Roof coating

[Guest]

What is the real difference between the silver/aluminum coating and the white elastnomeric type? Mine has been in need of coating for some time but today I replaced the sewer vent and realized it was much worse than I had thought. There is very little coating left of what once was. Which will provide the better coating and fill the cracks, gaps, etc. caused by time and weathering? How do you determine what will be needed and how much?

[Greg]

Amy, The Coolcoat white has a better rating than the basic silver coating. It requires a little more prep work, but it is supposed to be a better coating. I plan on using it on ours this spring. Perhaps JD will add to this, he is our roof expert. Greg

[Archie]

If I remember correctly we had a post awhile back about someone who tried to coat their roof with the white coating over the silver. Needless to say it didn't stick and peeled up. Be sure to check whether they will adhere together if you decide to go with a different coating over the old stuff.

[JD]

Hi Amy,

The main silver product is Alum-A-Seal. My personal opinon is that it is "old hat" product. It was the competitor to the off-white Plas-T-Cote many years ago. Even Plas-T-Cote has brought out an elastomeric coating product, keeping up with the changes in the coatings market.

I feel that years ago manufacturers were trying to come up with a bullet proof product that would last 20 years or more. Even under the best environments that didn't happen. What did happen was a products that became so brittle with age that it would just break up or crack badly. Then what actually managed to stay stuck to the roof was REALLY stuck and very hard to remove. This made resealing of the roof properly (removing all old sealants) very hard to do.

For many years now, the white elastomeric products have been the most popular. It is able to stretch much more than the silver and bondo style products. I feel that when it is properly applied, it will outlast the older products by quite a bit. The bonus is that it is not nearly as hard to get off when it is time to reseal the roof again.

The above opinion is for common mobile home roof products that cost $8 to $15 a gallon in 5 gallon buckets. There is Kool Seal, Anvil Elastomeric, Snow Roof, Henry's Elastomeric, and many more white elastomeric products. This is by far the most used products today.

There are far more premium products available though. The product I use, Rapid Roof III cost $225.00 for a 5 gallon bucket (retail). It comes out of the bucket like Elmer's glue instead of like white paint. I find it lasts much longer than the cheaper products under any situation. Another excellent premium product is Liquid Roof, a liquid EPDM rubber product. Doing a google on these products will bring them to the top of your results page.

Thanks for the kudos, Greg.

JD

[JD]

While many people will add coating to the top of old coatings, my company will not. We always remove the old coating. We use a large buffer with a braided wire brush to grind off old coatings. This does require a bit of experience or being very careful, to not over-grind the metal roof. Working an aluminum rolled roof requires a lot of experience because it is easy to damage thin aluminum.

If the old coating is peeling or cracking, a new coating will not stop the old coating from deteriorating. It may slow it down a bit. But it will continue to crack and peel. The new coating will not last nearly as long if it is applied over the old coating. You will also end up with a serious build up of coating material which will just exasperate the problems. JMO

JD

[JD]

What is the real difference between the silver/aluminum coating and the white elastnomeric type? Mine has been in need of coating for some time but today I replaced the sewer vent and realized it was much worse than I had thought. There is very little coating left of what once was. Which will provide the better coating and fill the cracks, gaps, etc. caused by time and weathering? How do you determine what will be needed and how much?

Sorry, I didn't address all your questions. I do not do or recommend total mops of the entire roof. And as mentioned above, I do not fill cracks I recommend removing old sealants.

Doing just a 5" to 6" area from the drip rail up along the edge of the roof, all vents and the ridge cap on a doublewide, we will use about 4 gallons of product. You want to use the fabric seam tape on the ridge cap. I don't use it on vents and edges.

This is just my opinion. Many people do total mops on their roofs. Many service professionals do also. There is a full explanation on my web page, http://www.centralvalleyrepair.com under roof repairs. I know... a shameless plug, but it is pertinent. If you do a total mop, you can figure about 100sf per gallon, or three 5 gallon buckets on a 24x60.

JD

[Guest]

Thanks for the input. When I replaced the sewer vent (have a pretty bad leak in the top of one of my closets that is next to where it runs - was hoping it was the problem) I took my putty knife up to help pry up the old one after I unscrewed it. I didn't need it. The mushroom vent came off in one tug after I removed the screws then it just crumbled. It had become hard & brittle and the back side was missing. Only a glob of some type gray sealant kept it on and was to seal the vent from leakage. Anyway, the present coating on the roof just flaked off. I was surprised at just how flimsy that the aluminum roof is. I was afraid to lean into it to place pressure while driving the screws into the new vent. The coating that isn't obviously flaking is missing. I guess it gave over time. The only thing that is constant up there is the mossy, dirt covering from being underneath thick tree coverage. How is the best way to cover it since the roof is so flimsy? There is no way one could get on top of it without doing major damage and causing leaks. Just the weight of my hand with the slightest pressure caused it to buckle and sink a few inches. The vent for the heating unit is in the middle of the roof and it is a must to go around. Any ideas? The way that the roof is now it would seem that a pressure washer would peel what was left off with no problem. Any thoughts?

[JD]

I really don't understand how the mobile home/RV industry came up with the idea that roof vents can be made of plastic. Maybe there is a space age plastic that could work, but that is not what they make these plumbing vents with. Always use metal vent caps. I use the bell type galvanized caps. When installing these vents, apply a large continuous bead under the flange of the of the vent to seal the vent to the roof and to act as an insulator between the metal roof and the metal vent cap flange. This is especially important when using galvanized vents on aluminum roofs.

If your roof metal is aluminum, it is a re-roof, basically a second roof installed over the original roof. This is a common and proper roof solution. Aluminum roofs come in two flavors, a rolled roof or a panel roof. Rolled roofs will be ~3'-4' sections of aluminum seamed together to make the length of roof you need. The seams will be like the old tin can seams and will be flat on the roof. A panel roof will have raised seams. The edges of the panels will be bent up to form an "L" of a "J" to allow the panels to be clipped together in some way.

If the roof has a lot of movement as you are describing, you do not have a very good installation. The roof should have a minimal amount of support throughout. Some give or movement is normal. Generally, walking only on top of the trusses will offer the roof enough support to not crack or tear sealants that are in good condition or freshly installed.

A rolled roof should be installed with a frame (usually 2x4s layed flat) around the perimeter of the roof, around vents and along the edges of the ridge cap. The voids between the frame will be filled with an appropriate amount of foam insulation board. If the original roof is very mushy and loose feeling, the reroof will be very mushy also. I was on a roof last week that was excellent. I couldn't see what they did, but it seems thay screwed 3/8 plywood to the trusses and installed the roof over that. It was very stable. I have seen bad installations where they used regular fiberglass batt insulation. These roofs offer no support whatsoever and are very difficult to deal with.

If walking on just the trusses does not offer you enough support to walk on top of your roof, you might try laying out a couple of 12' (or longer if needed) 2x4s next to the area you need to work, and use two 4' sections of plywood to get around. Just keep alternating the pieces of plywood to move further up or down the roof. If you span the vent on each side with the 2x4s, you can work the bottom half of the vent, then stpe over the vent to work the top half. Just an idea. Without seeing your roof, I don't know that this will work for you. Hope this helps.

JD