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Very Very Confused on Insulating a Basement

Post in 'DIY and General non-hearth advice' started by daveswoodhauler, Dec 15, 2009.

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  1. Gooserider

    Gooserider Mod Emeritus

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    For what it's worth, someone in another thread mentioned this Sanitred outfit as a possible source for stuff that might be useful in lining a thermal storage tank... Not sure if it would be suitable for that application w/o doing some conversation with their tech support department folks as its not mentioned, but they were doing a lot of pushing on basement waterproofing and radon control applications...

    I am NOT recommending them, but it does look like interesting stuff if one believes their claims, (I did feel my "hype" detector going off) and it sounds like your crack is the kind of application that they had in mind for the product. Might be worth talking to them and seeing what they have to say. The stuff is pricey, but probably less than a lot of the alternatives, and might be good IF it works...

    Gooserider

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  2. daveswoodhauler

    daveswoodhauler Minister of Fire

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    Thanks Dave.
    Its a poured concrete foundation wall. The crack is in the center of the wall (Foundation is 36 feet long by 24 feet wide), and wall height is appx 8 feet high.
    From the looks of it, it looks like the crack started from the top and worked its way down.
    Looks like the crack ran about 4 feet down when the prior owners tried to use some bathroom cauling or something, and now the crack runs from top to bottom...guessing the last 4 feet of crack is from 2005 to now.
    I would say the greatest gap is about 1mm..so its not like there is light shining through....might try to take some pics later.
  3. dave11

    dave11 Minister of Fire

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    The gradual lengthening of a crack, if that's what happened, suggests a gradual settling or subsidence on one end of the wall or the other. But in that case, the crack should be at least a tiny bit wider at the top than at the bottom. Is that the case?

    But if you're convinced that the crack has been growing, it really should be looked at by a foundations guy. Just sealing it might make no change in the end, if it keeps growing (ie. widening).
  4. daveswoodhauler

    daveswoodhauler Minister of Fire

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    Here are a few pics, and I found a similar crack on the opposite wall:

    Attached Files:

  5. daveswoodhauler

    daveswoodhauler Minister of Fire

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    2 more on the opposite wall

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  6. dave11

    dave11 Minister of Fire

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    If I had to guess, I'd say those are likely to be shrinkage cracks in the concrete wall that occurred after pouring. There appears to have been no displacement. These are usually not progressive, and sometimes happen naturally, though it often reflects a lack of proper reinforcement of the concrete when it was poured.

    But I'd still suggest you get a REPUTABLE foundation repair company to take a look. One with references. If the cracks are due to shrinkage, they'll probably tell you it's okay to seal them and cover them.

    And make sure to keep your outside foundation walls well-drained.
  7. NEDLAX

    NEDLAX New Member

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    Its a rule of thumb in the industry for unisulated basements as per terry brennan the go to guy for basements and how to condition them.
  8. fbelec

    fbelec Minister of Fire

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    don't know about the 30%, but my house totally changed when did basement work. i insulated with kraft faced 3.5 inch R13 and sheetrocked. only 3/4 of the basement. my basement went from high 30's to mid 50's. my upstairs floors were 10 times warmer. as far as gas for the boiler i'm not sure how much i saved there because i've been heating with wood since we moved in, in 2001. but i can say using the same wood stove that i went from having to feed the stove all day and night to 1 fire a day in shoulder season, and when it's normal cold 2 fires a day. and when we like the past few nights dipped into the 5 to 10 degree temps feed the stove with small fires in day and stuffed at night. no leaks, no mold. but i do run a dehumidifier in the summer. if i didn't the musty smell would be there. humidity always sinks to the lowest level of the house. the only thing i did as a precaution was to use pt 2x4's on the floor for the base plate. i have good sized spaces between the finished wall and the foundation wall. i have a 4 inch pvc pipe running around the wall. the finished wall is not to cold to the touch when it's in the 50's down there. and it takes 3 days to drop the temps from 70's to 50's when the stove goes out.
  9. velvetfoot

    velvetfoot Minister of Fire

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    fbelec, are you talking about a stove that is in your basement?
  10. semipro

    semipro Minister of Fire

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    The way I'd do it:

    - Use the Building Science publications that I suggested in your 1st post as a guide (or whichever B.S. doc applies best to your situation)

    - Use layers of foam to get the R value you want. Build the walls to the interior of that.

    - Don't create/install a vapor barrier. You want a wall that breathes. I believe that's what B.S. and others in the know suggest. If you install a vapor barrier then moisture will get trapped in the wall somewhere, potentially causing problems. Unless a vapor barrier was installed outside or underneath the concrete, water will come through the concrete. Standard concrete is not 100% impervious to water, not nearly. The key is how to deal with the water that makes its way through.

    - Avoid air gaps if at all possible. The problem with air gaps is not so much loss of insulation as it is a moisture problem. If air can infiltrate then moisture can get in. The water in the air will condense on the cold face and could cause problems. An ideal wall provides structure and insulation without retaining moisture (or critters).

    - Use a product like Densarmour for your wallboard. It uses non-organic materials that don't provide a substrate for mold to grow on. http://www.gp.com/build/Product.aspx?pid=4659

    - There are gauges that can be installed across masonry cracks to monitor movement. I suspect if you don't see signs of water migrating in (usually staining or mineral buildup) that you seal the best you can and move on. Maybe you want to build in an access panel to allow visual monitoring of the crack. There should be re-bar in there provide the structural strength that's needed.

    - Consider the coating you put on the wallboard. Don't use anything that will act as a vapor barrier like vinyl wallpaper or oil based paint.

    - Don't put wall sill plates in direct contact with the floor. Use the thin blue foam insulation made for that purpose or similar.

    - Insulate the concrete floor also if you really want a comfortable basement. I think B.S. covers this as well.

    - Put some Boric Acid powder (e.g. Roach Proof) in the bottom of wall cavities for potential bug issues.
  11. fbelec

    fbelec Minister of Fire

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    no, just using regular fiberglass insulation and what it did for my house. not a whole lot of money and 6 years with no problems.
  12. redhotz

    redhotz Member

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    I used Sanitred in my basement 4 years ago. I highly recommend it. It should be applied to bare block. It is a 2 part epoxy polyurethane. It's about $90.00 gallon. I used 4 gallons. It does what there web site says. I was skeptical at first but after trying it, I was sold. I had a lot of leaking cracks, some up to a 1/2". They have a filler for wide cracks. No leaks anymore, no condensation. Check it out.
  13. Brian in Michigan

    Brian in Michigan Member

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    I tried the stud wall and 3-1/2" of insulation with a vapor barier on a poured wall. After about a week there was so much water behind and on the face of the plastic, I ripped out all of the plastic. The rest of the walls I put in 1-1/2" foam board. All of it glued to the walls and then I used furing strips on the face of the foam board. I used tapcon screws to drive thru the furring strips and foam board into the concrete. This way no wood came into contact with the concrete and the drywall sets away from the insulation. It's been like this for 10 years and no problems.
  14. daveswoodhauler

    daveswoodhauler Minister of Fire

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    Thanks for your help Semipro.
    I was thinking of going the route you explained so well, but if I read your post right, all the insulation would be between the walls and framing, and then I would have an airspace in between the studs? (Again, thanks for the help, just want to make sure that I understand correctly)
  15. dave11

    dave11 Minister of Fire

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    I won't answer for semipro, but I believe he does mean to build a frame wall on the room side of the rigid panels. You could add 3.5 inch batts between these studs if you like, though again, you should do a heat loss analysis to see if its the best use of your money.

    The problem with doing it this way is that you remove a significant amount of floor space. If you use 2-inch rigid foam, then 3.5 inch studs, then 0.5 inch sheetrock, you'll have removed 6 inches of floor space all around the basement perimeter. If your basement is large, you might not miss it, but you might want to measure it out and see if you're happy with the result, before you do it.
  16. daveswoodhauler

    daveswoodhauler Minister of Fire

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  17. ansehnlich1

    ansehnlich1 Minister of Fire

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    I didn't read this whole thread, I admit.

    We built our home 3 years ago here in Pennsylvania. Code required basement wall insulation. We have an aluminum faced rolled fiberglass attached to our poured foundation walls with hilti fasteners.

    Have had no moisture problems

    When/If I decide to finish off any areas in the basement I will simply stud the wall along the insulation, no problem.

    Oh, I could tell a HUGE difference in the basement as soon as the insulation went up.....it was amazing.
  18. semipro

    semipro Minister of Fire

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    Yeah, the way I was suggesting would leave an airspace between the studs. To tell you truth I wouldn't use more than 2" thickness of foam because my basement is below grade so the exterior basement walls should never see a temp below about 50F. I'm not sure about your situation. I think Dave11's suggestion to put fiberglass batts in between studs is a good one if you're using full sized (2x4) studs. That is, as long as the batts used are unfaced so no vapor barrier is created. However in most cases, you don't need to use full 2x4s when framing the wall if you're attaching the studs to the wall through the foam with something like a Tapcon and this creates a pretty stout wall structure. You can use 2x2 studs instead but you won't want to pack 3.5" thick batts into a space 1.5" deep because it won't give you much R value.

    If you want more insulation than initial 2" of foam will provide than it would probably be best to put up the 2" foam against the wall, install the 2x2 studs on the face of the foam and to the wall, then insulate between the studs with 1" foam. If you can afford the interior space loss, use full 2x4 studs and insulate between them with either more foam or unfaced fiberglass batts as Dave11 suggested.

    I hadn't thought about it before but if you want to avoid any possible mold issues by removing growth substrates (wood in this case) you could use metal studs instead of wooden ones.

    If any of what I've suggested conflicts with the guys at Building Science, I'd do it their way. Those guys know what they are talking about and are highly respected in the profession.

    Good luck!
  19. semipro

    semipro Minister of Fire

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    Dave11,
    Your avatar mesmerizes me. I keep finding myself staring at it. ;)
  20. velvetfoot

    velvetfoot Minister of Fire

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    Two layers of foam with strapping tap conned to the wall in between with sheet rock on top attached to the strapping could take a good hit, have a complete thermal break, R20, and not support mold.
    (The wood strips at left are used to brace the top layer when gluing to the bottom layer.)

    [​IMG]
  21. dave11

    dave11 Minister of Fire

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    Ha! Semipro, let me tell you what it's meant to represent. That figure is me, chasing after the "perfect burn" in my 30NC.

    Regards.
  22. SPED

    SPED New Member

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    As soon as I saw this thread I was planning on suggesting that site. +1, great website and they have downloadable pdfs on how to do it. I followed their recommendations, foam board then unfaced batts in a stud wall, then sheetrock, then latex paint so water can slowly get out if it does get trapped. 3 yrs since I did it in my basement and no probs so far. I did thoroseal the walls first and make sure I had no leaks as well.
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