Finish TradesQuestion 275 of 700
Cement backer board (cementitious backer unit) joints on a wall are treated before tiling by:
a.Leaving the joints open and bare
b.Filling with drywall joint compound and paper tape
c.Caulking the joints with silicone only
d.Bedding alkali-resistant fiberglass mesh tape in thinset over the joint
Explanation
Backer board joints are reinforced with alkali-resistant fiberglass mesh tape set in thinset mortar, matching the wet-durable materials of a tile assembly. Bare joints crack, and drywall compound/paper tape and plain silicone are not moisture-durable substrates for tile.
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