Reroofing in the Great Northwest; for all us roofing contractors it is guaranteed future business. One of the questions that come up: should we roof over the existing roof? What should be considered?
Many homes in the towns and cities of the Puget Sound Region were built in the late 1800’s and early in the 20th Century. As asphalt shingles were not readily available until the 1940’s most of the original roofs were wood shingles. They were plentiful, cheap and easy to install. They worked very well and lasted a long time as the homes were either not or under insulated, board sheeting allowed more than adequate attic ventilation, and the fireplaces & oil furnaces keep the interior air dry and circulating.
As these wood shingles roofs started leaking they were usually recovered with asphalt shingles. This recovering was repeated as many times as necessary to keep the roof from leaking. As we start out the 21st Century we encounter old wood shingle roofs with as many as 5 layers of asphalt shingles nailed on top! Although this worked for decades it was deemed unacceptable during the writing of the 2003 International Building Code and the International Residential Code (Section R907.3 Recovering versus replacement. New roof coverings shall not be installed without first removing existing roof coverings where any of the following conditions occur: 3. Where the existing roof has two or more applications of any type of roof covering.)
So now it is “illegal” to recover a roof that has 2 layers existing. So, if your roof is only one layer, what should you do? Simple answer, recovers have worked for a long time and will continue to perform well in most conditions.
For more roofing facts and information please see our Seattle area roofing FAQ
“Greenness.” Which choice is the Green one? Most all asphalt shingles have “lifetime” warranties; what does this mean? Nationwide the average life of an asphalt shingle roof is 16 years or more. In the past the average in the Pacific Northwest is 19 years or more. With the latest technological improvements in asphalt shingle manufacturing they should last 25 years or more.
So, recovering the existing roof will keep all the existing roofing out of our waste and recycling pool. Granted, most building materials are recycled but the process uses additional resources to recycle. The Green choice is to recover and keep the existing roofing materials out of the system for an additional 20 to 25 years.
Existing Defects. The new shingles must be nailed to a solid surface that will keep its integrity during the expected life of the roofing system. If the roof has been leaking it would need to be
31 year old home, sheathing in great shape for recover
determine if this has caused permanent damage to the structure or roof deck. Another “defect” is old board sheathing; asphalt shingles should not be installed on this type of roof deck as they develop leaks after five years or so. Be sure to let the roof consultant know the location and term of prior or current roof leaks.
Growth on the roof. This is obviously a concern in our area; actually roof-destroying algae are a big concern in most of North America. Should it be covered with a new layer of roofing? Three things are necessary for growth; moisture, air and sunlight. When a new layer is put on it shuts out the three components of growth. Now algae and fungus will not die but when covered it becomes dormant and will not cause any further deterioration or damage.
If you have only one layer of asphalt shingles and the roof deck is solid, be “twice green” save some $money$ and the environment; do another layer.