Proper way to seal around mounting bolts in trailer roof?

[deagle]

Hello all. I've got a trailer I'm converting for off-road and camping, and I want to mount solar to the roof and some pelican cases to the sides. The trailer has a metal roof and walls over steel tube frame. I'm wondering what the correct way to handle sealing around mounting bolts would be to ensure no water intrusion. I'd like it to be bullet proof as possible so I don't have to worry about leaks. Thanks all.

 

[zgfiredude]

One way is to cover them with Eternabond tape.....

 

[bgenlvtex]

Sikaflex 221

 

[grubworm]

yeah, definitely go with a polyurethane like sikaflex and use a fender washer for more surface area contact. when you penetrate the roof, which is maybe 26ga at best, stick the bolt up thru the roof and then glob a good bit of sealant around the bolt and then drop a fender washer on top of that and then tighten with a nut. the fender washer gives more sealant area and will reduce flex around the bolt penetration. seal good around the threads because water will follow the threads since they are not tapered threads like on pipe fittings.



have you considered mounting unistrut on the roof? that way you have a fixed and very heavy duty rail that you can attach and detatch items to with ease and you wont be messing with the mounting bolts since everything will be mounting to the strut.

Superstrut 10 ft. 12-Gauge Half Slotted Metal Framing Strut Channel in Silver Galvanized ZA12HS10EG - The Home Depot

Use this Superstrut Strut Channel Electro-Galvanized Finished to hang conduit and other supports from ceilings. Rust resistant.

www.homedepot.com

you can also make a rack that mounts to the side. instead of penetrating the roof, attach strut to the side of the trailer bolted thru the metal frame and have it go up past the roofline a couple inches and bolt a crossmember. do that 2 or 3 times and you have a nice rack with no roof penetrations. lots of options

 

[deagle]

yeah, definitely go with a polyurethane like sikaflex and use a fender washer for more surface area contact. when you penetrate the roof, which is maybe 26ga at best, stick the bolt up thru the roof and then glob a good bit of sealant around the bolt and then drop a fender washer on top of that and then tighten with a nut. the fender washer gives more sealant area and will reduce flex around the bolt penetration. seal good around the threads because water will follow the threads since they are not tapered threads like on pipe fittings.

View attachment 237960

have you considered mounting unistrut on the roof? that way you have a fixed and very heavy duty rail that you can attach and detatch items to with ease and you wont be messing with the mounting bolts since everything will be mounting to the strut.

Superstrut 10 ft. 12-Gauge Half Slotted Metal Framing Strut Channel in Silver Galvanized ZA12HS10EG - The Home Depot

Use this Superstrut Strut Channel Electro-Galvanized Finished to hang conduit and other supports from ceilings. Rust resistant.

www.homedepot.com

you can also make a rack that mounts to the side. instead of penetrating the roof, attach strut to the side of the trailer bolted thru the metal frame and have it go up past the roofline a couple inches and bolt a crossmember. do that 2 or 3 times and you have a nice rack with no roof penetrations. lots of options

View attachment 237963

This is very useful advice thank you. I've got an aluminum rack on the back half of the trailer, maybe I should use side brackets and just extend it to provide the hard points for mounting. I sure am getting more and more tempted to get a TIG welder the more I dig into this project.

 

[Viking1204]

Like @grubworm said, rubber washers and sealant work wonders. I have a Diamondback bed cover I bolted Superstrut to for building the rack for my RTT and the rubber washers and sealant have made sure I have no leaks into the bed of my truck!

 

[socal geek guy]

x2 on the side rack idea. i have a DIY "rack" that i made for my awning that i mounted on the side of the trailer in order to have an adjustable height awning. i used silicone caulking that is good for outside and colder temps to seal up the holes. i have long through bolts that go into the steel tube frame so that i'm getting the most sturdy attachment point that i can, which would help you with the solar panels as well.

another thing that i need to get around to doing is putting a rubberized roof sealant on, and that's something additional you could used if you are dead set on mounting to the roof. this is what i was looking at applying to my roof since its just sheet metal on the outside. i would say do your sealing around the bolts of the mounts, install the mounts, but not the solar panels, apply the coating to the roof and around the mounts, then install the panels when the coating is dry.

Henry 289 Elastomeric White Roofing Sealant 0.90 gal. HE289146 - The Home Depot

Seal seams and roof leak areas in your home with the selection of this Henry 289 Elastocaulk Acrylic Roof Sealant. Easy to apply to dry or damp surface.

www.homedepot.com