Asked on Oct 20, 2019

How can I prevent water buildup btwn vinyl chair mat & heated floor?

Laura CooperKen EricksonShirley Pott

Answered

In my home office, an office chair sits on a 2 mm vinyl chair mat. The mat sits on heated terra cotta tile. Water accumulates between the floor mat and the tile. What solutions to this water issue exist and what damage is the accumulation likely to cause.Installation was as follows: Over an 87-year old existing six-eight inch slab (the vapor barrier for which is unknown and cannot be changed) we poured an additional six inch slab, which, after a 6-8 week cure period, was covered with an electric heat mat, 1/4-1/2 inch of self-leveling concrete, standard thin set and 1-1/2 centimeter thick sealed terracotta tile. Today the temperature-relative humidity inside the office are 70º-47%; the outside temperature-relative humidity are 53º-86%. A 12-inch split stone wall surrounds the old, original floor slab and the crawl-space adjacent to the slab floor is completely dry.

3 answers
  • Shirley Pott
    on Oct 20, 2019

    Why do you need a chair mat? Terra cotta tile seems sturdy enough to stand up to chair traffic. If you feel floor needs protection, change out the chair wheels for softer ones (if chair has wheels) or soft suitable glides for rigid legs.

  • Ken Erickson
    on Oct 20, 2019

    You might try adding some spacers under the map so humidity can escape.

  • Laura Cooper
    on Oct 21, 2019

    Usually moisture accumulates where there is a hot/cold junction. Was insulation placed under the heat mat? The plastic may be keeping this moisture trapped instead of simply wicking out into your air.

    • Laura Cooper
      on Oct 21, 2019

      Condensation can occur in a relatively dry environment. It's just where the warm and cold meet. I live in an area where winter relative humidity can be less than 10% but condensation will still occur wherever hot and cold meet. Also, all forms of masonry are porous and wick moisture.

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