Remove Old Layer Before Installing New Roof?
LESLIE: We’ve got Jim in North Carolina on the line with a roofing question.
JIM: I need a new roof. I’m originally from the Northeast – New York – and up there, it was very common to not strip the old fiberglass roof before putting a new roof on. I’m wondering what the advantage is to not stripping the roof versus stripping it to put a new one on.
TOM: That’s a great question, Jim, and the answer really depends on one thing and that is how long are you going to spend in this house? Is this a house that you’re going to be in for the next 20 years or do you see yourself more in the 5-to-10-year range?
JIM: We’re in the house for forever, the long – for long term.
TOM: Forever? OK.
JIM: Yeah, mm-hmm.
TOM: Alright. They’re going to bury you in this place. Is that what you’re trying to tell me?
JIM: Exact. We call it our “toes up.” We’re leaving toes up.
TOM: Alright. It’s your toes-up house? Alright.
So, if it’s your toes-up house, you’re going to want to make sure that that roof is going to last as long as possible and the way you’ll do that is by stripping the old layer. And here’s why I say that: if you have a second layer of roofing material under the exposed layer, that’s going to hold a lot of heat.
And heat is the enemy of the roof. The hotter the roof gets, the quicker the asphalt and the other chemicals that make up the roof sheathing’s – the roof shingle’s ability to keep water away dry out, the shorter the roof life. So if you have a roof that’s really warm, it’s not going to last as long.
And what I have found in the almost 20 years I spent as a professional home inspector, that when we saw roofs that had multiple layers, generally they lasted about a third less than a roof that was a single layer. So if the first roof lasted 20 years and you added a second layer, you might be looking at like, say, 14 or 15 years on the second layer. So that’s why I would suggest that you might be better off stripping off that first layer in your scenario and putting on just one layer.
But if you had told me that “no, Tom, I’m only going to be in that house for 5 or 10 years,” well, then, who cares? Because you’re not going to be around to enjoy the benefit of the longer roof life. That’s why it makes sense, if you’re going to be there for that whole life of the roof, to go ahead and pull off the first one.
A couple other things to keep in mind with that roofing project: also a good opportunity to take a look at your ventilation, Jim. Now, in a 20-year-old house, typically you don’t have enough ventilation, because they just didn’t vent roofs well back then. But you want to think about adding a continuous ridge vent down the entire peak of the roof and then a continuous soffit vent down both sides of the soffit. So that this way you’ll have plenty of opportunity for air to enter at the soffit, ride up under the roof sheathing and exit at the ridge. And that will give you a nice cycle of air, 24-7, that’s keeping that attic space cooler which, of course, makes your air conditioning more efficient and also helps the roof last longer, as well.
JIM: That’s great. That all makes perfectly good sense.
TOM: I had a good day. Jim, thanks so much for calling us at 1-888-MONEY-PIT.