2 nd layer roof shingles?

[Bedlam]

Hi, I have gotten so much off topic help on the forums here ,And after searching the web, I depend more on peoples opinions here. So The question I have is ..I have a single layer shingle (20 year) presently on the house. (small camp). There is ice and water shield under the lower 4 feet. I plan to install over the present roofing with a 30 year shingle. Yes, I would love to strip the roof. but age has creeped up on me. LOL Anyways the question is is it good or bad to add a layer of black felt paper under the new shingles? I have plenty of this and could get rid of it. Not mention that it would be a good surface to snap some lines. I wonder if the could be a reason why using the felt is a bad idea?
Thanks Allan

 

[Roadworthy]

The felt is probably not a bad idea. Leaving the prior shingles is - in my opinion. How can you check the condition of the sub roof if you leave the old roof in place? It used to be common practice to leave the old shingles. I don't think that's done so much any more. If you can't strip the old roof yourself perhaps you could hire it done. The people removing the roof need not be roofers, just warm bodies.

 

[oosik]

Fifteen years ago I had a second layer of 50 year shingles installed on my house roof. I did it at that time because the original layer were still good - as confirmed by the fellows who installed the second layer.

When they checked the original shingles they also confirmed that the original layer of felt paper was in good shape too.

So ...... no added layer of felt paper. Just shingles on top of shingles.

The 50 year shingles are - IKO 50 year Grandeur - Old World Slate.

 

[Larry Caldwell]

The IBC allows a second layer. I don't know why a layer of 15 lb. felt would hurt anything. A layer of 50 lb., of course, would be a layer all by itself, so shingles on top would make three layers.

 

[Buggs67]

I wouldn't do it. Hire someone to strip the old shingles; it sounds like a small house.

My last house had what appeared to be good shingles when I bought it. 30 year GAF Architectural. They were laid over the old shingles, which continue to degrade, maybe even faster because of the heat from the top layer. The top layer doesn't lay exactly flat since the bottom layer has aged. After less than 10 years the roof started to leak and we couldn't locate the leak because the water ran along the old roof and then found it's way through the old shingles.

Also check the warranty of the new shingles to insure it won't be voided by applying over an old layer.
And Roadworthy makes a good point; how will you know if the plywood is good?

 

[TractorGuy]

2010 Code in Florida specified that installing shingles on top of shingles didn't qualify as a reroof.

They updated the number and distance for underlayment nailing and it couldn't be verified unless it was stripped.

That said, I had two out of three contractors quote for roofing over my existing shingles. I went with the middle quote because it included a complete strip and qualified reroof.

 

[oosik]

I would guess if your roof is plywood it could be a problem. I have cathedral ceilings with exposed beams and can see my roof - it's 3 x 6 T&G Douglas fir.

 

[/pine]

Read the installation instructions on the bundle wrapper...most manufacturers include instructions for roofing over existing shingles...

 

[Doughknob]

If nothing wrong (other than age) with current shingles, no need for more felt. It is a backup for the shingles and u already have two backups.

Also, it is perfectly fine to shingle over existing shingles if u have no known issues with the roof. Double or even triple layering does, however, decrease the life of the new layer. But if not concerned wit this and u just want to go the cheaper route, no problem.

I have added a 2nd shingle layer to a roof. 17 years later, no problems.....

 

[PILOON]

A second layer is a fairly common practice.

What I like to do is totally cover my roof with self adhesive membrane in fact IKO even suggested it.
The shingles then provide the physical barrier while the membrane the actual waterproofing.
On smaller homes the % needed for complete coverage is often not all that much and labor is only how long it takes to unroll the membrane.

When I last did my roof I hired a couple of local handy guys to strip it and place the membrane.
Cost me a couple hundred and some cool ones.
Then with membrane I took my time to re shingle when and if I felt like it.
LOL, had to be cool or no shingle nailing.
BUT having a pneumatic nail gun is the way to go.

 

[TractorGuy]

Another risk of shingling over if your state has updated code and excluded the practice of a second layer as a qualified re-roof. Home owners insurance may require proof of a qualified re-roof after a period of time or for new policies.

Several friends and my mother in law were threatened of home owner policies not eligible for renewal if they didn't put a new roof on.

 

[oosik]

Hmmm ...... I've been out here 40+ years. My insurance company has never asked me anything about my house. Except when I initially applied.

Perhaps because I've faithfully paid and never had a claim.

 

[Midniteoyl]

Hi, I have gotten so much off topic help on the forums here ,And after searching the web, I depend more on peoples opinions here. So The question I have is ..I have a single layer shingle (20 year) presently on the house. (small camp). There is ice and water shield under the lower 4 feet. I plan to install over the present roofing with a 30 year shingle. Yes, I would love to strip the roof. but age has creeped up on me. LOL Anyways the question is is it good or bad to add a layer of black felt paper under the new shingles? I have plenty of this and could get rid of it. Not mention that it would be a good surface to snap some lines. I wonder if the could be a reason why using the felt is a bad idea?
Thanks Allan

Not sure its bad, persay, but I wouldn't. Use the old shingles to line up the new. Like butt the top of the new shingle up against the bottom of the old and just nail away. Might need to cut at the ridge, but the cap shingles covers all that anyways.

If these are architectural shingles though, you might have a hard time making it look smooth, especially after the sun warms them up for a few weeks. Not recommended to shingle over architectural ones.

 

[Midniteoyl]

Oh, also.. Do *not* expect that '30yr' life span out of those shingles. Even in a single layer they don't last as long as they say, 2nd layers are even less.

 

[PILOON]

Hmmm ...... I've been out here 40+ years. My insurance company has never asked me anything about my house. Except when I initially applied.

Perhaps because I've faithfully paid and never had a claim.

Well a couple years ago when renewing my insurance I for some reason did so over the phone.
I was asked a few questions and divulged that I had re done my roof.
That resulted in lowering my premiums, not by a whole lot, but appreciated.
I am aware of a few friends that have been warned that they would no longer be insured for water damage unless they re covered their roof.
Now that might vary with different insurers.

 

[jaydee325]

Just for a little humor!

Just got back from a few days in Michigan's north country. We rented a cabin on a lake that turned out to be a little more rustic than we expected. I noticed the shingles on the roof were well past their replace by date. Then, I noticed the layers. I counted 5!!!

At least it was clean.

 

[EddieWalker]

I bought my first house in 1993 in San Leandro, CA. It's right next to Oakland, in the East Bay. The house already had 2 layers of shingles, but the home inspector said that the roof was bad. On the advice of my realtor, I had the buyer install a 3rd layer. In hindsight, I would never have done that, but I was young and still had a lot to learn about houses and real estate.

I sold the house in 2002 when the housing market was going crazy, and I was expecting to have to put a new roof on it, but my realtor said that they can ask, buy you don't have to if I didn't want to. They would either have to agree to buy the house as is, or walk away.

I've always felt kind of guilty selling that house with 3 layers on the roof. I should have insisted on a tear off when I bought the place. Since then, every house that I've bought, I've stripped the roof, fixed the decking, installed new flashing and 50 year shingles.

You do not need a layer of tar paper for the second layer of shingles. The biggest issue is in using nails long enough to fully penetrate the decking. The shaft of the nail is where the holding power is, so the point has to be fully exposed through the decking. The point has zero holding power.

Short nails are cheaper, and it's a common way for roofers to save a buck. Staples are cheaper, and if installed properly, will hold better, but they are IMPOSSIBLE to consistently install properly because the thickness of the shingles changes with each row, and if a staple cuts the shingle, it's WORTHLESS!!!!

If the decking is bad, the nails will not hold. Plywood is great when it's brand new, but once it's been nailed, the bottom layer has a tendency to blow out, which doesn't leave enough wood to hold a nail. A very detailed inspection of the underside of the decking needs to be done before you go forward with a second layer. OSB doesn't blow out like plywood does, but there is also a limit to how many times it can be nailed and still hold a nail. If it's older and solid wood was used, like 1x4's and 1x6 pine, there is always areas that have broken off and there isn't any decking there at all.

Brand new flashing is super important if you want your fascia to last. Rotten fascia and soffits always start from bad flashing. It is pretty much impossible to replace the flashing and leave the original roof on.

Whatever the rating is for the shingle, cut it in half for the second layer. Because it doesn't lay flat on the first layer, it ages a lot faster. 30 year shingles should last 15 years, but they will be pretty ugly by then.

 

[NoTrespassing]

OP says he's not tearing off and asks about felt or no felt. Half the replies don't address his question. My reply; no felt, no problem. I've seen many many 2 layer roofs last a long time. Mine is 2 layers now, as was my last house.

 

[Larry Caldwell]

I was expecting a 2nd layer when I re-roofed 5 years ago. The roofing contractor wouldn't do it. He wanted to see the roof sheathing.

 

[Jstpssng]

Hmmm ...... I've been out here 40+ years. My insurance company has never asked me anything about my house. Except when I initially applied.

Perhaps because I've faithfully paid and never had a claim.

You just described my mother... until 2 months ago. Apparently an inspector visited her house, now she has a list of things which need to get done, including removing two trees growing over the garage then cleaning the moss off the roof; building a deck, stairs, or something to eliminate the 3 foot drop from the patio door they had installed thirty years ago and never did anything with; and a few other things. She won't let me cut the trees, and finding somebody with time to do it before the deadline has become a challenge.
My brother's going to put a screen door on the patio door, not sure how that qualifies but what I think doesn't matter. (I suggested putting in fiberglass steps like they should have done 30 years ago.)