New shingles over exsisting new shingles

New home built Jan 06 noticed right away that a lot of the shingles were sticking up or looked warped and wavy. Home had an 18 month warrenty for any problems or defects.
I addressed the warped and wavy shingles right away and the builder gave me a run around for awhile, but finally agreed it was a job done incorrectly and they would re shingle my house. I recieved that in writting just befor the warrenty expired.
The nails used to nail the shingles to the house were too short of a nail and did not penatrate to the wood in many areas. It seems that it is also possible that the felt lining under the shingles has winkles in it.
Now the builder wants to reroof over the exsisting shingles. He says he will shingle with 50 year warrenty instead of the exsisting shingle with a 20 year warrenty.
I don't want to agree to that
The builder is coming to talk to me about this option next tuesday & I would like advice & valid reasons to give them as to why I won't go along with that.
Seems to me that the warpped shingles will affect the "new" shingles. What if the tar paper or felt paper has wrinkles in it, won't that be a problem even if they remove all the warpped shingles?
What about the warrenty, doesn't a second layer shorten the shingle life by about half?
Do manufactures actually warrenty a 50 year shingle when it is placed over an exsisting layer. I've always heard they don't or won't hornor their warrenties if the shingles are placed over a layer of exsisting shingles.
Are there other good reasons why I shouldn't let them do this?

 

Do your homework. Check with the shingle manufacturer about valid installation methods. I have never liked the idea of more than one layer of shingles.

 

Tear them off. What[s underneath will telegraph right through. And 2 layers aren't the preferred method of installation if you're looking for longevity.

I won't do a layover. And be sure he uses the 50 year shingles. I personally feel the 20 year shingles are crap at best. I don't use them at all.

 

Some shingle manufacturers shingles are the exact same whether they are 20 or 50 year. Just like a tire on your car, you are paying for a warranty. Not a better shingle. It's costly, but he has to remove the first layer. Your roof is barely 2 years old. That's not what you payed for. What happens when it's time for another roof for you in 15, 20 or 30 years? Now you have to pay for the strip job when you could have had the option of just a re-roof. (Code says no more than 2 layers on a house.) Do not let him go over it! Threaten to take him to court if you have to.

 

Per the manufacturer, some shingles (example Owens-Corning's HP Weatherguard shingles) must not be installed as roof-overs, some others (for example most Certainteed 3-tab shingles) require or recommend specific installation methods and/or application patters (ex: nesting combined with a 6 course, stepped-off diagonal pattern) when doing a roof-over.

So if you have to settle for one, at least make sure it meets the manufacturer's requirements to maintain the warranty.

 

Don't reroof...look, in very simplistic terms shingle warranties are very much dependent upon installation and since there are so many variables in installation (witness the wrong nails used originally) there are many ways a shingle manufacturer can limit their warranty. I'm not saying they do so on purpose, it's just that there are too many variables that come into play for a warranty to be worth much to you.

At best you'll get the replacement cost of new shingles, not their installation and that may only be for a shingle defect. So don't put too much into what you hear from roofers about warranties, that's a sales job. It will all come down to "faulty installation" or "inappropriate product for the application"...translation? warranty to you = 0

If your original installation was faulty, what makes anyone think that covering it up will make faults go away? The only way you can make sure of a proper roof installation is to tear everything off and start from scratch, IMO.


I'm not knocking the manufacturers, nor the installers. But you have to find a good roofer with qualifications with a given system, not just guys who know how to shingle...