Dry
Wallboard
By Dermot Mack
Manufacturers introducing drywall products that resist moisture.
While gypsum wallboard - or "drywall" - has been standard in homes
for years, there was always the danger of moisture. Getting the gypsum wet during
construction often meant throwing it out and, if it got wet after installation
it could lead to the latest horror: mould.
Now, says Thad Goodman of Georgia-Pacific, a new interior wallboard called DensArmor
may put an end to all that, or at least reduce the problem.
DensArmor consists of a non-combustible gypsum core embedded with a coated glass
mat on the back and a smooth, heavy-duty paper on the face. The mat on the back
provides superior protection from incidental moisture in the stud cavity and
resists the growth of mould and mildew. The material cuts, scores, hangs and
finishes just like standard drywall, and it is possible to skim coat it similar
to blue board for veneer plaster applications.
The DensArmor, however, requires a bit different treatment on installation.
For instance, the joints should be sealed with a fibreglass mesh tape and a
setting-type compound to bed fibreglass tape. The board does feature a tapered
edge for joint finishing. Ready-mix joint compound can be used for subsequent
coats.
Also, the product is not actually mould resistant, since mould can grow on any
surface when exposed to the right elements. For that reason, it does not come
with a mould warranty, but it does carry a three-month in-place exposure limited
warranty and a three-year in-place (free from manufacturing defects) limited
warranty.
DensArmor can't be used as a tile backer in bathrooms. In fact it should not
be specified in areas that will see moisture levels higher than that of a bathroom.
According to GP Canada, it can be used as an exterior soffit material and on
any interior wall, basement wall or ceiling that is at risk of moisture. It
is not to be used as an exterior sheathing.
Here, GP has introduced its DensGuard line of paperless glass mat panels. These
moisture-resistant panels have proved such a hit that three of Georgia-Pacific
Canada's gypsum plants are now making it. The panels are being produced at facilities
in Surrey, British Columbia, in Edmonton and in Caledonia, Ontario. All three
plants will manufacture DensGuard for distribution in Canada and the United
States.
Other manufacturers are also offering moisture-resistant wallboards. BPB Canada
offers the moisture-resistant 1/2" ProRoc Moisture Resistant, which is
a moisture-resistant wallboard that will prevent warping or water damage to
your walls.
US Gypsum, which invented gypsum wallboard in 1917, has introduced a new line
of moisture-and mold-resistant wall panels called Sheetrock, available in Canada
through CGC, a subsidary of USG. For water-resistant and/or mould-resistant
panels, home builders an renovators can choose Sheetrock Brand WR (Water-Resistant)
gypsum panels or Sheetrock Humitek panels that are resistant to both moisture
and mould. CGC also offers Durock cement board, a tile backer for walls, floors
and counters that is not affected by water.
National Gypsum replies with XP Wallboard panels that consist of a fire-resistant,
moisture-resistant gypsum core encased in heavy moisture/mold/mildew-resistant
covering. HB
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