Would like to replace ply floor in Caravan

I just GOOGLED your question......lots of hits but try here.

.http://www.1carpc.co.uk/wcdr/delamination.htm

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I to have a 78 Viscount, firstly have you stripped the lino off the floor? I would need to craw under mine to check it out before giving more advice and sorry will not be able to do that today.

Hi My First Caravan,
My 82 Viscount had similar problems and I spent some time working it all out.
The floor is the first thing to go onto the frame when building the van, everything else is fixed on top of the floor, so I checked whether a false floor(12mm waterproof ply would fit under the cupboard doors when open.
It did, so this is what I did to solve my problem.

On my van I removed the worn vinyl floor covering from as much floor as possible, (cut it aIong the cupboard fronts etc) and glued the cut to fit 12mm ply false floor on top of all the existing floorspace, then replaced the old vinyl with new stuff.
It lowered the beds by 12mm and I had to adjust the table leg by 12mm (cut off) to keep the table level

In regard to the spongy bit at the door, you may well find that the sheetmetal used to create the dropdown step has rusted out in places, allowing the thin ply to sag as you step on it.

I fixed mine by making up an angle iron support to go under the rusty sheetmetal and bolted it to the chassis either side of the stapdown. I also replaced the thin (4mm) ply with something a bit thicker(12mm waterproof) and then replaced the vinyl floor covering.

Hope this helps you sort it out.

Disco.

I replaced (recovered would be a better word) the floor of my Viscount Ultra Light some 3 years ago and have never looked back. Like Disco Driver I removed all of the old lino (except under cupboards) even removing the bed to get at that lino. It is a big job if it is stuck down like mine BUT it is well worth it as it exposes your floor for a better assessment of it's condition. I then glued and screwed a new underlay floor down. Make sure your floor is spotlessly clean and free of any imperfections if you do it this way. This underlay tended to brace the floor nicely and then I had new lino glued down throughout the van (cutting around the cupboards).
My door step was a bit spongy and grotty so I had some aluminium chequer plate (about 5mm thick) cut for the bottom and 3 sides of the entry step, glued and screwed it in, looks smick and hasn't moved.
hope this helps.