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What is Oriented Strand Board
(OSB)?
OSB is a sheathing product manufactured from wood strands
glued together with waterproof, heat-cured adhesives.
Sheets are assembled in cross-oriented layers, similar
to plywood. Many applications where plywood was used
now use OSB. APA
Voluntary Standard PS 2-92 specifies performance standards
for OSB and plywood.
Is Oriented Strand Board
acceptable as a part of a tile system?
The most current ANSI standards for tile installation
(A108 - 1999) specifically exclude OSB. This is not
to say that tile cannot be installed reliably over an
OSB subfloor - however, there is significant debate
in the tile industry regarding the conditions necessary
for a long-lasting successful installation. The allowable
ambient moisture level, extent of moisture related swelling
before tiling, blocking and bracing and many other issues
are still being debated. Each installation materials
manufacturer has their own criteria and proprietary
methods and requirements. Some backerboard companies
will warrant installations using their products over
OSB - however, their specific methods must be followed.
Note, thinset manufacturers do not recommend installing
ceramic tile directly to OSB. Refer to the TCA handbook
for recommended systems that include OSB and follow
manufacturer's literature for instructions and cautions.
As with all installations, movement joints are necessary
to allow for expansion and contraction in the tile layer.
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