How to install roof decking

Intro to Roof Decking

How to install  4 x 8 sheets to a roof for decking. This simple procedure works the same for the thinnest 7/16″ OSB to the the thickest 3/4″ CDX.

The main priority for anything to do with a roof is safety. If you are not familiar with climbing, then you should at least hire at least one skilled carpenter who is comfortable with heights.  The thing is, you are going to need some assistance anyway.

Whether the building is trusses or stick framing, it should be complete with all bracing, ridge props, gable overhangs, collar ties, and purlins. This will help prevent a collapse and make straightening the framing members much easier. Only on rare occasions is it advisable to run the sub-fascia on the eave (end of the rafter tails) before the decking. A much better job can be done if you wait.

The most important part of any roof decking project is to strike a chalk line at the top edge of the bottom run. Make a mark at 47″ from the short point of the rafter tail on top of the rafter at each end as close as you can get to the edge on each end. This is to keep the sponge like edge of the roof decking as far as possible from the gutter.

The decking must break. In other words, it has to ride at the center of a rafter when it joins another piece. While the layout for the rafters should be on a standard placement so 8′ sheets will work, it is best to check the measurement of each piece before muscling it into position.

Each run should alternate the starting piece. If you start out with an 8′ piece on the bottom run, then you should try to make a 4′ piece work for the next run. This will ensure a much stronger construction for the entire building.

Use 8d coated framing nails only to fasten it down. They should be 4″ O.C. on the ends and 8″ O.C. in the fields. The heads should be slightly countersunk. Nail each sheet as you go. Have fun and be careful.