Solar Power World recently hosted a webinar with roof-mounting experts from EcoFasten Solar, IronRidge and SunModo. The speakers shared many best practices for mounting and experiences from the field. Below are tips offered for tile roofs by Brian Stearns, president of EcoFasten Solar. View the whole webinar here, or read tips for metals roofs or asphalt shingle roofs.
1. Evaluate the tiles. It’s common to find hairline cracks on tile roofs, the product of a dropped tool or a heavy foot long ago. Often cracks are sealed together with silicone or another adhesive. But just because you didn’t cause the blemish, doesn’t mean it’s not your responsibility. “What I’m finding in talking with integrators, regardless of who caused the damage, is the last person on the roof will be blamed for it,” Stearns said.
2. Watch the underlayment. In 1986, the building code was updated to require underlayment on tile roofs, protecting homes from snow, sleet and wind-driven rain. “I used to say that the tile was really a facade to protect the underlayment, which was your primary waterproofing,” Stearns said. “That’s probably a little bit of a stretch, but the underlayment is critical.” A well-done inspection of the underlayment before taking ownership of the roof is important. If the material is deteriorated, rotted or cracked, it could leak regardless of what you happen to do as an integrator on the roof.
3. Check for pests. Tile roofs are ideal homes for bats, packrats and squirrels. Damage from gnawing pests can lead to moisture intrusion, rapidly degrading waterproofing and the structure underneath. Pay special attention to holes and cracks in the roof. “If you have the ability to get inside the house and do a survey in the attic and get a sense for whether or not this roof has leaked in the past or is currently leaking, that’s a pretty critical point to acknowledge during your survey,” Stearns said.
4. You will break tile. Everybody does. “It happens on every project that I’m aware of and it’s important that you fix that material as you go, or certainly before you finish,” Stearns said. “Damaged tiles should be replaced before installing a PV system and during the installation.” Solar mounting solutions that replace a tile with a flashing are a great way to move forward.
5. Consider installation longevity. One way to install solar involves boring a hole for mounting posts through tiles. The tile is placed over the flashing and post, leaving a gap between post and tile. Somehow an installer has to make sure the area around the post remains watertight. In the Southwest, caulking and adhesives won’t last the life of an array. “Any time your solution is ‘somehow or another,’ it should really lead to the question: Is this a 25-year application?” Stearns said. Tile hooks should be evaluated for strength.
6. Consider tile removal. The popular “strip and go” installation method has installers remove tile from the roof and replace it with asphalt shingles. Solar is installed using typical flashing and attachment methods, and then the tile is reinstalled around the perimeter or the array so that it has the look of an array on a tile roof. In reality, the waterproofing layer is the asphalt shingles.
7. Install brackets into rafters. Structural engineers will sign off on installing into plywood, which will probably hold a solar array. “But a strong enough wind could pull the plywood away from the roof because it is held in place with just eight penny nails, typically,” Stearns said. And make sure installers are using pre-drilled holes for the lag bolts. Not doing so can split rafters.
8. Minimize additional weight. Tile is heavy. Limiting weight on the roof and gaining approval from a structural engineer will ensure structural integrity. “Make sure you’re doing your survey, getting a good feel for how the roof is assembled prior to jumping on there to do the installation,” Stearns said. And beware: Even the heaviest tiles can be brittle.
Ryan says
Get with the solar contractor before putting the tile down. Then have him coordinate with the roofing contractor. This is the best way to go because the solar contractor can put in all the mounts properly into trusses and then roofer can cut the tile to fit and seal up the gaps.
Brian Rockafellow says
My daughter and son in-law are preparing to build a new house with a tile roof in Naples florida. Any suggestions how they can prep the roof for solar panels?