Skip Sheathing (Spaced Sheathing)

Skip sheathing, also called spaced sheathing or open sheathing, is a roof deck made of individual boards nailed across the rafters with open gaps between them rather than as a solid surface. It is the traditional substrate for wood shingles and shakes in North America, where the open spaces allow air to reach the underside of the wood so it can dry after rain, which helps reduce decay.

How it is laid out

The boards are set at intervals related to the exposure of the shingles or shakes so that every course has a board to nail into. Because the deck is open, the attic below is visible through the gaps on older houses.

Relation to battens

Skip sheathing is the North American equivalent of the roof battens used in Britain, Europe, Australia and New Zealand to hang tiles and slates. Both provide spaced fixing points; battens are usually smaller-section strips and are often laid over an underlay and sometimes counter-battens.

Issues when re-roofing

When an old wood roof on skip sheathing is replaced with asphalt shingles or other materials that need a continuous deck, the usual practice is to cover the skip sheathing with structural panels such as plywood or OSB, or to fill the gaps with boards. Manufacturers of most modern roof coverings specify a solid deck. Some metal roofing systems can be fixed to spaced battens or purlins instead.

The open boards also provide less diaphragm stiffness than a solid panel deck, which can be relevant in high-wind and seismic upgrades.

Note

Exact board widths, spacing and nailing for skip sheathing are set by the shingle or shake manufacturer and local code, and vary by product.