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-   -   Torch down roofing question (http://www.diychatroom.com/f9/torch-down-roofing-question-58820/)

Z-man 12-08-2009 03:42 PM

Torch down roofing question
 
I recently hired a roofer to apply torch down roofing to a flat section of roof on my house. He was supposed to tear off the existing roof (also torchdown) but didn't, he just did a layover. Does anyone know if that is common practice with torch down roofs or if it will affect the integrity of the roof?

Bob Mariani 12-08-2009 04:59 PM

If you do not remove the old roofing how do you inspect the integrity of the roof sheathing? Just a poor way to do this work. Common practice does not make it any more than a common error in judgment.

johnk 12-08-2009 11:41 PM

It is very common to go over a flat roof...But there is a right way and a wrong way.

Slyfox 12-09-2009 08:42 AM

Lay overs save the home owners money and the contractor time.
Layovers are good for our environment by prolonging that waste from being dumped in our land fills for 10,15,20 years by which time we very well come up with better ways/methods of waste disposal and recycling.

Experienced roofers can do lay overs with out problems.
I'm doing a residential shingle roof right now in which the home owner asked if it could be a lay over instead of a re-roof "tear off" and i told him yes until i got on the roof to do my measurements and found that the front portion of the home had several leaks in the existing roof.
I went into the attic and found mold had developed under the sheathing in the areas where the existing shingles are leaking.
So on a 28 square roof we did a lay over on 22 square and when we go back to the job Saturday "weather permitting" we will tear off the remaining 6 square section of roof and replace roughly 12 sheets of plywood, install new underlayment and shingles.

With that said, if he told you it was a tear off and charged you for a tear off but than did a layover he was misleading/dishonest and even if he did a good job you should get a few dollars back from the original quoted price.

Michael Thomas 12-09-2009 09:01 AM

Depends a lot on the condition of the roof, and what its adjacent to, if there is significant ponding and deflection of the existing roof deck, or if the roof is flashed to an adjacent horizontal surface, it's more difficult to perform a satisfactory "roof-over" of an existing "rubber" roof.

Z-man 12-09-2009 09:52 AM

Thanks for the feedback. One side of the roof is flashed against a horizontal wall. Looks like rubber wet patch all along the roof where it meets the wall and then they put caulk inside the vinyl siding J-channel at the base of the wall.

Does roofing tend to last longer when it is torched down to the deck verses laying it over existing roofing?

Michael Thomas 12-09-2009 10:44 AM

Quote:

Originally Posted by Z-man (Post 363972)
Thanks for the feedback. One side of the roof is flashed against a horizontal wall. Looks like rubber wet patch all along the roof where it meets the wall and then they put caulk inside the vinyl siding J-channel at the base of the wall.

Can you post a link to a picture? What you are describing is likely done wrong in the first place (addition?) and then patched because the junction is/was leaking - if the roofer just did a "layover" there is a good chance problems at this junction were not corrected, and if so there is a good chance the roof decking under the roof membrane and adjacent to the wall is rotting and/or there is water in the wall at the junction, just not enough to see it yet at finished surfaces.

Here's a recent example from below such a junction between a vertical wall and a flat roof:

http://paragoninspects.com/images/ir..._01_170pix.jpg

Fig 1 Fig 2:Visible light image of leak at junction of vertical wall and flat roof - no leak is apparent (c) 2009 Paragon Property Services Inspections, Chicago.


http://paragoninspects.com/images/ir..._02_170pix.jpg

Fig 2:Infrared (thermographic) image of leak below junction of vertical wall and flat roof - (c) 2009 Paragon Property Services Inspections, Chicago.

If this type of junction is incorrect (and at least at my infrared and home and leak detection / water intrusion inspections here in Chicago, that's much of the time) it will be necessary to find a competent roofer to inspect the existing roofing and decking, repair or replace as necessary, and correctly (re)flash the junction. This usually involves (from the inside out) running the roof membrane 6" or so up the wall, flashing over the membrane, a WRB (such as Tyvek) over the flashing, and finally the vinyl siding over the WRB, held back above the roof.

Z-man 12-09-2009 01:02 PM

3 Attachment(s)
Here are some pics

Michael Thomas 12-09-2009 02:16 PM

Looks like a Cold Applied Adhesive/Cement. If that's what it is, water from the drainage plane behind the siding is likely being directed behind all that adhesive/cement and into the wall and/or roof decking if there are any defects in the original membrane (assuming the installers ran that up the wall to begin with).

It's done this way a lot.

It eventually (in a few years) fails a lot when done this way.

tinner666 12-09-2009 07:38 PM

Well now. A leak along the wall can be many things. One of the biggest is unflashed penetrations in the wall. Now, I've traced many leaks to windows and other trim issues. I even prepared a tutorial to help prevent a lot of these issues. http://www.albertsroofing.com/Window%20Flashing.htm
I wonder if the leak is under that window in the picture? Many roofs done this way get turned up under the siding, then all water hitting the windows is directed, intentionally, behind the siding, and behind the roof.

Siders seem to be blind to waterproofing and it's their standard line that vinyl 'leaks by nature'. Go figure.

tinner666 12-09-2009 07:50 PM

For the record:
I, and any competent roofer would have removed nearly everything on that gable, and the shingles where the flat roof and gable come together. 2 courses of siding would have come off at the wall, and I would have flashed that window too, as a normal part of the job. There would have been no bucket of mud spread around on the roof.

MOST roof cements are incompatible with torch-down material. It can eat through the roof clear to the deck.
Same is true of self-adhered Mod-bit material. Cans are marked so no mistakes will be made.

Reason I mention this is no real roofer would have made that mess. If the guy made that unnecessary mess, did he even bother to use a compatible material? :(

Michael Thomas 12-09-2009 10:10 PM

The leak in the IR photo was from a failing seam in the turn-up at the roof / wall transition (no cant strip, mostly).

tinner666 12-09-2009 11:02 PM

Quote:

Originally Posted by Michael Thomas (Post 364327)
The leak in the IR photo was from a failing seam in the turn-up at the roof / wall transition (no cant strip, mostly).

Yup. Doesn't surprise me. Maybe I should have mentioned that would have been noticable in my earlier post, after a good roofer finished the job.
I can say I always use cant because I have one tomorrow that would really be problamatic with cant strip..... Only ashort run, with the flow. I'll snadwich primed flashing into each layer, heated down, then a cap sheet. A 6" piece will go under the base to cause a step to the wall. Another between it and the mid sheet. Water will be shunted away from the wall.

johnk 12-10-2009 01:17 AM

Quote:

Originally Posted by Z-man (Post 363972)
Thanks for the feedback. One side of the roof is flashed against a horizontal wall. Looks like rubber wet patch all along the roof where it meets the wall and then they put caulk inside the vinyl siding J-channel at the base of the wall.

Does roofing tend to last longer when it is torched down to the deck verses laying it over existing roofing?

Torch-on should never be torched right to the deck,you would be just asking for a fire.Besides tear-off would be impossible without removing the deck.There must be a base sheet under the capsheet.I think the longevity would be equal in both situations.I think its a very good roof adding a capsheet over cap sheet.Nice and thick!Always prime and clean a granulated capsheet thoroughly before adding a new capsheet.You could also degranulate the old capsheet,although very time consuming,but IMO better than priming.

hooty1 10-06-2012 12:21 AM

Quote:

Originally Posted by Bob Mariani (Post 363573)
If you do not remove the old roofing how do you inspect the integrity of the roof sheathing? Just a poor way to do this work. Common practice does not make it any more than a common error in judgment.

you should just stick to be a remoldeling contractor. Maybe even interior design.. A professional roofer knows what he can and cannot do.. We have outr tools, and we know how to use them..


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