Which Paint For Roof

[musigenesis]

Originally Posted by Meathead

Yes, I think Henry’s works best if you don’t think of it as a waterproofer.

Here's what Henry says about their (his?) Tropi-Cool roof coating:

• 100% waterproof

It seems strange that their #1 feature is that, but everybody says you need to waterproof your roof first for it to work. It reminds me of the movie Go where the heroine sells kids fake X and tells them they need to smoke a lot of pot for it to work.

• Save energy by reflecting heat

This is kind of vague from a Physics standpoint. Your bus can absorb heat from the surrounding air via convection and conduction, or from sunlight via radiation. Paint can reflect radiation and in that sense can be said to "reflect heat". Tropi-Cool can't reflect heat absorbed via conduction or convection, so it can't "reflect heat" in any other sense but I guess the claim is technically true - it's just true about every other kind of paint as well.

[Meathead]

My point exactly. While is is waterproof, it’s best not to think of it as a cure all for your roof. It can be part of your roof system. It will not fix a rusty pin hole, seam gap, loose rivet, etc.

[EastCoastCB]

Its kind of a naive to think a paint product will be any kind of permanent fix for leaky roofs.
I just don't like thin rubberized coatings on stuff in general. FL is hell on that kinda stuff.

[AndiW]

Are any of these roof coatings not rubberized? When I think rubberized I thing decay and dirt getting into cracks. I'd prefer something smooth and shiny.

[Free Bird]

Originally Posted by Maggie01

Hey, I live in Texas where we stay in triple digits during summer. All of our buses down here come with white roofs. I don't think I've ever seen one that wasn't white.

How many coats and would the ceramic beads help? Also if the beads were added how much texture would they add? Even though the inside would be covered with insulation, then some kind of wood, would painting the metal skin of the walls and ceiling with white paint and ceramic beads before insulating help keep the bus any cooler?

To get maximum cooling from your paint job you need to paint your whole exterior white. The outer skin transfers heat so if you have hot spots on it, (say like from a dark colour below the windows) then that is going to negate some of the good work your roof is doing.

[kidharris]

Originally Posted by PNW_Steve

A member here did a pretty thorough test of various roof coatings. He cut uniform pieces of sheet metal and coated each one with a different coating. Then he set them on a rack out in the sun and took temperature readings from the under side of the metal.

In the end the ceramic beads mixed in white enamel paint performed the best by a tiny margin. A very close second was sawdust mixed with white enamel. Running a very close third was plain white enamel.

The elastomeric coatings did not perform as well as plain white paint.

The top three were close enough that going with just paint was an easy decision for me.

My Bluebird came from Western Oregon and had a yellow roof. The white shows the moss too much

Sorry, wrong place..............deleted post

[kidharris]

[QUOTE=EastCoastCB;390260]my strategy is- seal the roof properly and paint it with whatever you paint the bus with. NOT house paint.[/QUOTE

I agree, sort of.... you might want to paint it first to get good adhesion of the paint then seal the leaks with a elastomeric or sealant (the paint may not stick to the elastomeric /sealant or vice versa)

My 2cents...

Elastomerics are a roofing product, not a paint. Their big claim to fame is that they seal and stretch, allowing the seal to be maintained on roofs that move/expand/shrink a lot. They are white because it only makes sense to keep the roof temp down in the summer and its good for sales. Compared to the costs of re-roofing, they are cheap, although most applications are done incorrectly and therfore the warranty is void.

When they first came out they were sold mostly to repair metal roofs. Now they are used on most every type of roof. The early formulations were merely extra thick latex or acrylic latex paint, if I remember right. The roofing contractors salesmen that peddled them would paint pieces of glass with several coats, then peel off the paint and use it for samples to put in the customers hands so they could stretch and pull on it. Now there are many formulations including silicon. They are meant to be reapplied every so often and are not meant to last like paint. In roofing, reapplications are where the money is.


Remember...Elastomerics are a roofing product, not a paint. If you read the instructions you will see that caulks and reinforcing fabrics are supposed to be used on cracks and problem areas. Is your roof leaking? You can find out with a water hose. Did you make a lot of penetrations/holes in your roof installing stuff on your roof? If you did you should be more concerned with your roof leaking than how good it looks or how good an insulator/reflector it is.


I'm guessing that a good urethane or epoxy paint would be a good choice. Good prep is the key to good paint.

My question would be what kind of paint do/did the bus manufactures use? It seems to last and does a good job of sealing and they actually have a stake in whether it works good - or not.

[DeMac]

Last? Which layers come into contact with rain, before the paint does?

[musigenesis]

Originally Posted by DeMac

Last? Which layers come into contact with rain, before the paint does?

On my bus, it's the layer of spotted lanternfly poop.

[kidharris]

Originally Posted by surchicham

And yet, it seems to me that the paint plays a big role if we talk about water resistance. Yet, it is the last layer that comes into contact with moisture.

I am assuming that you mean "first and, hopefully, last layer that comes into contact with moisture"

Design and good counter flashing are probably more important for shedding water. Assuming that the steel is not galvanized, paints biggest role is in corrosion resistance/prevention. Appearance, reflection, and waterproofing are probably considered secondary uses. People were rain proofing structures long before caulk, paint, elastomeric coatings and other easy solutions came along and became detriments to good design and roofing practice. The secret is to really think out all of the possible ways that the water can flow and help it flow off and away..... unless you are building a submarine.

On the roof of the bus you will notice that all of the laps face away from the front so that the wind cannot force water under the lap. All surfaces are curved so that the water has as unrestricted of a flow down off the roof as possible. Diverters and tiny gutters direct the flow away from penetrations and windows, etc. as much as possible Everything is shingled (higher pieces overlap lower pieces) as much as possible. Weep holes (let water drain out) are provided somewhere lower down where they think that a leak could occur. This is design and counter flashing. A mistake here should be corrected/fixed, if possible, and only then think about sealing with caulk or coatings. Most common leaks are around skylights, vents, windows and other penetrations. Correct counter flashing first and foremost. What would you do if caulk was not available?

For instance, the numerous rivets in the roof do not leak because they are squeezed/compressed/hammered into the holes so tightly that they form a compression seal and is an example of good design doing a good job of both fastening, sealing, and not requiring maintenance. If, somehow?, they are loosened they will leak. If they are replaced with pop rivets, then you have a problem and they will benefit from sealing. The paints primary purpose is not to seal the rivets or metal from leaking water. The metal is sealing the roof and the paint is preventing the metal from corroding away. If the metal didn't need corrosion protection, the paint may not be "necessary" but may be used for other reasons - cosmetics, color change, solar reflectance, camouflage, electrical isolation/insulation, etc.

The windows that leak are caused by poor counter flashing and seal designs. Correcting the designs is the permanent solution, not smearing on a bunch of caulk.

Improperly applied caulk actually causes a lot of leaks (damming and trapping water, not sticking, hiding defects) yet people will look at it and and think that "there is no way it can leak with all of that caulk". People that don't understand counter flashing often defeat the counter flashing by applying caulk, creating a dam and sealing off a drainage point or weep hole. "Oh, this crack must be leaking, the idiots forgot to caulk it, I'll put some caulk here and stop that. Gee, I'm smart". I think of caulk/coatings as a last resort and hopefully after I have really thought it out. It is hard to clean up the mess if it doesn't work and it makes the leak worse or diverts the leak somewhere that you can't see it. Then what? You think that you succeeded until.....

Silicone, elastomeric or caulk, makes it very difficult to do repairs later because nothing wants to stick to it and it doesn't stick/adhere to other stuff very well either. Silicone will peel off easily if the surface is not prepped properly. I only used specialized silicone products for certain extreme heat applications (gas vent pipe seals) and some compression seals/gaskets, usually automotive

[kidharris]

Originally Posted by musigenesis

On my bus, it's the layer of spotted lanternfly poop.

That was last year. Are they back? or you just haven't cleaned it yet?

[musigenesis]

Originally Posted by kidharris

That was last year. Are they back? or you just haven't cleaned it yet?

I just haven't cleaned it yet. They are back, but the tree they were living in above my bus fortunately fell down last year.

[o1marc]

After hearing how much dirt sticks to the Henry's I have decided to not use the Tan Henry's on my roof and just go with either a white or tan paint. I'll return the Henry's to HD.

[Danjo]

I just got done doing repairs to a mobile home roof and reapplying Henry’s. I’d never put that on my bus. Performance characteristics aside, it’s just visually unappealing.

[MNbusboy]

So we are going with just white paint on the roof, but I also had a second thought. Has anyone tried a suspended canvas over the roof for built in shade when parked? It would just take a couple raised poles with loops on each end. When you park you hand the canvas and it would help block the radiation heat transfer. Just don't forget to take it down before driving, or you will make your bus into a parasail!!

[musigenesis]

Originally Posted by MNbusboy

So we are going with just white paint on the roof, but I also had a second thought. Has anyone tried a suspended canvas over the roof for built in shade when parked? It would just take a couple raised poles with loops on each end. When you park you hand the canvas and it would help block the radiation heat transfer. Just don't forget to take it down before driving, or you will make your bus into a parasail!!

The canvas is a good plan, but a lot of people put solar panels on the roof and the two would not combine so well. I'm thinking about having a solar-power trailer that has panels in a fold-out array on the roof, so I can park my bus in the shade with the trailer in sunlight.

However, I'm not sure any more that parking in the shade is all that important if your bus is well-insulated. Before I put up my insulation, my bus roof was measuring over 130°F in direct sunlight and the ceiling inside was the same temperature; with insulation on the ceiling now (1.5" XPS between the ribs and another layer of 3/4" XPS inside of the ribs), the ceiling inside is only measuring a few degrees above the ambient air temperature (this is with all the windows open, of course).

[DeMac]

I agree, Musigenesis. With good insulation, the exterior skin temperature is not much of a factor. Solar shading is more helpful at preventing ir & uv radiation waves from entering through the glass. The interior air and surface temperature increases, from solar radiation, are significant. Insulation could only trap this type of solar heat inside.
Best to leave the radiation outside. Shading the glass with canvas window awnings ought to yield larger gains.

[musigenesis]

Originally Posted by DeMac

I agree, Musigenesis. With good insulation, the exterior skin temperature is not much of a factor. Solar shading is more helpful at preventing ir & uv radiation waves from entering through the glass. The interior air and surface temperature increases, from solar radiation, are significant. Insulation could only trap this type of solar heat inside.
Best to leave the radiation outside. Shading the glass with canvas window awnings ought to yield larger gains.

My windows are tinted, and I was surprised to see how big an effect even that had. Spots on my floor where the sun was shining through open windows were as hot as the roof (130°F+) but where sunlight was shining through the tinted glass it was more like just over 100°F.

[mhaisten]

We used white Rustoleum industrial paint from HD. It is fairly thick and applied well with a roller. Dried very glossy and sealed over the seams. It has seen rain and snow and ice and is holding up well.

[Tuck]

Soooo...you still alive? It's been over 10 years so how's that roof? I'm about to paint my roof with tropicool too, lol