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-   -   TorchDownModifiedRoofingMaterial (http://www.diychatroom.com/f9/torchdownmodifiedroofingmaterial-308/)

idarose 01-25-2005 08:48 PM

TorchDownModifiedRoofingMaterial
 
I have been getting quotes from contractors to re-roof my garage. It has a slight pitch and has one layer of material on it that is 18 years old. It does not appear to be in bad shape but is developing leaks. A contractor wants to put down Torch Down Modifyied roofing material. He wants to apply it over the old material. What is Torch Down Modifyied Roofing Material? Is it any good? Should I allow him to put it down over the old materail?

johnboy52 01-28-2005 12:06 AM

torch down
 
I have my doubts about this roof contractor, first typicaly a garage roof isn't very big, so why leave the old roof on? Modified doesn't do to well when applied over old roofing, in fact when I sell a garage job I will redeck the entire surface, simply to have a smooth surface to work with, nail free. OSB 7/16 decking works real good for this purpose, It's not expensive. As to your question; what is modifed, well it's proper name is bitumen (I may not have spelled that right), however thats the way it sounds. Bitumen is a high grade of tar, like the tar used in Hot tar/ gravel roofing, only better. Now depending on what brand you use, the bitumen roll has a sheet of strong material thats been imbeded, then dipped in the bitumen. Now this material may be polyester or fiberglass, you can see what I mean. This gives the bitumen strength, it will shrink and expand with the weather, and doesn't tear. You can get it with or without a granuler surface, like shingles. It is among the best flat roof products out there. It can be applied with a torch, by melting the underside of the roll as you roll it. It can also be applied using the same tar used for tar and gravel roofing, it's set in the hot tar as you roll it out. Lastly it can be glued on the decking, however I don't reconmend this way as the glue is sensative to humidity and temprature, and may take forever to set up. The only thing you need to be concerened with is quality of installation, a good torch man, so find out how good he is!

Glasshousebltr 01-28-2005 06:47 PM

I just torched over existing shingles last fall. I didn't want to do it but the customer was dealing with a cost factor and wanted me to. I was surprised at how well it laid down and adheared to the existing shingle.

I don't think I would recomend it as standard practice but it did the job well.

Bob

AaronB 01-28-2005 10:18 PM

I see no reason to ever go over an exsiting roof. You will never get the life you expect out of it. It will not lay optimally flat, develop stress cracks prematurely at all the stress points produced by applying to a non-flat substrate.

I do not know where youre located, but never use 7/16" decking. It is against almost every mmunicipality's building code. 1/2" is the standard for up to 2' rafter centers, but only if you install clips.

I will never advise going directly over a plywood deck with even a base sheet first. There is too much inherent movement and you ren the likelyhood that your membrane will tear at the plywood joint when the dimensional movement occurs.

I would recommend min. 1/2" high density wood fiber anda 75# base both mechanically fastened with 3" steel stress plates and 2" screws. On top of that, I would heat weld an APP torch system with a granulated surface. The only maintenance on this roof is usually cleaning gutters and drains and checking any caulking at the terminations.

In other words, don't let him do it.

AaronB 01-28-2005 10:20 PM

And not so much that it is a high grade asphalt, but polymer modifed bitumen. It is modified with plasticizers to make it more flexible and give it a higher melting point than say steep asphalt.

johnboy52 01-30-2005 04:44 PM

Mr. Idarose even though AaronB. means well, he's just graguated from engineer's school. All this heavy duty talk isn't necessary! Just find out if the contractor has a good torch man.
As far as the new decking goes, it just helps the mod. lay flat, if your deck is smooth then us it. 1/2" decking is what you need if your tearing off the old decking, but why do that? laying new decking over the old is what you do if you need a new surface, and their is no code for that! As far as the right kind of paper, and wood, and type of fasteners goes, it not rocket science, if your unsure then ask at the roofing wholesalers. I'v been roofing longer that most these guys have been alive, and I've never herd of anybody using high density wood instead of plywood. The same goes for 75lb. paper I,ve never herd of that stuff either. All this talk sounds good on paper. In this day and age there's alot of people who try saying all this mumbo jumbo, like roofing is rocket science. A good roofer could put on a roof using suran wrap!

AaronB 01-30-2005 05:00 PM

ALTHOUGH YOU MIGHT USE SARAN WRAP, MOST OF THIS "ENGINEER" TALK IS SYSTEM SPEC. HDWF IS USED QUITE OFTEN IN COMMERCIAL RECOVER APPLICATIONS AS WELL AS NEW INSTALLS, AND IS A FRACTION OF THE COST OF PLYWOOD.

75# FIBERGLASS BASE (NOT PAPER) IS GAF'S BASE, IF NOT OTHER MFGS. LOL

SOME WILL SAY YOU SHOULD JUST FIND OUT IF THE ROOFER IS A GOOD TORCHMAN, BUT HOW COULD YOU EVER FIND THAT OUT BEFORE YOU HIRE HIM? ASK HIS MOMMY? :) IF HE ISNT A GOOD TORCHMAN THEN IT IS TOO LATE AT THIS POINT. aLSO, WHAT QUALITIES WOULD YOU, THE HOME/BUILDINGOWNER LOOK FOR IN A GOOD TORCH MAN? RIGHT, PROBABLY DOES NOT KNOW WHAT CONSTITUTES A GOOD TORCH MAN, IF HE DID, HE WOULDNT BE ASKING MOD BIT QUESTIONS. ALSO, BEING A GOOD TORCH MAN DOES NO GOOD IF YOU DONT INSTALL TO COMMON GOOD ROOFING PRACTICE (GOING OVER CRAP).

IF JOHNBOY'S BEST ADVICE IS TO GO ASK THE ROOFING WHOLESALERS, THEY DO NOT, MOST TIMES HAVE INSTALLATION EXPERIENCE OR EVEN KNOWLEDGE OF SYSTEM SPECIFICATIONS. THEY MOSTLY JUST SELL THE MATERIALS.

I DONT READ ANYTHING ABOUTTHE HOMEOWNER ASKING FOR NEW PLYWOOD, BUT JUST CUZ SOME OLD "ROOFER" DOES THINGS HIS WAY, DOESNT MEAN IT IS THE BEST WAY. I LOOK TO GIVE THE BEST ADVICE I CAN AFTER 15 YEARS OF ROOFING. YOU HAVE THE OPTION TO TAKE IT OR TO LEAVE IT. UP TO YOU.

I WOULD ALSO NEVER TORCH OVER SHINGLES.

AaronB 01-30-2005 05:02 PM

Tis Is, Of Course After A Deck Inspection And Dry-out (you Said It Has Been Leaking). :)

johnboy52 01-30-2005 07:12 PM

Aaron: I can tell your a commercial roofer, these materials you talk of are comerical type. No one uses these products on their homes. futher; the guys at the wholesalers may not Know the types of material like you do, but they dam sure know who the good roofers are!

AaronB 01-30-2005 07:18 PM

Ok. I will not comment.+

AaronB 03-02-2005 09:49 PM

How do they know who the good roofers are?

Grumpy 03-03-2005 07:44 PM

The suppliers know who buys the most materials. They don't hear about the installation complaints.

I'd personally walk if a customer wanted me to put modified over shingles, even if I got to nail a layer of base between. $1,000 profit just isn't worth my reputation.

AaronB 03-03-2005 10:52 PM

Thats what I wwas thinking aboutthe suppliers, too, Grumpy. I was waiting to see what Jonboy had to say about it, and now he may never respond. LOL :(

Mvpulsts 03-12-2005 11:20 AM

Modified Roof
 
I have a flat roofed house here in Atlanta and just had a Modified bitumen roof installed last year. The roofer I went with is a commercial roofer who does the occasional residential roof, but only torch down roofs.

The roof is 14 square. They replaced all of the decking, added a layer of 1/2 inch perlite(?) insulation boards, fiberglass rolled out over that which was screwed down with 3 inch washers, and torched down the roofing over that. It took them 2 days. All of the protrusions (plumbing vents etc..) were flashed by torching a piece around the pipe, cut out with "petals" to flat surface and another piece cut into a "donut" around that.

If your in the Atlanta area, I would recommend these guys.

Definately dont torch down over existing roof...

Matt

AaronB 03-12-2005 03:04 PM

Finally some sound advice. The only difference I like to make is to mop down the base sheet instead of screwing. This provides and additional waterproofing layer and ensures a good bond to the perlite.

I have done the screwdown method many times and it is successful.


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