Roofing Tips: "Roofing Over" vs. New Roof Part II
Today on In the House, Jared talks to another homeowner asking about shigle installation over the existing roof. Listen to Jared’s take on the subject...In the House
Jared: Hey, hey. Welcome back to In the House with Ken and Jared, brought to you by Universal Roof & Contracting and Renewal by Andersen of Central Florida. Thanks for joining us today. On the line is Charlie from Cocoa. Charlie, you're in the house. How can we help you?
Charlie: Hey, thanks for taking my call guys. I just have a quick question. Is it ever okay to build an asphalt shingle roof over an existing asphalt shingle roof?
Jared: Well, you're allowed in Florida to put a second layer over the top of the existing one, as long as it meets a few requirements. There can't be any blistering to the existing shingles. You have to make sure that there's no rotted wood or things like that. In general, you're allowed to, but I can't think of a single time where I'd actually recommend it. The problem is that when you put one layer over the top, is that you are marrying into - or you're stuck with - whatever problems are underneath it. I can tell you about thousands of times where I've inspected a roof, where you can't tell that there's any bad wood. You can't tell that there's some sort of rot or water intrusion problem. Then we tear the roof off and there's some hidden damage in an area where you didn't see it. I've found that so many times that I just wouldn't recommend.
The most expensive part of the roof, is the roof. The tear off actually is really not that expensive of a part of the process. No matter what, even if you go over the top, you have to remove a portion of it, because at all the transition points - meaning like where there's a vent, or where there's a roof to wall transition, where there's flashing - wherever there's a transition you have to install new flashing there and you have to install new vents, because that flashing has to be waterproofed up to the new shingles, instead of the old. You still have to tear into it in different spots anyways. Because, of that, it's just not worth it; the cost difference is minimal.
Then the other thing that happens is that roofing is a moisture barrier. Whenever you place a moisture barrier on top of a moisture barrier, what happens here in Florida, is that moisture gets trapped between those two layers. Then the sun comes along, heats up that moisture, vaporizes it, turns it into gas. Then it attacks the backing of the new shingle. What we find is that many times asphalt shingle roofs, I've replaced them at 20, 25, 35-years-old, but when you put another second layer over the top, it usually lasts about half as long. Because, of all those reasons, even though it is allowed, I personally would not recommend going over the top.
Charlie: Okay, that makes sense man. I really appreciate that. Thank you.
Not surprisingly, Jim is in agreement with Jared on this! Read his opinion on the same matter in Roofing Over vs. New Roof, Part I.
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