I need to replace my roof shingles, I am thinking of putting new shingles on top of the old shingles, is that a wise decision?
Thanks, Rick Lang
I need to replace my roof shingles, I am thinking of putting new shingles on top of the old shingles, is that a wise decision?
Thanks, Rick Lang
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Replies
Only if it's a cheap structure, you're using cheap shingles, and you don't plan to own the building very long.
happy?
No, in fact there may be no warranty if you do that.
Edited 1/23/2006 10:56 pm ET by shellbuilder
It can be. The old shingles should still be laying flat - not cupping or curling. The new should use the same exposure, and you will have to be very careful applyuing them. Flashings still need replacemenmt in most cases.
but be forwarned that most manufacturers will void their warrantee when not laid over solid substrate
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I appreciate your response, very helpful.
The long answer is that any irregularities in the old shingles will "telegraph" through the new ones. In particular, curling in the old shingles will badly affect the new ones, likely causing them to fail prematurely, in addition to looking like carp.
If the old shingles are flat and uncurled (or if they're relatively new and hail damaged, eg) then the effect isn't too bad, but the shingles won't look as nice as if you strip the roof, nor are they likely to last as long.
Another consideration is that disposal prices are only going to increase, and it's probably cheaper to dispose of the shingles now rather than 15 years from now.
happy?
If you are into long answers, there is more -if the climate is like Florida's, in the hot wet SE part of the country, by the time you are aware you have a need for a new roof, odds are good that you already have haad a small leak of some sort for a couple of years. That means that you have some rotted sheathing and maybe even framing to repair. That calls for a total tear off just to find and identify it.if you are in the mountains or have had problems with ice damns, you could have the same rot problems or have shingles damaged or missing from glaciers, wind, & ice removal tools to mnake the current surface uneven.going over architecturaal shingles is an almost definite no-no.having worked in several differnt states over 35 yeas or so, I would say there are areas where half or more of the roofs can get overlaid. There are other areas where every roof should always be torn down to the sheathing.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Thank you for the response
The strenght of your roof is also a consideration - if it is poorly framed, 2 or 3 layers of shingles (do you know for a fact that there is only one layer now?) may be more weight than it should carry -
Let me write that this is a reasonable alternative IF:
1) Your existing shingles have 5 or more years of life remaining to prevent cupping and splitting.
b. You are willing to accept the straightness (or lack) of the existing shingles.
third, you are willing to cut the overhangs off the existing shingles and install drip edges under the existing shingles/felt at the eaves and under the existing shingles/over the felt at the rakes. LOTS of hook blades and gloves, changing BOTH often. The old layer will have much more exposed fiberglass to install into your hands.
Then, you must know that the new roof will have a bit less lifespan before the big tearoff.
Lastly, I'd do so ONLY if your sheathing is dang tough and over-sized for your area's load requirements. You are, after all, adding the weight of a small car to the structure.
As you can read, it is a bunch of work anyway. BUT, if you are doing this on your own, you can do these things in steps that won't cause significant leaks as the project progresses.
If you do overlay, make sure your first course (over the gutter) is flat. Cut the starter course equal to the reveal, usually 5" for std three tab. THEN cut the top off the FIRST course to make the shingle nestle against the bottom of the existing shingle above it. If your reveal is 5", the first course of shingles will be 10" high (12" - 2*5" = 2" cut).
From there up, all shingles will be 12" standard height, will butt against the existing shingle above it and will lay flat with no issue of telegraphing.
FWIW I believe that you can be confident in two layers being quite strong and waterproof over its life. I've done it and was pleased with the appearance and function. You are NOT, in the overall picture, going to do LESS work than a tear-off, just different work.
GO ahead boys, I started the fire... now fan the flames! ;-).
Troy Sprout
Square, Level & Plumb Renovations
Edited 1/25/2006 1:45 pm by Hackinatit
A lot of people make an issue of weight on this question. A 15 or 20 year roof is adding less than three pounds per square foot to a roof system most likely designed for a minimum of 15 dead load. until you get 3-4 layers, the added weight is negligible unless the structure is questionable in thefirst place.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
I agree.
But 3#/sf may become an issue on 3/8" decking if walking on the roof to clean the gutters. Troy Sprout
Square, Level & Plumb Renovations
Like I said, if the place already has structural issues...
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
No question here...
Thousands upon thousands of 'em dutifully holding up shingles in this area for well over a quarter century. They even walk ok.
I don't knock success... In fact, I embrace it. Materials serving the purpose don't make me cringe or critique. Troy Sprout
Square, Level & Plumb Renovations
Wow, thanks for the info, it wore me out just reading it.
RE shingle overlays, if you really want to do this be aware that you only want a total of 2 layers of shingles on a roof - in other words, if it has already been done once, you can't/shouldn't do it again. Some areas (like mine) have building codes prohibiting more than one overlay.
Secondly, be aware that an overlay roof will not last as long as a "non-overlay" roof.