Why Is Moss Growing Inside My Gutters?

If you live around Seattle, you’ve probably seen it — that soft green fuzz creeping along your roofline or peeking out from your gutters. It looks harmless, almost pretty, until you realize it’s holding moisture, clogging drainage, and slowly eating away at your gutter system.

Moss loves Seattle as much as we do. Between our cool air, steady drizzle, and tall trees, there’s hardly a better place for it to thrive. At CR Gutters, Inc.™, we see it all the time — gutters packed with damp moss, leaves, and debris that just don’t dry out. And once it starts, it spreads fast.

Why Moss Grows in Gutters

Quick answer: Constant shade and moisture.

Seattle’s weather checks both boxes perfectly. Gutters sit right where sunlight is weakest — along roof edges and under tree cover. Add wet leaves and standing water, and you’ve got a perfect little garden for moss.

When moss takes hold, it traps even more moisture. Over time, that extra weight can make gutters sag or pull away from the fascia. Worse, moss keeps water from flowing properly, sending it over the edges and down your siding or into your foundation.

So while moss might seem like a small nuisance, it’s one of those slow, sneaky problems that can turn costly if you ignore it.

How to Keep Moss Out

Try this: Treat your gutters with a moss-control rinse once a year — ideally in early spring before the wet season returns.

You can also:

• Clean your gutters regularly. Twice a year — once in spring, once after fall leaves drop.
• Trim back nearby branches so sunlight can reach your roofline.
• Use gutter guards to block debris that moss feeds on.
• Avoid pressure washing. It’s too harsh for seams and coatings — use a soft brush and gentle cleaner instead.

If moss keeps showing up, it might be because your gutters aren’t draining evenly. A professional can check the slope and fix low spots where water sits.

When to Take Action

Stop signs:

• Green buildup along the roof edge
• Overflow even during light rain
• Gutters that look uneven or feel heavy
• Water dripping where it shouldn’t

If you notice any of these, the problem’s already growing. And with Seattle’s wet winters, it won’t fix itself.

Typical Costs

Here in the Seattle area, professional gutter cleaning usually costs between $250 and $450, while moss treatment typically starts around $150. Scheduling it once or twice a year keeps everything flowing and prevents the kind of water damage that can get expensive fast. A little upkeep now saves a lot of stress later.

Keep Your Gutters Moss-Free

Moss is part of what makes Seattle so green, but it has no place in your gutters. If you’ve noticed buildup starting or just want a little peace of mind before the next stretch of rain, give us a call. CR Gutters, Inc.™ is here to help — friendly advice, fair pricing, and work done right. Reach us at (253) 447-1419 for a free, no-pressure estimate and keep your home ready for whatever the weather brings.