how to attach and tape rigid foam

Discussion in 'Remodel Forum & Blog' started by Master Brian, Oct 30, 2009.

  1. Master Brian

    Master Brian DIY Senior Member

    Messages:
    368
    Location:
    Kansas
    Needing to attach some rigid foam insulation panels to a concrete block basement foundation wall. Do I use liquid nails or something else?

    Also, how do I go about taping the seams? Is there a special tape or could I possibly even use gap and crack spray foam? Not sure if that would eat into the rigid foam, if not it would seem more permanent than a tape.

    I will be building a 2x4 wall over the rigid panels, then insulating the 2x4 wall cavity with either fiberglass batting or cellulose, so I need these panels to provide a good moisture barrier so my insulation won't get wet.
  2. Lakee911

    Lakee911 I&C Engineer (mostly WWTP)

    Messages:
    1,328
    Location:
    Columbus, OH
    I've used construction adhesive before. I like the polyurethane type.

    They make a special tape for tyvek-type insulation taping. I'd use that. It's thin, but stickier than all get out. It'll stick to it just fine.
  3. North Jersey

    North Jersey New Member

    Messages:
    107
  4. frenchie

    frenchie Jack of all trades

    That's so they can sell you the pre-formed channelled foam panels.

    PL works fine.

    Spray foam doesn't eat the foam panels, but can bulge out & then you have to cut off the excess... pricey, too. But useful for filling the irrgular gaps if you had to cut around something.

    You'll need to cover the foam with sheetrock or wonderboard or something, otherwise you've got a serious fire hazard.
  5. export!

    export! DIY Member

    Messages:
    90
    Location:
    Ontario, Canada
    PL makes a foam board adhesive. Caulking tube. In Canada we use Tuck Tape to seal foam board, 6mil plastic, or house wrap. It sticks very well and maintains the vapour barrier for code.
  6. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    Tape the seams with Tuck Tape:
    [​IMG]

    LePage has PL 300 which is meant for this exact application:

    [​IMG]

    You might want to test other types of adhesives that you plan to use, some of them could eat the foam. Foam in a can does a good job of adhering rigid foam to concrete as well, but it is expensive, so I'd only use that on any cutouts or spots where tape wont cut it.

    Please do not add another vapour barrier (or housewrap) on top of the foam, once you have taped all of the seams you will have created a barrier and adding another will just create a pocket to TRAP any possible moisture.

    How do you plan on air sealing, and insulating your rim joist between the floor joists?
  7. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    This is true, you need to drywall over the studs and fibreglass when you're done.
  8. nukeman

    nukeman Nuclear Engineer

    Messages:
    709
    Location:
    VA
    In my basement project, I am using 3/4" foamboad (XPS) attached with PL 300 and using Tyvek tape for the seams. I've found that you need to use about a tube of PL 300 per sheet of foamboad to get good coverage. I am also building a 2x4 wall in front and using unfaced batts so that the cavity can dry to the inside. For the rim joist, I am using 2" XPS and filling the rim joist cavities with R30 unfaced fiberglass for additional insulation and for a fire barrier.

    On my top plate, I am using 2x6 PT lumber. This is so the top plate will go over the foamboad to create a fire block. I used PT for the top plate as it rests on top of the cinderblock wall.

    I'm using PT 2x4 for the bottom plate and I am putting sill gasket material underneath it. This keep the PT from being in direct contact with the concrete and should extend the life of everything.

    For drywall, I am still deciding. I have looked at Georgia Pacific DensArmor Plus, but many places around here no longer carry it. Lowe's has 15 sheets left here, but no longer get any new stock. I also hear that it is really difficult stuff to work with.

    You're probably well on your way on the project already, but just wanted to let you know what has worked for me so far. Also, remember hozizontal fire blocking at 10' intervals and vertical fire blocking (usually the top plate, use fire blocking foam for cracks and holes for electrical/plumbing).

    Good luck.
  9. frenchie

    frenchie Jack of all trades

    I LOVE watching engineers DIY.
  10. nukeman

    nukeman Nuclear Engineer

    Messages:
    709
    Location:
    VA

    Overkill, perhaps? :D

    I forgot to mention that I added horizontal blocking between all of the studs (eventhough they weren't needed). This way, I used up scraps, straightened out any studs that weren't straight, and sure made everything rigid as hell. :)

    Remember hot dipped galvanized nails for anything that touches the PT lumber. I used HDG nails everywhere so I didn't have to buy one type for PT lumber and another for non-PT lumber.

    I'm also a bit of a perfectionist when I make something. That plus the engineer side of me means that things take time to get done, but are also seriously overbuilt. You should see the deck I built. The ground will give away before the structure does. :lol:
  11. Master Brian

    Master Brian DIY Senior Member

    Messages:
    368
    Location:
    Kansas
    My thought was to buy a sheet of the pink rigid foam board and cut approx 7" x 16" pieces out and stick those into the space between the joists, rim joist and sill plate. I figure, which might change, that I'd stack enough to bring it close to flush with the new wall. I also thought about using some spray foam to seal the last piece to the joists, but not sure if that is a good idea or not. Don't want to trap moisture in the cavity.

    I may not have to buy a sheet, or two or three, I might have enough scrap left over from doing the walls. Just depends upon how it all lays out.
  12. Master Brian

    Master Brian DIY Senior Member

    Messages:
    368
    Location:
    Kansas
    These are my thoughts, which are subject to change. The framing is somewhat underway, but I'm not in a huge hurry....so feel free to correct me if an error is seen or a better method.

    Thanks for the heads up on the glue and tape.

    As for the batts, I thought they weren't a good idea in the basement? With that said, I have been using them for a bit of sound deadening in interior walls, to block furnace/sump pump/laundry room sounds, and in the ceiling area, to block upstairs sounds and to keep sounds from basement in basement. I realize, it's not the best method, but it does help a little and for the price, it's been an easy solution.

    So you think on the interior side of the XPS, the batting is ok? I was planning on the thin stuff, comes in an accordian bundle and is used a lot under vinyl siding, and glueing that against the wall. Then over that, I was planning on building my walls. Then filling the wall cavities with 1-1/2" pink/blue rigid foam. I'm guessing it is the XPS stuff, but I'm not sure of the tech names. They sell the white and the blue or pink. I'm bad remembering names....


    Good idea on the top plate, but I don't believe that will work well for me. In fact, only two walls, might, get top plates. The rest are going to be somewhat scabbed into place. Sounds messy and half-assed, but it's what works and is somewhat necessary in several spots. I left the gasket material out from underneath, as I wanted an escape if any moisture should get under there. Hmm... Since this is an old house, I am matching the baseboard trim with the 1"x6" stuff in the rest of the house which allows me to keep the drywall off the floor almost 2".


    I've already decided for less than about $100 more I can get the unfaced mold/mildew resistant rock. Not sure who makes it, but it's sold locally at Lowes. It will go on all exterior surfaces and at the very least on the bottom few feet of the interior walls. I am debating on using it for the ceiling, especially below ductwork or water lines. Though all are insulated well, I don't want a future mold problem.

    Over the rock I will be installing a beadboard wainscot (sp?), not sure if panel or true tongue and groove pieces. Have to price it up. When I did my bath, there didn't appear to be much savings on the panel type and the T&G looks more authentic.

    I am well under way, unfortuneatly not with the insulating or framing, but moving some duct work, water lines, etc...

    As for fireblocking. I know, it's a good idea in theory, but it is not something I'm even worried about. If this were a newer house, I'd do it. Being as this house has relatively little, if any, is there really any point?
  13. Master Brian

    Master Brian DIY Senior Member

    Messages:
    368
    Location:
    Kansas
    I will keep that in mind, but so far I have been using exterior grade decking screws for everything. My experience has been nails never drive well into the old joist material, even with a nail gun. Add to that, I don't want to create a lot of extra banging and chance knocking 100y/o plaster loose. I am also able to change my mind as I go and move studs around. Again, it's an added cost, but a minimal one.
  14. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    Wow...

    Okay. Just quickly, here if a joist is 16 ON CENTER then you subtract the width of one joist (1.5") you end up with 14.5" as a ROUGH cut... If that sounds odd to you, then you have a lot more learning to do before tackling this project.

    Nukeman, fibreglass does absolutely nothing to stop fire, and is absolutely useless as a fire barrier. Mineral fibre/rock wool is what you would require to do that.
  15. nukeman

    nukeman Nuclear Engineer

    Messages:
    709
    Location:
    VA
    To meet code, you need the vertical and horizontal fire blocking. This can be 2x material, drywall, etc. For the insulation, read this:

    http://www.buildingscience.com/documents/reports/rr-0202-basement-insulation-systems

    If you have the XPS, it becomes a vapor barrier and prevents warm/moist air from condesing on the cool wall. It also slows vapor coming from the wall to the interior. Batts are okay in this situation..if you don't used faced insulation or put up a plastic barrier. Since the ground is basically always wet, you can't dry to the outside very well. So, insulation, drywall, and paint has to let the wall dry to the inside.

    Perhaps I shouldn't have said firebarrier. Drywall will be the actual ba9in the barrier in my situation. Vertical fireblocking done with the top plate. Hortizontal fireblocking can be done with a strip of drywall (or similar) every 10' pressed tightly to the XPS.

    It sounds like you can still get the drywall I was looking at. They stopped carrying around here. I asked a few other places about here and they look at you like you are crazy when you mention paperless drywall.
    Last edited: Dec 5, 2009
  16. frenchie

    frenchie Jack of all trades

    Vapour retarder. Not barrier.


    It's a bit hellish to work with (wear a respirator & long sleeves, it's got fiberglass in it), and for a smooth surface you have to skimcoat it.
  17. nukeman

    nukeman Nuclear Engineer

    Messages:
    709
    Location:
    VA
    Yep. I also hear that it doesn't really dimple correctly when driving in screws. Perhaps it is more trouble than it's worth. I did read somewhere that they started putting a smoother surface on one side for easier finishing, but I don't know if that is true. Performance wise, it seems like a great option. Just seems hard to work with. It might be a good option for exterior walls or the bathroom where greenboard would normally be used.

    I wrote that last post quickly. I meant retarder when I said barrier.
  18. Master Brian

    Master Brian DIY Senior Member

    Messages:
    368
    Location:
    Kansas
    Sorry, I wasn't more technical for you, I just didn't want to take the time to type 14.5", which isn't even correct for my house. Old lumber, not all spaced as a house today would be spaced either. Some is 14", some is 14.25", some is 14.5", some joists are doubled up, etc....
  19. Master Brian

    Master Brian DIY Senior Member

    Messages:
    368
    Location:
    Kansas
    I may have seen that article before, it looked sort of familiar, but thank you for linkin it. I just skimmed it for my application and it was a good read.

    I like the idea, cost wise and R-value wise, of being told it's ok to use the foam against wall and then batting to the inside of that. Everyone always seems to say you don't loose a lot of heat to a basement, but that article proves it and I can feel it in my basement.

    I am curious though, do you think the 3/4" XPS with the batting on top is ok? They seem to show using 2" foam. I'm sure it's just an R-value thing, but figured I'd ask.

    Yeah, I can still get the paperless and the finishing is a bit of an issue, I've seen. I bought a couple of sheets for my hallway ceiling and a bath remodel. It is a bit rough to finish, but I plan on using beadboard wainscoting on the lower half of the walls. The ceilings and the tops of walls will likely be finished with wallpaper and ceiling paper, which tends to hide a lot of blemishes, so I shoud be good to go, if I do go that route.
  20. nukeman

    nukeman Nuclear Engineer

    Messages:
    709
    Location:
    VA
    I think that the 3/4" is just fine. Thicker will give higher R value and lower perm. This combo (XPS/batts) should work well and keep cost down. It would be a pain to cut the foam to fit between the studs. The spray in insulation works well, but it is expensive and makes it harder to run wires in the future. In my case, it is a walkout basement, so half is above grade. The rim joists were not insulated before and there was 2" thick fibergass compressed in the 1.5" furring space. I have AC and will probably run a dehumidifier as needed in the summer.

    From the article:

    Walls with 3.5 inches of extruded polystyrene (XPS) and no vapor barrier performed the best in this analysis. However, walls with 0.75 inches of extruded polystyrene and 3.5 inches of fiberglass batt insulation in the cavity would perform well as long as interior humidity was controlled below 50 percent during the summer. Increasing the extruded polystyrene to 1.0 or 1.5 inches would improve performance even with higher interior relative humidity during the summer months. This part of the analysis assumed that the concrete wall had a relative humidity of 100 percent at the exterior temperature. Since these studies were for a climate location similar to Minnesota, the thickness of rigid insulation (R-value) could be proportionately reduced in milder climates.



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