The replacement of a roof that is at the end of its lifespan but not yet damaged is relatively simple since only the shingles typically require replacement. Older roofs that have sprung leaks or begun to degrade, though, may require a more extensive replacement. The following are the main parts of a roof that may need to be replaced during the installation process.
The decking is the main wood base for your entire roof. It's typically made of 1/2 inch thick plywood or similar material, which is then affixed securely to the roof trusses. Your roofer will inspect the decking and trusses for damage. Trusses rarely require replacement, particularly if they are made of metal instead of wood, but the decking is more prone to issues. Undiagnosed water leaks can lead to excessive rot, which will necessitate the need for new decking. Punctures in the decking may also lead to the need for new decking installation. In some cases, only part of the decking will require replacement, while in others you may not need to replace the decking at all.
Underlayment is made of felt or a synthetic fabric that is then soaked in asphalt. There are also waterproof underlayment membranes that may contain a PVC liner. The underlayment is placed on top of the decking so that it forms a moisture barrier between the shingles and the roof deck. There may be an additional layer of underlayment placed along the eaves, as well, to further prevent moisture issues. Generally, you will need to replace the underlayment when you have new shingles installed since the underlayment is not reused. The only exception is if you are having a reroof performed, which is when the new shingles are installed directly on top of the old ones. In this case, the old shingles act as the new underlayment.
The final layer of your roof is the shingles. The old shingles are always removed except in the case of a reroofing installation. The most common type of shingles to install are asphalt, but these come in a range of designs and quality levels so you can find ones to fit your needs. You can also opt to have the shingles replaced with tile, metal, or wood shingles. Your roofing installer can help you determine which of these options will be the best fit for your home and budget.
Work with a roof installation service such as JCB Roofing to determine which aspects of your existing roof need to be replaced.