Ask when it was last taken out of the water, with proof.
The boat should be taken out of the water every 2-3 years. You can do this at a dry dock, by crane or using a slipway trailer (depending on size) to remove the boat from the water. All the essential inspection and maintenance is then done.
This is the time the survey is usually carried out. Of course you need to get a surveyor to check the boat before you commit to anything. But it’s also ideal to have the previous report in order to compare notes.
How thick is the hull?
Absolute minimum thickness for the hull is 4mm. From new, most narrowboats and barges are built with 10mm on the bottom, 6mm on the side and 4mm on the roof.
How many layers of blacking (bitumen) coats have been applied?
Blacking the hull protects it from rust; you need to redo this every 2-3 years when the boat is taken out of the water. Two coats at least. Ideally three.
Alternatively, you can use Two Pack Epoxy paint. It lasts longer (5-6 years), but is the more expensive option because the hull needs to be grit-blasted first, as opposed to just jet washed. In the long run, Epoxy will save you money on taking the boat out of the water for days at a time, so weigh up the pros and cons of this.
Does it have a Boat Safety Certificate?
If your boat has a motor – and it will need to, unless you plan on rowing it up and down the river – then you need one of these. Just like an MOT for your car, it’s down to you to keep the certificate up to date. The Boat Safety Scheme’s site tells you what you need to do and when, and has a list of examiners local to you.
When were the anodes replaced?
Sacrifical Anodes: Lumps of metal with a higher electrochemical value than steel. They corrode faster and so protect the hull. If the anodes are already half gone, you need to replace them to prevent the corrosion of the steel hull. This is one of the most expensive things to put right and could mean re-plating the hull completely.
And now for a cautionary tale…
A guy bought a boat. He was new to river living and so didn’t realise his boat came with a holding tank for the loo, and that it needed to be emptied every two months. Five months passed before he was finally told to take the boat to the pump-out station near a local lock. Pronto.
He pulled the boat up, tied up and undid the holding tank cap. Here, as if in slow motion, he was met with a barrage of pressurised shit, like a dam bursting, which went into his face and knocked him overboard.