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Old 04-09-2006, 09:18 AM   #1
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Backerboards & gaps in the subfloor

We tore up vinil & 1/2 inch plywoods and then hardwoods. So we are now down to subfloor on a 90+ year old house and are planning on putting down tile. Went to a store & picked up 1/2 inch hardibacker board and want to start laying it down. I have one concern about us putting the boards down-there are some gaps between the boards-is that OK? or should we do something else before putting thin-set & screwing in the backerboards. Thanks!


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Old 04-09-2006, 11:35 AM   #2
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What sustrate is ther now, are you talking about plank flooring or plywood sheets?, all backerboards have to be installed over plywood or OSB, never over demensional lumber.


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Old 04-09-2006, 08:15 PM   #3
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I always try to get at least a 1"-1/14" base prior to installing the thin set and backer board. So assuming your dealing with the typical old diagonal 1x subfloor, install new 1/2" plywood with screws in each joist, then install your thin set and lat down the backer board.

Kinda of a rough idea since we dont know exactly what your dealing with, but a push in the right direction none the less.
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Old 04-10-2006, 05:48 PM   #4
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Actually 3/4" ply would be better and it must be exterior grade. DO NOT fasten it to the joists, only fasten it to the existing subfloor material. Same goes for the cement board, don't fasten it to the joists and be sure to stagger all CBU joints with the plywood joints so that one never matches up with another. The cement board (CBU) is what gets set into the fresh thinset and you don't want to use pre-mixed thinset for any reason. Leave a 1/4" gap around the perimeter of the area for expansion.
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