Screw it or Glue it?

[unpilot]

So.....anyway of knowing what is running in the roof? Wire wise I mean?
Can't seem to find a diagram for the roof wire/duct runs.

[rarebear.nm]

Hard to say for sure where things are in the roof space. Even if you have a diagram. How things are designed and how they are built may vary without warning.

Duct work is almost always in straight runs from the AC units to each vent. Not likely to have plumbing in the ceiling. So you 12 and 120v power plus some other signal cables. Some stud finders can locate 120v wires in most walls. May not do much for low voltage wires.

When I have to drill a roof hole, I study the layout of lights, switches, etc. Cables are typically run in cable bundles or harnesses. Where wires are run varies by manufacture. Some place most of the run near the floor along the wall with branches going up to switches and lights. Others may have larger harnesses in the ceiling. Probably depends highly on roof construction. If foam insulation is bonded to roofing and ceiling materials then probably very few wires in the ceiling. If the roof is an open truss design with fiberglass batting insulation then it is easy to run wire harnesses in the ceiling. Some manufactures use cable conduct or cable chase ways in the ceiling.

No direct help but, but maybe some ideas what you are facing. There is far more "open" space for roof holes than danger spots. As I said above I study the roof construction and where things are located and go from there.

Always use a UV resistant self flange roof covering to bring the wire through the roof deck. I see some low cost solutions that use products that I know will bend and warp in years of UV light. Results are highly predictable.

Just a late note on your first question. Glue or screw, it depends on the type of roof construction and roofing material. There is not best answer for every kind of rv roof. Other posters have made very good comments on various roof types.

[CountryFit]

There're certainly some wires under the skin especially near the a/c units. I just found the old thread for the incident from the panel install that made me scratch my head very hard...

https://www.irv2.com/forums/f54/on-s...nt-251028.html

[rarebear.nm]

There is little good reason to use screws that much longer than the thickness of the roof deck. Keeping them short at least reduces the chance of the screws hitting anything.

If unsure of the thickness, pull off the flange around a 14 x 14 vent of you may be able to see it from there.

[unpilot]

Originally Posted by rarebear.nm

Hard to say for sure where things are in the roof space. Even if you have a diagram. How things are designed and how they are built may vary without warning.

Duct work is almost always in straight runs from the AC units to each vent. Not likely to have plumbing in the ceiling. So you 12 and 120v power plus some other signal cables. Some stud finders can locate 120v wires in most walls. May not do much for low voltage wires.

When I have to drill a roof hole, I study the layout of lights, switches, etc. Cables are typically run in cable bundles or harnesses. Where wires are run varies by manufacture. Some place most of the run near the floor along the wall with branches going up to switches and lights. Others may have larger harnesses in the ceiling. Probably depends highly on roof construction. If foam insulation is bonded to roofing and ceiling materials then probably very few wires in the ceiling. If the roof is an open truss design with fiberglass batting insulation then it is easy to run wire harnesses in the ceiling. Some manufactures use cable conduct or cable chase ways in the ceiling.

No direct help but, but maybe some ideas what you are facing. There is far more "open" space for roof holes than danger spots. As I said above I study the roof construction and where things are located and go from there.

Always use a UV resistant self flange roof covering to bring the wire through the roof deck. I see some low cost solutions that use products that I know will bend and warp in years of UV light. Results are highly predictable.

Just a late note on your first question. Glue or screw, it depends on the type of roof construction and roofing material. There is not best answer for every kind of rv roof. Other posters have made very good comments on various roof types.

Thanks for this. I followed your advice and decided there was a low chance of anything in the area I decided to drill at.

Worked like a charm!

[Rolling Ragu]

We screwed them down. However, I wish I had put eternabond over each bracket and then screwed. I wasn't pleased with how tight the screws bit into the roof. Didn't give me warm fuzzies.

[rarebear.nm]

When I mounted mine on a EPDM roof layered on 3/8-1/2 plywood, I did the following:

1) With brackets attached to the panel I moved the panels into place and marked where each bracket would mount.

2) Placed a piece of Eternabond over each mounting area for a cushion on the rubber roof.

3) Then ran a generous bead of roof sealant the length of the mount area. The screws picked up some sealant as they were screwed down.

4) moved the panel back into place.

5) Drilled piliot holes for each screw, used SS screws just 1/4" longer than the roof deck thickness.

6) Flooded the entire area around and over each bracket with self leveling sealant.



The brackets are made from 1/4" thick 4 x 5" aluminum angle, bolted together with SS bolts. Each bracket is six inches long. Used four SS bolts with safety nuts between bracket and panel and four SS screws to attach the bracket to the roof deck.

In the lower right corner of the image is a cable entry flange for three antenna cables also covered with sealant, exactly like one shown a few posts above.

To get the sealant on the backside of each bracket, I added a length of vinyl tubing on the end of the caulk gun so I could just guide it on easier.

[kendall69]

Screw it, Glue it, and then silicone caulk it.

Think about it with winds that could reach over 100 mph between your travel speed and them fighting a headwind.

After the screw, glue, the caulking prevents the wind from getting under the mount.

[Don Juane]

Got a good laugh out of this one. First anyone asking on a social media group how to do something is asking for more than trouble. Next issue .... thinking that solar tech won't improve often to the point that different size panels come along that you'll want to install which have much more output per sq/in. Next ..... not a single person here aware of what the pros use (hint, not screws or "glue") and next ... Anyone who uses silicone on the exterior of a motor home must love leak-repair as their number 1 hobby. I will not fill in the blanks here because this "advice column" is so off the wall, it's hopeless to provide any true advice in the midst of all the bad suggestions. Plus the majority line of thinking seems to prevail, so it's not worth it. Basically I'll just say to go somewhere else to figure out how to install solar. No screws or silicon. Adhesive on clean surface, yes. The fewer holes in the roof, the fewer leaks you will be fixing.

[rarebear.nm]

First I am not an air flow engineer. But, I have spent some time reading about air flow over roof tops. Difficult to find much on it so far.

With that said, air flow over an RV is usually very turbulent. When I designed my roof top solar system one panel was going crosswise near the front edge of the roof. These are 49 x 79" panels. I was much more concerned about a vacuum forming over the top of the top of the panel and not air getting under it. As for the other panels farther back on the roof, trying to determine what air flow might do was way too complex for me, with all of roof top "decorations" we have up there.

We don't seem to hear very much about solar panels flying off RVs, so I assume that reasonable effort seems to do the job. But that's my opinion.

[CountryFit]

Certainly some unlucky guys lost their panels on the road. Here's one:

https://www.youtube.com/watch?v=ZERE9T5vol0

[rarebear.nm]

We do not know very much from this video besides a panel came off. No real idea how it was attached, what the roof deck was made of, who did the work, etc. It appears he had six light weight brackets, perhaps standard Z brackets per panel.

None of us want anything to fly off our roofs or from anywhere on our RVs. I've seen plenty of stuff come off pickups and a few commercial trucks. Another reason I like to leave plenty of space in front of me when I permitted.

[packnrat]

screw it.
why would one want them to fly off going down the hwy? sure there are some good glues. but nothing that strong, or durable. the the “support” material. will it hold? or just rip apart.
i would like to do solar. but the cost. and i would do a rack system held off the roof about a 1/4-1/2 in. and screwed to every support in the roof.
i would rather go over kill then kill someone if a panel came off on the rd or a high wind event.

[jcurtisis]

Originally Posted by tcharsch

17 years ago AM Solar (Eugene, OR) installed our panels using short VHB tape strips on the bottom of the mounting brackets -- about 1" x 3"; no screws. Still holding fast after all these years. I'd go for no holes in the roof!

I’ve heard several others say the same thing.