How to tile under a forced hot-water baseboard heating

Discussion in 'HVAC Heating & Cooling' started by jdbs3, Jan 24, 2008.

  1. jdbs3

    jdbs3 New Member

    Messages:
    20
    Location:
    Massachusetts
    Insufficient space under one of the baseboards for backerboard and tiles - read on ...

    I am replacing a bathroom vinyl floor with tile and have forced hot water heat.

    The bottom of the heating fins is only 1†above the vinyl floor. There is no give (vertically) on the forced hot water pipe to pull it up a bit. And the front cover is a tight 7/8†above the vinyl floor.

    After putting down backerboard and tile, there will be an 1/8" or less clearance between the bottom of the fins and the tile. I guess this will be ok.

    BUT there would be 0†clearance between the cover and the tile floor. Thus no air circulation under the front cover.

    ARG! So what to do about the front cover???
  2. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,642
    Location:
    Cave Creek, Arizona
    cover

    No circulation means no heat so you either modify the cover or raise the baseboard, which would be the proper thing to do.
  3. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    While raising the heater might be the proper thing to do you could / may be able to modify the the cover by cutting it or drilling holes in it to allow for air circulation.
  4. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    If you decide to modify it be sure to not leave any sharp edges for feet to get cut on.
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,019
    Location:
    New England
    A couple of things on the tiling:
    -check out www.johnbridge.com for some suggestions
    -you really should remove the vinal and probably the 1/4" luan ply that's under the vinal. This may give you some leaway.
    -have you checked the deflection ratings for both the joists and the subflooring? Not all floors are suitable for tiling unless beefed up.
    -1/4" backer board is all that is needed on a floor; 1/2" doesn't buy you anything except more cost, weight, and maybe height matching - it adds not appreciable strength
    -there are membranes that are thinner than 1/4" cbu - Ditra for example is about 1/8" thick installed. This could give more flexibility (and it's easier to install, too).
  6. jdbs3

    jdbs3 New Member

    Messages:
    20
    Location:
    Massachusetts
    There is no underlay under vinyl floor. The vinyl was glued directly to the top layer of plywood.

    I had been considering a membrane, but in conversation with a local tile place, they suggested going with the cement backerboard since the plywood floor tends to swell and contract in New England, and this would lead to cracked grout and tiles. Will an isolation membrane like ditra avoid this potential cracking problem?

    RE: Floor sutiable for tiling:

    Yes, I found johnbridge.com - thanks

    There appear to be 2 layers of plywood, and initial rough layer (my guess) that the wall board sits on, and a finished layer that is 1/2" thick. So my guess is that I have 1" of plywood between the 2 layers.

    The joists that are of unknown wood, but in good condition, 9.25 inches tall, 1.5 inches wide, 14 inches on center, and 10 feet long (my guess) between supports.

    Not sure what kind of tile I will use other than 1/4" thick given my space limitations.

    I believe I will be able to get the tile and backerboard just under the heating fins with ~1/8" to spare. If I use ditra, then possibly a bit more clearance.

    However, in either case, the heating element cover would end up sitting right on the tile floor.

    So I either raise the heating element (which means cutting the pipes, and extending them, plus drain the system and refill - ugly),

    or, cut the cover along most of its length to allow air to flow under it, and cut the end caps (=> find a metal shop).

    Any other suggestions before I flip a coin?
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,019
    Location:
    New England
    Ditra, IMHO, is superior to cbu. Basically, the membrane is adhered to the subflooring, then the tile and thinset is attached to it. The fleece gives the DItra a little flex, too. The tile and thinset creates support pillars, but does not bond to the floor - the tile and thinset can move as a unit. The tile and thinset are locked into the membrane by the shape of the pockets in the Ditra. Basically, the Ditra can flex while the tile soft of floats as a unit. Take a look at www.schluter.com. plus, it's a whole lot easier to install - lighter, cuts easier, and works better for decoupling.
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