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1. The Roof Deck

The Roof Deck is the plywood sheet cladding of an American Shingles roof that is applied to the frame of the building.


Although an uncommon method of construction in Australia, the roof deck is utilised to support all types of roofing including tiles in the US.

The roof deck is required to support American Shingles, the workers, anchor the shingle nails and assist in providing the wind resistance offered by our shingle manufacturer, CertainTeed Corporation. The roof deck also provides outstanding bracing characteristics for the benefit of the building as a whole.

The roof deck is installed in accordance with the timber framing code and CertainTeed’s installation requirements to honour the International Warranty offered here in Australia. The roof deck should be ventilated by way of eaves and ridge vents to prevent condensation and evacuate accumulated heat that radiates through the roof plane on hotter days.

The plywood used for the roof deck is not required to be marine grade and is typically 12mm thick for 600mm centre rafters/trusses with a grade of DD or CD. Larger spans require the use of thicker ply commensurate with the expected load and in accordance with the manufacturers instructions.

What do we need for the roof deck?

Generally speaking the requirements for the application of the roof
deck is the same as with sheet flooring.

Whilst we have no for the need the use of 'battens' for the application 
of an American Shingles roof, the builder/carpenter erecting the roof frame must provide essential substrate support.

Structural support

The application of the roof deck requires support along the external areas of the roof planes that are unsupported by an underlying structural member such as a rafter, valley rafter, Hip Rafter or the 'Tongue & Groove' along the long edge of the plywood sheeting i.e. blocking needs to be installed. This is typically between the rafters along the eaves, both sides of the valleys (if there is no valley rafter), 
the ridges and where there may be penetrations coming through the roof plane such as chimneys and skylights.

Blocking on valley and at the eaves.jpg
Blocking on valley and at the eaves

Blocking isn't usually required along the hip or the valley rafter if the roof is constructed conventionally with stick timber. See examples of blocking above:

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