- Q.As a general contractor in
the Blue Ridge mountains of southwestern Virginia, we often
build vacation homes higher than 4,000 feet altitude, where
wind-driven rain is a regular weather feature. On one site, the
wind regularly reaches 50 to 80-plus miles per hour and
actually blows rain uphill. We have a south-facing window wall
full of fixed-glass and awning windows. The wall has 2x6
studs,1/2-inch OSB sheathing, Tyvek housewrap, and
1x10 horizontal ship-lapped pine. With only a 3/8-inch lap on
the siding, I can imagine that water might be driven behind it.
But how is it getting past the Tyvek and OSB through the wall?
Water drips from the interior window head jambs, and with the
interior wall paneling removed, it can be seen on top of the
sole plate. We had to replace some buckled hardwood flooring
after a vicious storm last January, and before we repair it
again, we want to make sure the wall won’t leak. Are
there any methods or materials that you could
A.Patricia Hamilton responds: We build homes
along the Delaware coast, where storms bring heavy rains and
winds of 40 to 80 mph on a routine basis, plus the occasional
hurricane. We take a few extra precautions to keep our houses
- Use siding with an adequate overlap and avoid diagonal
siding patterns. The scant 3/8-inch overlap you mention is
most likely contributing to the problem. Avoid vinyl
siding, as well as low grades of wood siding (they’re
more prone to shrinkage and cracking).
- Use the best windows you can buy — Grade 60, if
possible. We only use clad windows with integral nailing
- The house should be weatherproof even without its
siding. (The siding’s job is to hold paint and look
good.) Always use housewrap, installing it from the bottom
up so that water can’t get behind it, and tape all
- Back-caulk your window flanges as you install the
windows. Cut a slice in the wrap just above the window and
install a piece of tar paper or metal flashing that goes
behind the wrap and in front of the flange (see Figure 1).
If there is trim above the window, extend the flashing over
the trim, and tape the slice in the wrap.
- Under shingle siding, on the sides that get the worst
weather (east and northeast for us), install tar paper over
the wrap and tape all seams. Sidewall shingles let more
water past than bevel siding.
- Watch out for step flashings, since they usually go on
after the housewrap. It’s important to slice the
housewrap and install the step flashings behind it. In
tricky areas where valleys channel water up against
sidewalls, we lift the housewrap out of the way and install
a backup strip of Grace’s Ice and Water Shield over
the step flashings and behind the housewrap (Figure
- Caulk between the siding and the window trim.
- Hope for a bad storm before the drywall goes up to give
your weatherproofing a test run.
Patricia Hamilton is owner of Boardwalk Builders in
Rehoboth Beach, Del.