Need new Roof Shingles

larrylwill

I bought a house 2 years ago, it is a 60's rancher. The pitch is low maybe 4x12. I believe the current shingles were put on in 2000 or 2002. They are 20 year 3 tab. I am on a bluff and the winds get high at times, 25-35 with gusts to 45 or so. Since I moved in every strong wind storm bends back and breaks tabs off. I have noticed that many tabs were not stuck to the next shingle, I have also noticed that they seem to get debris under the tabs witch prevents them from sticking. The ones that are stuck down seem ok. I have been putting roof cement under the tabs of the ones I find not stuck.

I am thinking about a new roof with 30 year single tab shingles which look like these. They are 140mph rated and about 2x as heavy as the old ones.

The roof sheathing feels like 1/2" plywood and is a little wavy in places.
Although the underside looks good. I know the best thing to do would be remove the old shingles and re sheath it with 3/4" plywood.

My question is: If I just re shingle over the existing shingles just how would it affect the life and wind resistance? If I get 25 years out of them I would be 90 so I don't think I would still be in this house.

Opinions please.

GAF
30 Yr Natural Shadow Slate Sg
Model # 0600750
Store SKU # 779095
$23.95/BD-Bundle
Specifications

• Assembled Depth (In Inches) : 39.5 in
• Assembled Height (In Inches) : 2.75 in
• Assembled Weight (In LBS) : 72 lb
• Assembled Width (In Inches) : 13.5 in
• Color / Finish : Gray
• Color Family : Grays

johnk

For one you are paying way too much for shingles,but thats beside the point.I never do layovers,unless you have a persistant h/o.I tell them that IMO it reduces the life expectancy of the shingles.I would recommend a tear-off at the very least.That way you can inspect the deck.If you trusses are 2" on center,I would upgrade the plywood.You can go right over the old if its not that rough,if there is rot replace before you continue.A decent choice in shingle as well.

larrylwill

That picture was just for example of style. It was Home Depot.
The trusses are 2'. 3/4 plywood would cost about as much as the shingles. I suppose I could use 5/8 OSB.

"A decent choice in shingle as well. "
do you mean the one I showed?

johnk

Yes the ones shown-Gaf

Slyfox

While i was a crew leader for Harold Heater we did a lay over on a home that he had roofed as new construction, the first roof was a 24 year old 25 yr 3-tab shingles and we layed over with the same brand.
This summer i was called out to re-roof that home, the second layer was 22 years old and we had to replace one sheet of plywood.

My personal home originally had 20 yr 3-tabs and were 17 years old when i layed over them with a 25 yr 3-tab, that was 20 + years ago and the shingles are still holding up and have had -0- blow offs.

I have only done a couple dozen lay overs in 30 years of roofing, less than a dozen since I started Fox Roofing in 1994 but they all have held up well.

Installed properly they work.

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larrylwill

I guess its the same argument as applying a tin roof. I live in North Alabama and around here almost everyone I called apply tin directly to the roof over the old shingles. Most of the installers have been in business 25+ years and claim they have never been called back for repair. The ones that use a wood frame swear the tin directly on the old shingles wont last.