# Coating on built-up tar and gravel roof



## Jaxx (Dec 6, 2011)

Hello,

I have a 4-ply built-up tar and gravel roof (see picture for reference) which I would like to "recondition" using roof coating.
Ideally, I would like to eliminate the lose fine gravel that I have on the roof as it is a low pitched roof (2/12) and the gravel keeps getting washed off or blown down to the bottom end, exposing bald spots.

I'm looking for a coating that can be applied on the cleaned tar surface. On top I would like to apply a reflective roof coating/paint to protect the underlying coating.

Should I use a fibered coating?
Should the coating be rubberized?
Should the coating be solvent or water based?
Should the top layer reflective coating be rubberized?

There are so many products out there and it is hard to pinpoint the best set of products.

Thanks!


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## Windows on Wash (Aug 30, 2011)

What kind of shape is the BUR in?

Pics?

We have used Gaco with success and it looks quite good when done. Other popular systems are Hydrostop.


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## hotrod351 (Jun 15, 2012)

you could be asking for a lot of trouble. best is to tear it off, then you could elastomeric the whole thing, using the matting also. ive seen many attempts to do what you want to do and they have all been a nightmare.


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## Jaxx (Dec 6, 2011)

Windows on Wash said:


> What kind of shape is the BUR in?
> 
> Pics?
> 
> We have used Gaco with success and it looks quite good when done. Other popular systems are Hydrostop.


According to an inspector it has at least 10 yrs left in life. Please see pictures.



hotrod351 said:


> you could be asking for a lot of trouble. best is to tear it off, then you could elastomeric the whole thing, using the matting also. ive seen many attempts to do what you want to do and they have all been a nightmare.


what kind of issues could arise? Are there products with warranty out there?


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## 1985gt (Jan 8, 2011)

The gravel surface needs to be removed completely before any coating is applied. Removing the gravel can and most likely will damage the roofing plys.


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## Jaxx (Dec 6, 2011)

1985gt said:


> The gravel surface needs to be removed completely before any coating is applied. Removing the gravel can and most likely will damage the roofing plys.


It is very fine gravel and when I remove the lose gravel most small gravel is completely embedded in the tar.

I've been looking at fibered asphalt emulsions. They seem to work well but I was hoping to get some feedback here, about possible issues that could arise.


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## 1985gt (Jan 8, 2011)

Jaxx said:


> It is very fine gravel and when I remove the lose gravel most small gravel is completely embedded in the tar.
> 
> I've been looking at fibered asphalt emulsions. They seem to work well but I was hoping to get some feedback here, about possible issues that could arise.



All the gravel needs to be removed to apply a coating including the embedded gravel. 

If you are wanting a reflective coating why are you looking at fibered asphalt emulsion?


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## Jaxx (Dec 6, 2011)

1985gt said:


> If you are wanting a reflective coating why are you looking at fibered asphalt emulsion?


I wanted to reseal the surface before applying the reflective coating.
I was looking at Henry #307 which is an asphalt emulsion that can be used as a base coat for reflective coatings.

See here:
Henry #307 Datasheet


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## 1985gt (Jan 8, 2011)

If it is not currently leaking there is no need to reseal it. 

There is lots of different ways to do what you are trying to achieve. 

The tried and true method is using an alumacoating. With alumacoating the more aluminum content there is the longer they last, the more reflective they are. This is a case of how much the product cost the better it is. The aluminum they put in them is expensive. 

Elastomerics can and do work, they need to be specifically formulated for asphalt roofs, otherwise the asphalt will leach through the coating decreasing the reflective properties. Most of them are solvent based. We use GAF Top coat. It's a good product, there are many others out there. I've never used Gaco but I've heard they are the cats meow, they are expensive but from what I understand they are worth the money. I would make sure that they are compatible with asphalt roofs. 

A few things to remember, if you need to do repairs or if you chose to emulsion the whole thing these need to set after applied for 30+ days. If they don't the off gassing will break the bond of the coating and it will not last long. 

Prep work is of the most importance. The roof surface needs to be clean, dry and free of debris (dust, ect). All the rock needs to come off!

No coating should be applied if it is going to rain with in 48-72 hours. I know some say 24 but I've seen coatings get washed down in to a gutter. It's not fun to clean up let alone you will literally watch money being washed down the drain.

Most coatings will need to be reapplied. Depending on the coating that could be anywhere from 2 years to every 10 years.


I've never understood how people can say how long a life the roof has left. There is so many variables that go in to how long a roof lasts that it would be hard to know. The only time I will give a somewhat tight range of how long to expect a roof to last would be a roof that we installed. If it's someone else work the range I give would be much wider, with a side note of anything can happen between now and then.


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## 1985gt (Jan 8, 2011)

I also can not stress enough. All the gravel needs to be removed, even the embedded gravel.


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## ron45 (Feb 25, 2014)

5 Gal. $225.00 each.

http://www.homedepot.com/p/Gardner-5-Gal-Eterna-Kote-S-100-Silicone-Roof-Coating-5570-1-30/205314046


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## Jaxx (Dec 6, 2011)

1985gt said:


> I also can not stress enough. All the gravel needs to be removed, even the embedded gravel.


ok, got it! And I see the risk there.
So what other option do I have to add a little life to my current roof + fix a few smaller leaks?

Is this an option?



ron45 said:


> 5 Gal. $225.00 each.
> 
> http://www.homedepot.com/p/Gardner-5-Gal-Eterna-Kote-S-100-Silicone-Roof-Coating-5570-1-30/205314046


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## 1985gt (Jan 8, 2011)

Coatings generally do not fix leaks. They may for awhile but they are in no way a solution to the problem. 

Generally speaking on a BUR (asphalt and gravel) roof the leaks come from around the penetrations. If they are coming from the field of the roof then you are on borrowed time. 

If the roof is splitting in the field you can resaturate the felts with an emulsion like you were talking about before. then you would need to coat it also. I would still patch any breaks as needed.

You could also remove the rock and install a coverboard and a single ply membrane. 

If it was me, I would patch the leaking areas. Use the mastic to fill any bare spots in the rocks and save up to put a roof on. Even if the roof is in pretty bad shape you can limp it though a few years. It sounds like yours is in good shape just needs a little maintenance.


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## Paultergeist (Oct 13, 2014)

Jaxx said:


> I wanted to reseal the surface before applying the reflective coating.
> I was looking at Henry #307 which is an asphalt emulsion that can be used as a base coat for reflective coatings.


I did exactly as you propose: (2) coats of Henry's 307 followed by (2) more coats of the white elastomeric top coat. Did it help extend the life of my roof a little? Maybe....probably......but it was not a long-term solution. The stuff peels / degrades away over time. I have since come to the opinion that paint-on roof coatings are pretty limited in what they can accomplish.

If you are looking for a long-term solution, listen to the experts: get rid of the gravel and re-do it right.


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## Jaxx (Dec 6, 2011)

Paultergeist said:


> I did exactly as you propose: (2) coats of Henry's 307 followed by (2) more coats of the white elastomeric top coat. Did it help extend the life of my roof a little? Maybe....probably......but it was not a long-term solution. The stuff peels / degrades away over time. I have since come to the opinion that paint-on roof coatings are pretty limited in what they can accomplish.
> 
> If you are looking for a long-term solution, listen to the experts: get rid of the gravel and re-do it right.


How long did you have that stuff on the roof before it started to peel? Do you have a lot of sunshine in your area?



1985gt said:


> Coatings generally do not fix leaks. They may for awhile but they are in no way a solution to the problem.
> 
> Generally speaking on a BUR (asphalt and gravel) roof the leaks come from around the penetrations. If they are coming from the field of the roof then you are on borrowed time.
> 
> ...


Paultergeist and 1985gt, thanks to both of you for your detailed feedback!

There are a few smaller leaks at roof penetrations and they should be fixable locally. 2 penetrations were eliminated completely and now need to be patched.

To give you a little more insight, the reason why I want to refinish the roof are the following:

-It is a low slope gable roof so the gravel tends to be washed and blown off, exposing the tar -> Bad
-At the bottom end of the roof, the roof slopes back up to create a water collection and drainage path. Water tends to puddle there as the horizontal slope towards the drains is not continuous. I wanted to eliminate this "counter-slope" and instead continue the normal roof into gutters. Doing just this while leaving the gravel will result in all the gravel getting washed into the gutters.

For the two reasons listed above I wanted to keep the BUR in place but add a coating and reflective paint.

Thanks again for your support!


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## Paultergeist (Oct 13, 2014)

Jaxx said:


> How long did you have that stuff on the roof before it started to peel? Do you have a lot of sunshine in your area?
> 
> Paultergeist and 1985gt, thanks to both of you for your detailed feedback!


You are welcome. I think it may be worth to mention: 1985gt is a pro with much experience; as for myself, I am only a DIY-er (and learning).

I have had the coating (described earlier) on my roof for probably 3-4 years now. In a few spots, there is clear peeling away of the coating; in other places, the coating simply appears to have gradually weathered / worn-away such that it looks like the granulated cap-sheet is again showing. It is a flat roof which receives lots of direct sunlight (So Cal).



Jaxx said:


> -At the bottom end of the roof, the roof slopes back up to create a water collection and drainage path. Water tends to puddle there as the horizontal slope towards the drains is not continuous. I wanted to eliminate this "counter-slope" and instead continue the normal roof into gutters.


It is not clear to me from your description how the "counter-slope" will be remediated -- the coatings alone will not do that.

I CAN tell you with some experience that the *ponding* of water on a roof tends to be very hard on many roofing materials. My roof has some areas of shallow concavity which allow for water to puddle -- these are the areas where the cap-sheet material degraded most rapidly. These are ALSO the areas where the paint-on coating deteriorated most rapidly. Again, I am only a beginner at these matters, but you may derive some added insights from the photos on this thread (started by me):

http://www.diychatroom.com/f9/epdm-vs-pvc-vs-tpo-flat-roof-293018/index2/

I do not think you'll hurt anything by adding the paint-on coatings, but doing so will take time and money, resulting in the achievement of -- in my opinion -- a relatively temporary (possible) improvement in your roof performance, but not a long-term solution.

Just my 2 cents.


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## ron45 (Feb 25, 2014)

You said, " According to an inspector it has at least 10 yrs left in life."

This was someone on site.
According to the pictures I see no cause for alarm. 

Coatings are designed to protect what is underneath. Coatings will prolong the life of the roof. It's much cheaper to add coatings then to replace a roof. 

I would get a roofing company to look at it or.......
Sweep the roof gathering the extra stone, install it properly in the areas appearing bare/r and then put two coats of what I posted earlier...........


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## Jaxx (Dec 6, 2011)

ron45 said:


> I would get a roofing company to look at it or.......
> Sweep the roof gathering the extra stone, install it properly in the areas appearing bare/r and then put two coats of what I posted earlier...........


ok, I will do that (both).



Paultergeist said:


> It is not clear to me from your description how the "counter-slope" will be remediated -- the coatings alone will not do that.
> 
> I CAN tell you with some experience that the *ponding* of water on a roof tends to be very hard on many roofing materials. My roof has some areas of shallow concavity which allow for water to puddle -- these are the areas where the cap-sheet material degraded most rapidly. These are ALSO the areas where the paint-on coating deteriorated most rapidly. Again, I am only a beginner at these matters, but you may derive some added insights from the photos on this thread (started by me):
> 
> ...


1st of all sorry for the lack of usage of the proper terms when I described the roof and the "counter-slope". The counter-slope was created by boards that were attached at the bottom end of the roof onto which the BUR felt layers were attached. You can barely see this counter-slop on the pictures I posted earlier in this thread:

















By eliminating the boards and flattening / straightening out the bottom end of the felt it would turn into a continuous slope right into the gutters. This would eliminate the puddling completely.


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## troyks (Feb 17, 2015)

Roof coatings can extend the life, but if your roof is in otherwise decent shape and has several years left I'd save that money towards a new roof instead. High quality coatings can get pretty expensive, cheaper than a re-roof but will still cost thousands. The stuff you get at the big box stores for $75 a 5 gallon pail will fail sooner than later, and you need to keep asphaltic roofs covered with something (whether it be a coating or gravel) or the UV rays will degrade it, so if you knock the gravel off to coat it you need to keep it coated. 

I have a 2/12 pitch roof as well and re-roofed earlier this spring, BUR roofs are a thing of the past around here for residential roofing so I went with EPDM. If you're in CA then a reflective roof will save you on AC costs in the summer, I'd skip the coating and save the money until the roof is at it's end of life and look into doing a new roof in single ply (TPO, PVC, IB) installed over ISO insulation, with any low spots that have ponding water worked out.


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