DIY Eavestrough Joint Sealing: When Leaky Seams Can Be Fixed Without a Pro

A dripping seam is one of the few eavestrough repairs a careful homeowner can do. This guide shows how to find the leak, decide whether it is a DIY job, seal it properly and avoid the mistakes that reopen the joint.

Share feedback

Find the leak before you buy a tube

Seams leak in a handful of places: end caps, mitred corners, the joins between sections, and around the outlet where the downspout starts. A hose test finds the culprit.

1. Clean the trough first. Debris hides leaks and blocks the flow.
2. Run a hose slowly into the high end and let the water travel along the run.
3. Watch from the ground, or from a well-set ladder at a single-storey eave, for drips at each joint.
4. Mark every leak with painter's tape on the wall below, so you can find it again once the ladder is moved.

Dry evidence helps too. Look for dirty streaks below a joint, whitish trails on the metal and clean patches where water keeps washing the wall.

Can you fix it yourself? A quick screen

It is a reasonable DIY job if:

• The leak is at one seam, at a single-storey eave.
• The metal is sound, with no holes, cracks or flaking rust around the joint.
• The trough is straight and firmly hung, so the seam has not been pulled apart.
• The ground is firm and level, with no wires within 3 metres of the ladder.

Hold off, and get advice, if:

• Several seams leak at once, which suggests the whole run has moved or aged.
• The trough sags or the fascia is soft.
• The metal is corroded through, or the vinyl is cracked. Those parts need replacing, not sealing.
• The joint is soldered copper, which is a specialist repair.
• The leak is at second-storey height.

Sealing a seam, step by step

You need a sealant labelled for eavestroughs and your trough material, a plastic scraper, a stiff brush, clean rags, the cleaner named on the sealant label, gloves and eye protection.

1. Pick the weather. Sealants have a minimum application temperature on the label, so wait for a dry, mild spell in spring or early fall, with no rain forecast until the cure time has passed.
2. Remove the old sealant. Scrape away loose or cracked material with the plastic scraper, taking care not to gouge the metal.
3. Clean the joint. Brush off grit, wipe with the recommended cleaner, then let it dry completely. Sealant does not stick to dirt or damp metal.
4. Apply a continuous bead along the inside of the seam, overlapping a little onto both sides of the joint. Press it into the gap and smooth it with a gloved finger or plastic tool.
5. Cure and test. Follow the cure time on the label, then run the hose along the trough again and check the seam from below.

Check the label for your trough type, since vinyl often needs a product made for it, and test a small hidden spot if the trough has a painted finish. Keep pets and children away while the sealant cures.

Our guide to repairing leaking gutter joints covers extra tips for particular joint types.

Mistakes that reopen a seam

• Sealing over dirt, damp metal or old flaking sealant.
• Using a product not made for your material or for freezing weather.
• Applying it on the outside only, where water never touches it.
• Sealing in the rain, or just before rain arrives.
• Skipping the hose test, then finding the leak in the next storm.
• Sealing a joint that is moving. A sagging run pulls seams open again, and no sealant can win against that.

Ladder rules apply throughout. Use a standoff, keep three points of contact and never lean the ladder on the trough. See ladder safety for exterior home maintenance for a full checklist.

When the seam is a symptom

A seam that opens again after a good repair is telling you something. The run may be sagging, the hangers loose, the sealant worn out by decades of freeze-thaw movement, or the metal simply at the end of its life. The repair versus replacement guide helps you weigh another patch against a new run.

D&D Home Services offers gutter cleaning in Kitchener, Waterloo, Cambridge and Guelph, and quotes eavestrough installation case by case. Quotes are free and confirmed in writing before work begins.

Devon Moore, Operations Lead Co-Founder & Operations Lead, D&D Home Services

Devon Moore is the co-founder and Operations Lead at D&D Home Services, with hands-on experience cleaning hundreds of homes across Kitchener-Waterloo, Cambridge, and Guelph.