A.Ron Webber, owner of Prime Plastering in
Irvine, Calif., responds: There are many available deck
waterproofing systems, and they aren't all installed the same
way, so check with the manufacturer for the correct
installation technique. Generally speaking, most leaks occur at
termination points, including the transitions between deck and
wall metal, deck and door threshold, and deck and door jambs.
Other trouble areas include the attachment point for handrails
and the area around scuppers and drains.
All penetrations and terminations should be flashed in a
weatherboard (overlapping) fashion, with a minimum horizontal
overlap of 2 inches and a minimum vertical overlap of 6 inches.
Deck-to-wall joints must be lapped and caulked or soldered.
A door will require the following installation details:
- Install a watertight door pan, like the Jamsill Guard
(Jamsill, P.O. Box 485, Talent, OR 97540; 800/526-7455;
www.jamsill.com). The door pan and finished floor inside
must be at least 3/4 inch above the finished deck.
- Tack the flexible flashing membrane (such as Moistop
from Fortifiber) around the perimeter of the rough opening,
being careful to lap the flashing over the deck-to-wall
metal. The top piece of flexible flashing should overlap
the side pieces.
- Run a liberal amount of good quality urethane caulk
around the rough opening, on top of the flexible flashing.
Then install the pre-cased door jamb, pushing the stucco
mold trim into the wet caulk.
- When lathing, be sure to lap the felt or kraft-paper
weather barrier in a weatherboard fashion. The felt should
lap over the flexible flashing at the head of the door, and
over the deck-to-wall metal.
- If there are any holes, rips, or tears in the flashing
membrane or weather barrier, repair the holes.
The deck should be sloped away from the door, toward the
drains. The deck should be watertight before the base coat of
stucco goes on. To check for watertightness, take a hose and
squirt the deck and then the walls, starting at the bottom and
working your way up. If anything leaks, locate the holes and
For more information, see the article "Stucco Flashing
Flashing Details for
a Balcony Door