Almost all metal building panels may be used over open structural framing. However, they also can be easily adapted for use over solid substrate; typically 1/2" – 5/8” plywood with a synthetic underlayment is sufficient. In a high-wind area, your decking will be on the heavier side, closer to 5/8”. Your solid decking should be supported with rafters placed 24” OC (on center). When working on a residential roof, use hat channels or 2x4s with a synthetic underlayment.
Avoid panel distortion by ensuring a square and uniform structure. In all applications, purlins must be carefully measured, cut, and installed to avoid panel damage and water infiltration. This is especially true should you pre-drill fastener holes in your panels.
- Purlin spacing for 29-gauge panels is typically 24” OC, but can be as much as 30” OC. Purlin spacing for 26-gauge panels should be no more than 60” OC.
- Metal building panels can be applied over existing shingle roofs in most applications.
- Roof pitch of no less than 3/12 is recommended for non-standing seam/architectural panels. A pitch of less than 3/12 requires use of butyl tape and stitch screws.
- Panels such as 1 1/4" Corrugated are NOT recommended for roofing applications.
Prior to beginning installation, consult your local building commission regarding both local and regional codes and requirements, as these supersede any generalized guidelines provided by Weathertite.
The First Panel
Whether you’re installing a new roof or over an existing roof, the placement of the first panel is extremely important.
The first panel is placed on the roof opposite the direction of the prevailing wind. This helps moisture from being wind-driven under the side lap. What would be the overlap edge of the panel should be positioned flush with the edge of the gable end of the roof. The panel should overhang the eave by the desired amount of drip edge.
Attach the first panel completely before installing subsequent panels. Begin by fastening your panel on the ends and working your way toward the center. This prevents panel creeping, which ultimately affects its weather resistance.
In cases where more than one single panel can cover a run from eave to ridge, always install the lower (eave) panel first. Then install the subsequent panels up towards the ridge, remembering to end-lap panels. In this case, you will temporarily fasten all of the panels in the first run until all have been placed. Once satisfied with placement, permanently fasten all panels and begin the second run.
For other installation tips and accessory detailing as well as fastener placement, Weather Tite offers a Post-Frame/Residential Trim manual, as well as manuals for each of our panel types.
There are a variety of tools which may be necessary to have on hand when installing metal roofing and siding. This is not an all-inclusive list, but the following items are recommended.
- Metal nibblers
- Pop rivet gun
- Utility knife
- Screw gun
- Tin snips
- Drill and bits
- Portable circular saw
- Rubber-soled shoes
- Chalk line
- Marking pencil
- Saw horses
- Safety goggles
- Magnetic bits
- Tape measure
- Crimp tool
- Ear plugs
Cutting Metal Panels
A portable or hand shear profiled to conform to the configuration of the metal that you are using is the best tool for cutting across the profile of a metal panel. These may be expensive and difficult to find.
Tin snips, a nibbler, or a metal-cutting blade on an electric saw may also be used to cut metal building panels.
Nibbler blades have a tendency to leave hot metal particles behind that can burn paint surfaces or leave rust marks on metal panels and trims.
Any type of cutting generates slivers or metal chips. Removal of these must be immediate as they may damage the finish on the panel and shorten the life of the product.
Panels should be cut individually.
To prevent a damaged finish, flip the panel over and cut it with the bottom side up. The hot metal filings and particles generated by cutting will not become embedded in the finish and cause rust to the exterior face of the panel.
Carefully brush off all metal particles after cutting to further reduce the possibility of rust marks and bleeding on the panel after it is installed.