Tile Over Tile: Radiant Heated Bathroom Floor
Tile over tile means exactly what it says, but in this case you’re going to sandwich
a layer of radiant heating mats between the old and the new tile. Tile over tile is
an easy way to avoid the mess associated with tearing up the old bathroom
floor, but requires thorough planning.
Deflection:
Before you install an electric radiant heat mat over the old bathroom tile and
install new tile over the mat, you should check the floor for deflection. This is the
maximum amount the floor can move under the anticipated load (you). Ceramic
tile is hard and will break or dislodge if the surface bends under the load. Here’s
a simple test:
Stand in the middle of the bathroom floor and jump up and down. If the floor
moves it has a deflection problem and is not a good candidate for tile over tile
installation until you reinforce the sub-floor.
Avoid That Sinking Feeling:
Since you’re tiling over tile, you must plan in advance to avoid making the vanity,
toilet and tub look like they’re “sinking” into the new floor.
Fortunately, many of the new radiant heating mats are no thicker than the depth
of the mortar you would ordinarily apply for most tile installations. Combine this
with a tile thickness of ¼ inch and the maximum elevation above the old floor
would be only ½ inch.
One way to keep the bathroom fixtures from looking swallowed up by the new
floor is to remove and reinstall the baseboard. Better yet, why not buy new
baseboard tile to complement the new floor?
The raised height of the new floor will also require you to adjust the length of the
door(s) and possibly install a new threshold.
Preparation:
Remove or re-attach broken tile pieces. If you remove them, wait until the floor
has been sanded and thoroughly vacuumed before you fill the spaces with mortar.
If any of the tiles have checks wider than 1/8”, you should consider a crack
isolation membrane. This membrane is a roll on product that you apply to the old
tile. The membrane allows the new floor to move independently of the old.
Next, sand the old tile so the mortar has a good bonding surface. A belt sander
would ensure a consistent bonding surface.
Please make sure you wear a face mask and safety glasses while sanding. The
tiles may have been fired with toxic lead glaze.
After sanding, vacuum the tile and wipe down with an all purpose cleaner. Pay
special attention to the areas untouched by the sander.
Installation:
Roll out the mats prefabricated to your specifications by the manufacturer. Some
electric radiant systems, like Quickmat, are self-adhesive and require no mortar to
secure them to the old tile floor.
If you’re re-tiling the only bathroom, keep a board and some scrap 2 x 4’s handy
to protect the mats when the bathroom is being used.
Throughout the installation process, use a digital ohm meter to check the
resistance of the heating mats. This will help you monitor the mats for short
circuits.
Have your electrician connect the heating mats to the power source and install
the thermostat. Depending on the local electrical inspection procedures, you
might have to wait until the job is inspected before you start laying tile.
Trowel out the mortar over the mats. Some manufacturers recommend latex-
modified or epoxy-modified mortar and grout instead of water-based multi-
purpose adhesives. Mortar beds thicker than 3/8 inch should work fine for most
systems; they just take slightly longer to heat up.
Since you won’t be covering the entire floor with heating mats, make sure the
mortar applied over open areas, (under the toilet) is level with the mortar
covered mats.
Don’t bang the trowel on the mat or heating wire to remove excess mortar from
the trowel. This could sever the heating wire.
At this point, you would lay the tile. If you have no experience tiling, practice on
your neighbor’s bathroom floor.
Fire It Up!
Your new radiant heated bathroom floor looks beautiful and you can’t wait to get
warm feet. Go ahead, but only for 10 minutes. Don’t put the system into full
operation until the mortar is fully cured. This can take up to four weeks. See why
thorough planning is so important?
Tile over tile means exactly what it says, but in this case you’re going to sandwich
a layer of radiant heating mats between the old and the new tile. Tile over tile is
an easy way to avoid the mess associated with tearing up the old bathroom
floor, but requires thorough planning.
Deflection:
Before you install an electric radiant heat mat over the old bathroom tile and
install new tile over the mat, you should check the floor for deflection. This is the
maximum amount the floor can move under the anticipated load (you). Ceramic
tile is hard and will break or dislodge if the surface bends under the load. Here’s
a simple test:
Stand in the middle of the bathroom floor and jump up and down. If the floor
moves it has a deflection problem and is not a good candidate for tile over tile
installation until you reinforce the sub-floor.
Avoid That Sinking Feeling:
Since you’re tiling over tile, you must plan in advance to avoid making the vanity,
toilet and tub look like they’re “sinking” into the new floor.
Fortunately, many of the new radiant heating mats are no thicker than the depth
of the mortar you would ordinarily apply for most tile installations. Combine this
with a tile thickness of ¼ inch and the maximum elevation above the old floor
would be only ½ inch.
One way to keep the bathroom fixtures from looking swallowed up by the new
floor is to remove and reinstall the baseboard. Better yet, why not buy new
baseboard tile to complement the new floor?
The raised height of the new floor will also require you to adjust the length of the
door(s) and possibly install a new threshold.
Preparation:
Remove or re-attach broken tile pieces. If you remove them, wait until the floor
has been sanded and thoroughly vacuumed before you fill the spaces with mortar.
If any of the tiles have checks wider than 1/8”, you should consider a crack
isolation membrane. This membrane is a roll on product that you apply to the old
tile. The membrane allows the new floor to move independently of the old.
Next, sand the old tile so the mortar has a good bonding surface. A belt sander
would ensure a consistent bonding surface.
Please make sure you wear a face mask and safety glasses while sanding. The
tiles may have been fired with toxic lead glaze.
After sanding, vacuum the tile and wipe down with an all purpose cleaner. Pay
special attention to the areas untouched by the sander.
Installation:
Roll out the mats prefabricated to your specifications by the manufacturer. Some
electric radiant systems, like Quickmat, are self-adhesive and require no mortar to
secure them to the old tile floor.
If you’re re-tiling the only bathroom, keep a board and some scrap 2 x 4’s handy
to protect the mats when the bathroom is being used.
Throughout the installation process, use a digital ohm meter to check the
resistance of the heating mats. This will help you monitor the mats for short
circuits.
Have your electrician connect the heating mats to the power source and install
the thermostat. Depending on the local electrical inspection procedures, you
might have to wait until the job is inspected before you start laying tile.
Trowel out the mortar over the mats. Some manufacturers recommend latex-
modified or epoxy-modified mortar and grout instead of water-based multi-
purpose adhesives. Mortar beds thicker than 3/8 inch should work fine for most
systems; they just take slightly longer to heat up.
Since you won’t be covering the entire floor with heating mats, make sure the
mortar applied over open areas, (under the toilet) is level with the mortar
covered mats.
Don’t bang the trowel on the mat or heating wire to remove excess mortar from
the trowel. This could sever the heating wire.
At this point, you would lay the tile. If you have no experience tiling, practice on
your neighbor’s bathroom floor.
Fire It Up!
Your new radiant heated bathroom floor looks beautiful and you can’t wait to get
warm feet. Go ahead, but only for 10 minutes. Don’t put the system into full
operation until the mortar is fully cured. This can take up to four weeks. See why
thorough planning is so important?
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