Rooftop Decks for Coastal Homes, continued
We frame the parapet wall with 2x6 plates and studs, and
sheath it on both faces with plywood (Figure 3). It supports
the deck and also serves in place of a railing; it needs to be
high enough so that when the depth of the deck framing and
decking is considered, the wall cap will reach the required
height for a deck rail.
Figure 3.Half-height parapet walls framed on top
of the sheathed roof (left) enclose most of the deck area, with
just a small front panel left open (right). The front opening
will receive a cedar railing and will be provided with
roof-edge flashing, draining into a painted and copper-lined
Because the roof edge it sits on is sloped away from the
house, the studs for the wall have to be individually measured
and cut to the proper length, so that the wall height will be
uniform above the level walking deck.
The main room walls beneath the parapet walls are mostly full
of windows and doors. The headers in those openings are sized
to support both the uppermost deck, with its allowable live
loads from snow and people, and the more lightly loaded
lower-room ceiling frame.
EPDM roofing is a known quantity, with billions of square feet
in service and decades of accumulated installer experience.
There are several ways to attach EPDM to roofs in the
commercial market; for our jobs we use a fully adhered system.
First, we screw a rigid insulation board to the plywood roof
sheathing, then we apply adhesive to the foam board and lay the
rubber over it (Figure 4).
Figure 4.A roofer lays out the specified fasteners
for the rigid-foam underlayment (top). After the screws are
driven in (bottom left), the EPDM is adhered to the deck
It takes several pieces to completely cover the whole shape of
our roof and its parapet walls; seams are formed according to
manufacturer specifications, with either applied adhesive or a
special seaming tape. We also run the rubber roofing up the
main house wall and into the rough window and door openings
— when all the seams have cured, we're left with one
continuous, integrated waterproof membrane protecting not just
the roof, but also all the vertical walls around the deck, as
well as the main house wall and its rough openings (Figure
Figure 5.The roofing contractor rolls adhesive
onto the back of the EPDM in preparation for covering the
parapet walls (top). Lapping and seaming the rubber into wall
openings and at intersections and transitions creates a
continuous watertight drainage plane capable of protecting
vulnerable points in the building envelope against brutal
oceanfront weather (bottom).
The contractors I use for my rubber roofs come out of the
commercial roofing industry, of course — that's where
most EPDM is used. These little jobs are attractive to them,
however: They can make good money on a weekend, and some of my
smaller roofs they could just about cover with scraps left over
from one of their regular commercial low-slope roofing