Common Roof Leak Sources on Foam Roofs: What You Need to Know
When it comes to roof leaks—especially on foam roofs—skylights and scuppers are often the usual suspects. In fact, this applies to nearly all roof systems. Leaks rarely originate from the membrane itself. Instead, they typically come from failed penetrations, meaning anything that cuts through the roof system (like vents, drains, and skylights).
One of the most overlooked but frequent offenders? Skylights.
Understanding Skylight Leaks
Most leaks around skylights happen due to:
- Improper installation
- Cracked or aged flashing
- Failed seals or caulking
- Poor maintenance
When water finds its way into the gap between the curb and the skylight—or into a single dome with a cracked lens—it can create serious moisture damage below.
What You Should Know About Skylight Types
The most common skylights you’ll encounter are curb-mount skylights, which are also the easiest to replace. They typically come in two standard sizes:
- 2′ x 2′
- 2′ x 4′
You can find them at most hardware stores like Home Depot or Lowe’s.
There are two main types:
- Single Dome Skylight: One lens layer
- Double Dome Skylight: Two lens layers for added insulation and impact resistance
Pro Tip: If the skylight covers a livable space (like a kitchen, bedroom, or hallway), you’re required to use a double dome for code compliance and insulation purposes.
But even in non-livable areas like garages or sheds, I still recommend double domes—they offer double the protection for just a few extra dollars (usually around $10 more).
Don’t Do This: Sealing Off a Damaged Skylight
In the photo below, you’ll see an example of a skylight that’s been sealed shut with caulk or foam. While this may seem like a quick fix, it’s not a long-term solution.
In fact, sealing off a damaged skylight can cause:
- Trapped moisture
- Faster deterioration of the surrounding roof system
- More expensive repairs down the line
For the time, effort, and cost it takes to seal it shut, you could’ve simply replaced it with a new one—and done it right.
How to Replace a Skylight (Yes, You Can Do It)
Believe it or not, replacing a skylight is pretty straightforward. Here’s how:
- Locate and remove the screws or nails holding the old skylight in place.
- Gently lift and remove the skylight from the curb.
- Position the new skylight onto the curb so it sits flush with the top.
- Secure it with new nails or screws along the perimeter.
That’s it. If you’re handy, you can usually swap one out in 15 to 20 minutes.
Final Thoughts
If your foam roof is leaking, always check penetrations first—and skylights are a good place to start. Don’t patch over a problem that’s easy to fix.
With minimal tools and under half an hour of work, you can replace a leaking skylight with a high-quality, double-dome unit that will protect your home for years.
