Deck and Wall Overlays

Jump to: navigation, search

Deck and Wall Overlays

Revision as of 23:23, 7 January 2016 by James Klassen (talk | contribs)

1 General

See Section 2.1, A2.5

A roof system underlay is installed under the roof system and over the roof deck assembly. Underlays are most commonly placed over steel decks to provide a level surface for the membrane, or as a thermal barrier between the roof deck and combustible insulations.

RGC requires either minimum 12.7 mm (1/2") gypsum with fibreglass facers and a silicone treated gypsum core (See Section 2.1, A2.5) or minimum 12.7 mm (1/2") plywood as an underlay for membranes installed directly over steel decks. Where an underlay is used as a thermal barrier, it must conform to the applicable code and insurance requirements for the roof assembly.

2 Underlays for Metal Roofing

Acceptable membrane underlays for metal roofing are listed in Section 8.2 and in Section 2.2 (accepted Materials list) of this manual.


Back to Essential Elements

Vapour Retarders