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TedW 10-24-2013 01:04 AM

What substrate for torch down on unheated roof?
I'm looking at replacing a small roof over a front porch. It's very low pitch, about 1 or 1-1/2 in 12, so I'm thinking a torch down is the best option. When I tear off the old roof I pretty much know what I'll find... 80 year old 1x sheathing (like old subfloor) that probably needs replaced in a few spots.

My question is what to put over the sheathing, whether it will need something like dense board or plywood, or whether I should just nail down 30 lb felt or something else altogether.

I can post some pics of the roof tomorrow, if that helps any.


oldognewtrick 10-24-2013 05:22 AM

Ted, there are a lot better and safer systems than torch down available for application on low slopes today. All the major MFG's have a system of a self adhering base sheet and a self adhering cap sheet that provides a easier and cleaner installation than torch downs. Once the sheets are placed you cannot separate the plys.

Certainteed's system is ...Flintlastic.

GAF'S system is... Liberty

ABC Roofing Supply has a system...Mule Hide.

We've used all 3 systems with great success.

TedW 10-24-2013 09:48 AM

Thanks oldognewtrick. I guess I should have first asked which is better? The home owner wants the same thing she has on the main roof of the building, which is GAF Ruberoid torch-down white granule. It doesn't have to be the exact same brand but is must look the same and she wants the longest lasting. So sticky seams vs welded seams, I can't imagine peel and stick will outperform torch-down.

Mostly, I just need to know what goes between the deck and the cap to provide the best quality installation.

TedW 10-24-2013 12:10 PM

6 Attachment(s)
Update, the customer is not bent on using the same material as the main roof, so I'm open to other options.

Here's some pics of what I'm dealing with. The roof has almost no pitch at all, maybe 1" in 4' if that. It's a metal roof, or at least it used to be, with built-in gutter along the front edge. As you can see, the asphalt is completely shot. It's also pulling away where it meets the limestone, with no flashing that I can see.

The customer's main concern is to get it fixed so it will last a good long time. She is not concerned about cosmetics, since only the tenant on the 2nd floor will ever see it.

the roof measures roughly 14' x 6'

So let me ask plain and simple, what would you do? Step by step if you don't mind. :o

oldognewtrick 10-24-2013 03:27 PM

Id put down the SA sheets, no tar bleed out, safer.

Here's the short version of installation and what are acceptable roof decks. cation_Instructions.pdf

TedW 10-25-2013 01:09 AM

Thanks. I was looking at the Liberty system on you tube the other day and it does look pretty straight forward.

I'll price the materials and run it by the customer, see what she thinks. Wish me luck!

oldognewtrick 10-25-2013 09:30 AM

If I remember correctly, the Liberty granules are the same as Ruberoids color.

TedW 10-26-2013 10:45 AM

Well, I haven't received a response from the customer yet. I think she plans to put it off till spring, against my better advice because A) it just that much more snow melt that's going to seep into the roof structure and cause that much more damage, and B) because I really need the work :)

I didn't mention it but the roof job is not actually the work I'm interested in. The paint on the porch overhang is peeling like crazy, which is the job I'm really after. But of course, there's no point in doing that until the roof is fixed. She got estimates from a few roofers, a couple whom she has done business with in the past, but they all want to put it off till Nov or Dec, which means I can't do the painting until spring.

Oh well... but thanks for the advice.

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