The Floor – Deconstruction

Most narrowboats have a base of treated 18mm marine plywood laid across the boat’s steel transverse bearers or “ribs” as I like to refer to them. However, we’re all about longevity, sustainability, cost-saving, time-saving, materials reuse and insulation in our rebuild… a tall order!

Firstly, let’s look at why we had to rebuild the floor that Thames Solar Electric built after just 18 months afloat…

The pretty 12mm wood laminate flooring “finish” was glued onto 18mm untreated non-marine plywood sheets. The plywood was supported on 20mm battens positioned using glue and screws into 25mm insulation boards. The underfloor heating pipes were then pinned into the insulation with plastic clips and surrounded by pea shingle. Ryan Collingwood’s idea was that the stones would form a “heat mass” to spread the heat from the underfloor heating pipes. However, to do this the stones would need to be set in resin or concrete, as the air space between them just acted as an insulator, and most of the stones never got warm. Even if they had got warm, it’s unlikely that the heat would be able to penetrate the 30mm of laminated wood above them. It was never going to work, and it didn’t. I’ve also included a picture of the space under the shower tray which had just been filled with sprayfoam, covering waste pipes, heating pipes and a couple of 12v cables with no way of accessing, maintaining or replacing anything.

It was a proper mess.

We lifted the flooring but as it was glued to the plywood it was impossible to salvage it in a reusable state; this went to the local recycling centre. We unscrewed the plywood sheets, which were mostly salvageable if we could remove the glue and sprayfoam – these will be reused later in the build, since plywood is really expensive these days, and from looking up the FSC certification that was terminated shortly after our build completed in September 2021, I’m not convinced it came from well-managed forests after all! We’d better make the most of this precious material!

We carefully bagged up the shingle; avoiding the sawdust and sprayfoam and removing the random screws that had contaminated it, and our fabulous marina used it to fill gaps in the gravel car park. The little plastic clips were carefully removed from the insulation boards and and deposited in the plastic skip at the local recycling centre. The battens, since they were glued to the insulation sheets, were covered in glue and not recoverable, and were taken to the recycling centre. The underfloor heating pipes (and the 500L buffer tank) were drained into containers and the water (along with any additives that had been put in it) was poured down the Elsan ashore, as would happen in a domestic house, avoiding any chemicals entering the river. The pipes (a mix of plastic and aluminium) went to the tip and the buffer tank was collected by a friend who wanted to recover the copper pipes and heat exchanger inside.

The 25mm insulation boards were lifted, cleaned up and salvaged, using aluminium tape to cover the areas where the aluminium cover layer had been pierced with the stones, clips and screws, or torn during removal of the glued battens. Polyurethane is a plastic foam that can’t be recycled, so we wanted to reuse as much of this material as possible.

So, what was underneath?

Extra bricks had been added to the bow third of the boat, and the original, larger, ballast blocks had been completely removed from the stern third, to counterbalance the weight of the batteries. Between the blocks was thick with sprayfoam, muck and sawdust, meaning that any moisture that got down there would be retained in the dust against the metal hull, exacerbating the rust patches. In order support the insulation board at the stern end where there were no ballast blocks, Thames Solar Electric had laid untreated non-marine plywood that was around 16mm thick directly on the steel “ribs”. The rear two sheets of this were completely rotten.

The next blog post will share the process of cleaning up and treating of the floor, my floating floor design, the materials we chose to use and how it all came together; and it should now last the lifetime of the boat!

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