You ever notice, mid-July, when the sun’s out like it’s trying to pick a fight, that your solar shingles—those shiny critters—start dogging it a little? Not in performance, necessarily, but physically. Just a smidge of space there, at the seams. Where they should handshake tight, now there’s this barely-there sliver of a gap, like the roof’s raising its eyebrow.
Thermal expansion’s the culprit, yes, but that’s just the book-learned name slapped on something more fidgety. You’ve got materials doing a little watusi every scorching afternoon. Expanding, contracting, exhaling, gritting teeth maybe. Most roofs can handle it, slapping on some flashing and calling it Thursday. But when solar shingles enter the ring, oh boy. They bring their own fuss.
Lipstick over cracked lips
What a lot of folks do—some rightly, some half-blind to it—is slap some high-temp sealant along the gaps and call ‘er sealed. Like painting toenails after stubbing your toe. And fair enough, it’ll mask the issue for a tick. But by October, freeze-thaw cycles will have that gunk shriveled like old chewing gum. And we’re back scuttling up the ladder again.
Someone tried a silicone pad once, cut it to size, tucked it in like a missing tooth. That lasted what… three rainstorms? Then the squirrels found it interesting. Chewed it up like licorice. Whole patch gone by Columbus Day.
Roof sealants are adhesive coatings made of rubber, silicone, tape, polyurethane, or acrylic that form a protective leak barrier and can serve as a preventative in areas that are likely to leak over time or as a patch to cover existing roof damage. While roof sealants are part of new roof installations, you can also add them as roofs age to bolster leakproof properties or in reaction to active leaks.
https://www.angi.com/articles/roof-sealant-types.htm
Alright, so what then works?
They don’t tell you much about this in the brochures. Too messy. Too small-potatoes for clean marketing. Here’s what I’ve done, cobbled from three winters and one very hot Labor Day:
You start by identifying the actual movement. How much wiggle do these suckers show? Few millimeters? You measure it over the day — early morning vs. sundown. Not the most thrilling party trick, but you’ll learn things. Then, you check what’s under those shingles: underlayment, battens (if you have ‘em), the fasteners.
Nine times out of a box of mismatched screws, it’s not the shingle that’s to blame, but the give beneath it. Something bowed. Something loosened. So before any goo tubes come out, tighten what oughta be tight. Reinforce what should be steady. You’re not fixing the surface — you’re convincing it not to dance anymore.
The rubber edge idea (only kinda worked)
Back in 2019, a neighbor two blocks over — Allen, I think? Or maybe Allan? Never wrote it down — tried this thing where he sliced nitrile rubber gaskets lengthwise and jammed them under the edge of each adjacent tile pair. Sort of like a pressure buffer. Clever. Looked real tidy too that first week.
Then birds pooped on it. A lot. Turns out nitrile heats like mad under fecal acidity (Don’t ask how I confirmed this) and the gasket edges warped up like drying orange peels. So that’s… maybe not the one I’d pick.
The kid had the sense of it right
Somewhere along the way, my nephew — all braces and sarcasm — said, “Why not install ’em a little looser to start with?” And wouldn’t you know it, that might be the smartest off-hand jab I’d heard in months. The idea being: allow for wiggle from the beginning. A quarter-millimeter shim inserted during install, then pulled out once hot. Like pre-stretching jeans.
It worked better than I care to admit. The thermal expansion still happens, sure, but now it doesn’t fight its neighbors. Like a dinner party where everyone got their own chair this time. Heat still huffs and puffs, but it doesn’t blow anything down.
Thermal expansion is a critical factor to consider when maintaining the integrity of your roofing system. As temperatures fluctuate, roofing materials expand and contract, which can lead to various issues if not properly managed. Understanding the causes and repercussions of thermal expansion is essential for homeowners to ensure the longevity and durability of their roofs.
https://roofinspectionreports.com.au/thermal-expansion-of-roofing/
Cracks ain’t always catastrophes
A lotta homeowners get wigged out by the gaps, think it means the whole system’s on the fritz. But small gaps — thermal or otherwise — ain’t impending doom. They’re just signs that materials are breathing. What matters is if water’s getting in. If you can stick a kitchen knife in the edge, it’s worth worrying. If it’s barely enough to slide a guitar pick, maybe just pour a beer and watch it set with the evening sun.
Sealing every hairline split only makes sense if they lead somewhere. And unless you’re up there with half a science lab, you’re better off watching patterns than spots.
No one has it solved
It’s funny, how folks think there’s a final answer to this. Got a buddy who works with one of those high-end integrated systems — fancy German-manufactured things that hum like refrigerator dreams. Guess what? Same problem. Slightly neater terminology, maybe. But still, gaps.
The trick isn’t some silver bullet patch. It’s routine. Habit. Getting up that ladder twice a year. Listening for buzzes. Tapping fasteners with a spanner like they owe you money. Light hands, sharp eyes, dull expectations.
Eventually, you find peace with it. Not perfection. Just something close enough that the rain stays out and the lights stay on and the roof doesn’t hum like a sad harmonica every time it hits 102 Fahrenheit.
Keep your weird
And this bit’s optional, but I stand by it — each gap, before I do anything, I name it. Randall. Pookie. Third toe. Dumb, yeah. But it makes the rooftop check feel less mechanical. You ain’t just sealing a thermoplastic attach point. You’re checking on Randall. And if Randall hasn’t grown, then maybe nothing’s broken, and you can climb down, knees cracking like popcorn, feeling weirdly okay about the whole thing.
Anyway. Bring snacks. It’s a two-hour job, minimum.
And never trust a shingle that doesn’t creak.
