New Roof Over Old Roof or Not?

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I have a twenty-two year old home. I am assuming that the builder quality shingles used in construction of the house mean I should be looking at a new roof...soon!
This will be the first roof I have ever replaced. One company, check-rated in the local consumer guide, came and gave me an estimate for reshingling over the old roof.
Another company, with a good reputation but not check-rated in the same guide, said they would not re-roof over an old roof and gave me what sounded like reasonable reasons for so arguing.
Leaves me up in the air: two seemingly good companies, one saying reshingle, the other saying don't.
What's the common wisdom on this? Reshingle or tear up the old shingles and do a new roof?
Many thanks, bob
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In alt.home.repair

Bob,
It is "acceptable" to reroof over old shingles but not recommended. In no time it will look lumpy. It will also not last as long and may cost you more on insurance.
When I bought my home, I had asphalt over cedar shingles. Allstate wanted a 30% additional premium for it. Others wouldn't even insure it at all. And, when you replace it again, it will cost more to remove 2 layers. And you will replace it sooner because the shingles can't dissipate heat as well. It may also void your warranty.
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I'm not surprised.
Asphalt over cedar shingles is like carpeting over gravel. It'll look okay for a little while, and then it'll look awful. If you ever walked on it, you'd puncture it.
Not to mention making the cedar even drier.
Sounds like California, where they often use the cedar shingles as the only roof sheathing. You can see through these roofs from the bottom.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.
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the insurance prob may have been "fire concern" related. I've torn off a lot of "asphalt over cedar" roofs, as not too long ago, cedar was relatively inexpensive.The puncture problem will most likely depend on whether the original roof is shakes (very rough)or machine-cut shingles(quite smooth). The cedar was/is applied to scabboards of varying widths, roughly 10 inches on center for handsplit shakes, and 5 inches for machine cut cedar shingles, depending on the pitch. They allowed for excellent ventilation, and when done correctly, the roof would last about twice that (or more) of today's composition shingles. I miss cedar roofs! Tom Someday, it'll all be over....
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In alt.home.repair snipped-for-privacy@aol.comEDY (Tom) wrote:

It was Texas. I thought the excess premium was because of the extra price of having to deck it when it was torn down.
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On a house 21 years old, with the existing asphalt shingles in reasonably good physical shape and no existing damage, there's no particular reason to _not_ simply lay on another layer of shingles.
You start thinking differently if:
1) if it'd be a third layer (many building codes prohibit three).
2) you have roof leaks, and/or you want/need to upgrade/install new tar paper or waterproof membranes.
3) A lot of shingles are broken.
4) You have problems with the roof sheathing (ie: rot).
It's a compromise. A tear-off is _clearly_ better - but usually a lot more costly. For a roof otherwise in just fine condition, a tearoff might only gain you a year before the next reroof.
If the cost of tear-off is minimal, go for it.
--
Chris Lewis, Una confibula non set est
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Seeker wrote:

There's something to be said for the old adage: "it it ain't broke, don't fix it." Having any problems with it?? The 25, 30, ?? year guarantees on shingles are all *relative* indicators of quality, there is no clock ticking that says your shingles *must* fall apart when they reach 25 years old. Just food for thought.

The "rule of thumb" is two layers, max. You can tear off every time, or every other time but never shall ye try to put a third layer on top. That's mostly derived from the weight factor of shingles, and a safe estimate of how much weight your framework will hold.
Some people consider tearing off for every re-roofing the only way to fly, some consider tear offs a total waste of money unless you're taking off 2 layers.
I know that didn't really answer your question, but I want you to see that you may be jumping the gun. Twice!
--
Ha'i D-suhlami
filling in for I-zheet M'drurz
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tearing up the shingles is a small part of a large job. there are reasons to just roof over it, and most of them begin with 'if'. and there is a fundamental assumption that what is under the shingles is in good shape. if you roof over it you 'may' get a good roof job. if you tear them off, you 'will' get a good roof job. you will find any problem areas right now and be able to easily fix them. much easier and cheaper than doing a patch job later.
if you want to do it 'right', tear off the old roof.
or as my dad used to say, if you dont have the time to do it right the first time around, when are you going to find the time to fix it?
randy

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xrongor wrote:

That's a good one.
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Seeker spilled my beer when they jumped on the table and proclaimed in
<snip>

My general thought on this is to tear the old off since you don't know what shape the wood underneath is in...
NOI
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When you walk around the roof are there any spongy areas? If so then you probably want to rip out the old and install new. Just make sure they replace any damaged areas. If the roof is relatively flat with no leaks or spongy areas then simply re-roof over the existing roof. I had my roof done about 9 years ago and it is doing great. It was a second layer.
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I recently encountered an insurance company that would not insure a home with a composition roof over a cedar shake roof. The required that all roofing be removed first, new particle board or plywood installed and then the new roofing placed on.
RB
houseslave wrote:

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This is Turtle.
When you have new carpet laid in your house , do you lay new carpet over the old or take the old up and put new ? Your Choice.
A lot of professional don't like to over lay old shingles for it will not be smooth and have high and low places. Also you have the old felt which helps the shingle last , will become dry and not help the shingles retain the oil of the shingles.
TURTLE
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wrote in message

said, how much longer are you planning on living there? And the dimensional-type shingles look even better (more "woody")when they're overlaid, IMNSHO. What _about_ carpeting? And the roofing felt has nothing to do with the shingle's longevity, more so to help keep the tradespeople and their tools dry during early phases of construction, and as a second line of defense against ice dams. A good roof _will_ last longer if it's allowed to breathe. A properly insulated and ventilated roof can get away with NO felt underlayment at all (I think the building code writers may be in bed with some manufacturers!). Possibly one of the biggest problems in getting a re-roof done is the propensity for roofers to try to re-use the old flashings. Don't allow the re-use of a plumbing vent flashing, or step flashing.Certain counterflashings may be okay. Tom Someday, it'll all be over....
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In alt.home.repair snipped-for-privacy@aol.comEDY (Tom) wrote:

1. It is chickenshit to screw over the new owner. 2. You will pay for it anyway when the inspection shows the overlay. You will probably pay more so may as well quit being a cheapskate and do the job right.
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Chickenshit happens. Someday, it'll all be over....
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This is Turtle.
I was told by the Roofers around here that felt would be good for a roof but it will not hold up to the wind, sun, and storms. So they put shingles over the real water proofer to protect the real roofing material. If water gets past the shingles. The felt will take care of it. I don't know about ice dams for i have not seen snow in 10 years or more here. I think it snow here one time in the early 1980's.
TURTLE
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This is just not true. A roof-over will last LONGER than a single layer roof, but you do have the extra weight on your roof which increases the liklihood of rafter failures.
Les
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Les, how many roofs have you installed? Real question. Tom Les wrote:>This is just not true. A roof-over will last LONGER than a single

Someday, it'll all be over....
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"Tom" wrote in message

Wrong. You are apparently not familiar with ice dams at all. Felt does absolutely ziltch for protection against ice dams, you must use a water & ice guard which is manufactured under several names.

Yeah, don't use felt if you want the back of the tar strip to stick to the decking. Felt is layed for a purpose other than a dry in feature as you suggest.
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