# Flat roof coating



## kayakertom (Jun 22, 2007)

*RE: Flat Roof Coating*

I've got a problem flat roof with the epdm rubber coating and after doing a lot of research, I will be applying products made by Ames Research. Just bought the products Sunday and will start applying this next weekend.

http://www.amesresearch.com/roof_coatings.htm

Intend to write up something for this forum.


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## Grumpy (Dec 12, 2003)

First off you have to ask yourself why are you doing this. In your case you stated to prolongue the life of the roof. Assuming the roof is in a condition that it's worth coating there are several things you can do to the roof to protect and prolongue the life.

The first step, no matter what, would be to fix any problems the roof may have. This may take a skilled roofer. Inspect all the seams, penetrations and wall flashings. Ensure there are no splits, that everything is tight and there is no ridging or blisters in the membrane. The coating will do nothing to fix these problems, they must be fixed first. 

Next was the existing roof ever coated before? If so what is the condition of that coating? I ask because the new coating may not stick to the old coating. A controlled adhesion pull test must be performed. This is essentially coating a small area of a few square inches and imbedding a fabric into the coating. You would then pull the fabric to inspect the back side. The fabric WILL pull free, the point is to see if the existing coating comes up with the fabric or not. If not, you're good to go. If the existing coating comes up with the fabric, you'll have to do something to remove it. 

Washing is also a must. A power washer with a detergent mixture is important to remove any existing crud and grime. However untrained use of a power washer on a roof will cause more harm than good. This is another area that either takes a lot of patience so you don't destroy the roof, or a skilled roofer.

Finally the coating is yours. If you intend to coat for UV protection, a simple aluminum coating would work. If you intend to apply a liquid applied elastomeric membrane to add another 10 years life to the roof, then the type of coating and application rates would vary on your roof type. Typically an acrylic based elastomeric is the cheapest, however if there is any standing water anywhere on the roof, this will wash the coating away since acrylic is water based. You can't go wrong with a SEBS or Urethane based elastomeric althoguh both will cost more. My current favorite is the Lucas #6000 universal SEBS. At a rate of 3 gallons per 100 square feet it'll cure approximately 24 dry mills thick. That'll definetly add life to your roof.

You can learn more about Roof Coatings at my website.


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## Grumpy (Dec 12, 2003)

Hi, you double posted. Here is a copy of my reply to your other post...

First off you have to ask yourself why are you doing this. In your case you stated to prolongue the life of the roof. Assuming the roof is in a condition that it's worth coating there are several things you can do to the roof to protect and prolongue the life.

The first step, no matter what, would be to fix any problems the roof may have. This may take a skilled roofer. Inspect all the seams, penetrations and wall flashings. Ensure there are no splits, that everything is tight and there is no ridging or blisters in the membrane. The coating will do nothing to fix these problems, they must be fixed first. 

Next was the existing roof ever coated before? If so what is the condition of that coating? I ask because the new coating may not stick to the old coating. A controlled adhesion pull test must be performed. This is essentially coating a small area of a few square inches and imbedding a fabric into the coating and allow to cure a day or two. You would then pull the fabric to inspect the back side. The fabric WILL pull free, the point is to see if the existing coating comes up with the fabric or not. If not, you're good to go. If the existing coating comes up with the fabric, you'll have to do something to remove it. 

Washing is also a must. A power washer with a detergent mixture is important to remove any existing crud and grime. However untrained use of a power washer on a roof will cause more harm than good. This is another area that either takes a lot of patience so you don't destroy the roof, or a skilled roofer.

Finally the coating is yours. If you intend to coat for UV protection, a simple aluminum coating would work. If you intend to apply a liquid applied elastomeric membrane to add another 10 years life to the roof, then the type of coating and application rates would vary on your roof type. Typically an acrylic based elastomeric is the cheapest, however if there is any standing water anywhere on the roof, this will wash the coating away since acrylic is water based. You can't go wrong with a SEBS or Urethane based elastomeric althoguh both will cost more. My current favorite is the Lucas #6000 universal SEBS. At a rate of 3 gallons per 100 square feet it'll cure approximately 24 dry mills thick. That'll definetly add life to your roof.

You can learn more about Roof Coatings at my website.


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## Grumpy (Dec 12, 2003)

teo11003 said:


> My rowhome in Philadelphia has a flat roof which has been applied with rubber (black) on the rooftop in May 2005 (according to the receipt from the contractor). This job has a 10 years warranty. I bought this home in 2006. It's been 5 years and I plan to coat the roof with something energy efficient. Is it a good time for me to coat (after 5 years) and what are the suitable coating materials for this rubber top? I heard that certain coating material only works best on certain top. I also plan to do the coating myself so any DYI advice is appreciated.
> 
> t


Hi, your other thread said that the membrane was APP. APP is not at all rubber but is a type of asphalt based modified bitumen. There is no rubber in APP and it's one of my biggest pet peeves when someone calls it rubber. EPDM is true rubber, APP and SBS are Asphalt.


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## slickgt1 (Apr 1, 2010)

Grumpy, so everything you stated above is for EPDM, or does this apply to modbit too. I coated my roof with silver paint after I applied it. I was thinking of doing another coat, but thinking elastomeric coating would be more durable. thanks in advance.


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## Grumpy (Dec 12, 2003)

Everything I stated is for modified bitumen. EPDM sometimes requires a special primer with some elastomeric manufacturers and I would never dare dream of using any aluminum silver coating which was engineered for asphalt based roofing systems, on EPDM.


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## slickgt1 (Apr 1, 2010)

Great thanks. I just checked the lucas product out. Looks interesting. I think I have a solution now for my mothers 6 year old mod-bit roof.


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## Homerepairguy (Aug 1, 2010)

Grumpy,

A friend just had his roof re-coated with an elastomeric product and told me that there are a lot of bubble blisters all over the whole roof. I didn't see it personally but from his description it sounded like the blisters were about 6 inches in diameter.

His home is a ranch style with a low pitch of about 2.5" per foot. It previously had a smooth type of roof that looked like felt covered with a coating but I don't know what kind of roof covering it was. In other words, it was easy to see the horizontal lines where the felt like material overlapped. The roof was a gray color.

The re-roofing was with a fabric and elastomeric type of coating which is white in color. Unfortunately, it was a slightly rainy week when the re-roofing was done. It would rain in the mornings and during the night but mostly didn't rain during the day.

With the limited info of not knowing what type of previous roofing he had and the exact type of elastomeric re-coating he had, can you speculate why there are a lot of bubble blisters? What would the remedy be? Just leave it or what?

Thanks,
HomeRepairGuy


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## johnk (May 1, 2007)

The blisters/bubbles are more than likely from trapped moisture


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## Grumpy (Dec 12, 2003)

John is most likely right. It is probably trapped moisture but also an oily surface could have been coated as well. Regardless the blisters are a delamination of the elastomeric from the roofing substrate. 

Then again as you said it was previously coated so maybe the new elastomeric is not delaminating at all. Perhaps the original coating is delaminating and the new elastomeric has adhered to the previous coating. This is the reason for a pull test before coating over coating. 

Another possibility is as you said it is a fabric system, what I call fully reinforced, and it was rainy. If it rained shortly after the application of the base coat before the resin or elastomeric had a chance to cure, then it is possible in some areas the fabric lost the liquid around it and is now just floating in those areas. This happened to me once where it started raining and alot of the elastomeric washed away. We cut the blisters and recoated the whole surface with another application of the base coat resin. It definetly set back our schedule and it definetly cost me some extra money, but at the end of the job we've got to do it right.



My recomendation is to cut out the loose blisters, re-reinforce with fabric saturated with a compatible elastomeric at a rate of 1.25-2.0 gallons per 100 square foot and allow to cure then allow a top coat over at least these areas but preferrably the entire surface at a rate of 1-1.5 gallons per square. A pull test should first be performed to ensure the new product is compatible with the previous product.

Depending on the design of the roof deck, one way breather vents may be a good ideas as well... assuming it's a warm deck/ insulated deck design. However being a 2/12 it's likely a cold deck/ventilated deck design therefore should already have ventilation. Does it have ventilation to vent the space between the ceiling and roof deck?


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## slickgt1 (Apr 1, 2010)

Question, what fabric is used here for this membrane.


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## Homerepairguy (Aug 1, 2010)

johnk said:


> The blisters/bubbles are more than likely from trapped moisture


If it rained the night before but not during the day when the application was actually being made, would that still trap moisture?


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## Homerepairguy (Aug 1, 2010)

Grumpy said:


> ...snip...
> My recomendation is to cut out the loose blisters, re-reinforce with fabric saturated with a compatible elastomeric at a rate of 1.25-2.0 gallons per 100 square foot and allow to cure then allow a top coat over at least these areas but preferrably the entire surface at a rate of 1-1.5 gallons per square. A pull test should first be performed to ensure the new product is compatible with the previous product.
> 
> Depending on the design of the roof deck, one way breather vents may be a good ideas as well... assuming it's a warm deck/ insulated deck design. However being a 2/12 it's likely a cold deck/ventilated deck design therefore should already have ventilation. Does it have ventilation to vent the space between the ceiling and roof deck?


Grumpy,

Thanks for your detailed reply. If the loose blisters are cut out, how much overlap would you recommend for the patch fabric over the non-cutout fabric?

It's really not a roof deck where people would walk on. Just a low pitched ranch style roof. There are no vents in the roof itself. Half of the house is open beam (living room, kitchen, family room) and half has ceiling (bedrooms, bathrooms). Venting for the attic portion above the bedrooms and bathrooms is in the 2x6 spacers between the 2x6 rafters. Typical venting method for our area.

Could you explain the exact procedure for doing a pull test? 

Sky


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## Homerepairguy (Aug 1, 2010)

slickgt1 said:


> Question, what fabric is used here for this membrane.


Sorry, I don't know. All I know is that it is an elastomeric type coating over a fabric.


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## Grumpy (Dec 12, 2003)

slickgt1 said:


> Question, what fabric is used here for this membrane.


Typically a polyester fabric is used. See http://reliableamerican.us/services/roof-coatings.htm and scroll to the bottom, the last picture is of a fully reinforced with the polyester roll being installed.


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## Grumpy (Dec 12, 2003)

Homerepairguy said:


> If it rained the night before but not during the day when the application was actually being made, would that still trap moisture?


Definetly if there was moisture trapped within the roofing system which is very common when coating multiple layer roofs. This is why an infrared roof scan should be performed to get a good indication of any areas that may be saturated. Then these areas of wet roofing should be removed. 

Alternatively if an infrared scan is out of the question for what ever reason, a series of core custs can be taken in a grid fashion about 10' on center. However the infra red scan will be much more accurate. 

Having said that, most contractors don't bother to scan or core cut.


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## Grumpy (Dec 12, 2003)

Homerepairguy said:


> Grumpy,
> 
> Thanks for your detailed reply. If the loose blisters are cut out, how much overlap would you recommend for the patch fabric over the non-cutout fabric?
> 
> ...


The roof deck, sometimes called decking is slang for the substrate. It has nothing to do in this case with a walkable surface. To aleviate confusion, in my previous reply youc an substitute the word deck for substrate. 

What you described is likely a "Warm deck" design meaning the roof is insulated since the ceiling is not insulated... at least in the areas where you see the exposed framing, as you described "open beam". 

The overlap of the fabric when cutting out the blisters should be not less than 3" on all sides, more is better. 


for a pull test you'd need to buy small quantities of the elastomeric or coating product(s) that you intend to use. Thuroughly clean a few small areas about 6"x6" each. You can use a solvent like xylene, for this. Allow the cleaner to evaporate completely then apply a liberal ammount of the coating product you intend to use to the area. Imbed a small piece of fabric, not completely, leave an inch or two uncoated and exposed. Then apply a little more of the elastomeric or coating product to ensure that a good portion of the fabric is completely saturated. Allow to cure for a day or two and pull off the fabric.

If the fabric pulls with resistance and you see no original coating on the bottom of the fabric you're good. if the fabric pulls ez or you see the original coating stuck to the fabric, you've got problems.


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## Homerepairguy (Aug 1, 2010)

Grumpy said:


> ---snip---
> The overlap of the fabric when cutting out the blisters should be not less than 3" on all sides, more is better.
> 
> for a pull test you'd need to buy small quantities of the elastomeric or coating product(s) that you intend to use. Thuroughly clean a few small areas about 6"x6" each. You can use a solvent like xylene, for this. Allow the cleaner to evaporate completely then apply a liberal ammount of the coating product you intend to use to the area. Imbed a small piece of fabric, not completely, leave an inch or two uncoated and exposed. Then apply a little more of the elastomeric or coating product to ensure that a good portion of the fabric is completely saturated. Allow to cure for a day or two and pull off the fabric.
> ...


Grumpy,

Thanks much for all of your excellent information. Regarding the pull test, if the fabric pulls with resistance but original coating is stuck to the fabric, is that good? It would seem that the coating has a really good bond with the original coating if that happens.

I'll pass all of your info to my friend and he can proceed with what he thinks is best.

Thanks!
HomeRepairGuy


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## Grumpy (Dec 12, 2003)

Original coating stuck to the fabric is very bad when performing a pull test. It means the new coating won't stick to the old.


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