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Bruce Page
03-13-2014, 4:59 PM
It’s time for a new roof on the old abode. What are the disadvantages of re-shingling on top of old shingles? I’m told I can save ~$1200 if I don’t have the roofers strip the old roof off. My inclination is to strip and start new but is it that important?

Jim Matthews
03-13-2014, 5:17 PM
You won't know the condition of the roof and underlayment, unless you strip off.

If the contractor has a track record you can verify, and a can be held liable for any future leaks,
overlaying the old shingles means less in the landfill, and lower expense (removing the old roof takes heavy labor).

Check with your building inspector about how many layers are legal for your structure, and how many are currently applied.
https://pro.homeadvisor.com/article.show.Reroofing-Over-Asphalt-Shingles.13861.html

Here in "Hurricane alley" overlay roofs are the first to shed shingles when the wind howls.

FYI - If you do need to strip off, consider a metal roof or elastomer covering.
The lighter colored membranes and metal roofs reflect a great deal of the sunlight
that otherwise heats the building interior.

Bruce Volden
03-13-2014, 5:19 PM
You won't know the condition of the roof and underlayment, unless you strip off.

If the contractor has a track record you can verify, and a can be held liable for any future leaks,
overlaying the old shingles means less in the landfill, and lower expense (removing the old roof takes heavy labor).

Check with your building inspector about how many layers are legal for your structure, and how many are currently applied.
https://pro.homeadvisor.com/article.show.Reroofing-Over-Asphalt-Shingles.13861.html

Here in "Hurricane alley" overlay roofs are the first to shed shingles when the wind howls.

FYI - If you do need to strip off, consider a metal roof or elastomer covering.
The lighter colored membranes and metal roofs reflect a great deal of the sunlight
that otherwise heats the building interior.

I 2nd the metal roof. Be done with it.

Bruce

Bruce Page
03-13-2014, 5:38 PM
Jim, thanks for the link. There’s just one layer on it now and I was told a second layer is both legal & common. We do get some big canyon springtime winds here, I saw 90mph once. Your point on not knowing what is under the shingles is a good one..
I have a guy coming next week to give me a quote on a metal roof but I think the cost is going to be more than I want to spend.

Jessica Pierce-LaRose
03-13-2014, 6:33 PM
I was surprised to find our roof had two layers, given that we thought it was a hundred years old. Turns out there's cedar shake under the slate!

Frederick Skelly
03-13-2014, 6:35 PM
If I can afford it at the time, I prefer to strip the old roof and start fresh. As noted, you can verify the underlayment. You also reduce the weight on the roof.

But youre absolutely right - its common and legal, though it always "feels" like cutting a corner. But Ive done it both ways, depending on cash flow and how long I planned to keep the house.

Metal roofs are always tempting, but they cost more.

Good luck!
Fred

Pat Barry
03-13-2014, 6:55 PM
2 layers very common. Lets assume they are laying flat, well adhered a 2nd layer is perfectly acceptable. Lets assume they are curling up, etc. then start fresh. Lets assume you get the low bidder to do your work - they will strip it and be putting on new before you get home for your lunch break. Lets say you want to inspect it then - you better be there when its time or you may not get the re-roof completed in the one day planned. Bottom line - you have to trust your crew to do the right thing.

Michael Mahan
03-13-2014, 7:01 PM
when I did mine there were 4 layers & the 2 bottom layers were mostly just dust & small gravel . the tar paper was all but gone too.
here local code is 2 layer only allowed how they got away with the other 2 I'll never know , but when they got the layers off the roof there were slats underlayment & they were too wide of a gap for code as well , so I laid down 1/2" OSB , added a ridge line vent , installed a photo solar array
because of the 4 layers the roof "Had" a slight sag now that is gone
40 year single on it now went with a light sand color to reflect the heat off & now the house is much cooler in the summer (that ridge vent really helps cool )

Steve Rozmiarek
03-13-2014, 7:11 PM
Only 1200 to strip it? That's pretty cheap, and then you won't be worrying about it later. Adding to what Pat said, you have to trust the crew though, some fly by night outfits do some pretty ridiculous stuff.

Mel Fulks
03-13-2014, 7:12 PM
Metal is great but a LOT more money. Got bids few years back from 16,OOO to 25,OOO for different types made of metal.
Bought a thick top rated asphalt for thousands under low bid. If you use the thick asphalt you must tear off old roof as it is much heavier than standard.

Andrew Fleck
03-13-2014, 7:59 PM
Your new shingles won't last quite as long if they are nailed over existing ones. It typically takes 5-10 years off of the life of your shingles. I used to be a roofer once upon a time and the premature shingle failures were almost always on roofs that had two layers on them already. It may not matter to you much if you get some good quality 30 year shingles though.

Matt Meiser
03-13-2014, 8:04 PM
That question sounds familiar....http://www.sawmillcreek.org/showthread.php?139002-Shop-Roof-tear-off-or-reroof

My parents didn't do a tearoff about 15 years ago and are doing a new roof this summer. If we have summer...

Lee Schierer
03-13-2014, 8:09 PM
I vote for removing the old shingles. Getting the new shingles to lay right even on fairly flat old shingles makes for a less than perfect looking roof. With the shingles removed, you can see how the sheathing looks and make quality repairs as needed. I also refuse to have OSB used on my roofs as the heat seems to destroy the glue over time and even a minor leak results in major problems with OSB.

Ed Aumiller
03-13-2014, 8:48 PM
How old are you and how long do you intend to stay in that house...

When I was 25 about 7-8 friends all built a house at the same time I did... I put metal on mine.. Standing seam galvanized...
Still have same roof with absolutely no problems.... the others have had to replace shingles at least once and most of them twice...

So in the long run, even though the metal roof cost more initially, it is cheaper in the end... my wife is younger than I am and will probably
live another 30+ years and she will not have to worry about the roof....

Brian Libby
03-13-2014, 9:22 PM
Strip the shingles! Your replacement shingles will last longer and have a flat surface to lay on plus you will know the condition of the roof boards

Jason Roehl
03-13-2014, 10:15 PM
I say strip it also.

However, I have not yet seen a very important step recommended if your sheathing is still good: re-nail the sheathing. That's not just hammering down any nails that popped up when the shingles were stripped, but running all new nails through the sheathing next to the old. No part of your house sees a greater swing in temperature and humidity than roofing materials, which will weaken the ability of those old nails to hold. A pneumatic framing nailer with sheathing nails (2" or 2.5") will make quick work of it, and most are now coated in a hot-melt glue that activates from the friction of the nail being driven.

Peter Elliott
03-13-2014, 10:56 PM
Can't tell you how many roofs I've done in my lifetime (I worked in construction).

Going over an existing roof is somewhat old trade. Local code generally would allow 2 layers and that was for weight concern.
DON'T DO IT.

Why?

1. New roof will never lay flat.
2. You'll reduce the overall life of the replacement shingle
3. Some companies will not warranty a shingle being placed over another.
4. It's a good time to inspect the sheathing and replace the black tar paper.
5. 2 layers may trap moisture which will destroy the shingle and cause potential leaks.

Not sure what part you live in but go with a 30yr Architecture Shingle. If you are prone to ice, have them ice/water all the edges, valleys, etc. Install power-vent mushrooms if you are in very hot area. Make sure they put on ridge-vent and that the plywood is cut back from the ridge to allow air flow.

Get 3-5 bids no matter how painful it is.

Bruce Page
03-13-2014, 11:26 PM
Thanks for the great info. I will go with my original instinct had have the old shingles removed. A $1200 savings would be nice but it's not going to break the bank.

Chris Damm
03-14-2014, 7:52 AM
I've done it and never will again. The new shingles will last about half of what a complete tear off and new ones will.

Mike Wilkins
03-14-2014, 9:26 AM
Having worked as an insurance claims adjuster for the past 20 years, I have my own opinions about multiple layers of roofing. They are more suseptable to wind damage, your roof framing may not be adequate for the increased load, if there are any leaks, it would be near impossible to locate it. Plus any future re-roofing needs are complicated, and more $$$ to strip more than one layer of shingles. And if you elect to try metal roofing, please remove the old shingles first.

Chris Padilla
03-14-2014, 12:31 PM
Strip the shingles if for no other reason than to ensure your underlayment is in good repair. It could also be a good time to consider moving plumbing vents and adding/moving attic fans and such. Remember, shingles protect the tar paper as that is what weatherproofs your roof.

I had a complete redo about 5 years ago and they wanted to use OSB but I paid a little extra to get plywood instead. I also moved some plumbing vents to facilitate a future cleaner install of solar and water heating on my roof. In other words, I moved the vents further up towards the the top of the roof and I also added solar attic fans and located them in better spots than the old one. I also added 3 sky lights to my living room at the same time. The "while yer at its" can get you but it IS a good time to do such things.

It could also be a good time to string wires for satellite TV or anything else needed up there. Do you need to add insulation maybe? Think think think!!!! ;)

Raymond Fries
03-14-2014, 12:32 PM
About 6 years age we replaced ours. We had to do a tear off because it already had two layers. We went with a 50 year shingle. We also had valleys installed because the water running in this area wears out shingles faster. We also had lead flashing around the vent pipes so we would not have to worry about replacing rubber seals.

So I will be due for a new roof when I am 106. I better start saving cause it will be really expensive by then. LOL


Enjoy Life...

Ole Anderson
03-14-2014, 3:10 PM
Here in Michigan, ice dams at the edge of the roof are a concern when the snow on the roof melts and refreezes at the eve allowing water to pool behind the dam. All new roofs and tear offs get an adhesive self sealing "ice shield" 3'-6' wide that adheres to your roof deck and that is a major step up from tar paper. You can't install an ice shield without at least stripping off shingles near the edge. Not sure if that is a concern in your neck of the woods.

Jak Kelly
03-15-2014, 10:24 PM
I have heard of some insurance companys giving discounts on homes with metal roofs.
If it was up to me and I had the money, and was probably going to stay in the house, metal would be my choice hands down!
I have aslo been told that a lot of insurance companys are trying to deture their customers from multiple layers, that they say one layer is better and less likely to get dimppled during a hail storm.

Larry Edgerton
03-16-2014, 9:14 AM
Ole, 6' of ice sheild is code here in Michigan now on new and reroofs. I think it is a bandaid for poorly designed roofs myself, but as long as people keep building unventable designs it is a good addition.

I just built a new house of my own and found a site that recorded numbers of lawsuits for shingle manufacturers, and based off of this I bought GAF Timberline lifetimes [ 50 year] shingles. I too would be about a 106 when they were due for replacement, so we registered them in my wife's name, she is twenty years younger.......

You may not need Ice & Water sheild where you are but if you decide to use it there is a high heat version that I would recommend in you're latitude. I use it here under dark shingles.

Larry

Mike Cutler
03-16-2014, 9:55 AM
Bruce

I believe you made the correct decision stripping the roof first. Two layers of shingles is an awful lot of weight,and when it finally comes off, it's twice the mess, DAMHIKT.
I know that our codes allow for two layers, but there is a restriction on roof pitch. Too shallow and you can't do it.

David Helm
03-16-2014, 12:59 PM
I agree fully with the tear off responders. In addition, have it hand nailed with high wind nailing pattern (the difference is 6 nails per strip rather than 4). Hand nailing is better because gun nails have a tendency to be done at angles, or go too deep, both of which will tear the shingle membrane and reduce the efficacy of the roof.

Jason Roehl
03-16-2014, 1:16 PM
I agree fully with the tear off responders. In addition, have it hand nailed with high wind nailing pattern (the difference is 6 nails per strip rather than 4). Hand nailing is better because gun nails have a tendency to be done at angles, or go too deep, both of which will tear the shingle membrane and reduce the efficacy of the roof.

Since he's hiring it out, I highly doubt he'll be able to find a roofer who will hand nail. I've done both, and even as a rank rookie roofer, it's not hard to get the pneumatic nails straight and to get the depth adjusted correctly. As for number of nails, I would go with the manufacturer instructions--more nails means more opportunities for leaks, and manufacturers' warranties often also depend on nail placement (not closer than 1" or 2" to the end of the shingle or the end of the shingle above, which limits placement).

Mel Fulks
03-16-2014, 1:34 PM
The company we used always hand nails. I worked for a GC who always uses them and no longer gets quotes from anyone else. We did and they were no higher. There are a few people who do not routinely just go with the flow. But you can always get your quotes according to your own spec.

Mike Lassiter
03-16-2014, 1:55 PM
I just reroofed my house a few months ago. I live in a double wide mobile home. Wanted to leave the original shingles and install new as I was doing it myself. I used GAF Timberline shingles with lifetime warranty from HD because they had a special on them when I did the roof. Not recommended to put these over conventional 12" x 36" shingles as these are metric and you will have a wavy roof due to the rows of shingles mismatching going up the roof. I found numerous issues on my roof BECAUSE I stripped the shingles. Several places the sheathing had been cut short - too short to fully lay on rafter and as a result the installer decided to shoot dozens of staples in the narrow strip that did sit on a rafter. As a result the staples disintegrated the sheathing by breaking it into crumbs. I had to cut out and replace the sheathing is several places because of this. Also one spot looked like someone took a hammer and beat a hole in the sheathing, then used a thin piece of paneling to cover that hole up. I patched the 4 holes that where cut for vents that were WAY too small even for the vents placed over them and installed 2 solar powered roof vents that required cutting a 15" diameter hole for each.

It was a tremendous amount of work for my wife and I to do alone, but I replaced a crappy plastic skylight that had been leaking with a real Velux one; fixed issues that I didn't know about until the roof was removed and replaced the poor vents with a much better setup that now really vents the air out. I know what I have on my roof and the piece of mind for that (and aggravation of finding those issues) was worth the trouble. I cut almost a full 4x8 sheet of sheathing patching and repairing. If you are in a mobile home I would especially advise to tear everything off. Roof truss rafters are 2"x2" on my roof.

Several decades ago now I worked in construction. I delivered some shingles to a small job my company got were lighting had hit a roof on a very old house. Widow lady living in it, and it appeared lighting struck the tv antenna. Roof was very "cut up" with dormers and small roof sections more for style and looks than function. I was on the roof with the carpenter doing the work while he was working. he told me the small area lighting had hit had SEVEN (7!!) layers of shingles on it. I had to bring a more shingles out so he could build that area back up to what was undamaged. He said it was a miracle the roof hadn't caved in if the whole house had that much. Hole in the shingles was over 2" deep. Shingles only held on with nails that were driven into shingles. No roofing nails long enough to go thru that many layers and still go into sheathing. The question was WHY anyone would do that? The house was very old - likely had the original 1st layer put on it when built.

David Helm
03-16-2014, 4:26 PM
Since he's hiring it out, I highly doubt he'll be able to find a roofer who will hand nail. I've done both, and even as a rank rookie roofer, it's not hard to get the pneumatic nails straight and to get the depth adjusted correctly. As for number of nails, I would go with the manufacturer instructions--more nails means more opportunities for leaks, and manufacturers' warranties often also depend on nail placement (not closer than 1" or 2" to the end of the shingle or the end of the shingle above, which limits placement).

Many roofing companies will still hand nail. Gun nailing, no matter how good one is, will be rushed and problems will ensue. High wind nailing will be found on the manufacturers instructions. I speak from 40 years of building experience.

Dave Sheldrake
03-16-2014, 6:34 PM
You're lucky Bruce, I have 4,600 sqft home to re-roof with Welsh slate :(

cheers

Dave

Bruce Page
03-16-2014, 6:40 PM
Welsh slate is forever, isn't it? :cool:

Dave Sheldrake
03-16-2014, 7:05 PM
about 400 years if it's laid well but the existing roof is just over that at around 460 years so needs attention :)

cheers

Dave

Bruce Page
03-16-2014, 8:32 PM
Do you live in a castle?

Dave Sheldrake
03-16-2014, 8:54 PM
An old Rectory :)

Ken Fitzgerald
03-16-2014, 9:19 PM
Bruce,

First, as advised, check with local building codes.

I put on a 2nd roof over the first one and it last 28 years with 25 year warrantee shingles. I did this myself in 1983.

After retiring due to sudden deafness, I worried about 2 things. I had the roof stripped and had it reroofed using 30 year shingles. Then I also had the incoming galvanized domestic water line replaced with copper pipe. Those were the two long term items that had me worried.

John Brad
03-17-2014, 8:34 AM
If the roof only has 1 layer of shingles amd you are not having any problems with leaks I would save the $1200 and just re-shingle. If you are noticing leaks I would strip it down and find out the condition of the roof boards.

julian abram
03-17-2014, 11:09 AM
Strip & re-shingle, it will solve the unknown and you will sleep better.