Hull blacking: how often, and what it costs
Most steel narrowboats are blacked every two to three years. It is not a licence condition, but leaving it is how a hull thins — and a thin hull is the difference between a boat worth selling and a boat worth scrapping.
Blacking is the bituminous coating on the underwater steel. It is the only thing between the hull and the water, and water wins eventually.
How often
Two to three years is the common interval for standard bitumen. Two-pack epoxy costs considerably more and lasts far longer — five to ten years — which changes the arithmetic if you plan to keep the boat.
Boats that move constantly, or sit in water with more current, tend to need it sooner than a boat that spends the year in a marina.
Why it matters more than it looks
The coating is not cosmetic. Bare steel in water pits, and pitting is measured in millimetres of hull thickness you cannot get back. A survey that finds thin plating is expensive at best and terminal at worst, and it is the first thing a buyer's surveyor looks for.
What is involved
- —The boat comes out of the water, usually into a dry dock or onto a slipway
- —The hull is pressure-washed and prepared
- —Two or more coats go on, with drying time between them
- —Anodes are usually checked and replaced at the same time
It takes days rather than hours, and dry docks book up — particularly in the drier months when everyone else has also remembered. Knowing the date is coming two months out is worth more than knowing it has passed.
Blacking is not a licence condition, so nobody chases you for it. That is exactly why it slips.
Keep a record as you go
CruiseProof logs every mooring with a date and position, counts the days from when you arrived, and produces a cruising log you can send when you are asked for one.
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