It is important to perform a thorough roof evaluation prior to the solar installation. Any irregularities should be noted prior to installation, so that you can deal with them more effectively on installation day. The remaining life of the roofing system should be determined in the site assessment, and any repairs or replacement should occur prior to solar installation. On a comp/asphalt shingle roof, we recommend documenting the following roof details: roofing materials and manufacturer(s), the age of roof, the type of sheathing (plywood or oriented strand board “OSB”), rafter size, spacing, and span, age of roof structure and covering, who roofed it, and who built it.
Photos should be taken of all of the roof variables and then kept with the job file for any future reference. Often the building owner can check their records to verify the comp shingle manufacturer. If not, take a section of shingle to a roofing distributor to identify the manufacturer and age of the shingle and obtain the manufacturer’s installation instructions for the roofing materials. The manufacturer’s instructions will spell out exactly what does and does not void the warranty of their roofing product. Most have a clause about roof temperature. This is commonly missed, but can easily be noted if you read the instructions. Officially, the roofing manufacturer’s instructions supersede Quick Mount PV instructions, as our product is weaving into theirs. It is also important to have their instructions in the job file for any future reference. If the manufacturer cannot be found, there is obviously no warranty in place.
On a roof that has a material and labor warranty in place (new roof), it is recommended to contact the roofer of record and discuss what would be necessary to maintain the product and workmanship warranties. Often the roofing contractor will void the labor portion of their warranty if another trade modifies their work. Give the roofing contractor the option of performing the installation of the flashed mounts. At the very least, allow the roofer the opportunity to inspect and approve the modifications you make.
The Classic Comp Mount, E-Mount, and QBase Comp Mounts work on most composition and wood shingle roof systems. They are sized to fit 5" to 5- 1/2" course spacing. To confirm that these mounts will match your roof, measure the course exposure of your roof. The “exposed” shingle should measure no more than 5-3/4". If the shingles are a non-standard size greater than 5-¾", it might be possible to use the Quick Mount PV Classic Shake Mount, or you can cut up into the second course of shingles and position the flashed mount making sure the upper edge of the flashing is positioned above the bottom edge of the third course of the shingles. If the roof uses architectural shingles (aka High Definition, Presidential, etc.) it is important to make sure there is full support under the flashing. This may require using a piece of asphalt shingle as a shim under the flashing to insure there are no voids under the flashing.
Irregular tooth pattern - If the shingles have a tooth pattern, it is important to understand that the teeth are for looks only and can be removed without adversely impacting the waterproofing of the shingles. The actual bottom edge of the shingle is located at the top of the tooth. If a tooth interferes with the mount block, cut the tooth off.
How Many Mounts Per Module?
Consult with a qualified solar installer to determine if the roof can handle the weight of the solar system and the uplift forces from strong winds. Many states and building departments have standard practices to determine if a roof has the structural capacity to handle these additional loads. If there are any questions as to whether the roof has the structural capacity to support a solar system, it is necessary to consult a licensed structural engineer to make this determination. Many racking manufacturers have web-based tools to calculate the spacing and number of mounts required. Many variables must be considered including strength of rail, distance between parallel rails, cantilever of modules over rails, pullout strength of mount, shear strength of mount, roof slope, height of roof, wind zone, array location on the roof, roof type, structural integrity of roof framing, wind speed requirements for the local area, etc. Quick Mount PV provides pullout and shear capacity as well as engineering test reports for all of our mounts on our website. We recommend reviewing our Wheel of Accountability, which is a summary of all the entities that govern waterproofing, electrical, fire, and structural requirements to comply with industry codes, standards, and installation best practices. A description of each entity and links to their websites can be found at www.quickmountpv.com/waterproof/code-compliant.html.
Rafter Vs. Sheathing Attachment
All Quick Mount PV flashed mounts are designed for attachment directly into a lumber rafter or truss. Attaching to the roof sheathing is inadvisable as uplift forces from wind load could pull up on the sheathing, loosening the nails or staples that secure the sheathing to the rafters. Mounts are usually laid out based on the location of the rafters. In some cases it is desired to place a mount where there is no rafter. Whenever this occurs, it is necessary to install wood blocking between rafters, then install the lag screw into the wood block. This is also the method for attaching to metal rafters, however, it would be best to verify this structural attachment with a qualified structural engineer.
Quick Mount PV mounts include all the necessary mounting and flashing hardware as well as written installation instructions.
Shared Rail Racking Systems
OShared rail systems use a rail positioned between two rows of modules. Since the location of the rail is a function of the module length, the roof attachment will often be located in a position on the roof that falls above or below the typical location of our mounts. When this occurs, the best approach is to cut the shingles to position the flashed mount so the upper edge of the flashing falls uphill of the bottom edge of the third course of shingles.
It is important to put a roofing compatible sealant into any and all holes drilled into a roof. Most roofing manufacturers provide an approved sealant in their specifications. In freeze-thaw zones, it is important to follow the manufacturer’s rules for freeze-thaw conditions. Use the properly rated sealant for each specific application and condition. Some sealants that are appropriate for asphalt/composition roofs include Geocell 3500 and ChemLink M-1, but be sure to do your own research to confirm a compatible and appropriate sealant with the roofing materials you are using.