Considerations Prior to Installing New Asphalt Shingles
At some time in the future your asphalt roof will likely need to be replaced. Prior to doing this several things need to be considered prior to the actual installation. Here are helpful tips, guidelines and common mistakes I often encounter while conducting home inspections.
The first thing you need to ask yourself once the decision has been made to re-roof is, “Will I hire this job out or can I do it myself?” Unless you have a substantial amount of roofing experience and done it properly, enjoy back breaking labor in the heat of the day and you are comfortable on high and often times very steep inclines and have the proper tools to do the job it is suggested that you have the roof professionally installed.
If you decide to do the job yourself it is recommended that you research the proper procedures in detail prior to attempting the job. The shingle manufacturer’s instructions are included on the wrapper of every bundle of shingles. These instructions are rarely followed by do-it-yourselfers. Unfortunately, something as simple as using the wrong length of roofing nail, improper placement or spacing of nails or incorrect shingle exposure will turn your 30 year shingle into a non-warrantied shingle.
So, now you have decided that you will have a professional install your roof. You call several roofing contractors and decide to go with the lowest bidder. The contractor tells you he can save you $1,500.00 if he doesn’t do a tear off and roofs over the existing shingles! Excellent, if you choose to do this you have just invalidated any warranty your new shingles had. It is recommended to always do a tear off. This will help preserve your warranty and allow the roofer to examine the roof sheathing and make any necessary repairs.
One other consideration if you elect to roof over existing shingles is the weight added to the roof. A square of shingles can weigh 200-350 pounds per square. If you have a 20 square roof this means you already have approximately 4,000 – 7,000 pounds of shingles on your roof structure. Add another 4–7,000 pounds on top of this. In most areas it is acceptable to have two layers of shingles on your roof. Theoretically your rafters or trusses should be able to support this load without any stress. Theoretically.
While your roofing contractor is doing his estimate ask him to evaluate your attic/roof ventilation. Inadequate attic ventilation is one of the primary causes of premature roof deterioration. Numerous advances in attic/roof ventilation have been made in recent years.
I often inspect new roofs only to find that the old and often times deteriorated plumbing vent boots or flashing have been re-used. If the boot is damaged you may find yourself tearing into your newly installed roof to replace the boot that is now leaking into your ceiling. It is recommended that new boots always be installed.
Roof replacement can be expensive. If you have to have it done you will save yourself time, money and heartache by doing it right the first time.