Uneven walkout basement external wall's insulation

Discussion in 'Remodel Forum & Blog' started by ziit, Feb 2, 2013.

  1. ziit

    ziit New Member

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    Ontario
    Hello,
    I'm preparing to finish my walkout basement. All basement has drywalls just the external wall not. Basement has no water problems (the house is on hill and the balcony is above the wall that I want to work on) and is relatively warm also all wall is painted.The problem is that the wall is uneven. I want to use rigid foam and 1x3 attached right to the wall, but the upper part is disaster. Not just different uneven, but different material too (concrete and probably dry wall or wood). Because it's not a big surface I want to level the wall's upper part with some wood shims (pieces of 2x2 or 1x3) and use can spray foam to fill into empty spaces between the rigid foam and the wall. Does it sound totally stupid or it's possibility? here are a few pic for more visuals. Will be very thankful for any advice.

    IMG_6184c.jpg IMG_6185c.jpg wall.jpg
  2. cacher_chick

    cacher_chick Test, Don't Guess!

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    I would use an appropriate thickness of foam board to shim it out even with the concrete, and then foam board the entire wall over that. The fanfold foam is about 1/4" thick, and can be applied in layers to fine-tune your thickness.

    You will need to use strips of wood to shim out all your window and door frames so you can apply window and door casing when the drywall is complete.
  3. ziit

    ziit New Member

    Messages:
    11
    Location:
    Ontario
    Thank you for the quick answer. That is the problem, in Canada to find folding foam - mission impossible. So far I couldn't find, the thinnest rigid foam is 0.5"
    You gave me another idea - if I will even vertically the surface with some wood strips/shims (that later will work for windows and doors casing), then use 0.5" rigid foam and spray foam in between the strips (we are talking here just about the upper part) and then put full rigid foam which should attach to the sprayed foam (I think so) and even from top to bottom? The difference from one side to other varies approximately from 4cm to 1 cm. Am I too obsessed with spray foam? but in my case it looks like the simplest way to go with this kind of jazzy wall:) I just not sure if it's OK to use spray foam on external wall?!
  4. cacher_chick

    cacher_chick Test, Don't Guess!

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    Once of my concerns would be what is behind the board? Is is a hollow cavity or maybe has some fiberglass batting in it? Air sealing would be my primary concern before going further. The spray foam is not an adhesive. They made caulk-style tubes of foam board adhesive which is meant for that purpose. Because you only have to shim a small area, you could layer some strips of foam sill plate gasket or fan-fold insulation. Wood shims would work. Trying to fill gaps with expanding spray foam and to have everything come out flat and flush would be possible, but probably more challenging than of value.

    Personally, I would never finish a wall with furring strips, as it prohibits running electric and plumbing in the wall. If you are finishing a room, it is required to have electrical receptacles and lighting, and I don't care for the surface mounting options.

    There is some great reading on basement finishing in regards to insulation here- http://www.buildingscience.com/search?SearchableText=basement insulation
    Last edited: Feb 3, 2013
  5. Dana

    Dana In the trades

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    The problem with filling in behind less-rigid materials with can-foam is that the expansion pressure can be fairly high, so it won't really sit very flat. (Even when using closed cell foam between framing they usually leave a centimeter or so of space because the stuff is so difficult to trim flat.)

    If you have more than 2cm of depth to fill and you're dying to try a spray foam solution buy a 12 board foot "FrothPak" from many home center stores and you can fill up a reasonable amount of space. It's more expensive than rigid foam, but goes up really quickly. Any left over material can be used to seal up other stuff.

    It's fine to use closed cell foam on exterior walls, but if it's more than ~5cm thick you don't want to sandwich wood between it and a poly vapor barrier or it will create something of a moisture trap. If it's 6-7cm at some thick spot but less than 5cm on average you'll be fine.

    Air-leakage transport of moisture is by far a bigger problem than vapor diffusion, and foam is inherently self-sealing.
  6. ziit

    ziit New Member

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    Location:
    Ontario
    Thank you all for suggestions. I'm reading and reading and more measuring and measuring and appears that the wall is total disaster, more uneven (everywhere) then I thought from the beginning. I'm thinking of going with "normal" framing and fiberglass batts (and I hate fiberglass:() "FrothPak" sounds very very tempting, but my "little" project will go over the roof with all these goodies:rolleyes: need to do some math:)
  7. Dana

    Dana In the trades

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    Buying closed cell foam in 12 bd-ft FrothPak kits is about 3x the cost of buying the same volume of foam in rigid XPS form, but you can even-up uneven surfaces with it.

    The material stackup of the existing walls and any insulation matter in terms of what you do with the rest, the biggest problem area being pre-existing poly vapor barriers. In a new stackup you may need to get rid of any prior vapor retarders, or you'll need to skip interior side vapor retarders &/or balance the R-values of the insulation outside the vapor barrier & interior side vapor barrier to keep the average temp at the vapor barrier above the dew point of the air.

    For insulating concrete foundations it's usually better to use some amount of rigid-foam against the concrete and trap it to the wall with a studwall, then insulate the studwall with unfaced stone wool or fiberglass. This can work for your wood sections as well, but to get the R-balance right we need to know the existing constuction stackup, and your location (for weather data/climate information- Ontario is a big place, covering climates ranging from near-arctic to fairly temperate near the southern Great Lakes shores, and the "right" stackup will vary.)
  8. ziit

    ziit New Member

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    The location is Toronto and the house is townhouse, so from all other sides we have "insulation", also the external wall that I'm talking about is brick faced from outside (if that was the question about stackup?)
  9. Dana

    Dana In the trades

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    Brick veneer over a studwall with a vented cavity between structural sheathing & brick?

    Brick veneer outside of a poured concrete wall, with (or without) vented cavity between concrete & brick?

    Are there any vapor barriers (poly or foil) or vapor retarders (foam insulation or kraft facers) in the stackup?
  10. ziit

    ziit New Member

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    Location:
    Ontario
    What i can see (including the garage that is part of ground floor) and feel, it's the second option(with vented cavities). The house has been built in 80ies, so I don't think there is any foam insulation....
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