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.