Rigid Insulation Roof Over Decking

The bottom layer of a single ply membrane roofing system is the roof deck or substrate.

Rigid insulation roof over decking.

This construction approach was first used in the 1970s and it has been implemented much more widely since it was first included in the international code council s icc model building code in 2007 irc section 806 4. The insulation installed over the roof deck must be installed in multiple layers with joints offset in order to control convective looping at joints between insulation panels. The rigid insulation over roof would have controlled the temperature of the condensing surface the underside of the roof deck so that i would not have had to use the spray foam except at the perimeter to provide the air seal to the tops of the walls. Steel deck with fully adhered single ply membrane over a cover board with xps insulation over gypsum board thermal barrier or applied directly to the metal roof deck.

Start at the bottom of the roof and place the first piece of rigid foam insulation against the metal flashing starting at the center line. The purpose of the requirement that rigid foam installed above roof sheathing meet certain minimum r values is to ensure that the roof sheathing stays warm enough during the winter to avoid moisture accumulation and possible sheathing rot. Suited for a wide range of applications foamular extruded polystyrene xps insulation is ideal for roofi ng applications including single ply protected roof membrane assemblies prma tapered vegetative roofs plaza decks architectural metal roofi ng and recover roofi ng. Nail it around the edges with roofing nails.

After the roof deck is prepared the rigid foam boards need to be cut to size to fit snugly together on. Polyisocyanurate extruded polystyrene xps. It is an acceptable practice to install a new roof over an existing roof membrane system provided that the roof deck is structurally sound and has been properly prepared to support the added load. Attach to deck board.

Rigid foam insulation installation prepare roof deck. Specify this solution zip 8 39 mb.