# Flat Roof coating



## twildey (Dec 17, 2008)

Hi,

I have a small (7'x20') flat porch roof that needs some attention. I looks like it is a tin roof, but the previous owner coated it with something, maybe that silver aluminum coating, and it is beginning to crack in many spots and is just really wearing away. Can I just coat over the whole thing with Henry Fibered Asphalt roof coating now and then come back in the spring and coat it with an elastomeric coating once the weather warms up? Thanks!


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## Slyfox (Jun 13, 2008)

It's hard to give advice with pictures to look at,
it's impossible to do with out them.

Before using any coating,
you should first do a thorough inspection of the entire area checking for bad/soft spots in the decking,
check to make sure water is flowing properly into and through the gutters, and check where the flat ties into the sloped roof 'if any' and walls, etc.
in other words try and pin point the actual leak before you cover everything.

The surface will need to be clean and dry before you start as well,
and will need to remain dry for several hours afterword's,
thus do not install the coating in the AM if there's a chance of rain/snow that same day in the PM.


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## twildey (Dec 17, 2008)

thanks for the reply. I don't think there are any leaks and the decking seems to be solid in all places. Water is running to gutters as it should in all areas. I am just figuring that I should coat it before it gets too cold out and to avoid any potential leaks. Just wanted to get some opinions of the roof coating material.


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## BornaRoofer (Sep 19, 2008)

Coating on a metal roof only prevents rust and looks pretty. It doesn't stop leaks. If its metal and isn't rusty and doesn't leak id leave it alone.


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## AaronB (Jan 29, 2005)

BornaRoofer said:


> Coating on a metal roof only prevents rust and looks pretty. It doesn't stop leaks..


Severely ignorant comment.


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## BornaRoofer (Sep 19, 2008)

I beg to differ. If I paid for a nice new metal roof and had to put a coating on it to stop the leaks? Please. Do you paint over holes in drywall to?
The metal is what is supposed to keep out the water not the paint. The paint and coatings typically applied are to prevent rust not water proof.
If your talking about the thick mil spray coatings that's a different story but still your apparently covering a metal roof with holes and leaks.
So I stick to my severely ignorant comment.


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## poppameth (Oct 2, 2008)

Some coatings, especially elastomerics, are designed in part to seal leaks. I'm talking pinholes, nothing major. But yes such coatings do serve this purpose. 

As for the original question, if you want elastomeric on it, don't coat it with asphalt now. Asphalt is one of the hardest products to coat over on a roof. You can do it. Acrylic DTMs work and Elastomerics work better than anything else over it. It's still an iffy proposition though. Any asphalt coating you put on needs to age a fair while to weather the solvents out of it before recoating with an acrylic product. No paint company is going to stand behind their product if you use it this way.

I'd wait until spring to tackle it. Once the weather is good, scrape down and if possible power wash as much of the old coating off as you can get (since it's already disappearing.) If you have any major rust problems, I'd hit it with a coat of Ospho or similar product. This is an acid wash that will chemically neutralize the rust. Then I'd prime it with a red oxide DTM primer to avoid future rust issues. Patch any spots you suspect are leaking or you expect to leak with a good quality elastomeric patching compound and then put a couple coats of a good elastomeric roof coating on there. That's the full scale treatment I'd recommend. It may seem excessive, but if you do it right to begin with you won't have to touch that roof again for a very long time.

For this type of stuff we usually use product from Richards Paint company. www.richardspaint.com
They have some very good elastomerics for less than many of the other big brands.
Recommended:
290 Roof Shield Thermal Elastomeric Ceramic Roof Coating
http://richardspaint.com/datasheets/290%20pds.pdf

P830 Seal-Flex Smooth Brush Grade Elastomeric Patch
http://richardspaint.com/datasheets/P-830 pds.pdf

Ospho
http://www.ospho.com/


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## AaronB (Jan 29, 2005)

BornaRoofer said:


> I beg to differ. If I paid for a nice new metal roof and had to put a coating on it to stop the leaks? Please. Do you paint over holes in drywall to?
> The metal is what is supposed to keep out the water not the paint. The paint and coatings typically applied are to prevent rust not water proof.
> If your talking about the thick mil spray coatings that's a different story but still your apparently covering a metal roof with holes and leaks.
> So I stick to my severely ignorant comment.


Yes, I am talking about thick film build instant set polyurea membranes. They are used to completely encapsulate and seal metal roofs. Quite successfully, I might add.

We go with a 48 mil average. Some want more life so we go thicker. One pass. No wash offs even when it rains a minute after we stop spraying.


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