Designing for Building Maintainability - Effective Building Maintenance: Protection of Capital Assets - page 142

be driven through the minor imperfections likely to be present in the ex-
terior seal. The compartmentalization of the window-wall system also
makes it easier to isolate any eventual leaks. With the earlier window-
wall systems, water might find its way down a few stories from its point
of entry before any sign of water ingress was visible on the interior. With
a compartmentalized system, it is unlikely that water can travel far from
its point of entry.
Roofing
All roofs will leak; it is just a matter of when. But, pitched or high-
sloped roofs shed water better than flat or “low-slope” roofs (roofs with
less than 3:12 slope) simply because gravity alwaysworks and roof de-
sign and construction may not. High slope roofs (with pitch greater than
3:12) have the advantage of shedding rainwater and reducing the poten-
tial of roof leaks into buildings since the roof doesn't actually have to be
a water barrier. Aroofslopeofatleast3:12ishighlyrecommended , the result
will be a roof that lasts 2-3 times as long, leaks far less, and significantly
reduces the cost of maintenance.
As part of a high slope roof system, the use of an architectural
standing seam metal roof (ASSM) as the primary rain barrier is becom-
ing standard. Asphalt shingle roofs wear poorly in almost all climates,
wood shingle roofs are a fire hazard and maintenance nightmare, and
tile, cement, and slate roofs are too expensive and too heavy to ordinar-
ily considered. ASSM is typically made of galvanized steel with an alu-
minum coating, covered with a baked-on enamel or powder-coat finish,
has a long design service life, and requires very little maintenance.
If, however, after a thorough evaluation, the decision is made to
utilize a low slope roof, the next step is to decide the type of low slope
roof to install. Roof slope should never be less than 1:50 (approximately
1/4” per foot) and the slope must be uniform to prevent “ponding.”
There are basically two types (with many variations) to consider:
Type1
Single-ply materials that can be attached chemically, mechanically,
or held in place with ballast, usually gravel or aggregate. Examples of
single-ply products include:
— EPDM: Ethylene propylene diene monomer (synthetic rubber)
is a flexible elastomeric material.