Solid roof decks provide the ability to attach all types of roofing material, including shingles, metal siding, corrugated panels and rubber-based roofing products. You can install plywood sheets to create a roof deck, and this ties the roof rafter structure together. It is important to buy the right type of plywood for the job so that it tolerates the roof load and is suitable for all weather conditions. Successful installation of plywood sheets for roofing is achievable with some planning and care.
Use a safety harness and attach yourself to the roof rafters in all areas where the footing is precarious. Measure the roof area to determine the amount of plywood you need by measuring across the eave from gable to gable and from the roof peak to the eave. Use a measuring tape and measure from the centre of each rafter to the next to determine the on-centre gaps.
Order plywood sheets cut to the on-centre measurements. Use a minimum thickness of ½-inch plywood for 16-inch rafter gaps and 5/8-inch thickness for 24-inch rafter gaps. Check that the plywood sheeting is Exposure 1 rated and is suitable for structural use as standardised by the APA.
Position the first plywood sheet at the eave edge and line it up with the side of the roof. Wear safety glasses, and using a nail gun, attach the sheet to the rafter with 2.5-inch steel wire nails. Use the nail gun and secure the vertical edge of the plywood at 6-inch intervals up the rafter.
Position the next panel adjacent to the first and leave 1/8-inch between the panels as recommended by the APA. This allows the plywood to expand and contract without causing damage to the roof. Attach the plywood to the rafter in the same way as before.
Continue to attach plywood sheeting to the rafters across the roof, making sure that all side edges secure to rafters and are not floating in the rafter gaps. Apply a second course in the same way and leave a 1/8-inch gap between the horizontal edges of the first and second tiers.
Use a fine-toothed wood saw to cut a plywood sheet if you find any sheets going off-centre on the rafters. Continue to install the plywood across the roof and up in tiers until the roof deck is complete.
Things you need
- Safety harness
- Measuring tape
- Safety glasses
- Plywood sheets
- Nail gun
- 2.5-inch steel wire nails
- Wood saw