01 May 1999
(6) Individual roofing components may be held in place by adhesives, fasteners, ballast,
or a combination of these methods.
(7) Perimeter flashings are waterproof vertical terminations of the membrane (perimeter
flashing) (figure 2-10).
(8) Roof edging and fascia are usually low profile roof edge terminations and side trim.
(9) Roof penetrations include drains, vents, curbs, equipment supports, and the like.
(10) Surfacing materials screen UV light, improve fire ratings, and may improve water
h. Attachment for Low-Slope Roof Systems.
(1) Full Anchorage. For relatively inelastic roof membranes such as BUR and MB, solid
adhesion helps restrain the roof membrane and uniformly distribute thermal stresses. When
insulation is used, it is fastened or adhered to the deck. The membrane is fully adhered to the
thermal insulation using hot asphalt or cold adhesive. Polyurethane foam is sprayed directly to
the substrate, especially in re-cover of existing BUR thereby being fully adhered as well.
(2) Partial Attachment. In partially attached systems the membrane is mechanically
anchored through the insulation into the deck, or in a few cases, partially adhered with strips or
spots of adhesive. This is common with flexible single-ply roof membranes. Fasteners are
typically placed in the seams area where by can be covered by the overlapping sheet.
(3) Loose-Laid Attachment. For loose-laid systems the membrane is unattached to the
substrate and is held in place by ballast. Restraint is required only at perimeters and curbs.
Loose-laid roofs are used with elastomeric (EPDM) and some thermoplastic (e.g., TPO) systems.
These are very inexpensive roof systems if the structure can handle the ballast weight. Caution:
In positive pressure buildings air barriers should be used with loose laid and partially attached
membranes to avoid billowing and peeling.
(1) Highly Intensive: BUR, MB
(2) Moderately Intensive:
SSSMR--The system is very unforgiving of installation
(3) Medium Intensity: Fully adhered and mechanically fastened single-ply.
(4) Low Intensity: Spray Foam requires the smallest crew (but is the most machine
intensive and weather sensitive).