/2004 1:38:05 PM ET by Clay
Thanks Clay,
The first time I quickly looked at the photo and I thought it was the ceiling -- I see your clamping method now.
It seems that spraying the foam on the panels will go a heck of a lot faster than using a manual caulk gun to apply construction adhesive. And since it covers more surface area on the foamboard, it may have better overall holding power. With a bead of construction adhesive, it is a real mismatch to have hundreds of pounds of holding power on a 1/4 inch wide strip of flimsy foamboard.
Billy
Mike did you mean to link to my thread or did you mean to link to one showing your "system" of foam and osb?
If you ment to link to my does that mean that you thing that my idea of "foam wall" is workable?
Thanks, Bill.
bill... i'm dazed & confused.. there are so many threads discussing basement insulation that i got lost ..
almost anything is workable... i was trying to link to the thread that showed pics of the foam & OSB panels i used..Mike Smith Rhode Island : Design / Build / Repair / Restore