It is imperative that a thorough roof evaluation be completed prior to your project installation. While many roofs look the same from the surface, low slope roofs in particular can be very different in their physical properties. It is important to have 100% confidence in any alterations made or even considered on a low slope roof. If there is a roofer of record for the roof, utilize their talent and up-to-date knowledge of the materials involved. Your primary concern should be completing a solid, quality installation without damaging the roofing material and/or its warranty. If you cannot contract with the roofer of record, find a roofer who is qualified for the specific type of roof and building you are dealing with. Some roofs will require boring test holes to analyze the physical properties of the existing layers. This will determine not only the exact underlying structure you are attaching to, but also whether modifying is even possible in the first place. It is very important to inform both the owner of the building and the owner of the solar system (who may be different parties) about the problems and solutions that are roofing related and those that are solar related.
Know Your Structure
Equally important to the roofing is the engineering. Low slope roofs may have a multitude of substructures under the roofing. Often insulation is encountered between the roofing and the structure. We recommend boring through the insulation and mounting the Quick Mount QBase Low Slope Mount (formerly called Low Slope Mount) to the actual substructure below the insulation. The insulation could be a wide variety of thicknesses, or even tapered. Tapered insulation is used to increase the roof slope on buildings that are too flat for good drainage. When you do find the substructure it might be concrete, steel, lumber, plywood over metal trusses, or plywood over wood trusses.
Determining point loads and positioning the QBase Low Slope Mounts is next. In a lumber and truss/rafter application, you want to attach to the truss/rafter. On a concrete substrate that is not post-tension slab, you can position the QBase Low Slope Mount anywhere on the roof plane. If the deck is post-tension slab, call an x-ray service to identify and mark the cable locations to avoid driving a fastener through the support cables. Ideally, the engineer of record for the building gets involved and defines the location and spanning of the mounts in the system installation based on the specific variables of the building, its location, and the new load being applied.
Choosing the Right Flashing
The roofer should be in charge of making sure the flashings are correctly spec’d for the project at hand. In general, the roofing material should match the flashing material. If the roof is TPO single ply, the flashing should be a custom boot also made of TPO single ply – and from the same manufacturer whenever possible – which then gets heat welded in place by a trained heat welder. The same is true of any single ply material. The physical properties of the flashing are paired to match the physical properties of the roofing. Many roofing manufacturers dictate the use of specific flashings that have been tested for safe chemical interaction with their roofs. When dealing with built-up roofing, you typically use a metal flashing which is roofed over and either mopped in or torch applied in a three-course method.
Choosing the Right Mount
Our mounts are sold in three post lengths: 7-inch, 9-inch, and 12-inch. These are intended to cover the most common insulation thicknesses, giving the installer a few options. We also make longer posts, but the engineer of record needs to review anything over 12 inches. We sell the metal flashing for a built-up roof. They are all-aluminum and sized in 4-inch and 8-inch cone heights. Both flashings are 17x17 inches.
The waterproofing up the post, whether accomplished with a metal cone on a built-up roof or a plastic sleeve (aka “witch’s hat”) on a membrane roof, should always extend high enough up the post to be above the opening at the top of the secondary overflow drain on the roof. This is known as the “flood line.” The primary drain is located at the low point in the roof and usually pipes the water away sight unseen. If water flows through the secondary overflow drain it is an immediate message that the primary drain is clogged and the roof needs service. In theory, water should never build up above the flood line.
It is important to put a compatible sealant into any and all holes drilled into a roof. Most roofing manufacturers list a recommended, approved sealant in their specifications. In the 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.
Mounting Kit Contents
Each box includes all necessary mounting hardware, mounts, and printed instructions. Due to the many different low slope membrane roof types, our mounting kits do not include flashing. Choosing the proper flashing for any given membrane is critically important, so be sure the roofer of record on the job selects and applies the correct flashing for the job. Please call us if you have any questions or uncertainty about membrane roof flashings.
For built-up roofs, Quick Mount PV sells aluminum 17x17- inch cone flashing in 4-inch and 8-inch heights. These are sold separately.