For most roof types, you have two options when it comes to re-roofing Asbestos shingles:
- Complete tear-off of the roofing material down to the decking (the wood covering the trusses).
This should be done if your roof has already had a roof over, where new shingles were put on over the old shingles. - A roof over. This is where new roof is laid directly over the old roof.
This works well where the original roof has a very flat pattern or type of shingle; otherwise your new roof will not lie flat.
Dimensional shingles cannot be roofed over
Roof Overs
A roof over can only be done one time. In other words, there can be no more than two layers of shingles on the home at any one time.
Yes, non-profess
ional roofing companies will tell you it is no problem, or code does not matter, you can put three or even four layers of shingles on the roof.
Remember, shingles are heavy! The more weight you put on the top of the house, the greater the possibility that something below bends (the rafters or trusses), sags (the decking), or sinks (the house). Shingles weigh between 220 lbs and 380 lbs per square. When you consider that a small home can easily use 20 squares, that?s 4,400 lbs to 7,600 lbs or 2 ¼ to 3 ¾ tons weight.
With a roof over, it’s twice the necessary weight on the roof.
Or, to put it in perspective, it’s the same weight as parking a Chevy Suburban on the roof!
NOTE: One square of shingles covers 100 sq feet (10 feet x 10 feet).
Examine the Pitch
Before re-roofing with shingles, examine the roof paying particular attention to the slope or pitch. If there is an area that does not have a good slope, (such as over a front porch or an add-on to the back, 2:12 pitch is the minimum for shingles with a standard instillation) it would be wise to consider an alternative form of roofing material for this area. For shingles to work properly there must be a good pitch or slope to the roof. This gets the rainwater off the shingles and into the gutters quickly.
A poor pitch causes water to remain on the roof longer, rotting and deteriorating the shingles at an accelerated rate.
Alternative roofing materials could be metal (yes, it does come in a variety of colors) rubber, or rolled asphalt.
Shingles Life Expectancy
When choosing fiberglass shingles, choose wisely. Shingles are sold as 20, 25, or 30 year shingles. You may presume this to be how long they will last. Wrong!
- Twenty year shingles do not usually last longer than about 15 years and may show signs of serious deterioration between 10 and 12 years.
- Twenty-five year shingles have a useful life of about 18 to 20 years.
- Thirty-year shingles have about a 25 year life expectancy.
Choosing a Roofing Company
Be careful choosing your roofer, get written estimates explaining exactly what is to be done.
(Remove and dispose of old shingles, new decking, new felt, drip edge all round, type of flashing, type and brand of shingle, roof vents – these issues need to be addressed before you sign on the bottom line!).
- Ask for references, call them and visit the home, talk to their neighbors and establish that the work was not done by someone else.
- Ask for a copy of their insurance (bonded probably means nothing).
- Check with the Better Business Bureau.
- Get at least three estimates!
NOTE: In Ohio there are no licensed roofers. Understand what the roofer is talking about, check out our roofing terminology page.
