basement floor XPS foam

Discussion in 'Remodel Forum & Blog' started by lmei007, Mar 3, 2012.

  1. lmei007

    lmei007 Member

    Messages:
    179
    Location:
    Maryland
    My unfinished basement has a 87" ceiling height right now. I don't know I should use 1", 1.5" or 2" XPS foam on the floor? The whole basement floor plan will be 6mil poly + XPS foam + 23/32" T&G plywood + engineered wood floor.
  2. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    Personal preference, how tall are the people who live there?
  3. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,259
    Location:
    Land of Cheese
    One thing to consider is that a standard door rough-in is 82-1/2 tall. Additional height will be required to install a standard casing around the opening.
  4. lmei007

    lmei007 Member

    Messages:
    179
    Location:
    Maryland
    5'10" for now.
  5. grahamW

    grahamW New Member

    Messages:
    30
    Location:
    Ontario, Canada
    Can I ask the purpose of the poly? If your basement floor is allowing water up from beneath then you're likely going to have issues no matter what you do (IMHO).

    I use ship-lapped, rigid foam insulation and use 2" on the walls and 1" on the floor. Glue to the walls & floor with the correcct adhesive and each seam should be tuck-taped, and spray foam used to fill any gaps around the edges. All rigid foam insulation is mould and mildew resistant and won't hold moisture, even if you have a flood in your basement. You can use mould-resistant drywall as well.

    The goal of insulating in this manner is creating a thermal break between the air inside your basement and the air outside. It will eliminate any air movement behind the walls that could lead to condensation.
  6. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    Mold only grows on organic materials, concrete, poly, foam, etc. etc. none of them support the growth of mold.

    If your basement floods, having gimmicky drywall wont make a difference.
  7. lmei007

    lmei007 Member

    Messages:
    179
    Location:
    Maryland
    The poly is to reduce moisture vapor from the ground and to prevent small amount of water from ground if any. But it will be bad if water is from inside (water pipe), I think.

    In my case, that poly layer is for moisture only because I have added french drain inside my basement and outside grading has been addressed as well.
  8. lmei007

    lmei007 Member

    Messages:
    179
    Location:
    Maryland
    I plan to attach the drywall at least one inch above from the plywood. That means as long as there is no more than 1" water in my basement, the drywall will be safe. I have floor drain and french drain. I think my basement probably should be good enough.
  9. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    4,140
    Location:
    NW Ontario, Canada
    If you need an interior weeping system, then you probably should have a gap as well. Something like dimpled plastic under the insulation, or skip the insulation and put in DRIcore. Insulation on the floor has little payback.

    http://www.dricore.com/en/eIndex.aspx
  10. lmei007

    lmei007 Member

    Messages:
    179
    Location:
    Maryland
    We only get water in 100yr's storm and at that time the outside surface water was not handled properly. Normally there is no water issue and the sum pump basin is dry all seasons
    Last edited by a moderator: Mar 4, 2012
  11. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    I'm really getting fed up with all of the mis-information going on here...
  12. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    4,140
    Location:
    NW Ontario, Canada
    PFFT! We are talking about a basement below grade were the temps are nothing like a room over the garage. Try some ROLAIDS®.
  13. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    4,140
    Location:
    NW Ontario, Canada
    If there really was so much payback, you'd think the DRIcore engineers would be all over it and manufacture a version of their product with an inch or two of XPS sandwiched in it. DRIcore has an R value of 1.7 plus the engineered wood that is going on top of that. I don't know the degree days in the state of MA, but for sure less than ours. Summer cooling costs may even factor in.
  14. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    You need to do some research outside of the Home Depot flyer my friend. The main reason DriCore engineers (you think they actually have engineers?), don't add 2" of XPS is COST...

    It is already over priced and uses OSB instead of proper plywood, they wont sell a single 2'x2' tile if they double their price point again.

    Oh and p.s., the other reason is because someone else already came out with such a product. Again, over priced.

    http://www.ovrx.com/

    I think it is hilarious that you figure it takes a team of engineers to glue 2 building materials together and come up with a marketing scheme.

    I would use Delta FL and plywood any day of the week over DriCore, and I would use XPS and plywood any day of the week over any xps+osb glue together crap.
  15. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    For anyone out there listening LLigetfa also recommends MDF baseboards in basements with dampness issues.

    I'll have to head over to Home Depot and ask the experts there, then report back on whether or not having a cold floor in a finished basement is a good idea.
  16. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    4,140
    Location:
    NW Ontario, Canada
    Well.. if you think the Barricade® system you linked to supports your arguement, it falls way short. They claim 1% heat loss through the floor. Their product does not laminate two inches of XPS, not even one inch.

    http://www.ovrx.com/subfloor-comparison.html

    Don't get me started on engineers and marketeers. Maybe you could design something and then get Vince to pitch it for you. I hear he lost a lot of business after the hooker bit his lip.
    [​IMG]
  17. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    Like I mentioned I'm not fond of any of the 2' square products.
  18. Dana

    Dana In the trades

    Messages:
    2,974
    Location:
    01609
    Since you're not spanning 16" o.c. joists, there's no rationale for going with 23/32" plywood subfloor- XPS hard-sandwiched between even half-inch t&g sheathing for the sub-floor and a concrete slab has PLENTY of structural strength, and flexes far less than 23/32" plywood spanning joists. You don't want to go thinner than 7/16" though (for fastener retention reasons.)

    There's an economic rationale for R5 (1") XPS on space heating savings (as well as a comfort rationale) in a MA climate zone & subsoil temp. There's a long term economic rationale for R7.5 (1.5"), but R10 only makes economic sense if

    A: It's a DIY and you discount you fully discount the value of your labor

    B: You use reclaimed XPS at 25-30% of virgin-stock costs

    C: You are stuck only with very high space heating fuel options (propane, or oil, or >12 cent electricity & no heat pumps)

    D: You are installing radiant floor to heat the place (in which case R12-R15 might even make sense.)

    If you stagger the seams of the subflooring with that of the foam by at least a foot or so for least mechanical creepage you can just float the floor, using foam board construction adhesive between the foam & subfloor. If there's any detectable flex to it you can throw in a few tapcons through-screwed to the floor per panel of subfloor.
  19. Dana

    Dana In the trades

    Messages:
    2,974
    Location:
    01609
    Take it from some people who actually do the math:


    http://www.buildingscience.com/documents/reports/rr-1005-building-america-high-r-value-high-performance-residential-buildings-all-climate-zones


    MA is US zone 5. (See the R recommendations in Table 2, p10, but read the first chapter to understand the rationale.)

    See also: http://www.buildingscience.com/documents/reports/rr-1003-building-america-high-r-foundations-case-study-analysis

    There's more to it than simply blocking ground moisture or heating season utility savings (but those all count too.) Putting real R-value between the subfloor and slab further reduces the mold & rot potential of the subfloor by increasing it's summertime temp to above the summertime dew point of the ventilation air. At MA outdoor summertime dew points R3 would be the minimum in central MA to mitigate summertime moisture accumulation and mold on the subfloor under a padded carpet finish floor (or area-rug over wood flooring), and the labor cost of putting down 1" or 1.5" is the same as for putting down 1/2-3/4". Without the under-floor R the mechanical dehumidification requirements to protect against mold are much higher than they would be otherwise.
  20. nukeman

    nukeman Nuclear Engineer

    Messages:
    711
    Location:
    VA
    One thing to remember is that you will probably have to do something with the basement stairs (probably for any of these options). Your last step will be too short, otherwise. Doors can also be an issue with the increased floor height.
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