Can you install solar panels on a tile roof and avoid leaks?
When it comes to installing solar panels, tile roofs represent the biggest challenge for solar installers. Not only can installing on a tile roof be more expensive, but there can be a higher risk of a poor installation causing damage to the waterproof integrity of the roof, leading to expensive repairs down the road.
That doesn’t mean that you should shy away from solar if you’re a homeowner with a tile roof. In this article, we’ll talk about the challenges, equipment that manufacturers have designed to make solar tile installations better, and things to watch out for when hiring a contractor to work around your tile roof.
Roofing tiles are brittle
Roof tiles made of clay or concrete are strong when it comes to holding up to wind and rain, but they are brittle. This is a problem for workers who have to climb on your roof to install solar panels and the racking that holds them in place.
Simply stepping on a clay tile can fracture it. For a solar installer who normally has to spend a day or more on top of your roof, this means taking extra precautions when working around tile. This means being careful and slowing down - but time is money for contractors, so this can mean a more expensive install.
Also, because it’s so easy to break a tile by stepping on it, the installer will be responsible for replacing any broken materials that result from their solar install. This can also increase the costs of a solar install on a tile roof.
How your tile roof stays waterproof
Whether your tiles are made of clay or concrete, neither of these materials alone will keep the rain out of your house.
While tiles do shed water, both clay and concrete are porous, which means that rain will eventually soak through. In addition, wind can drive water underneath the front lip of the tiles.
This means that the waterproof membrane underneath the tiles, known as underlayment, is the final barrier that keeps your house dry. It’s these two components working together that make a tile roof so durable. The tiles do most of the work of blocking the sun, wind, and rain, allowing the more delicate underlayment to do its job as a waterproof barrier.
Good installation practices and the use of correct materials are critical for this system to work properly. This is why when you hire a solar installer it is important to ask some key questions.
Solar installers and your roof
Solar installers are usually not roofing professionals. Instead, their skillset tends to be electrical work.
This means that installers are often learning roofing skills as they go, or the company is subcontracting the roofing work to a roofing company.
Metal roofs are the best for solar installers to work with. Often, solar panels can be mounted on a metal roof without even drilling holes.
But tile roofs present a technical challenge. Fortunately, there are great products on the market that make it easier to do a quality installation.
As a homeowner, there are steps you can take to make sure that your installer is doing the right thing.
Solar mounting options with a tile roof
Solar panels are attached to a roof with a racking system that must be anchored to the roof deck in some way. With a tile roof, there are a few common techniques an installer might use.
The comp-out technique involves removing all the tiles underneath the area where the panels will go, installing a layer of composite shingles in the gap, and then mounting the solar rack by bolting through that new layer into the wood sheathing underneath.
Some of the tiles are then reinstalled around the perimeter to maintain the look of the roof. The finished result is that the composite shingles aren’t visible under the array, and the solar panels sit lower on the roof line - often flush with the tiles.
For the installer, a comp-out involves less time and effort, and also results in fewer accidentally broken tiles.
But there are serious disadvantages to the comp-out approach:
Waterproof integrity can be compromised. The gap in tile coverage with a comp-out allows water to flow underneath the tiles. While the area directly underneath the array will have new shingles, the water will eventually flow over the underlayment underneath the tiles. Remember how the tile and underlayment work together to protect your roof? With a gap in coverage, the underlayment will be exposed to more water and even wind, which will get underneath the array in high winds. If you live in a climate that experiences freezing temperatures, that extra water can accelerate damage due to freeze-thaw cycles.
Solar panels experience higher heat. A roof-mounted solar array will normally stand a few inches away from the roof surface. This is important because it allows air to flow underneath, providing cooling to the panels. Solar cells produce less electricity when hot, so extra heat will reduce how much electricity you get out of your system. Also, high heat can shorten the life of your panels. If you have power optimizers or microinverters, those are mounted on the rear of the panels, which means they will also experience higher heat.
Because of these concerns, we generally recommend that you avoid any installation that relies on a comp-out.
Cutting the tiles
Another method of attaching solar racking to a tile roof is by removing individual tiles and cutting or drilling holes through them. The holes then allow the installer to poke the mounts through the tile and bolt into the wood sheathing underneath.
While in many ways this is better than a comp-out, it’s tricky for an installer to pull off, especially with clay tiles which are quite brittle. The installer may under up fracturing quite a few tiles in the process.
In addition, holes or broken tiles will allow more water to seep through. Again, this isn’t ideal.
There are several manufacturers that design S-shaped hooks for mounting on tile roofs. The S-shape of the hook allows it to fit around the edge of a tile. The s-hook terminates in a plate that is then bolted into the roof deck.
Waterproofing is then used around the plate to ensure that the penetrations don’t leak.
Overall, this is a much better alternative than the other approaches mentioned above because it’s non-destructive and doesn’t leave any gaps in your tile coverage. Your array will sit a few inches off the roof surface, allowing an adequate amount of air to flow through.
Keep reading for a list of some manufacturers that make s-hooks.
Replacement tile mounts
Finally, some manufacturers make roof mounts in the shape of common roof tiles. Made of composite or aluminium, each of these mounts will take the place of a whole tile on your roof. They include all the hardware required to securely bolt into the roof deck and are designed to keep the wind and rain off the delicate membrane underneath.
These tile mounts are a great option, but you may be limited by the available shapes.
Questions to ask your installer
If you’re planning to go solar, be sure to ask your installer these questions if you have a tile roof. Do this at the proposal stage, before you sign any contract.
Do you do the roofing work yourself, or do you subcontract?
What method will you use to attach the racking to my roof?
Is this method non-destructive (ie. drilling through tile or using the comp-out method)?
If yes: are you able to use a non-destructive method such as tile replacement or s-hooks?
How do you waterproof the attachment points?
Will you replace, for no cost, any tiles that you damage during the installation?
Does your installer warranty cover roof damage, such as leaks? For how many years?
Would you consider working with a roofer that I hire? (see below)
Consider hiring your own roofer
Interviewing a solar installer isn’t much different from hiring any home contractor. You want a company that gives unambiguous answers to all of your questions. If you feel like a company is being cagey when responding to your questions, don’t be afraid to drop that company from your list.
If none of the installers you interview have much experience with tile roofs, or you aren’t getting a great feeling from any of them, consider finding your own roofer to handle the roofing part of the job. This would especially be a good idea if you’re able to hire the same company that originally installed the roof.
If you go this route, the solar installer will handle the electrical work while the roofer handles all the structural work. You’ll get separate quotes from each company for their part of the project. This will reduce the cost from your solar company, but be sure to double check the line-by-line cost breakdown in the contract.
And don’t worry that this might offend your solar installer. In fact, many solar companies would be happy with this arrangement, because it frees them from one of the riskier parts of the job, allowing them to concentrate on what they’re best at.