Portland Roofing Contractor

Podcast: Why Should You Care If Your Roof Expands & Contracts?

Aerial View

In this episode, we talk to Daniel about what happens to your roof during the winter and how to make sure it keeps you and your family safe and dry.

Podcast Transcription: RoofLifeB37-228

Shayla: Thank you for joining us today for the Roof Life of Oregon podcast. I’m talking with Daniel today. Daniel, tell us about expansion and contraction on our roofs and why we should even think about that and consider it when it comes to maintenance.

Daniel: That’s an important thing to think about with re-roofing. Homeowners think, well, we’re just going to take off the roof, put a new roof on and we’re good. Would you believe that everything expands and contracts? I know that sounds crazy. You look at the sidewalk. Do you ever notice the lines cut in the sidewalk? Those are called expansion joints. That allows the concrete to move around. As things heat up, they expand. As they cool down, they shrink. And if you didn’t have those expansion joints, the concrete would break, they would crack, it would move. You have expansion joints in almost anything. A great big commercial building, you ever see the big seams going down those big panel walls? Those are expansion joints. They allow everything just to keep from falling apart.

Your roof does the same thing. It’s heating up. It’s cooling down. So what we’ve talked about in the past is the plywood. When a plywood deck goes down, it has to leave a gap. That gap allows the plywood to expand and contract and move. A lot of roofers just put the new plywood on, nail it on, move on, and put the new roof on. Two years later, after a few cycles, the plywood gets too close together, has nowhere to go, and the plywood pops. Then you get that little lift on the roof. You’ve seen them from the road where you look up and go, “What’s that weird bubble?” That’s a plywood pop. And it’s from expansion.

There are other things that can expand and contract on the roof. Would you believe that your chimney and your house are separate? They are actually not connected. I know they look like they are, but the only thing that makes them look connected would be caulking and flashing. So that brick expands and contracts at a slower rate than wood. Wood’s going to expand and contract more. So your chimney and your house actually move around separately. So you have two different pieces of flashing that have to allow them to move. So you have the flashing that comes out of the brick and the flashing that comes up from the roof, and they allow them to move back and forth. A lot of roofers don’t address that flashing when they’re redoing it. Another spot that’s a really prime spot, usually right on the front of the house. You’ve got this beautiful dormer, the roof comes down, a beautiful window, and then you have a little roof below that. You have what’s called roof-to-wall metal. That’s the metal that goes behind the siding, right below that window, right over the top of the roof, usually right over your front door. And all of sudden, you get this new roof on, and a couple of years later, the metal’s popping up. Why is it doing that? The roofer put a nail in there. Expansion and contraction. The metal is heating up and cooling down, the composition at a different rate. That metal didn’t have that original angle. It has a specific angle, about sixty degrees, if your roof is less or usually steeper, that metal’s going to want to go back to its memory. So if they put a nail in there, cycles back and forth, it slowly moves up and down, it pulls the nails out, it lifts up, you can get a leak there. We use a grommet-ed screw to hold that in place so that it doesn’t have that problem. If someone uses a nail or a screw, it’s going to cycle and start to pop up.

We see that with wood shakes where a new shake roof is put on and the shake has a curl to it. Well, the roofer just goes, well, we’ll just push that down and put a staple in. That’s never going to hold. We’ve seen it. Five, six, or seven years later, that shake is pulled completely out, now the staple is lifted up. That’s the wood going back to its original memory. So expansion and contraction on a roof are huge. Does your roofer do the right thing to combat that? Are they gapping the plywood?

Shayla: So it sounds like the best thing to do is to hire the right roofer in the first place who would take care of those issues, but what if someone didn’t hire Roof Life of Oregon and now they have a plywood pop, or they’re seeing some of those issues? What do they need to do?

Daniel: Some of them are relatively easy fixes. We can do it from the top. Plywood pop is a little more difficult because to correct that we have to pull the shingles, get down to the plywood, re-gap the plywood, screw it in place, and put new shingles. The downside is, after a few years, those shingles aren’t going to match. We can do it. We have done it. Some of the easier ones, so a chimney flashing, we can do that pretty well. That roof to the wall in the front, usually we just pull all those nails out of there, clean it up nicely, set it back down, seal the holes, and then put that grommet-ed screw. So some of them can be done in a couple of hours. For some of them, it’s going to take a little bit more time. So if you are seeing those problems, most of them can be corrected. With re-roofing, let’s take care of those before they ever become an issue.

Shayla: Alright, so if you have any questions about expansion and contraction on your roof, or if you are seeing any issues that Daniel talked about today, make sure you reach out to the team at Roof Life of Oregon.

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