New shingles over old?

Old 07-11-08, 04:01 PM
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Unhappy New shingles over old?

My husband is going to redo our roof this weekend. He is positive that we don't have to remove the old asphalt shingles to put on the new. Our roof is almost 27 years old and has been patched in atleast one area, plus that room has a couple of water marks on the ceiling. Other than that, there aren't any real signs of damage. He has been up on the roof and says that the plywood underneath seems strong everywhere. I don't know anything about anything and just don't want to waste the time and money to do it now when we may have to redo it in the near future because he left the old shingles on. So, do we have to take them off or not?
Old 07-11-08, 05:08 PM
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it is often a matter of preference. He should climb in the attic and inspect, very thouroughly, for damage.

Personally, I prefer to do a tear off every time. The old shingles often cause a bad looking new layer as they conform to the old shingles.

one thing to check; local building codes. Most places I have worked allowed 3 total layers. Maybe not that way in your area.
Old 07-12-08, 01:51 PM
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Some put it over the old, but if you have water marks ther may be a leak. I would take it off, and put all new. You may have to fix some bad wood that you cant see yet. Thats just me. Good luck.
Old 07-12-08, 02:20 PM
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Installing new shingles over old places your roof at risk. You can not inspect the sheathing for damage, and you will be covering over potential problems. As indicated, new shingles will take the shape of old ones, decrease life span of new roof due to heat, and may void shingle warranty. Ideally, all flashing should be replaced and ice and watershield installed on sheathing 3-6' feet along gutters. One layer of roofing is preferred.
Old 07-19-08, 08:23 PM
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that`s a cheap way to do it,he will have to seal all pipes and walls with flashing cement,and will have no protection against ice damming,with a 2nd roof the plywood tends to go bad in the 10-15 year range regardless of the shingle warranty,when that happens you have to change all the plywood,if you rip it off now you can check for bad wood,and replace what`s necessary,install flashings with proper amt.s of ice and water shield,and re-integrate shingles into existing wall flashings,be sure to add ridge and soffit ventilation as well,done properly with the removal,you shouldn`t have a problem reaching the shingle manufacturers warranty either---and if you were gonna go over the top,those 27 year old shingles are probably well past the point where you could expect to get a decent job of it--usually those will fail even earlier than I previously stated
Old 07-29-08, 03:46 PM
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Wink Remove it

I'm in the insurance industry as a property rep and from my experience, it's best to remove the layer. If you get a hail storm and have 2 layers, the cushioning effect will actually do more damage to the top layer of shingles. Physics formulas, etc. Engineering reports will confirm same. As others have pointed out, this is a good time to check the decking too. Yes it's more work, but not much more money if you are paying someone to do it. Check the weather forecast and prepare for the worst ( tarps ready, etc. ....).
Old 07-29-08, 05:46 PM
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Speaking of hail, many shingle manufacturers won't warranty shingles unless all the old shingles are removed.
Old 07-30-08, 11:23 AM
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Remove the old shingles for all the above reasons.
Old 07-31-08, 06:06 PM
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Forget it. Like TRG said.

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