That floor looks pretty good compared to others I have seen. No rot through and it looks like mainly surface rust.

I did the same with my floors (which were in good shape) but removed any loose rust and as much as the black sound deadening material as I could, then treated all with POR-15. The seam between the floor and the side rocker panel is usually the worst spot as the water collects there. I found and plugged any spots where there was water ingress. The culprit was where the steering column went through the firewall. The original foam piece to stop water ingress had rotted away - so I replaced that with a heavy density foam piece that was caulked into place (there is a spring that holds it in position).

There are large plastic plugs that cover holes that run alongside the inside rocker - you can remove them and shine a light inside to check the condition of the rocker from the inside. I sprayed a runny wax based rust inhibtor through these holes (the runny waxy material coats the inside but does not plug drain holes).

Others on this board say the jute felt under the rubber floor mat can turn the sitting water into a weak acid (thereby making the rust problem worse) - so remove what is left of it. I used an asphalt roofing, peel and stick roll-out material (Snow and Ice I think it is called) to lay down over the floors. It is a poor-man's sound deadening material and I put down a couple of layers.

Check the outside underneath the floors for rust. Inspect the black underside protection coat volvo put on at the factory. This stuff is amazingly durable, but can crack and rust can form underneath (water is caught between it and the metal) so check for cracks and flakes.

Put on some music while doing this and enjoy quality time with your volvo, restoring her to her original glory.

waggin

1965 220 wagon
1985 245 turbo wagon