+ Reply to Thread
Results 1 to 2 of 2
  1. #1
    Join Date
    Apr 2009
    Waterloo, Onatrio Canada

    Default framed and foamed old rubble foundation

    Greetings friends!

    first post so go easy on me.
    We acted on a contractor friend's recommendation that we frame up, insulate our basement with 3" spray foam, and then drywall.
    The winters had been brutal up to this point, our rubble foundation being very very leaky. Have had minor moisture issues but nothing major...in the summer it gets a little smelly down there -again, nothing too serious.
    Now I'm hearing that we've left nowhere for the moisture to 'migrate' and that our lives are in peril...ok, not YET anyway. Did we screw up by sealing it all in? Could I cut 'portholes' into the drywall, through to the foundation to allow the moisture to wick? Any input or advice would be wonderful!
    many thanks


  2. #2
    Join Date
    Aug 2007
    The Great White North

    Default Re: framed and foamed old rubble foundation

    Stephen from K-W .... welcome to the forum.

    As mentioned in the private message this thread would be helpful to post comments regarding this issue. This way anyone that might be following may benifit as well others may have ideas or suggestions to contribute.

    A number of years ago I lived in a 100 year old home with a stone foundation. The home had undergone an extensive renovation that had been done very well. This included a insulated and finshed bedroom in part of the basement. Even though the finished space was well insulated .... the basement was always cold and damp. The one thing that hadn't been addressed was waterproofing and installing a proper drain system on the exterior of the foundation walls.

    These vintage homes with stone or brick foundations have mortar joints that are constantly moist being under ground. The mortar is porous and will naturally allow moisture to pass through from the exterior surrounding soil into the interior .... this moisture can be liquid or vapour ..... resulting in a cold damp space.
    Over the years the mortar will deteriorate and if not maintained will create more issues for moisture to infiltrate.

    Back in the day when these homes were built the basements were mainly allocated for things like cold storage , mechanicals , coal or oil tanks and general storage. They weren't generally considered to incorporate conditioned ( living ) space ... like we do today.
    So , when moisture would pentrate into the basements .... creating the damp cold space .... it was commonly accepted considering the intended use back in the day.

    It's unclear as to the condition of the mortar joints for both the exterior and interior. If they are deteriorated prior to insulating they will allow moisture to infiltrate from the exterior and continue to deteriorate. Regardless of which type of insulation ... closed cell or open cell spray foam or fiberglass batts , etc. ..... will allow moisture to infiltrate from behind the insulation.

    The 2 lb Closed cell spray foam would have the advantge since it adheres to the stone surface adding some structural rigidity , air sealing as well since it is closed cell doesn't allow moisture ( vapour or liquid ) to readilly pass through.

    With the 1/2 lb open cell spray foam will adhere to the stone surface ... will provide an air seal with sufficient density ... but doesn't add much to structural rigidity and since it is open cell will allow vapour to pass through.

    Fiberglass batts doesn't adhere to the stone surface , doesn't provide any air seal or add any structural rigidity and readily allows vapour to pass through ... as well when wet is pretty much useless for insulating.

    In my opinion I don't believe insulating the basement with foam would be the source for your stone foundation deterioration.
    As long as moisture is allowed through the joints in the stone or brick .... there will be deterioration of the mortar and the basement will still be damp and cold.

    One thing that I feel is important with foundations is a proper waterproofing system applied to exterior of any foundation.

    This method is more expensive and invasive since it requires excavating the outside perimeter of the home down to the footings repairing the mortar joints ....... Applying an elastromeric coating along with a drainage membrane to exterior of the foundation walls .... as well an external perimeter drain ( weeping tiles ) installed or replaced will be the 3 main components to the system.

    With this system the moisture is held back at the source ..... the exterior ... not allowing it to penetrate the motar deteriorating it and allowing infiltration to the interior.

    This method is the more effective in my opinion.

    Another method would be to repair the motar joints ..... apply a drainage membrane to the interior walls. An inside perimeter drain system can be installed by excavating a trench along the floor near the walls. The weepers are laid in the trench and would run to a sump pit with a pump.

    However .... I'm not a fan of this system since it still allows the moisture to penetrate from the exterior into the interior and will still allow the motar to detriorate over time.
    It is an alternative that would be cheaper than the outside system.

    When you asked for my 2 cdn cents I guess it turned out to be a twooney but might be only worth 2 cents.

    Hopefully this helps.
    "" an ounce of perception -- a pound of obscure "
    - Rush

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts