Replace an Asphalt Shingle Roof
LESLIE: Now we’re going to take a call from Jeff in Mississippi who’s about ready to undergo a pretty big project: replacing his roof.
Jeff, what are you looking to do?
JEFF: Well, I was wondering when do you determine it’s time to change your shingle roof? I’m having my shingles, in bad storms, blow and break.
LESLIE: What kind of shingles are they, do you know?
JEFF: Asphalt. Or fiberglass asphalt.
TOM: Jeff, normally what happens is, as a roof ages, the oil in the asphalt evaporates and the shingles become brittle and they also lose their adhesive ability. And so the fact that you’re getting more shingles that are blowing off in recent years is not unusual.
What I would recommend you do is get a ladder and, from the edge of your roof, look directly down on top of the shingles and look for shingles that are cracked or fissured or broken. Because as shingles dry out, that’s what they look like. They look cracked and checked, especially in the shadow line; that’s the slot between the shingles. If you start to see that and you’re noticing the shingle edges perhaps are curling up, then really the roof is reaching the end of a normal lifecycle and it’s time to think about replacement.
If you’re going to replace the roof, you have to make the next decision and that is whether or not you remove the existing shingles – presuming there’s one layer – or you go on top of them. If you’re going to be in the house for another 20 years, I would recommend that you remove them because that’s going to make the new roof last as long as possible. If you’re going to be in the house for, say, 5 to 10 years, then you could probably put a second layer on because it’s not going to make that much of a difference. But by leaving the old shingles there, you actually cut back the life of the roof by about one-third because it holds a lot of heat and it accelerates the deterioration of the upper layer of shingles. Do you follow me?
JEFF: Mm-hmm. OK, I’m not having that on the edges, like you said. If you look at my shingles …
JEFF: … they’re pretty nice. And I had to replace some, so I peeled them back. I took my wrecking bar and broke the seal loose, lifted them up, and cut the piece out and put a new piece in. They’re not breaking. It’s only in the front of my house and it’s just recently. Through all of the 20 years, I’ve never had any problems til just like the last month. I’ve lost 10 of them.
TOM: Remember that 20 to 25 years is a pretty normal lifecycle, so it might be that you’re just getting close to it. But also keep in mind that roofs seldom need immediate replacement, so you may have some time on this but it’s something you need to carefully monitor.
JEFF: Yeah, I’ve got a hip roof, so I was thinking of doing a fourth at a time.
TOM: Oh, that makes sense.
JEFF: Yeah. I’ve got 3/8-inch plywood up there, I found, on the roof there.
JEFF: And I was thinking about peeling it back off and then going over the 3/8 another 3/8. Would that be a good idea?
TOM: You know, while it would be a good idea, you don’t really have to do that. The 3/8 is actually not that uncommon for roof sheathing. I mean, frankly, today you wouldn’t use anything more than – you know, less than 1/2-inch. But I wouldn’t recommend that you put a second layer of sheathing on there. It’s really not necessary. If you pull those shingles off and you have wood there that’s not delaminated and not soft in any way, you should be able to go on top of that.
JEFF: Yeah. Well, I notice underneath the shingles, on the very edge, the wood has rotted a little bit.
TOM: Well then, what you do is you cut back that first foot or so and you repair the edge.
JEFF: And then put drip-edge on, too, would be a smart idea; wouldn’t it?
TOM: Put ice and water shield on and a drip edge, yes.
JEFF: OK, sounds good to me.
TOM: Thanks very much for calling us at 1-888-MONEY-PIT, 888-666-3974.