How To Fill Gap Between Roof and Wall in 3 Simple Steps

Ben Kissam
Written by Ben Kissam
Updated November 3, 2021
Family home exterior at sunset
Soupstock - stock.adobe.com

Curious animals and sideways rain are no match for a homeowner with a caulk gun and a ladder

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Fear, panic, anger, confusion. Homeowners may experience a wide range of emotions when they notice a gap between their roof and wall, especially if the roof is new or if water or outside critters have found their way inside. 

Luckily, filling a gap is a pretty straightforward process you can tackle in a couple of different ways—one of which is totally hands-off. Learn how below.

Difficulty: 3/5Time: 1 to 3 hoursTools and Materials Needed: (Depending on the course of action)

  • Caulking gun and caulk OR expanding spray foam

  • Wire mesh (optional)

  • Staple gun (optional)

1. Determine the Best Course of Action

There are a couple different approaches homeowners can take to fill a gap between their roof and wall. Factors may include:

  • Whether it’s a new or old roof

  • How accessible your roof is

  • How large the gap is

  • Whether insulation, weather, or keeping out animals is your main concern

Look carefully at the space at the top of your home, then choose an appropriate solution from the steps below.

2a. Call Your Contractor

Close up of roof and wall on home exterior
Alex White - stock.adobe.com

Best for: New roofs recently installed by a contractor

If the gap between your roof and wall is brand new, this might be an issue to take up with your roofing contractor. Read your contract carefully, then without making accusations, call to inquire about the gap. Ask them to come close the space as soon as possible—especially if cold weather is around the corner.

A roofing professional may install new flashing in the area or apply one of the same sealants you might use for an older roof-wall gap. But if you just paid for the new roof, they should finish the job they started, especially if closing the gap is contingent on shingles that still need removing or other incomplete work.

2b. Apply a Sealant

Best for: Surprise or sudden leaks and insulation issues

Gaps between the roof and an adjacent wall, like a second story or dormer, most likely need sealing up to prevent leaks, insulation issues, and rodent infestations. Two popular sealants for this kind of project are caulk and expanding spray foam. Both will help close the gap between your roof and wall and insulate your home.

  • Use spray foam for smaller (1- to 6-inch gaps) that are free of objects

  • Use silicone construction caulk for insulation and weather-proofing or an exterior-based caulking product for outdoor application

The cost to hire a roof expanding foam spray pro could be around $1,650. If you choose to tackle it yourself, note that spray foam shouldn’t be used near electrical boxes, near ceiling lightboxes, or directly on top of your roof.

2c. Consider Adding Wire Meshing

Best for: Keeping animals out and eave ventilation gaps (which are intentional)

Some gaps, such as an eave gap between the top of the wall and the underside of the roof are there for attic ventilation. Without it, moisture could build up and cause a plethora of other issues. 

If your main concern is animals getting under your roof or into your attic, you might consider installing a wire mesh along the gap instead of using a sealant. This option works well for homeowners living in warm or drier climates, where rain seeping in isn’t as big an issue.

Measure the gap and purchase an appropriately sized outdoor wire mesh. Using a staple gun, carefully attach the mesh wire to close the gap. (For safety reasons, it’s best to do this with a partner holding the ladder below.)

3. Check for Other Areas That May Be Letting In Moisture

Since you’re up on the ladder anyway, now’s also a good time to look for other gaps or holes in your roof. If you’re going the sealant route, you can close these areas off simultaneously.

If winter is approaching, cleaning your gutters of leaves and debris can help prevent winter gutter problems.

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