View Full Version : OT: Flat Roof Coatings

10-09-2011, 07:50 PM
We have, unfortunately, a flat roof over part of our house. The built-up-roof is about 20 years old, and had an expected life of about 15 years, so it is living on borrowed time. However, we have spent a fair amount of time keeping it cleaned and coated with silver coatings. We do have some ponding, but make a valiant effort to keep the ponds siphoned off.

We are ready to coat it again, so I'd be interested if anyone here has had good or bad experiences with specific silver or white roof coatings. Seems as though oil-based coatings are becoming harder to come by.

10-09-2011, 08:58 PM
I probably can't help. Here in Maine, anybody who has a flat roof is crazy! (There are a few.)

Have you considered replacing the built-up roof with a rubber membrane roof? Or is roof replacement something that is going to have to happen "later?"

Chris S.
10-09-2011, 09:23 PM
Ace hardware has been advertising a coating thats either rolled or sprayed on.
Check out their web page.

10-09-2011, 09:25 PM
By far, the second best coating for a flat roof is sprayed polyurea coatings, the same stuff they coat the Pentagon with. I have a 40 square flat roof with that on it.

BUT the best, #1, can't be beat coating for a flat roof is a combination of trusses, plywood deck, roofing felt and shingles. :D

10-09-2011, 10:15 PM
Flat roofs are a nightmare. Eventually they leak, always. Never mind things like snow load, even in a warm climate they are nothing but trouble. It has always amazed me that any architect would consider using a swimming pool as the roof of a structure.

10-09-2011, 10:38 PM
Amen to that, all flat roofs leak its just a matter of time. And not much at that.

Paul Alciatore
10-09-2011, 11:04 PM
Flat roofs are a nightmare. Eventually they leak, always. Never mind things like snow load, even in a warm climate they are nothing but trouble. It has always amazed me that any architect would consider using a swimming pool as the roof of a structure.

Any architect worth his salt knows that a flat roof may be flat, but it should NEVER be level. It must have some slope, even if it is just one or two inches in 10 feet. Six or more inches in that distance is a lot better. Such properly pitched, flat roofs do not have ponds and stand a lot better chance of not leaking.

Heck, I know it, so architects must know it. Perhaps it is the cheap contractors who don't know or care.

10-09-2011, 11:12 PM
Maybe it's time to add a pitched roof over that part. It shouldn't be a problem to add the aluminum flashing where the new meets the old, and you would get to add an eave if you so desired. Good old asphalt shingles and tar paper over standard roofing sheet aspenite or whatever- end of flat roof problems.

10-09-2011, 11:19 PM
We've tried for years to add pitch to the roof. Unfortunately, this roof covers only half the house, and the non-eave side cannot be raised more than a few inches before it encounters clerestory windows. This few inches would probably not be enough to assure drainage over the 25 feet of run. So, we're stuck with this unless we want to buy and install 5 new, large (but shorter than existing) windows.

We'll probably just keep it maintained and coated until we sell in a few years.

10-09-2011, 11:41 PM
I had our roof resurfaced about a year ago. It had a modified bitumen roll roofing on it and the roofing company used a fiberglass mesh reinforced plastic material that's heat sealed between strips. It's white and reflects more sun and heat than the previous one, important in this latitude where cooling is the larger energy load. About the same 15 year guarantee.

10-10-2011, 03:49 AM
Got a flat-root on the house extension built by previous owners.

Yep - it started leaking about a year or so after we moved in. Had a look and it was obvious where the roofing felt had failed through age/heat/cold/etc and rain had got to the chipboard underneath causing it to sag and so create a nice little pond on the roof (there's actually about a 4inch rise over the 16 foot depth of the roof).

I took the old felt off with a shovel. replaced the old chipboard (what was left of it) with fresh wood and then covered it with this stuff
I'm guessing this or similar must be available in the US...

Uses a water-based contact adhesive that goes on with a mop/broom/paint-rollers/etc.

The only "problem" we had was working out how to handle a single sheet of rubber that size. Basically you start in the middle and work across to one edge then go back to the middle and work across to the other edge. Also make sure it's a nice, warm, sunny day as that helps the contact adhesive dry faster plus makes the membrane much more flexible.

Took me and a friend the weekend to re-do the flat roof; about 16ft by 40ft. total cost about 800 including a couple of cases of beer that i put on the back seat of his car when he wasn't looking.....


mike os
10-10-2011, 07:42 AM
as above.. the only flat roof solution I will fit these days is EPDM... bitumen/asphalt, felt & fiberglass are all less effective, more difficult to maintain and repair.

Nothing wrong with flat roofs that are properly designed, detailed and installed, its when people dont know what they are doing that trouble starts. Like all roofs they have a limited life that is pretty much reflected in teh price... half the price of a pitched roof & half the working life...

10-10-2011, 08:00 AM
I just had a standing seam metal roof put on the house, but the company also does flat roofs with rubber membrane: http://cobeckroofing.com/flat_roofing.php
There must be similar outfits in California. (Though that still doesn't answer your question about coatings.)

10-10-2011, 08:30 AM
We have a 100 year old garage with a flat roof. For about 40 years my parents tried one thing after another to stop the leaking and fix the roof.

About 4 years ago now I put on a rubber roof for them and it has yet to leak and is holding up perfectly! I have been using the left over rubber for all kinds of little projects as well. Great stuff, would recommend it to anyone especially with a flat roof.

10-10-2011, 07:05 PM
Batman has it. EDPM or TPO is the only logical flat roof solution. It has to have a taper/grade to drain, to either roof drains or scuppers, but they are the only way to go.

Firestone, Carlise, both make good roof material.

10-10-2011, 09:48 PM
I agree a EPDM is the only way to go & put on white & it will outlive you if done right,