Taping Cement Backer Board Joints and Corners
is a Must before Tiling
By Mark J. Donovan
When installing ceramic tile over
cement backer board it is important to first apply tile backer board tape over
the joint and corner seams, followed by a skim coat layer of thinset mortar.
Tile backer board tape helps to reinforce the joint seams of cement backer
Do not use drywall fiberglass mesh
tape and joint compound to seal cement backer board seams. It will not hold up.
Over time it will breakdown and fail.
Tile backer tape, on the other hand,
is specifically designed for cement backer board applications and it is
engineered to resist cracking. It has an anti-corrosive polymer coating and is
alkaline resistant. Portland cement mortars are high in alkaline and will
quickly breakdown standard drywall fiberglass mesh tape.
Tile backer board tape has a sticky
surface. To apply tile backer board tape simply cut it to length, and press the
sticky side firmly up against the cement backer board and centered over the
seams. Use 2 wide tile backer board tape for interior applications and 4 wide
backer tape for exterior applications.
Next, apply a skim coat layer of
thinset mortar over the tile backer board tape. When applying the thinset mortar
over the backer board tape you dont need to be extremely neat, however it is
important to not leave any ridges or humps.
Photos by Mark Donovan
If you do, make sure to scrape them
down after the mortar has cured or you will have a difficult time installing the
ceramic tiles. The tiles have a tenancy to not sit flat and rock over humps, so
make sure you remove any high spots in the thinset mortar before starting your
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