roof replacement


Old 01-15-08, 01:09 PM
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Question roof replacement

I'm planning to redo the roof because the layer is about 20 yrs old. Can I put the new shingle over the old one? Condition is still okay on the old shingle. also, what are the advantages and disadvantages of putting two layer of shingles? thanks in advance
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Old 01-15-08, 01:41 PM
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You'll hear a lot very soon, but I got here first.

Yes you can shingle over, but should you?

No ripoff required, therefore less to haul off

uhhhh...thats all I can think of.

Additional weight on the roof

Decreased lifespan of new roof due to additional heat retention

No chance to inspect sheathing and underlay for damage/correct initial install

Need for longer fasteners to ensure penetration to sheathing

Appearance on edges

That said, if the old roof is still good per your post, why are you replacing it?

Old 01-15-08, 05:08 PM
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Vic did good! I'll just add "Ditto". Don't bother with a reroof.
Old 01-16-08, 08:33 AM
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thanks guys
I'm not sure why too but neighbors are doing it.
I guess the words still stand if it's not broken, don't fix it.
Old 01-16-08, 08:46 AM
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As a practical matter the biggest problem I find at “re-roofs” during home inspections here in Chicago is that roofers often do not bother to properly install and/or re-install flashings at roof penetrations and at junctions with other surfaces such as dormers and chimneys.

Since on composition shingle roofs it's flashing defects than deteriorated roof coverings which are the usual cause of “roof leaks", a re-roof often provides far less than the value of the “new roof" the homeowner paid for.
Old 01-17-08, 12:25 PM
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Ditto from me also. Some premium dimensional shingles require a complete tear off of the old roof to qualify for warranty and provide maximum hail protection.

I just did the roof on my 47 year old house this summer. The top layer was still good, but the two layers beneath it (yes, two reroofs!) were crumbling and not providing the proper support at the edges for the top layer, giving me problems that required a reroof.
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