- Q.The red cedar clapboard
siding on a house in the Boston area was not backprimed
and has typical moisture-related paint failure. It has
been painted five times in 25 years. The house has no
interior vapor barrier. I am considering removing the
siding and installing new backprimed clapboards over a
vented rainscreen. Will the rainscreen installation
solve the problem of premature paint failure, or must I
address the lack of an interior vapor
barrier?
A.Mark Snyder, a builder
who works in Massachusetts and Vermont,
responds: Installing new backprimed clapboards
over a rainscreen will almost certainly solve the
problem of premature paint failure, regardless of
whether the house has an interior vapor barrier. If
you think an interior vapor barrier is important,
you could paint the interior walls with a vapor
barrier paint. In addition, the homeowner should
know that every house needs adequate mechanical
ventilation, both to maintain indoor air quality
and to reduce the chance that interior humidity
could migrate into the walls.