Roof Patches

[Andre3MC]

I am gearing up to make some patches in my roof and looking for opinions on material selection.

The most important patch will be for the emergency hatch opening where I will be installing fan, I will make the other patches from the extra material that I cut out. I am thinking about using either 20 ga 304ss or 18 ga mild steel that I would prime before installing. What have people used and liked? I will be installing them with rivets and sealing with dynatron 550.

I will have to buy whatever I go with, the sheet metal that came out of the bus is either spoken for or scrapped.

[Dead pirate]

I used fiberglass. It shapes nice

[TheHubbardBus]

I used 18g cold rolled steel for the e-hatch patch, prepped & painted before install. On our roof, this appears to be the approximate thickness of the outer shell. We accidentally purchased a 16g patch first and it was way too thick/stiff. For every other patch, the largest being for the passive vent, we used the steel sheet removed from the interior (20-22?). 3/16 stainless steel blind closed-end rivets, 0-.125" grip range where the two sheets overlap, & .126-.250" grip range for where I had to also penetrate the edges of the hat channel / rib. Sealed both the edges & each rivet hole with 3m 550FC polyurethane.

[EastCoastCB]

Originally Posted by Andre3MC

I am gearing up to make some patches in my roof and looking for opinions on material selection.

The most important patch will be for the emergency hatch opening where I will be installing fan, I will make the other patches from the extra material that I cut out. I am thinking about using either 20 ga 304ss or 18 ga mild steel that I would prime before installing. What have people used and liked? I will be installing them with rivets and sealing with dynatron 550.

I will have to buy whatever I go with, the sheet metal that came out of the bus is either spoken for or scrapped.

I've done a few of them now. 18ga or 16ga. Regular mild steel.

[Andre3MC]

I bought some 18ga mild steel and will be installing this weekend, Ill see how it goes.

I wanted to go with 304 but I couldn't find someone locally to give me a small piece.

[Andre3MC]

Should I prime the bare metal roof before putting the patch down and sealing? I am going to clean and prime the steel patch on both sides before it goes up.

[EastCoastCB]

It wouldn't hurt.

[musigenesis]

The directions for the 'tron say to apply to bare steel, but it seems to adhere just peachy to primer or paint also (as well as wood and plastic, for that matter). I'd do it either way based on what was convenient.

I think wearing gloves when applying the stuff is also important. The instructions say to avoid skin contact; I've done a lot with it bare-fingered and while it's not like my ears immediately started bleeding or anything like that, it's possible that it had some negative physical effects on me.

[TheHubbardBus]

Dang... you've been busy!
Check your sealant's TDS (technical data sheet). It should list what materials it stick to. Bare steel may or may not be one.
If the sealant can be used on bare steel, I personally wouldn't prime the mating surfaces. Just prep the metal like you would for paint (degrease / 320 grit). Reason being: a good urethane sealant will adhere better than most spray paints (I'm assuming you're talking spray paint here), and most spray paints will leach solvents for some time that may interfere with both their own adhesion (when not allowed to gas out due to the sealant), as well as the sealant.
For the exterior surface, or the interior not mated, maybe so if you're not going to be painting right away & want to prevent corrosion.

[Andre3MC]

I went ahead and put rusty metal primer and paint on. The surface under the hatch had quite a bit of pitted rust and sealing it back up bare didn’t feel right. I’m going to give them 24 hrs to cure and try sealing it up with the 550.

[Andre3MC]

I got the patch in last night. I did rivets every 1.5” and put sealant on each one before pulling down. Made a huge mess with the dynatron 550 but I am definitely not worried about leaks at least.