How To: Mount Panels to an RV Roof

HRTKD

Boondocker
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.

TrailerRoof.JPG

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.

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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.

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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.

20200822_154215.jpg

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.
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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.


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...
 
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HRTKD

Boondocker
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.

20200829_164516.jpg

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.

20200829_164534.jpg

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.

20200829_165954.jpg

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.

20200829_174044.jpg

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.

20200916_165924.jpg

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.

20200916_165947.jpg

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.
 
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HRTKD

Boondocker
One more picture. :)

I use the Z brackets to keep my PV wires in place using weather resistant zip ties.

20200916_170001.jpg
 

LanduytG

Solar Enthusiast
I'm in the process of installing everything in my 40ft 5th wheel and the panels are going to be the last thing I mount. Put 4 255 watt Canadian Solar on the roof. I have been back and forth about what I'm going to use to mount them. My roof is not flat and has a slight curve to it. I want to be able to tilt them at some point so whatever I come up with will need to be compatible too.

Greg
 

HRTKD

Boondocker
Every trailer roof should have some arch to it. Otherwise, water would puddle in the middle.

I considered a tilt mechanism and came around to keeping it simple with a fixed install.

Be glad we have "normal" trailers. Imagine how limited you would be on an Airstream!
 

namesgolden

Solar Addict
Great write-up.

I'm following someone that is re-roofing a rig just like mine (97 newmar DP) and am considering doing the same thing. I have so much to eliminate (horns, antennas, vents) and it's got some soft spots. Gotta find a tall barn to rent for a few weeks.

I want as much solar as possible (2000w minimum goal), I'm considering putting aluminum channel or unistrut all over the roof. I have 64x39 250w panels but I'm gonna try to plan for the ability to upgrade to 78x39 370w panels.
 

HRTKD

Boondocker
Great write-up.

I'm following someone that is re-roofing a rig just like mine (97 newmar DP) and am considering doing the same thing. I have so much to eliminate (horns, antennas, vents) and it's got some soft spots. Gotta find a tall barn to rent for a few weeks.

I want as much solar as possible (2000w minimum goal), I'm considering putting aluminum channel or unistrut all over the roof. I have 64x39 250w panels but I'm gonna try to plan for the ability to upgrade to 78x39 370w panels.

I had to repair sidewall delamination last year on both sides. I rented a covered parking spot at the storage lot for a month. That helped tremendously as we had a long spell of rain.

If I knew I was going to upgrade panels, unistrut - or an equivalent - would be the way to go. My biggest concern with the actual unistrut product is how heavy it is. I looked at using an aluminum version of it and that would be my choice. Adding too much weight on the roof can't be a good thing.
 

Tgmontague

New Member
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.
Great info. Thank you for detailing your install. I am in process of installing 4 solar panels using Z brackets by Renogy. My quandary is how the brackets can be robustly attached to the EPDM roof. Brackets came with self tapping screws. I've mounted 1 panel with VHB tape under each of 4 brackets and then installed 2 screws per bracket. But the screws are just going into the wood deck of the roof which is a concern. Major concern? Finding and hitting trusses is doable but major slow down. So many RV videos happily mount anywhere on roof seemingly. Am I smoking something good here?
 

HRTKD

Boondocker
Great info. Thank you for detailing your install. I am in process of installing 4 solar panels using Z brackets by Renogy. My quandary is how the brackets can be robustly attached to the EPDM roof. Brackets came with self tapping screws. I've mounted 1 panel with VHB tape under each of 4 brackets and then installed 2 screws per bracket. But the screws are just going into the wood deck of the roof which is a concern. Major concern? Finding and hitting trusses is doable but major slow down. So many RV videos happily mount anywhere on roof seemingly. Am I smoking something good here?

Some roofs have thicker decking than others. A roof that is (clearly) rated to be walked on should be thicker than one that is not rated to be walked on.

I spent considerable time finding my trusses so that each bracket had at least one screw going into a truss. VHB tape on EPDM isn't going to help much. I camp in some windy locations (describes pretty much all of Wyoming!) and I didn't want to have any worries about panels coming loose.

I did not use the screws that came with the brackets. I used my own, which are longer and thicker.
 

Bob B

Photon Sorcerer
The only thing I would have done differently is to use Sikaflex-221 in place of the butyl. I have found that the tension on the butyl will vary with temperature and allow things to "squirm" around and loosen up.

I had a problem with my truck camper where the jacks would try to twist inward or outward when fully extended .... not a real comfortable situation. I tightened the bolt to the jack brackets multiple times and the problem would come back.
I saw a post on another forum where a guy had removed the brackets, cleaned out the butyl and then re-attached after apply a liberal amount of Sikaflex-221 ..... So I decided to give that a try. It worked like a charm. The jacks are now rock solid, and that has been a few years now.

It is now part of my routine if I remove something that has butyl to clean off all the butyl and put back together using the Sikaflex. I have been VERY happy with the result in all cases.
 

MrNatural22

🌞SW sunshine =⚡️⚡️lit up thru the darkness✌️
SikaFlex 221 is indeed a potent, very strong and solid adhesive but anything it’s used on pretty much becomes permanent. It’s very difficult to remove anything Sikaflexed without causing some sort of damage. 😎✌️
 

HRTKD

Boondocker
The argument I've read against using any liquid-ish product under the solar panel brackets is that the product is almost completely squeezed out once the screws are tightened down. I have very little squeeze-out with the butyl tape.

Butyl tape certainly doesn't last forever, that's for sure. If it isn't properly maintained it can break down. I've replaced most of the butyl tape on my 2006 trailer.

I need to repair the front wall that has delaminated. I was planning to use the 3M 5200 adhesive, but I'll take a look at the Sikaflex adhesive.
 

Bob B

Photon Sorcerer
As Mr Natural said .... the only drawback is that it is difficult to remove Don't get it on your clothes .... wear disposable gloves.

I think a razor blade or sharp putty knife are the most common removal methods. So far, I haven't had any reason to take apart anything I put together with it.

When putting on something like the bracket, I would put some on the bracket itself and let it develop a slight skin ... then put some on the other surface and screw down.

I have seen it recommended to seal an open tube well then put in a freezer to be able to re-use what's left. Haven't tried that yet.

One of the benefits is that it won't be as thick as butyl and prone to moving around and loosing the seal.
 
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