How do I enter roof framing specifications into SolarAPP+?
Depending on the AHJ, SolarAPP+ may require specifications on the roof framing supporting the roof on which the solar panels will be mounted. Different structural roof framing types are allowed with specifications required for each roof framing:
Example framing differences would be, different rafter spacing, different rafter size, having trusses in one location and rafters in another, having plywood i-joist in one and trusses in another. These changes can occur on different roof planes or within a single roof plane. Each difference needs to be entered for verification. Note: having the same rafter size and spacing but a different span is not a different type, this common type could be entered as one type and checked using the longest span of the different areas.
For each roof framing type, the user enters the spacing in inches between the roof framing members. The spacing must be at least 12 inches but less than 100 inches.
Next, the user enters the type of roof framing which can be either prefabricated truss framing or rafter framing:
A prefabricated wood truss is wooden framing typically in a triangular pattern built of lumber providing support for the roof between outside walls of the house. They are built in a factory and carefully designed to carry the load to the outside walls. They are held together with light gauge metal plates that are punched to create teeth. The tops of the framing supports the roof sheathing while the bottom supports the ceiling finishes.
Rafters should be selected when site-built stick framing of lumber, plywood joists, or site-built truss framing is the system used to support the roof plane. When the rafter selection is made additional questions will be asked to further clarify what framing is used.
In the case of prefabricated trusses, SolarAPP+ will inquire if any modifications are performed. If modifications have occurred, the project is not eligible for SolarAPP+.
In case of rafter framing, SolarAPP+ inquires about the type of rafter framing. Options are nominal lumber, plywood I-joist or “other”. Nominal lumber is designated by the board size before it has been planed smooth – Two examples are 2x4 is planed to 1.5”x3.5” and 2x10 is planed to 1.5”x9.25”. A response to this question of “Other” should be used when the lumber used in the framing does not meet the definition of nominal lumber or some unknown/uncommon framing is used. One example would be true dimension lumber or site built truss framing (carpenter trusses).
In case of nominal lumber for rafter framing type, the user provides the size, which can be 2x4, 2x6, 2x8, 2x10 or 2.12:
In case the rafter framing type is Plywood I-joist, SolarAPP+ will inquire regarding the depth of the plywood joists which can be 10, 12, 14 or 16 inches. The user should select the value from the dropdown that is closest to the actual depth of the I-joist. If nothing is reasonably close, the user should revise the answer to the the question on rafter type to “other” instead of Plywood I-joists.
In addition, SolarAPP+ will inquire if any modifications were performed to the Plywood I-joists. Again, no modifications are allowed using SolarAPP+.
For any type of rafter framing, the user provides the largest horizontal span in feet. Only values between 1 and 25 feet are allowed. This dimension is generally the dimension from the center of the exterior bearing wall to the ridge of the mounting plane. If there are midspan supports along the rake such as a purlin and strut support, the horizontal span of that mounting plane should be the maximum span between any two of those supports.
For rafter framing, SolarAPP+ also inquires regarding the presence of ceiling joists. Ceiling joists or rafter ties are framing members that are parallel to the roof framing members that resist the outward thrust of the sloped framing.
If ceiling joists are not provided, SolarAPP+ will inquire whether there is vertical support at the ridge of the roof framing. SolarAPP+ requires alternate support to be present in case ceiling joists are not provided.
