Preparing Your Roofing Deck for Asphalt Shingles

Preparing the Roof Deck

Whatever type of roof you are looking to lay, the roofing deck will have to be prepared accordingly. This is whether it is a stripped roof or a brand new construction. The roofing material you have chosen to use will decide how the roofing deck is best prepared. Always make sure to take the correct measurements before installing the sheathing and underlayment and you will be on the right track for when it comes to apply the roof shingles. If you are using asphalt shingles for your new roof, make sure that you have used a solid sheathing underneath, such as either wood boards or plywood. I recommend that the underlayment used should be of 15 pound felt.

Plywood Sheathing

When you are installing plywood sheathing, make sure to lay them down horizontally and perpendicularly to the roof rafters. Make sure to stagger the panels so no vertical seams are in line. Always allow for expansion between adjoining panel ends and panel sides. I would use either box nails or 2-inch common nails when it comes to nailing down the plywood. Drive a nail down every 12 inches where panels and rafter cross paths and every 6 inches along the vertical panel edges. Always measure any irregular areas and write down the measurements on the plywood before cutting it. The edges of the plywood should line up with the ridge beam at the centre. After you have laid the plywood, install the drip edges nearest to the eaves. Once this is done you can apply the underlayment.

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Underlayment

Repair any damage to the wood surface before rolling out the roofing felt. This is easiest done by cleaning out knotholes and resin pockets and nailing down sheet metal over it and any cracks that you see. Then you can install the drip edge near the eaves. A great way to make sure that the alignments are even is to use the ‘snap the chalk’ trick. Get a piece of chalked string and attach it to one end of the roof, pull it taut across the roof, lift the line up and let it snap back, leaving a nice and straight chalk line behind. This is then done across the entire roof plane, guiding you in your work. Just make sure to get all the measurements done first.

It is best to start with the felt at the eave, leaving a bit of an overhang by the drip edge. Work horizontally and towards the ridge, laying the strips a bit layered. The felt should also overlap at hips, ridges and valleys. Always trim it flush by the rake. Only use enough nails to keep the felt in place and then use shorter nails near the eave – especially if the actual overhang deck is a lot thinner than the standard roofing nail. Once you have finished applying the underlayment you can install the flashings. Always take care cleaning up after yourself once any type of work on the roof has been done, as you do not want any dirt and debris to end up in the guttering.

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