EPDM roof coating: Project notes
It is funny to recollect, but when I bought a 19 year old Class C I did not pay much attention to the roof. Right on time at 20 years, the roof began to leak in spots. Well, it had leaked for the previous owner too. But the white ablative coating had now weathered away in spots leaving black EPDM. The roof was done.
Or was it? The membrane itself was mostly intact. Twenty years of UV and weather had simply removed the white coating, exactly as designed. I decided to recoat with white liquid EPDM rather than do a complete tear-off and reroof with EPDM membrane. It seemed like liquid EPDM could keep the roof going for another 10 years at least.
I couldn’t see spending a couple thousand dollars (?) on an RV that was only worth a few times that. Better to keep the money in investments and buy another used RV in 10 years. Maybe even an RV with a fiberglass roof.
These project notes document what I did and learned. This is a large and complex project, but it can be fun and satisfying if you plan and prepare well.
Recoating is an expensive and complex project that most people have not done before. I watched a lot of videos, but they mostly show what is easy not what is difficult.
Watching smiling people applying EPDM to the center of the roof under cloudless skies is really not very helpful. Because the real challenges are the edges of the roof and the timing of applications to avoid weather.
Key point: You are going to be on a schedule driven by chemical reactions. Polymerization waits for no one. And unfortunately the drying times vary widely and unpredictably. You have to choose a period of stable weather and be prepared for the possibility of rain.
If the primer is curing and it starts to rain... you have a problem. If your 3/8-inch drill burns up while your coating is half mixed... you have a problem. These detailed notes on what worked and what did not work should help you avoid these problems.
== Dicor seam sealing ==
Items needed:
. Old clothes
. Rags
. Box of disposable gloves
. Scrapers
. Dicor self-leveling sealant
. Caulking gun
. Stiff plastic for shaping Dicor
About half of the project consisted of sealing seams along the roof edges. My RV had multiple generations of Dicor along the front, back, and side seams. I decided to scrape out all the old Dicor and replace it.
This work was mostly done with a hook-shaped Hyde tool used for scoring plexiglass. It was good for reaching under the metal side moulding and ripping out the old Dicor.
I used rubbing alcohol to clean the seam areas, then applied fresh Dicor being sure to push it back under the metal moulding. Then I added a second layer, smoothing this with an old credit card.
In the process I discovered two tiny cuts in the EPDM membrane. These explained the leaks I had been seeing but I had not spotted them before. I also slipped with the scraper and caused one small cut. All of these cuts were patched with Dicor Diseal patch.
(But just buy a roll of Eternabond tape instead of the little Diseal Band-Aid patch that costs $20. $56 will get you 2400 square inches of tape vs. 36 square inches for the patch. Basically you are looking at 2 cents per square inch vs. 55 cents per square inch for the patch.)
During this phase I also replaced the two vent caps. I decided to leave the AC unit gasket alone, per http://www.irv2.com/forums/f54/need-new-a-c-gasket-257462.html. Some will want to replace this gasket.
This phase took about 6 hours and 3 tubes of self-leveling Dicor sealant.
Or was it? The membrane itself was mostly intact. Twenty years of UV and weather had simply removed the white coating, exactly as designed. I decided to recoat with white liquid EPDM rather than do a complete tear-off and reroof with EPDM membrane. It seemed like liquid EPDM could keep the roof going for another 10 years at least.
I couldn’t see spending a couple thousand dollars (?) on an RV that was only worth a few times that. Better to keep the money in investments and buy another used RV in 10 years. Maybe even an RV with a fiberglass roof.
These project notes document what I did and learned. This is a large and complex project, but it can be fun and satisfying if you plan and prepare well.
Recoating is an expensive and complex project that most people have not done before. I watched a lot of videos, but they mostly show what is easy not what is difficult.
Watching smiling people applying EPDM to the center of the roof under cloudless skies is really not very helpful. Because the real challenges are the edges of the roof and the timing of applications to avoid weather.
Key point: You are going to be on a schedule driven by chemical reactions. Polymerization waits for no one. And unfortunately the drying times vary widely and unpredictably. You have to choose a period of stable weather and be prepared for the possibility of rain.
If the primer is curing and it starts to rain... you have a problem. If your 3/8-inch drill burns up while your coating is half mixed... you have a problem. These detailed notes on what worked and what did not work should help you avoid these problems.
== Dicor seam sealing ==
Items needed:
. Old clothes
. Rags
. Box of disposable gloves
. Scrapers
. Dicor self-leveling sealant
. Caulking gun
. Stiff plastic for shaping Dicor
About half of the project consisted of sealing seams along the roof edges. My RV had multiple generations of Dicor along the front, back, and side seams. I decided to scrape out all the old Dicor and replace it.
This work was mostly done with a hook-shaped Hyde tool used for scoring plexiglass. It was good for reaching under the metal side moulding and ripping out the old Dicor.
I used rubbing alcohol to clean the seam areas, then applied fresh Dicor being sure to push it back under the metal moulding. Then I added a second layer, smoothing this with an old credit card.
In the process I discovered two tiny cuts in the EPDM membrane. These explained the leaks I had been seeing but I had not spotted them before. I also slipped with the scraper and caused one small cut. All of these cuts were patched with Dicor Diseal patch.
(But just buy a roll of Eternabond tape instead of the little Diseal Band-Aid patch that costs $20. $56 will get you 2400 square inches of tape vs. 36 square inches for the patch. Basically you are looking at 2 cents per square inch vs. 55 cents per square inch for the patch.)
During this phase I also replaced the two vent caps. I decided to leave the AC unit gasket alone, per http://www.irv2.com/forums/f54/need-new-a-c-gasket-257462.html. Some will want to replace this gasket.
This phase took about 6 hours and 3 tubes of self-leveling Dicor sealant.
