A roof installation can take different forms. The type of work you'll have done depends on the condition of your old roof. New asphalt shingles could be all you need, but if your roof is in bad shape, it could need additional repairs. Here's a look at some of the work you might need to have done when you get your new roof installation.

Replace Plywood Decking

The deck is the plywood part of your roof that the shingles are nailed to. If you've had a roof leak, the deck might be soggy and rotted. If so, part of the plywood may need to be pulled off and replaced.

The plywood is nailed to the rafters to hold it securely. When plywood has to be replaced, it's taken off at the rafters so the new piece has something solid for the nails to drive into. When replacing rotted decking, the contractor only has to cut out the part that is damaged. That might only be a few pieces across your entire roof or it could be a large section of the deck.

Repair Rotted Rafters

When your roof leaks, the rain can roll down the rafters and cause them to start rotting away. The rafters are an important part of your roof since they hold up the deck. When rafters are rotted, they may be reinforced by adding a sister board along the side of each bad rafter.

Improve Attic Ventilation

If your roof wore out prematurely due to overheating in your attic, the roofing contractor may recommend improving attic ventilation when you have your new roof installed.

Normal ventilation is a passive process of circulation through soffit and ridge vents. If you have a gable roof, it may have a vent grate on the side. If these vents are not sufficient, your contractor might add a turbine vent to your roof so your attic stays cooler and doesn't make the shingles too hot.

Apply New Shingles

When you get a new roof, you will, at the very least, get new shingles applied. You might have the option of applying the new shingles over the old ones, but the roofer may tear off the old shingles and put the new shingles down over new underlayment.

There are pros and cons to both methods, and your roofing contractor can help you decide what's right for you. However, building codes usually limit roofing to two layers, so if your home already has two layers of shingles, they both have to come off before having your new roof installed.