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Basement fixes for walls and floor

user-7600779 | Posted in General Questions on

Hello all;

I am a residential energy and durability junior advisor who is dealing right now with a problem related to the constructive elements being in contact with the soil, without any water barrier.

This country house is located in a mixed-humid climate. It is a residential building with 2 stories from 1912. The ground floor walls are partially in contact with the ground (thick stone walls). No waterproof system. The ground slab is also in contact with the ground, with no waterproof system.

Effects:
Mold on the walls;
Extensive efflorescence on the walls (mainly near the base-raising damp);
Painting peeling off on the walls;
Wood ground tiles being detached from the slab.
No liquid water entering the rooms.

Plan:
Floor – Install a dimple mat on the ground floor, OSB subflooring and new wood tiles. I plan to avoid all the humidity to ruin the tiles again by blocking its upward movement. All the seam will be taped with a gas-tight material.

Walls – Since there is no liquid water entering I was thinking about just apply a heat applied bituminous against the wall and then apply some gypsum wallboard over some furring strips with mineral wool in between.

Question:
Floor – Won’t be that space between the ground slab and the dimple mat a nasty place for mold? I mean, evaporation and ventilation will be cancelled.

Walls – Am I thinking correctly? The wall won´t be able to dry inside, they will always be damp (durability problems ?).  Won’t the inward vapour drive affect my membrane?

Many thanks in advance
Rock

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Replies

  1. Expert Member
    BILL WICHERS | | #1

    I’d put some drainage under that floor to make sure you don’t have any hidden water accumulation. I wouldn’t worry about mold so much since you’re sealing that area off from the living space. Have you considered dricore tiles here?

    Masonry doesn’t really need to dry except to avoid freezing issues with brick walls. Aside from that, I don’t really have any experience with stone walls so I can’t offer you much advice on that part.

    Bill

  2. GBA Editor
    Brian Pontolilo | | #2

    Hi Rock,

    I think the dimple mat or, as Bill suggests, Dricore subflooring are probably a good idea. Often the best solution for stone basement walls is to use closed-cell spray foam. A word of caution, it's super important that you make sure that the basement is not getting wet from bulk water. If surface or ground water is getting in, you need to deal with that first before installing anything on the floor or wall or you'll just be doing this all over again in a few years. You may need regular dehumidification too. Here are some articles that you may find helpful:

    How to Fix a Wet Basement
    All About Basements
    Stay Dry, No Mold Basement
    How to Insulate a Basement Wall

    1. user-7600779 | | #6

      Hi Brian;

      Thank you for your help and extra info material.

      I think this question is pretty common: What to do with damp basement walls? Only vapour is kind of OK, bu salts? neh. That will ruin the paint job constantly. If there was bulk water, simple, internal drainage. But there is no need for that with just vapour and salts.

      Spraying some close cell foam will create a vapour barrier. However, Lstiburek advises against vapour barriers inside basements.

      I am also concerned about applying some dimple mat over the walls and floor. That air space between the dimple mat and the wall/floor will be a mould nest. And even if sealed, those sealants will fail someday and spray nasty stuff into indoor air.

      Additionally, this is an old vacation house. Meaning that it will not be dehumidified on a regular basis.

      Kind Regards,
      ER

  3. Jon_R | | #3

    Lstiburek is a strong proponent of fully adhered waterproof coatings. You may want to provide a gap above/inside that to distribute small amounts of water - but I'd make it somewhat vapor permeable, allowing inward drying.

  4. walta100 | | #4

    The way I see it this building made it 108 years the way it was and if you are not carful you could mess that up.

    100 years ago no one expected a bone dry basement, no one willingly lived in a basement, and no one expected a basement to smell nice.

    What has changed is our expiations of what a basement should be. If you want a modern dry basement you need a modern exterior drainage system that can drain to daylight.

    Before you seal up the air leaks and insulate remember this house survived the test of time because the walls were warm enough and leaks enough to carried away the moisture before it could rot the wood

    Walt

  5. user-7600779 | | #5

    Thank you so much for your opinions.

    The client really insists in take advantage of that space and retrofit it.

    I think this question is pretty common: What to do with damp basement walls? Only vapour is kind of OK, bu salts? neh. That will ruin the paint job constantly. If there was bulk water, simple, internal drainage. But there is no need for that with just vapour and salts.

    Spraying some close cell foam will create a vapour barrier. However, Lstiburek advises against vapour barriers inside basements.

    I am also concerned about applying some dimple mat over the walls and floor. That air space between the dimple mat and the wall/floor will be a mould nest. And even if sealed, those sealants will fail someday and spray nasty stuff into indoor air.

    Kind Regards

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