Hot Mop Flashing Repair Materials/Technique...??? - Roofing - Contractor Talk

Hot Mop Flashing Repair Materials/Technique...???

 
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Old 06-09-2015, 09:21 PM   #1
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Hot Mop Flashing Repair Materials/Technique...???


Hi Guys.. Been absent awhile... but looking for some technical personal advice/help

Think you may know I'm a GC..not a roof pro.. and from snow load Colorado... not flat roof Cali.

I'm at my sons in SoCal..( just became a grandfather).. but we have an issue I know Jack about.

He has a good/relatively new BUR/Hot Mop/Tar-Gravel roof.

We just tore out all his cast iron DWV and redoing with abs.

The old main stack was 4" with a sheetmetal cone hat/boot flashing with multiple tar layers built up sealing it. We have removed the old 4" cast.

We want to run either 3" or 4" abs main stack up and out without f"en up the flashing and seal it well. Orininally we thought we would just run 4" abs up thru existing cone/boot and everything fine....

BUT the old CI main is smaller than 4" abs... and obviously larger than 3" abs.

HOW BEST TO PROCEED... we have three thoughts.

1) Slice/split the old flashing such that we can get 4" abs thru... Question.. how and what mastic do we use to reseal it for a good seal..

2) Similar to 1, we run 3 abs thru... do we wrap some fiberglass matt around the extra size and what mastic do we use for a seal to tar.

3) Maybe we drop a new sheet metal hat/boot for 3" abs over the old existing boot... get a goot seal around our main.... but how do and what product do we use to marry that new boot to the old tarred over flaqshing..

Any advice is really appreciated... as always, that job was supposed to be yesterday;

TIA

Best

Peter

(Doubt there is any confusion, but we are not going to rip into the good/new roof to replace the actual boot jack flashing.)
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Old 06-09-2015, 09:32 PM   #2
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Re: Hot Mop Flashing Repair Materials/Technique...???


Hey Peter, good to hear from you again.

Congrats on that grandkid....

They are our revenge on our kids...

Now, your roofing issue....

Split the flashing to allow pipe to go through.

Wrap with butyl tape.

Then fashion a storm collar around your vent stack, much the same as you see on a wood stove pipe. A little caulk around the storm collar and you should be good.

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Old 06-10-2015, 12:26 AM   #3
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Re: Hot Mop Flashing Repair Materials/Technique...???


Ditto on the butyl tape. One of my plumbers also swears by Dottie 10mil tape for this application.
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Old 06-10-2015, 09:59 AM   #4
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Re: Hot Mop Flashing Repair Materials/Technique...???


Griz and Bob...... Thank ya guys for such a quick response... and with your two's collaborateing recommendation... I'm off to get butyl tape

and I guess no mastic (black jack etc) at all is necessary...????

Best

Peter
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Old 06-10-2015, 07:12 PM   #5
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Re: Hot Mop Flashing Repair Materials/Technique...???


Griz... Just as you suggested

When I got up there today.... I was able to just slit the metal cone boot at the top after cleaning cutting some of the heavy tar ... and got a tight fit around the abs.... almost like original fit...



put a wrap of butyl tape around it and dropped a nice tight storm collar over it....



Worked great.... guess I just thought hot mop was going to present an issue... but not in this case...



Thank Ya



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