[xiaodoupi]

You can use quite a few different coatings on a built up asphalt / bitumen surface like this. Its going to depend on your budget and what you are looking to get out of the effort you put into it. It will also matter if its leaking in spots or not. The picture looks like a roof that has been weathered pretty well but those are just as you stated surface cracks and may not be leaking yet, its also a small section of a larger area.
I would address any spots that are leaking first with a heavier fibered petroleum based roof coating/ which is a filler and refresher for built up/ bitumen/asphalt roofs. Its heavy enough to fill in some of those larger cracks but will spread well enough to get good coverage of larger areas. If some of the cracks are close to the width of the pen in the picture then an asphalt or modified roof cement would be better for just the cracks, and then coating over the top. Think of it like treating an asphalt driveway every couple of years. There are fibered Aluminum roof coatings that can be used which add reflectivity and longevity but also are more expensive and there are also white/colored polymer coatings that you could use to almost get a "new roof" thickness(40 mills) out of but those are considerably more money. A 5 gal pail of Fib Roof coating may go for around $25-$30( I have not checked current pricing) where as the Aluminum coating may go for $65-$70 both coverage rates are about 1-1.5 gals per 100 sqft. So you can figure out your area and what your going to spend from there. A covering with out the Aluminum may last you 2-4 years depending on the weather, and the Alum may add another 3-5 years depending. I hope some of this makes sense and helps. I am a newbie to this webpage and I have 18 years experience in the roofing industry on the distribution side and some installation and some in between. There may be some better suggestions out there also but this is a good place to start.

Thank you somuch oldtimer.
That's very helpful.
When I apply the coating, is the final effect really sensitive to the surface cleaness and moisture? If so, I have to wait until next summer or spring.
It doesn't leak rightnow, except a little bit drip on one of the draining point with water accumulated on the roof.

I found this on homedepot website, homedepot is only one block away.
http://www.homedepot.com/p/Henry-4-75-Gal-555-Premium-Aluminum-Roof-Coating-HE555019/100094951
Is it work? What does the 'aluminum' mean?

 

[xiaodoupi]

Does the roof currently leak? If the roof does not have any leaks then all you need to do is clean the roof very good. Broom brush and wash. Let it dry for at least 24 hours and coat it with aluma coating. You can get fibered and non fibered aluma coating. Various manufactures have different rates of Aluminum in the coated that effects reflectivity. We rarely use fibered Aluma coating, and to be honest the last time we used some it was Henrys, like was stated before plan to coat ever 3-5 years. 3-5 years is what should be expected, and this is generally what happens, people do not keep up with the coatings. It is a maintenance item. I wouldn't fool around with mastic in the cracks as it is not needed. Any repairs you do with mastic the mastic will need to cure for 30 days before coating.




Yes the roof must be very clean and free of debris. Clean it well and wait at least 24 hours if in a good sunny area before coating. Fix the leak first, there shouldn't be any leaks even with standing water. A low slope roof should be water proof, they should be able to hold water. Unlike a sloped roof that is water repellent/shedding.


The Henry coating is fine, like I said the fibered is not needed but if that's what they have that's what they have. The non fibered will be a little less expensive.

Post some actual pictures of your roof. Specifically the leaking area.

Thanks mate.
It doesn't really leak currently, except a little bit drip at the connection betwwen the roof surface and a draining point on the center, if water ponded arround.

Recently it rains alot, and leaves fell on the roof. A line of tall poplar trees beside the building. So there is alot of debrits, especially in the fall, and the debrits clog the draining points sometime, I have to clear it manually.

I will post some actual pictures later. The picture from internet that I posted looks pretty similar with some parts of my roof.
Should I wait until rain season over to do it?
What't the best way to clean the surface throughtly?

Here is a link to homedepot roof coating catalog, which one work for me?
http://www.homedepot.com/s/roof%20coating?NCNI-5

 

[xiaodoupi]

Here is a picture I just took. It shows some cracks on the surface.

 

[xiaodoupi]

I'd stick with the the fibered or non fibered aluma coating. From that one picture it doesn't look terrible.

The only symptom is a little bit water stain on storage floor beneath the draining hole.
I tried to put a piece of steel wool on the hole, acting as strainer. In summer it works okay. But in fall, the debrits and leaves will clog the steel wool even quicker. So I removed it weeks ago, letting tiny debrits flushed away freely.
The building is too close to tall trees. The guy who designed it is a pure moron.

PS. What't the best way to clean the surface throughtly?

 

[xiaodoupi]

So no strainer... I'm going to guess that there is no clamping ring either. Does it drain to a down spout or to a sewer drain? A picture would really help. Aluma coating will not help you solve this leak.

The guy who designed it is not a moron. The issue really has nothing to do with being a flat or sloped roof. If it was a sloped roof would you be complaining about cleaning out the gutters? Or calling that person a moron?

What its starting to sound like is the roof has been a "lay over" and the existing drain clamping ring is buried, a picture would really help see what we are dealing with. A leak is a leak and it needs to be addressed before any coating is applied.

No such drain clamping ring. There are 2 new draining holes in the center of the roof, due to roof deformation and pond in center (roof sag). Just brake a hole on the roof and installed pipe beneath.
It will be much better if has even 5 degree slope.

 

[xiaodoupi]

So you broke a hole in the roof and put a pipe under it and then call low slope roofing a dumb idea? Of course that is going to leak, there is a lot of steps in to making a drain work properly and a whole lot of ways to make it leak. IMO I wouldn't waste a penny coating the roof until it's fixed properly.

Not me. The previous owner.
One drainage is ok, the other has minor leak if some water ponded.

 

[xiaodoupi]

if iit were mine id use elastomeric with the matting. wouldnt have to worry about it for many many years. if your going cheap, well cant help you there, i dont do cheap, but then i have to guarantee my work.

What's the difference between Elastomeric and Fibred Aluminum coatings? Which one will works better for me? Thanks