How To: Mount Panels to an RV Roof

DIDDLYV

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Mar 1, 2021
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Going to mount mine with green anodized strut channel from Grainger.
 

Stepandwolf

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Nov 14, 2020
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Going to mount mine with green anodized strut channel from Grainger.
Several use that or similar products found at the big box. Are you mounting on a flat surface or a curved roof you will be compensating for?
 

DIDDLYV

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Mostly flat one way a bit of a curve the other but will be using the 4 inch angle adjustable mounts hooked into the channel so should be pretty good to go. Not at home right now when I get back next week will get my 12 foot ladder and map out everything on the top of the RV then order panels and the strut channel prolly 4 x 10 ft from grainger as Grainger had the least expensive anodized which in theory should not rust. If you have a better idea or better place to get anodized I am all ears so to speak
 

Stepandwolf

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I am on the verge of buying the material so this is only what I chose to do based on my own research.
I sized my panels so they can be placed in a row along the edge of the roof, just clearing the AC. I am going to use 1.5" aluminum box for the frame. The frame will run continuous for a string of six panels on one side (they sell it in 20' lengths). I will install legs only at the trusses. At each set of legs, there will be a cross beam. Shorter legs to the interior and longer legs on the exterior. This rail method allows me (as it would you) the opportunity to mount the rail on trusses, and the panels wherever .

I lost my quotes on the aluminum so I need to call around again. Panels are on the way. I am far from ready as none of the system is installed yet.

trailer roof4.jpg
I fit the optimum panel size that fits in the space I have. As you can see, a string of six on one side, then a string of five on the other side with a sixth offset panel. That one might have it's own mini-rail system as I don't want it on the roof surface. I could put a panel over the front sun roof and I could put one somewhere on the rail, but I think 1200W on my small TT is reasonable.
 
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HRTKD

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Apr 24, 2020
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Somewhere South of Denver
Mostly flat one way a bit of a curve the other but will be using the 4 inch angle adjustable mounts hooked into the channel so should be pretty good to go. Not at home right now when I get back next week will get my 12 foot ladder and map out everything on the top of the RV then order panels and the strut channel prolly 4 x 10 ft from grainger as Grainger had the least expensive anodized which in theory should not rust. If you have a better idea or better place to get anodized I am all ears so to speak

If you look hard enough you can find channel made out of aluminum. No anodizing needed.
 

koho

New Member
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Aug 27, 2021
Messages
9
This details the steps I went through for mounting my Mission Solar 320 watt panels to the roof of my RV trailer. While there are multiple methods to secure a panel to an RV roof, this focuses on using standard Z brackets. Other methods include DIY brackets, Unistrut, adhesive tape and all the other third party mounting methods. I went with the Z brackets because they were simple and lightweight.

I am highly skeptical of the adhesive-only mounting method on an EPDM roof. In my opinion, you are setting yourself up for catastrophic failure if you try to secure rigid PV panels to an EPDM roof with only adhesive tape. Flexible PV panels that have no air gap are a different issue and adhesive-only mounting should work OK there.

Step 1: Measure The Roof
Measure the roof of the RV, including all the objects mounted on the roof. I used the CAD application Sketchup to draw everything out.

View attachment 22933

The advantage of the CAD tool was that I could draw my solar panels to the correct dimensions and then place them on the roof. This was a huge benefit as I had originally intended to go with four 200 watt panels. Arranging them on the roof showed that they weren't going to fit. That prompted me to change to a completely different panel setup and I went with two 320 watt panels from Mission Solar instead.

The big mistake I made with this is that I forgot to include the Z brackets in the footprint of the panels on the roof. Fortunately, when it came time to do the install I had a few inches to play with and it turned out OK.

While looking at the placement of the panels on your drawn roof, consider how existing objects could throw shade on the panels. Placing the panels near the air conditioning unit is likely to result in some shade on the panels for a few hours a day.

Here's what the target area of my roof looked liked before I got started.

View attachment 22934

Step 2: Verify The Integrity Of The Roof
Is your roof in good shape? Have you actually checked every inch of the target area? You need to look for tears, holes, cuts and soft spots in the EPDM (rubber) roof material. Any flaw needs to be addressed now. You CANNOT get to anything under the panel once the panel is installed.

My roof turned out to NOT be in good shape. In fact, it was so bad it was like bouncing a small object on a trampoline. Here's what I found when I pulled back the EPDM.

View attachment 22935

View attachment 22936

Fixing the water damage was not optional. It HAD to be done because one of the Z brackets needed to be placed right in the middle of all the damage. I removed as much rotted wood as possible and replaced it with like material. I also put as much new insulation in as possible.

View attachment 22937

This is the last photo before I applied butyl tape to the edges and glued the EPDM back down using a Dicor adhesive. It took a couple hours to clean all the rotted wood from the EPDM. This was a five day project, with a pause of two days waiting for the adhesive to be delivered. I got lucky that the damage was at a corner. If this was in the middle it would have been a much longer and difficult job.
View attachment 22938

Step 3: Find your Roof Trusses
If your trailer has roof trusses, like mine did, you need to find them. This is what you want to secure your Z brackets into. Finding the trusses is a bit like an Easter Egg hunt. Here are the techniques I used.

A. Stud Finder - I was using a 20+ year old Zircon Stud Finder at first and getting random results. I upgraded to a Zircon 900c stud finder and got better - but not perfect - results. The stud finder would find a truss going one way, but not the other way. It was quite frustrating, but I ran it enough times to verify the results in multiple locations. If you're getting lousy results using the stud finder on the roof, go inside the trailer and use it on the ceiling.
B. Thump Method - Using the butt end of a large screwdriver I thumped the roof and listened for hollow and solid sounds. This was a fairly good method.
C. Tape Measure - My trusses were usually located on 16" centers. This wasn't always the case, such as when the 16" mark was right in the middle of a vent. This caused the installer to shift the truss forward a few inches.
D. Open the Ceiling - Since a roof vent was in the right position, I opened the vent mount from the inside of the trailer. That gave me easy access to the "attic". From there I could see the trusses that were forward and backward from the vent. With attic access I was also able to stick my tape measure in and measure to the next truss.

Using all four methods, I was able to accurately map out the locations of my trusses. In the first photo in the thread you can see blue tape on the roof. I used the tape to mark the location of the trusses. All my Z brackets have at least one screw in a truss. Due to the width of the truss - usually no more than 1.5" - one screw in a truss per bracket is about all you'll get. I would rather get one screw solidly in the middle of a truss, than two screws on the edge of a truss.

Step 4: Remove Obstructions
As you can see in the first photo of the thread, there was a roof rack right in the way of my target location. That had to come out. I considered trying to mount the panels to the rack, but it wasn't that secure and I needed the entire space. I had to seal the holes where the rack was screwed into the roof.

Step 5: Prepare The Roof
If you need to clean and seal the roof, do it now. I added a few Eternabond patches in locations that had cuts. I removed and replaced the Dicor Lap Sealant on the rear edge of the trailer. These are things that are very difficult to do once the panels are in place.

Step 6: Install The Z brackets On The PV Panels
Using your carefully calculated measurements, figure out where on the panel the brackets need to be placed. Don't assume that you have to use the existing holes in the panel's frame. I drilled seven new holes in each side of the panel's frame. I used three brackets on each side instead of the more common two on each side. I did this for two reasons. First, the forward and rearward brackets needed to be moved closer to the front and back of the panel to be on the truss. Second, because of the longer distance between the brackets, I felt the need to support the middle of the panel better.

Should you need to drill new holes in the panel's frame, be sure you place a block of wood or other suitable material that will "catch" the drill bit when it comes through the aluminum frame. That last thing you want to do is nick or drill into the back of the panel.

The Rich Solar bracket kits I bought came with bolts, washers and nuts. I chose to toss the nuts and use my own nylon lock nuts. If I had used the provided nuts I would have added some blue Loctite.

Do the bracket install on the ground. It's going to take a while. A socket wrench and a box end wrench will make the tightening of the bolts go a lot faster. Get the nuts snug, but don't overtighten.

Which way do the brackets go? In the picture below you can see there is a slot end and a two-hole end. I chose to mount the two-hole end on the panel frame. My thinking on this is that I wanted the flexibility of placing the roof screw anywhere in the bracket so I could hit the truss exactly. The two-hole end didn't give me that flexibility.
RICH_SOLAR_Solar_Panel_Mounting_Hardware_Z_Brackets_RS-ZB4B_1-6_1001x1001.jpg


A comment on bracket color: The chance that anyone is going to see the brackets is low. Just because your panel frames are black, doesn't mean you need matching black brackets. Had I realized how hidden the brackets are, I would have gone with a plain aluminum colored bracket. I may be the only one that knows my brackets are color coordinated.

Also in this step you need to prepare your supplies for the final installation.
A. Butyl Tape: I used 1" wide Butyl Tape, cut to match the length of the foot of the Z bracket. I cut the tape to length on the ground so I didn't have to do that on the RV roof. If you put the roll of Butyl Tape in the freezer or refrigerator it is a lot easier to work with. When it's hot it can be very messy. Leave the backing tape on for now.
B. Screws: I used #10 hex head sheet metal screws, 1.5" long. You shouldn't need a self-tapping screw, but that would be OK to use. I also used washers, which are probably optional.
C. Lap Sealant: I use Dicor Self-Leveling Lap Sealant. One tube should do the job for three panels if you're not too sloppy. Don't forget to take the caulk gun up. Bring a couple of rags for cleanup. Don't ever use silicone caulk on your trailer!

Step 7: Get The Panels On The Roof
I included this as a separate step for safety. My panels weigh 44 lbs each without any brackets and they measure 66"x40". They are very unwieldy. I put the side of my F-350 pickup as close to the rear of the trailer as I could. I tied rope to two of the brackets so I had something to grab. My wife and son - standing in the bed of the truck - lifted the panels to me on the roof.

Once you have the panel on the roof, be very careful with the brackets. They can be sharp enough to cut the EPDM. Avoid sliding the panel across the roof.

Continued in the next post due to the limit of 10 attached pictures per post and 10K character limit...
 

koho

New Member
Joined
Aug 27, 2021
Messages
9
Step 8: Position The Panel
Using the marks you put on the roof - I marked my roof with a permanent marker since it would get covered up - position the brackets into the final position. Double check your positioning. Clean the area around the bracket, as well as the bracket, if needed.

View attachment 22985

Step 9: Install The Butyl Tape
Remove the backing tape from one of your pre-cut pieces of Butyl Tape. Lift the panel as little as possible and put the Butyl Tape under the bracket foot. Repeat this step for each bracket.

Here is a piece of Butyl Tape prior to install. It still has the backing tape on it.

View attachment 22986

Step 10: Install The Fasteners
Using a drill with a hex head bit, install the hex head screw. Press down firmly on the drill so that the tip of the screw quickly pierces the EPDM and goes into the roof decking and then the truss. Do not over tighten the screw. This is especially important for those screws that won't be going into the truss. I used two screws per bracket even though only one was going all the way into the truss. Make sure the head of the screw is flush with the bracket.

Installing the fasteners will cause the Butyl Tape to squeeze out a bit. That's normal.

View attachment 22987

Trim the excess Butyl Tape from around the bracket. Use a plastic knife to do this. Trimming the excess from the back side of the bracket is difficult. Get it if you can.

View attachment 22988

Step 11: Seal The Bracket
Using your tube of Dicor Lap Sealant, cover the foot of the bracket and the screws. Dicor, being a self-leveling product, will slowly spread out. Don't be stingy with it. There's no such thing as too much lap sealant (until you have to remove it, which really isn't that bad). Use the Dicor like you're frosting a birthday cake and you know the birthday boy really likes frosting.

If you can get the Dicor behind the bracket, that's great. For this round, I didn't even try.

Here's how one of mine looks after two weeks. Dicor can take up to 30 days to fully cure. I hit the road after four days of cure time.

View attachment 22989

Dicor will pick up dust/dirt/crud. It won't stay white forever. It will last a long time, but you need to inspect it annually. If you need to add more, be sure to clean it first with the lowest impact cleaner you have available. For some tough spots I use mineral spirits, while other spots just need a little soap and water.

Here's a picture showing how close my Z brackets are to the edge of the roof.

View attachment 22991

Thanks for reading, I hope this was helpful. When I looked on the net for tips there wasn't much there. There were plenty of YouTube videos that glossed over the finer points. Hopefully I covered those here.
 

koho

New Member
Joined
Aug 27, 2021
Messages
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I was stunned by your pictures of the rotted roof. What company would use wafer board on a roof? Terrible choice. Anywhere there is moisture(roofs?) you use exterior plywood, preferably marine grade or even treated but marine is waterproof and is good enough. Then you can seal the seams with polyurethane sealant and cover with something durable. I recommend epoxy/fiberglass but other options exist like a rubberized coating. I have built 2 tiny houses and 4 ocean going boats and that is what I have always used. The only rvs I have ever owned were ones that I built and now I know why. I recently finisihed a cargo trailer which is now an off grid RV, The roof members were steel 1.5" Channel with a slight arch. Roof was plywood with aluminum covering. Attaching the panels was easy of course. Your work amd pictures showed care and attention to detail but on boats if you see rot in one portion of the deck you have to assume rot elsewhere.
 

HRTKD

Boondocker
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Apr 24, 2020
Messages
6,474
Location
Somewhere South of Denver
Your work amd pictures showed care and attention to detail but on boats if you see rot in one portion of the deck you have to assume rot elsewhere.

Thanks! With a rubber roof, it's fairly easy to tell if there is rot. Unfortunately, by the time you can feel that there's rot, it's spread.
 
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