Any flat roof experts here?

3 years ago

Most of the roof on my house is standing seam steel, but there is one area -- 6' X 20' -- which is flat. The flat roof was put on when the house was built 22 years old ago, and I've been wondering about when it might need replacement, so I'm looking for opinions on what people think of its present condition. It has no holes or tears, but it does have an alligatored appearance. I live in the Seattle area, so we don't get weather extremes here. Snow is only a few days a year, and mostly it's just overcast and drizzly in the late fall through spring. Summers are in the 70's with the occasional really hot summer day breaking 90F. Here are a couple of pix. If you have any experience with this, please let me know your thoughts. Thanks.

Featured Answer

res2architect

3 years ago

last modified: 3 years ago

No roof should be flat. This looks like a "low-sloped' roof with built-up layers of roofing felt in asphalt or tar. It should slope a fraction of an inch per foot to scuppers, gutters or roof drains. If it doesn't slope enough to drain well, you will need to modify the roofing so it does.

Alligatoring of the surface of built-up roofing (BUR) is common and can usually be repaired with a coating as mentioned above. Pay someone to do it and warranty it; it's definitely not a DIY task. Tar (coal based) is less common than asphalt (petrolium based) BUR but tar will repair itself on a hot day in the sun. You should limit your exposure to asphalt and tar.

You can encapsulate BUR with a mechanically attached fiber recovery board and a fully adhered EPDM (synthetic rubber) single-ply membrane or a similar one of PVC, etc.

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Comments (10)

Seabornman
3 years ago
The alligatoring is a result of sun baking the asphalt. If roofing is solid, look at applying a coating like https://www.homedepot.com/p/Henry-4-75-Gal-Premium-Fibered-Aluminum-Reflective-Roof-Coating-HE555019/100094951. It'll also cool the roof slightly.
kudzu9 thanked Seabornman
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kudzu9
Original Author
3 years ago
res2architect-

Yes, it does have a slight slope as it drains well to a drain at the perimeter. My main concern was its overall condition. Based on advice from you and Seabornman I am going to have it coated.
kudzu9
Original Author
3 years ago
Seabornman-

I went to my local Home Depot to get some roof coating. Beside the one you provided a link to, they had two other Henry products for a few more bucks: Dura-Brite 100% Acrylic White Elastomeric Roof Coating, and Enviro-White 100% Acrylic Extreme Elastomeric Roof Coating. Do either of these offer any advantage over the Fibered Aluminum Roof Coating you recommended other than being somewhat whiter and more reflective?
Seabornman
3 years ago
It's been a while since I've used the aluminum stuff, but I believe it's oil based, so will (slightly) rejuvenate and work into the asphalt. I put some on an older modified bitumen roof and it never flaked or peeled. I've used one of the acrylic products on a rubber roof. It worked well, but it's just a glorified paint.
kudzu9 thanked Seabornman
millworkman
3 years ago
From my past the aluminum coating was always used as it was a better, longer lasting product. Sold it and was always recommended and used by the roofers I supplied. That was during the Blackjack brand days,
kudzu9 thanked millworkman
kudzu9
Original Author
3 years ago
last modified: 3 years ago
Seabornman and millworkman-

Thanks. From other posts, I know you both have lots of experience, and I always find your advice helpful and insightful. I'm going with the aluminum coating. :-)
PRO
Windows on Washington Ltd
3 years ago
GACO is what we use. Or you could put down some ballast.
kudzu9 thanked Windows on Washington Ltd
klem1
3 years ago
Howdy kudz,I'm late to the party but i have solid advice when the day comes for replacing the roof. I wish it was this easy for hvac,plumbing and other things that require repair or replacement. Only hire a contractor who is an otherized installer for one of the commercial roofing manufactures. Most don't want to talk to residential homeowners and I certainly don't blame them. It isn't worth them getting mixed up with fly-by-night residential roofers but a clever guy like you knows how to arange taking someone in their office to lunch or other occasion which give's you opportunity to show you aren't the typical shopper looking for the cheapest bid. That isn't to say commercial roofers overcharge,they just don't want to play price games residential roofers are known for. While I was still working and for a few years after retirement I was able to get mine and close friends' rv roofs replaced by a couple of EPDM contractors I used for commercial work. The replacements actually costed less than had an rv dealer done them. The cherry on top is workmanship is light years better than techs at rv dealers that must preform all types of work on rvs. The downside ,no warranty but for me that's not an issue because 90% of rv roofs require replacement due to storm damage long before they wear out.

It's good to see you still plugging along kudz.
kudzu9 thanked klem1
lizzierobin
3 years ago
I had TPO, a commercial product, installed on my ”flat roof.” It should last quite a while and replaced the black rubber roof we previously had (15+years old). I would call a pro just for an inspection, get an opinion, and find out replacement cost. Based on size you mentioned, might be worth it to replace now. At least you will know what your options are.