Roofing ?: rubber vs metal

I have seen roof "systems" on This Old House on PBS, which consist of a rubber "membrane" which then has shingles or metal roof put over the top of it. THAT is supposed to last forever -- 50 years plus. The particular membrane I saw described was soft enough so that when it was penetrated by the roofing nails, the membrane sucked back around the nail to make it waterproof around the nails. I am going to investigate this type of thing for my place which will need a new roof fairly soon. You need to be sure whoever is putting on such a roof for you really knows how to install that membrane properly. It is sealed together somehow (heat I think) and is totally impervious to water if it is done properly.

Good luck!

MaryNY

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The single ply rubber roof covering will eventually fail, 12 to 20 years here in Florida, due to the afternoon showers where the temps go from 180 to about 60 during the showers. The standing standard seam is less prone to temp changes, and can last a life time.

What is known as a bald top would be my recommendation. Its basically a hot tar and layers of tar paper but without the addition of gravel, quite common on commercial buildings here. It does get re coated about every 3 years with insinuative aluminum reflective fibered coating.

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I have a roof on a portion of my house that is 2/12, and it was done in regular asphalt shingles with 4" tab exposure. Has not leaked a drop in a decade, and we get some heavy rains here.

If you must use something else, standing seam metal is an excellent choice. If properly installed, there will be no exposed holes or fasteners. The seams are "standing" up, and so water running off will not be able to get in them. It will last your lifetime.

In fact, I am going to have my whole house done in standing seam next time around.

Do not use the rib metal, that is probably going to leak on you with less than 4/12 pitch. 4/12 or more is considered ideal pitch.

I wrote all this without reading other responses! Now I'll post it and read them.

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Jim Steele
Sweetpea Farms
"To avoid criticism, say nothing, do nothing, be nothing." -- Robert Gates

This is a controversial point. No two people will agree on it.

I never nail a tin roof down (or screw it down, which is what I do) through the rib. I always do it through the flats next to the rib. That ensures a better seal than the rib method. If you want a perfect seal and have the time, the best seal is to dab each screw with clear silicone before you drive it in. The silicone oozes around the rubber gasket as it hits the steel. Never leaks, ever.

I have a shop that was nailed through the rib by someone before me. Leaks, leaks leaks! There is no way to stop them but to reroof it, the current roof has been ruined by nailing through the ribs. Right next to it is a shop I did, screwed through the flats. No leaks ever.

As far as metal roofing materials, if you buy galvalume, even though the paint may be scratched or broken at the bend, it will not rust. There is a difference in metal roofing and siding. The galvalume here costs more but also has a much higher warranty period, typically 30+ years. Top of the line is aluminum, with higher costs to boot. Likewise, buy the heaviest gauge metal you can get.

The standing seam roof if properly applied is extremely wind-resistant. Even nailed-down metal roofs can come all up once the wind gets under a single piece, due to the metal acting like a wing under wind lift conditions.

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Jim Steele
Sweetpea Farms
"To avoid criticism, say nothing, do nothing, be nothing." -- Robert Gates

It depends on what they are calling rubber .
EPDM membrane is warrenteed for 30 years and comes in 10x50,20x50,and 10 or 20x100 ft rolls . from 45 mill upto 125 mill . its a good choice for a very flat roof as for most flat home roofs you will only have one seam to deal with.
if how ever they are talking about brye or awlplan I'd avoid them on an extremely flat roof due to the number of seams . either way heat is a major draw back of rubber the dark color makes a great solar collector . also if installed properly rubber or metal should provide a good roof for 25-30 years ,beyond that short of slate with soldered copper flashings or a properly maintained wood shingle roof(cyperous not ceder) its all luck .
Metals the big thing these days but paint fades and steel rusts ,neoprane washers get over torqued or damaged and it leaks too . Nailed metal roofing is a waste of money, just as mechanically fastened rubber is .
if at all possible repitch the roof to at least a 4/12 , other wise I would personally go with epdm membrane with nylon re-enforcing glued down over rigid insulation to add some drainage.

Yep on what Junkmanme said, flat roofs are inheritently build to fail because they are flat. You are much better off putting up some type of trusswork to change the pitch and then using shingles.

THANK YOU, Ohiogal !
YOU are CORRECT! Put slope on the roof for drainage and then roof it! Stops the otherwise "unending problems"!

Have a pleasant weekend!
Bruce (Junkmanme in New Mexico)

Thanks, everyone, for the advice. Right now I'm leaning toward the metal. The pitch can only be changed just enough to cause the water to run off. Anything more would be a major renovation due to the style of the house.

EPDM .060 is the rubber that has been suggested, with a fully adhered system. That's an option, but even the roofers say it's a bit fragile when it comes to critter traffic. Not to mention rubber roofs are just plain ugly. :P

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