Roofing Question

We're having a drought here in central Texas, and I've finally gotten around to having a new roof put on my single-family house. Problem is, it started raining. And raining, and raining, and raining. (I may be single-handedly responsible for ending the drought! Remember when it used to be washing and waxing your car would bring the rain?)
The first day it rained the roofers continued working. What concerns me is that this means they were putting shingles over wet shingles. (They're putting the new shingles over the old ones.) It seems to me that this is a bad idea. Would it be? Would it cause mold or mildew? Or are the shingles mold and mildew resistant?
The shingles are the standard, common house shingles, sort of like these:
http://www.lowes.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&s toreId151&catalogId051&cId=SEARCH&productId367230&cm_mmc=SCE_gps- _-gps-_-gps-_-CertainTeed%203-Tab%20Weathered%20Wood%20Fiberglass%20Aspha lt%20Roofing%20Shingles&CAWELAID24124139
or
http://low.es/t6XW4J
Thanks for your input and advice.
8^)~~~~~~ Sue (remove x to email) ~~~~~~~~~
http://suzie-q-wacvet.com / http://intergnat.com/malebashing /
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On 12/5/2011 6:24 PM, Suzie-Q wrote:

Nothing to worry about. It'll all dry when the sun comes out. It's also common practice to install new shingles over old ones. Thirty years from now, when you need another new roof, have them strip it down to the sheeting.
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Suzie-Q wrote:

Most people here will say you can easily put a second layer over the first. I think that's easier done if you have a simple roof - one that doesn'a have a lot of different features (coves, different sections meeting each other at different angles, etc).
It's certainly not perceived to be a "clean" way to do it (just as in a lot of cases when you restore something you don't just slap new paint over old paint).
It's not really about whether or not the roof can support the weight of 2 layers of shingles (almost certainly it can).
Reasons I can think of to remove the old shingles:
- to fix any rot or dammage in the existing wood deck (because you can see it with the shingles removed)
- to improve the ventilation (easier to add a ridge vent or other vents when the roof is stripped down to the wood)
- better prepare the wood deck against leaks by applying new felt, ice-guard, other underlayment, metal drip edges and sheathing in valleys and where the roof butts against walls, chimneys, etc.
- new shingles may not "settle" properly over existing shingles, leading to cracking, folding or other irregularities
- you might (or will) void the warranty that comes with the new shingles when they specify that it not be installed over existing shingles
- if you know you have leaks with existing roof, then slapping a new layer of shingles over the old is (I'm pretty sure) not recommended
- you might think you have only one layer, but you might actually have two layers already (!)
As for having the roof wet when you're putting on the new shingles - totally irrelavent. That water will evaporate sooner or later (maybe not so fast now in the winter, but not so slow that it will cause problems).
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If you take the time to remove the old shingles, it reveals any deeper issues in the roof which may need repairing. If you are doing just a slam bam reshingling and don't care, then that's the way you do it. Or maybe the contractor is not good enough to actually "repair" a roof. There is no brainpower required to just nail on new shingles, and a monkey can be trained to do it in less time than it takes to train some humans.
I would never ever consider refoofing without removing the old first. Yes, there are arguments either way, but if I'm going to spend all that money, I'd like to know if there are any other things to do with the roof that need fixing. How is anyone able to see that without removing the current shingles?
Or, you could just fix it later .............
Steve
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Agree with HomeGuy and Steve. For the additional cost, IMO it's worth it to take off the existing shingles for the reasons they've given. Expecially if there is any reason to suspect problems with the exising roof sheathing, etc. But if the existing roof is OK I would not lose sleep over putting a second layer on. It's done all the time.
As for the rain, it doesn't matter. The water will quickly find it's way out and not be a problem,
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On Mon, 5 Dec 2011 18:23:54 -0800 (PST), " snipped-for-privacy@optonline.net"

Having had my own roof replaced earlier this year while watching many around having the same thing done, I think I know about roofs now (at least shingle roofs in my area). Most replies in this thread are correct. Personally I would prefer to not roof over an existing roof for reasons already mentioned including perhaps underlying rotten plywood. But to answer your question, roofers tell me that you don't have to worry about the rain. I already asked that question myself earlier this year because I had the same concern before my own roof was replaced. And where I'm located they say rule of thumb is 2 layers of roofing is acceptable but structurally it depends on loads, wood sizes, spacing, slopes, etc... .
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