I'm in the beginning stages of R/R the floor in the 1973 GTC we just purchased. The predictable spots need attention; one next to the entrance side door; the second is just behind the passenger seat near the front of the cabin. Those spots are rotted through, and have old patching material on top.

What is the thickness of the subfloor?
Any suggestions about the best way to fix these spots?

Thanks.

I need to do the same on mine. Mainly in the front area. I think it's caused by the windows leaking. I seem to remember there being multiple layers. Been a while since I looked at it. And I still need to pull the windows out and reseal them.

_________________
Nick Taylor - Green & White 1974 Hall GTC.
www.NicksGarage.com == www.HallGTC.com == www.NicksTeardrop.com

I'll check the subfloor construction when I get back to it next week. Thanks Nick.
I'm hoping I can remove just what's bad and cut new pieces for it. I also need to determine if the subfloor goes under the inside wall or just up to it.

This is the spot I'm focusing on.

We measured and cut the bad portion of the subfloor, It's 1/4 inch plywood. Once we removed it, what was revealed is is a closed-cell, rigid foam board insulation. We carefully removed it so we can reinstall it later. What is revealed is more rotted wood just under the outer shell of the body. This appears to be a one inch spacer with bolts inserted through the fiberglass shell lip, through the space board with a nut visible from the outside bottom of the coach.

To expose the edge of the subfloor, and to inspect related damage, we removed the lower wall panels. I was not a surprise to find water damage and mold in the wall insulation. It will be easy to cut out the bad insulation and use a new spray-in foam to re-insulate. We will do this after the floor is replaced.

After removing the foam insulation, we worked on removing the rotten spacer 1 x 2

After removing the spacer (see above) we could see the bolts that held it in place. Several are in bad condition / rusted, and we will need to use an angle grinder to remove them. The metal vertical structure in this photo is is part of the main frame, and it is solid.

After sweeping most of the dirt up, we could see the bolts that hold the subfloor in place, and how the 1" spacer will run the full length of this wall, just under the exposed fiberglass lip. The metal under the floor appears to be stainless (?) and is thin (about 1/8"; we believe this simply functions to prevent road dirt from hitting the bottom of the floor but does not appear to be structural. Some patching or sealing will be needed. We will use the angle grinder to cut off the bolts and replace them with stainless bolts.

Options for finishing the subfloor - after removing and cleaning the bad areas:
1. Re-install the blue closed cell insulation panels; then cover with 1/4" plywood to match with the original subfloor.

2. Or... simply install 1' material without the insulation, to bring it up to level with the original subfloor. With this approach, you can use self-tapping screws to fasten the new subfloor to the frame. Of course you will need to consider the implications of not having the insulation in the floor. Our area is relatively small, and our climate is not too extreme during the use seasons. You might also use a wood planer to clean up the material so it is level and flush.

You might consider other options, depending on your local conditions and preferences. These are the two options we considered. The challenge with option #1 is the challenge to secure the whole thing adequately, meaning you will need to line up the bolt holes in order to be sure the subfloor is securely attached to the bottom frame.

We decided to complete the subfloor repairs using option 2 (see prior post). Pilot holes were aligned with the bolt/screw locations in the remaining original floor. Then countersinks were added before driving the self-tapping screws/bolts into the frame below. Worked great.

After option 2 was finished, we decided to paint the old floor with a strong primer... used a Zinzer product. This is giving a cleaner surface and will seal out any old odors... these were not bad but noticeable.

The floor is finished, and we are ready to reinstall the threshold, wall panels and table.

Thanks for posting all the great photos and details. I fear this is what I'm headed for on mine one day.

Nick.

_________________
Nick Taylor - Green & White 1974 Hall GTC.
www.NicksGarage.com == www.HallGTC.com == www.NicksTeardrop.com

Glad to post our experiences with this project Nick. Working with the wall is a bit awkward, and we used new screws to refasten everything. The floor was easier to remove than we expected, but fitting the new material at the front behind the passenger seat can be tricky. Try making a cardboard template first. Once that’s done the rest goes easier. Have “fun”!

Niiice. Do you have an instagram? I'd love to follow. We had to repair damaged cabin floor. We changed the flooring too for the rest. Luckily it had minimal to none damage. We went with cork flooring.

I don’t use Instagram but try to keep our projects posed regularly in the GTC Forum. Thanks for the compliment. I like your cork option for your floor.


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