Results of 6-year rubber roof coating experiment


By Russ and Tiña De Maris

To hear RV manufacturers talk, EPDM rubber roofs are the greatest thing since sliced bread. Problem is, even sliced bread eventually gets stale. After a few years in the elements, rubber roofs take the hit of weathering and exposure to UV radiation. From personal experience we can say that a non-maintained rubber roof is a tragedy just waiting to happen. How can you keep your rubber roof happy? It may mean a new coat of rubber to keep things sound and leak free.

EPDM rubber is a persnickety product. The use of petroleum-containing chemicals or citrus-based cleaners on a rubber roof is to ask for swelling and deterioration. Use the “wrong” kind of coating and you’ll reap a similar result. There are few coatings that are truly safe (or even effective) for use on an RV’s rubber roof. Among them are Dicor’s Roof Coating System and Heng’s Rubber Roof Coating. A quick glance at the roof coating section at the hardware store will show there are other products that “look” like they may do the job. Read the fine print carefully – you’ll find most specifically tell you NOT to use their product on a rubber roof.

Even if the product you look at isn’t specifically ruled out for use on a rubber roof, take note of these factors: An RV roof coating needs to be elastomeric, meaning having the elastic properties associated with natural rubber. Rubber roofs expand and contract with heating and cooling. Any coating you add to the roof must likewise do the same, otherwise it will simply crack and break off.

Additionally, since many RV roofs have little pitch and may even have areas where water collects (called “ponding”), whatever coating used must resist ponding. A popular product called “Snow Roof” can supposedly be used on EPDM roofs, provided their brand of primer is first applied. Elsewhere on the label, you’ll find a warning that the stuff can’t be used on a flat roof. Plenty of older RVs have a dent in the roof near the air conditioning unit where water effectively ponds and won’t run off.

Back in 2011, we were faced with the issue of “coating” our elderly travel trailer’s roof. After doing a lot of research, we decided to try the Heng’s product. Here’s what we wrote about the subject, shortly after we put the stuff on the roof. We’ll tell you how things have shaped up in the six years since we treated the roof – down farther in this article.

Here’s a step-by-step on how we used Heng’s Rubber Roof Coat to recoat an aging travel trailer roof:

1. Prepare the surface. Use a scrub brush and a bucket of soapy water. CAREFUL! Heng’s tells us it’s extremely important to use the right kind of soap. They recommend a solution of Tide powdered laundry detergent mixed with water. DON’T use Dawn dishwashing detergent – if you do, the Heng’s may later peel off. Scrub the roof fore-and-aft, rinsing with plenty of water. Allow the roof to dry completely.

2. If there are tears or punctures, we recommend fixing the damage with EternaBond roof repair tape.

3. Apply a base coat of Heng’s following the instructions on the can. While Heng’s says you can thin its product, we don’t recommend it. The thinner it is, the less likely you’ll have the best protection. We use a short-nap paint roller, applying the coating at a rate of about a gallon per 200 square feet of roof surface. You’ll find a paintbrush invaluable for working around a/c units and around edges. A rag can be used to wipe up drips before they dry.

4. Allow a minimum of four hours’ dry time before sticking on a second coat. The roof we did most recently was on a 14-year-old trailer and while the roof had no damage, it was decidedly getting thin. We opted to put on a second coat to enhance our feelings of security. Don’t apply a single thick coat; you’re much better off with two thin ones.

As to cost, we were out about $110 for materials and supplies, having paid a little less than $50 a gallon for the roof coating. In the end, we had a half-gallon of the Heng’s left over which we kept for doping seams in the future.

So here we are in 2017 – six years after we coated our roof with Heng’s. How did it go?

From our perspective, Heng’s has really stood the test of time. One-half of our team braved the extension ladder for a roof inspection and maintenance tour. We found a couple of seams that needed to be coated – and that wasn’t the Heng’s that was at issue, it was a transition between the rig’s front cap and the rubber roof. Another area requiring attention was the sealant around the roof vents. No surprises here – this is a regular maintenance issue for all RVers.

As far as the roof itself – the Heng’s was still thoroughly “stuck on” the original EPDM rubber roof like a barnacle to a ship’s hull. It was decidedly tight, free of cracking, and oddly enough, still fairly white (and hence heat reflective) after six years baking in mostly Arizona sunlight, and with no scrubbing or washing in the interim. We compared this with an OEM EPDM rubber roof on our big park trailer. In the six years since we put the Heng’s on the traveling rig – the park trailer’s original roof had begun a definite change to a brownish color. Looks like it’s time we treat that roof!

No complaints! We’ll use Heng’s the next time we need to treat a roof. And when we buy our next batch, it doesn’t matter if we buy the can with the blue label, or the one with an orange label. If it says, “Heng’s Rubber Roof” it’s the same stuff, orange or blue. The big park trailer, yep, probably will see a dress up with Heng’s this fall. The travel trailer? It may have a new owner long before it needs another roof coating!