How many layers can I cover my roof with?
You may have no more than 3 total layers of roof
covering. If your roof currently contains 3 or more layers of shingles, you will be required to remove all layers down to the sheathing prior to installing the new roof. This is required due to the possibility that the existing roof structure may not be able to withstand the weight of additional layers being added.
Can I use my existing sheathing, and if not, what type of sheathing will I need?
You can use your existing sheathing as long as it is in good condition. Any damaged sheathing must be
replaced prior to re-roofing. A minimum 1/2-inch
exterior-rated plywood is required on all sheathing
replacements. Existing 3/8-inch sheathing may be
allowed to remain if it’s in good condition, and can
support the weight of the new roofing material.
Will I need to apply a layer of roof felt prior to
applying the new shingles?
You will need to apply 2 layers of nonperforated Type 15 felt when placing the new roofing directly on the sheathing, and when the roof slope is between 2:12 and 4:12. Only 1 layer of nonperforated Type 15 felt is required when placing the new roof directly on the sheathing, and when the roof slope is 4:12 and over. When re-roofing over existing shingles, a minimum
nonperforated Type 30 felt underlayment is required prior to applying the new roofing materials.
What types of inspections will be completed, and
when should I call for them?
If you will be covering over your existing shingles,
you will be required to have a Roof Pre-Inspection prior to performing any work. During this inspection we will verify that the roof is sound, and that there are no more than 2 layers of shingles already existing.
If you will be stripping off the existing roof and
exposing the sheathing, you will be required to obtain a Roof Nail inspection in place of a Roof Pre-Inspection. During this inspection we will verify that the sheathing is in good condition, and that any areas where sheathing has been replaced was done so properly. We will also be verifying that the nailing which is holding down the sheathing is done properly and per code (6 inches on center on the edges of the panels, 12 inches on center in the field of the panels, using a minimum 8d nail). Once the re-roof is completely finished, the last inspection you will need is a Final.
During this inspection we will verify that the roof and flashings were installed properly, that all roof vent caps have been replaced, and that all exposed PVC pipes have been painted. During your Final inspection a ladder must be supplied for the inspector. The ladder shall extend at least 3 feet above the roof, and shall be tied to the structure.
My current shingles are not made of asphalt. Can I still cover over them with asphalt shingles?
You may cover over the following existing roofing
materials with asphalt shingles: Built Up Roofing, Wood Shingles, Asphalt Shingles and Modified Bitumen. You may not place asphalt shingles over the following types of roofing materials: Wood Shakes, Concrete/Clay Tiles and Metal Roofs.
Questions regarding this handout can be directed to the Building Inspector’s Office at City Hall located at 118 Arizona Street in Bisbee Arizona. Phone 520-432-6015