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

Everyone wants a solid home, so it can be disconcerting to find a gap between your exterior walls and roofing. Surprisingly, though, those gaps may be intentional—builders often leave slight gaps to allow building materials to expand. However, large gaps can let in pests and water, and they can be a sign of a bigger underlying problem. 

Here’s what you should know about how to fill gaps between the roof and walls.

Should I Fill Gaps Between My Roof and the Wall?

The decision of whether to fill gaps between your roof and wall isn’t as simple as it might seem. Sometimes these gaps are intentional and even necessary; and, sometimes they’re the result of poor construction, wear and tear, damage, aging, or precursors to bigger problems.

Before you fill a gap between your roof and wall, you need to determine if the gap is a problem. You may be able to do this yourself, based on the location and size of the gap, or you may want to call a local roofing or siding contractor near you for an expert opinion.

One of the best ways to tell if a gap needs to be filled is its location and size. If the gap is relatively small, and is located on the outside of your home, under the eaves and between your roof and the siding, it’s most likely a builder’s gap. This is intentional space that’s left to allow for attic airflow, and the subtle shifting of construction materials. Most of the time, this gap doesn’t need to be filled; however, if you have issues with pests of water entering your home through this crack, you can seal it with flashing, a drip edge, flexible spray foam, wire mesh, or another substance that still allows for movement and airflow.

If the gap is large or growing, missing attachment points like screws, is the result of obvious damage, is located along the length of the gutter system, allows pests and water to enter your home, or is causing other issues–you should seal it. If the gap is growing increasingly wide, you should consult with a pro to confirm it isn’t the result of a foundational or structural problem. 

How Much Do Roof Repairs Cost? 

The cost to fill a gap between your roof and wall will vary greatly, depending on the cause and severity of the gap, its location, and the repair method used. On the low end, a DIY patch using spray foam or an inexpensive wire mesh–to keep pests out and the air circulating–can cost as little as $20, or nothing at all if you already have the supplies. Hiring a pro to apply expanding foam spray around your entire home will cost around $1,650. A gap that is the result of a foundational or structural issue can cost thousands of dollars to fix.

If the cracks are related to an old or damaged roof, or if the leaks turn out to be roof leaks rather than from a gap, you should talk with a roofing company about how to fix a leaking roof or roof repair costs.

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:

• Age of your roof

• Accessibility of your roof

• Size of the gap

• Your main concern (i.e., insulation, weather, pests) 

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

3 Ways to Fill A Gap Between Roof and Wall 

There are three main ways you can fill a gap between your roof and wall. The best method for your job will depend on your specific problem, so you’ll need to determine the best solution for your situation. 

Call Your Contractor

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 a new roof, your contractor should finish the job they started, especially if closing the gap is contingent on shingles that still need to be removed, or other incomplete work. 

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 silicon 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 light boxes, or directly on top of your roof.

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 and other pests 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.)

DIY Roofing Gap Repairs vs. Hiring a Pro 

If you’re reasonably handy and have some experience with similar home repairs, it is possible to fix a roof gap yourself. You can also hire a professional; they’ll likely be able to do the job faster and already have the tools and materials on hand. This can also save you a lot of time and keep you safe, as you won’t need to climb up and down a ladder.

If you’re not sure whether your roof gap is a problem, or whether you need to hire out the job, it’s a good idea to have a contractor come and assess the issue and give you a bid for any work they recommend. This will help you know whether the gap needs attention and whether the fix is a big or small job.