Under the floor of my boat – Part One

Location: my boat

Now, unless you buy a sailaway there is very little chance that you will have seen under the floor of your boat unless there has been a problem. Now I was in that fortunate position until I started to feel that the floor was moving.

For those of you who don’t know the story of my boat, my boat layout when I brought the boat was; nose, well deck, living room, kitchen, bathroom, bedroom, stairs to back deck over engine, back deck. In the bathroom there was a bath and a sink. When I took out the bath I found that it had been leaking. Goodness knows how long for. The pipework under the sink was leaking as well. So I mopped up any water that was left and I left everything open to dry.

Months later I started to notice that the bulkheads (boaty term for walls) were sinking a bit so I propped them up. Thinking nothing of it as the bulkheads had cupboards at the top of them which now had stuff in them. I thought that it was normal. Over a year later the floor started to bounce when walked upon. This I knew was not normal. One day when I had the time my boss and I took up the floor to find that it was quite rotten and we had a look under the floor. A stroke of good fortune was that although the floor was rotten the steel that made up the base plate was not rusty.

Luckily for me our friend Cliff had given me a few large sheets of marine plywood to get it out of his garage. This is going to be perfect for the floor. Having the floor up does give me a chance to re-arrange the ballast (weights under the floor to help balance the boat, mine is concrete blocks, other people use steel blocks or shingle) under the floor in my boat, in my boat layout all the cupboards are on one side and the walkway is along the other side of the boat. This means that all the stored weight is on one side of the boat. If I take the ballast out from that side then the boat will sit a little straighter in the water (silver linings).

Under the floor of my boat
As you can see there are metal joists running along under the floor

The underfloor of the boat is not smooth, there are metal joists running along it, presumably to prop up the floor on the boat. I suppose it also separates the various areas so that there is a chance that if there is a leak that it will fill less of the boat making it easier to clean up.

Now under the floor is also cooler as it is closer to the water. It would be the perfect place for a wine cellar (if I liked wine, which I don’t). Adding some insulation would probably make the boat warmer, but would make the floor less level with the bit in the front (living room and kitchen areas) and I don’t want to end up tripping over the floor repeatedly when walking from one end of the boat to the other.

At least the floor is not rusty. That means that the hull of my boat has not been compromised and she will not need a lot of expensive work done on her to give her new bottom plates. As they are new steel they get very expensive very quickly. I remember talking to someone on the towpath when I was still looking to buy a boat and they told me that it had cost them ยฃ7000 to re-plate the bottom of their boat. I do not want that to happen to me.

A load of ballast under the floor of my boat
Here is the concrete ballast under the walkway

Taking up the floor you end up with bags and bags of rotten timber, you wonder how it all fitted in the boat in the first place. I have to make sure that everything is cleaned out so I am not left with rotting timber in my boat anymore so it will not contaminate the new stuff.

To be on the safe side I am considering painting the bottom of the boat with rust eating paint and then blackjack to make sure that it is totally in good condition and protected if anything else should happen. The rust eating paint will stop any rusting and cure any tiny rust spots there are and the blackjack will cut off any oxygen so that it cannot rust anymore. I don’t want to end up with a leak for the lack of a ha’penny of tar.

Once I have painted and tarred the bottom of my boat my boss and I will put some treated timber above the metal joists to make the floor level. Then we will put on some marine ply timber to make the floor. He will put it down in pieces so that if I ever need to take up any of the floor again it will be easier (he is a good boss). Once I have taken up the lino I can then unscrew it piece by piece. Above that we will put the lino back down so that it looks all nice again.

This morning my boss surprised me with 8 lengths of 2×2 treated timber on his roof rack and a very large tin of blackjack. Carry on reading next week to find out how we finished building the floor back up and making it look as good as new again. To be continued inย Part Two.


  1. Vicky Quinlan November 17, 2018
    • Fiona nb Rosey November 18, 2018
  2. Brian November 23, 2018
    • Fiona nb Rosey November 23, 2018
  3. frolep rotrem May 18, 2020

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