Adding underbelly weather protection, is it safe?

I think you’ll be fine just going over it. If it looks questionable to you just replace it before you cover it. Even if it should somehow develop a leak, there is normally nothing under the floor that has a spark. You could also pressure test it before you do anything a check for a leak.
It should be a fun project. Enjoy!

I have a propane gas line running through about 50 feet of my house to the kitchen stove....legally installed as per building code.

Pretty sure it should be ok in your trailer.

profdant139 wrote:
Many manufacturers use coroplast underbellies. It comes in a wide range of thicknesses. I would guess that it is easier to work with than metal.

I have never seen a metal underbelly -- there might be a reason that metal is rarely, if ever, used for that purpose?

I just discovered the coroplast underbelly today. Looks to be easier to install, and covers more area than doing straps of 20" sections. I was only going to use the sheet metal because I have access to it from my job.

Thanks for the suggestion!

Guy Roan wrote:
If it was me, I would never use sheet metal. If any of that comes loose while you are driving down the road at 60 MPH, you'll be in a heap of trouble and have a lot of damage.

Why not redo it like all of the new trailers with the insulation held up by what ever that water proof fabric is (don't know the name) that they use.
Then if you need to get at any of the pipes, you just cut out a piece, pull out the insulation and then replace it and use a patch

Guy

I wasn't sure of the longevity of that fabric. It looks like that is what was used before and someone had cut it away. I will be living in it and traveling full time with my girlfriend full time, going all over the US, Canada, and probably Mexico as well.

This is the first time I have done a project like this, so I appreciate the help.

One of the challenges you will face when replacing the bottom sheeting of choice is putting it on and making it watertight.

From the factory, the frame goes on as the final step prior to the flooring, walls, partitions etc. The floor is upside down when they run wiring, plumbing, insulation etc, and then the bottom membrane.
Then the complete frame is lowered on and fastened to the floor.
Then it gets flipped over onto the wheels for flooring and the rest of it.
This assembly process is general, and varies a bit depending on the manufacturer. I worked at a trailer factory in the early 70s and that's how it was done. The ones I worked on utilized lag bolts to fasten the frame. Most RVs I have repaired use carriage bolts through the floor to the frame outriggers.

So to attempt to replace the sheet metal, coroplast or other membrane, you are faced with cutting it around everything, making it near impossible to seal at the frame and anything hanging down.

It can be done, I have done it but it requires a lot of planning and work to disconnect the frame and jack the trailer up for access.

My 81 Citation had a galvanized steel underbelly.

Many manufacturers use coroplast underbellies. It comes in a wide range of thicknesses. I would guess that it is easier to work with than metal.

I have never seen a metal underbelly -- there might be a reason that metal is rarely, if ever, used for that purpose?

JMO, but the main steel propane line, would not likely be a leak risk, but more likely the area of appliance connections. That being said, the steel pipe for propane line is on the outside of the coroplast cover under my FW. I have the reflectix insulation laying above the coroplast, and another layer of reflectix attached to all floor bottoms. It seems to insulate well, would be easy to install, plus the waterproof benefit.

Jerry

No different than a utility line within the confines of your home.
Not sure why the other guy thinks sheet metal is bad. How it’s worse than plywood or any other rigid sheathing on a trailer?
Both of you are worried about non issues. Provided you’re competent enough to do competent work and can recognize dangers (like a bad gas line that no one else who doesn’t rebuilt their camper would ever see).

If it was me, I would never use sheet metal. If any of that comes loose while you are driving down the road at 60 MPH, you'll be in a heap of trouble and have a lot of damage.

Why not redo it like all of the new trailers with the insulation held up by what ever that water proof fabric is (don't know the name) that they use.
Then if you need to get at any of the pipes, you just cut out a piece, pull out the insulation and then replace it and use a patch

Guy