Perform a thorough project evaluation prior to system installation including developing a proposed array layout to ensure the system will fit as intended. Any irregularities should be noted during the planning stage, so that you can deal with them easily on installation day.
The standard sequence for installation is to install the QBase mount to the roof deck after the underlayment has been installed. The post and rack mounting hardware should be installed next. The roofer will then lay down the shingle courses and install the flashing as the courses are installed up the roof. The roofer will need to cut a semicircular portion out of the second course of shingles to ensure the upper edge of the flashing is positioned slightly uphill of the bottom edge of the third course of shingles. The solar installer then installs the racking system and solar panels.
It is important to coordinate carefully with the roofer to make sure both labor and material warranties of the roof are preserved.
Using the QBase® Comp Mount on an existing shingle roof
It is possible to use the QBase Comp Mount on existing shingle roofs. Sometimes AHJ’s require using two lag screws per mount. Determine the location of the rafter and cut a semicircle out of the second course of shingles and drill the pilot holes for the two lag screws ensuring they are centered on the rafter. Inject a roofing compatible sealant into the holes and bolt the QBase to the rafter. Slide the flashing under the second course of shingles (removing any nails that interfere). Make sure the upper edge of the flashing is positioned uphill of the bottom edge of the third course of shingles. Next, thread the post on, place the rubber collar seal around the post sliding it downward so it securely contacts the metal cone of the flashing, and finally install the racking of choice.
The QBase Composition Mount is intended to fit most composition roof systems. It is sized to fit within a standard 5" to 5 1/2" row spacing (aka coursing). To confirm that the QBase Composition Mount will match your roof, measure the course exposure of your roof. The “exposed” portion of the shingle should measure no more than 5 3/4". If the shingles are a non-standard size with exposure greater than 5 3/4", the proper installation procedure is to cut further up into the second course of shingles and shift the flashing upslope to make sure the upper edge of the flashing extends up under the third course of shingles by at least ½". This method will work on exposures of up to 8". If the exposure is greater than 8", please contact us by phone or email in order to customize a solution to your application.
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, 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 quickmountpv.com/waterproof/code-compliant.html.
Alternative Attachment Methods
The QBase Composition Mount should be secured to a lumber rafter. 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. In this case it is necessary to install wood blocking between the rafters, then secure the lag screws into the wood block. In the case of metal rafters, lumber blocking the rafters is a solution, but should be done per the building’s engineer of record.
Shared Rail Racking Systems
Shared 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 must be carefully positioned to make sure the rail lines up with the top of the modules. It is important to ensure the upper edge of the flashing is positioned uphill of the bottom edge of the third course of shingles. This may require that the second course of shingles be cut further up than is common on a standard rail system
The manufacturer of the TJI should be consulted to determine the fastener type and size. It is important to identify the specific TJI used. Installing wood blocking between TJI joists may be the best approach if inserting fasteners into the TJI is not permissible or does not provide sufficient pull out strength.
Rafter vs. sheathing attachment
All Quick Mount PV flashed mounts are designed for attachment 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 advisable to verify this structural attachment with a qualified structural engineer.
It is important to put a roofing compatible sealant into any and all holes drilled into a roof. Most roofing manufactures list a suggested, 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 that may be more 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.
Quick Mount PV mounts include all the necessary mounting and flashing hardware as well as written installation instructions.