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-   -   Second layer of asphalt roofing (http://www.diychatroom.com/f9/second-layer-asphalt-roofing-41497/)

eefromjersey 03-31-2009 11:04 AM

Second layer of asphalt roofing
 
Hey all...I have the original layer of asphalt and want to go over with a second layer my question is do I need to cover with an underlayment are there any reasons why I wouldn't put a second layer over the first also what ever advice would be appreciated it's an almost flat roof and i'm planning to do it myself, don't seem all that difficult.

hey, thanks in advance

Ernie

Ed the Roofer 03-31-2009 01:35 PM

A 2nd layer, although less expensive to do, will not provide the same life longevity cycle as a one layer roof. As a guess from past experiences, i would say about 25% less life from that roof.

So, are you really saving money, if 10 years down the road, if you still live there, you are now obligated to pay for a 2 layer tear-off and new reroof?

Adding a felt paper underlayment between the 2 layers will trap in moisture that will cause excessive trapped moisture under the top layer, creating premature blistering.

Without removing the original layer, any decking deflections or beginning stages of deterioration can not be readily observed and repaired.

If the old original roof is starting to deteriorate and curl or buckle, those defects will telegraph through the newly installed shingles early on in its life, creating the appearance of an already aged roof layer.

Ed

adelaide11 04-04-2009 12:55 AM

All three points which you hace mentioned here is really useful and helpful. Here are they -

Adding a felt paper underlayment between the 2 layers will trap in moisture that will cause excessive trapped moisture under the top layer, creating premature blistering.

Without removing the original layer, any decking deflections or beginning stages of deterioration can not be readily observed and repaired.

If the old original roof is starting to deteriorate and curl or buckle, those defects will telegraph through the newly installed shingles early on in its life, creating the appearance of an already aged roof layer.

Certainly you have clear concept and I admire the way you make them understand.

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johnk 04-04-2009 01:24 AM

And of course the part about being "almost flat".Instant red flag with me.How flat?

Ed the Roofer 04-04-2009 03:26 AM

Quote:

Originally Posted by adelaide11 (Post 254792)
All three points which you hace mentioned here is really useful and helpful. Here are they -

Adding a felt paper underlayment between the 2 layers will trap in moisture that will cause excessive trapped moisture under the top layer, creating premature blistering.

Without removing the original layer, any decking deflections or beginning stages of deterioration can not be readily observed and repaired.

If the old original roof is starting to deteriorate and curl or buckle, those defects will telegraph through the newly installed shingles early on in its life, creating the appearance of an already aged roof layer.

Certainly you have clear concept and I admire the way you make them understand.


Thank you, Mr. German Guy who is now from Australia.

What is your name please?

Ed


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