Repairing an RV door.

Some RV doors in the '70's were made of cardboard corrugations in place of the polystyrene insulation. Talk about falling apart when wet!

In defense of the original door manufacturer, it did last 30 years, through all kinds of weather, vibration and abuse. One reason for the type of construction and materials used was to keep weight to a minimum. Sure, you can build a new door and make it really strong, but imagine if you built a whole trailer like that, really strong, square and rigid, and HEAVY !!!
But it sounds like you've done an awesome job of repairing that door, and as mentioned, it should outlive the RV. Good job!

TNGW1500SE wrote:
The bottom of mine rotted out. It was soaked inside. The bottom aluminum trim that surrounds the door held water and caused the rot.

I used treated lumber for the frame that I ripped down to 2 x 1 1/2" to save weight. I used stainless screws and glued it up. I filled the inside with 3 layers of 1/2 Styrofoam board that I bought at Home Depot in a 4x8 sheet. It has an aluminum film on both sides of it. They have a pink colored product also but some glues eat it alive. I then glued the three layers together. Then I "great stuff" foamed it all together on the workbench overnight. After the foam was dry I cut off the overflow. I reused the fiberglass exterior panel by sanding off the rotted wood that was glued on the backside of the fiberglass. I glued that onto the new wood and foam board. I covered the inside with a sheet of white plastic from home depot and glued it on with contact adhesive. Then I reused the aluminum that wrapped the door. Looks stock except for the plastic inside. That was made of a underlayment covered in paper. I caulked all the aluminum that ran around the outside of the door. I drilled some drain holes in the bottom channel so water can get out if it gets in. I think it will outlast the RV.

That's one more thing I have to do, caulk around the exterior edge of the aluminum trim and door panel and maybe the deadbolt and doorknob. Not a bad idea to put a couple of drain holes in there.

The bottom of mine rotted out. It was soaked inside. The bottom aluminum trim that surrounds the door held water and caused the rot.

I used treated lumber for the frame that I ripped down to 2 x 1 1/2" to save weight. I used stainless screws and glued it up. I filled the inside with 3 layers of 1/2 Styrofoam board that I bought at Home Depot in a 4x8 sheet. It has an aluminum film on both sides of it. They have a pink colored product also but some glues eat it alive. I then glued the three layers together. Then I "great stuff" foamed it all together on the workbench overnight. After the foam was dry I cut off the overflow. I reused the fiberglass exterior panel by sanding off the rotted wood that was glued on the backside of the fiberglass. I glued that onto the new wood and foam board. I covered the inside with a sheet of white plastic from home depot and glued it on with contact adhesive. Then I reused the aluminum that wrapped the door. Looks stock except for the plastic inside. That was made of a underlayment covered in paper. I caulked all the aluminum that ran around the outside of the door. I drilled some drain holes in the bottom channel so water can get out if it gets in. I think it will outlast the RV.