Monday, September 15, 2014
Drywall is gypsum board. We want it
to look nice, give us some fire protection, reduce air flow, etc.
Sheetrock,
itself, can expand and contract fairly nicely. When it’s cracking it’s because
the substrate supporting it is moving. We know that all building materials
move, so our goal is to build in expansion joints to allow the substrates to
move.
Property
installed and taped drywall makes a good air barrier. When you add your paint
you have a nice vapor retarder. This is why architects like the versatility of
drywall. Also, you’ll notice fire code drywall being used as draftstops, smoke
walls, and firewalls.
Treated
gypsum board is frequently specified to be used in wet areas. If the budget
will allow it, substitute their “green board” for cement board. Cement board
will last longer.
Although
not specified all over, we like to use 5/8” fire code drywall all over. The
5/8” F.C. is not extremely more expensive and when applied properly over each side
of a wall you’ll get a one hour fire rated system all over.
Stain
breaks down in ultraviolet light more quickly than paints. This is why you have
to “re-stain” so often. Quite often “solid body” stain is really a thin paint,
so its value is limited.
Primers
are used to provide a surface to keep the finished paint from over absorbing
and provide a more adhesive surface for the paint. Primers also attempt to
reduce the effect of tannic acid and salts from wood. Normally, oil based
primers hold back tannic acid in wood. Latex primers seem to work okay on
masonry, drywall and concrete. Generally, redwood and cedar should be primed
with an oil base primer.
Thank you for sharing this interesting and informative article, painting with airless spray gun will be faster and more interesting!
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