How Many Coats Are on That Bottom, and What Removing Them Costs
Thirty years of antifouling is a structural layer in its own right, and one day somebody pays to take it off.
By Boatmere Brokerage Desk · Updated · 6 min read
Nobody asks about bottom paint history and it is one of the more predictable four-figure surprises in boat ownership.
Every haul-out, a yard scuffs the old antifouling and rolls on two fresh coats. Do that annually for twenty years and the bottom is carrying something like forty coats. At some point that layer starts failing under its own weight, and the next paint job becomes a removal job.
How much does it cost to remove boat bottom paint?
Soda or media blasting is the standard route on fibreglass, at roughly $40 to $75 per foot in 2026.
| Boat | Blast | Fair and barrier | Repaint | Total |
|---|---|---|---|---|
| 28 ft | $1,100 to $2,100 | $1,500 to $3,000 | $900 to $1,600 | $3,500 to $6,700 |
| 40 ft | $1,600 to $3,000 | $2,500 to $5,000 | $1,400 to $2,400 | $5,500 to $10,400 |
| 55 ft | $2,200 to $4,100 | $4,000 to $8,000 | $2,000 to $3,500 | $8,200 to $15,600 |
The blast itself is the cheap part. What lands afterwards is the fairing, any blister repair the strip reveals, and the barrier coat that a sensible owner applies while the hull is bare.
That is the real reason this job gets deferred. You go in expecting a $2,000 blast and the yard finds forty years of history underneath.
Why paint eventually has to come off
Antifouling is designed to erode or leach, not to be permanent. Layers build unevenly, thicker at the waterline and around fittings, and the deep stack starts to crack. Once it cracks it flakes, and once it flakes new paint has nothing sound to bond to.
You can see it coming. Look for a bottom that feels like tree bark rather than paint, edges where you can count the strata like sediment, and patches where the layer has sheeted off to reveal a completely different colour underneath.
There is also a weight argument that people overstate. Forty coats on a 40-footer is real weight, tens of kilos, but you would not spend eight thousand dollars for that alone.
What to ask before you buy
Get the last three haul-out invoices. They are usually easy for a seller to produce and they tell you:
- What paint was applied, and whether anyone kept to one system. Mixing incompatible antifoulings is a common cause of premature failure.
- How often. Annual repainting in a warm climate is normal. Annual repainting for fifteen years with no strip is a countdown.
- Whether the hull has ever been stripped to gelcoat, and when.
Then look yourself at the haul-out. Along the waterline, around the transducers and at the leading edge of the keel are where build-up shows first.
The bit worth planning
If a strip is coming, do it in the same haul-out as everything else.
You have the boat out, the pressure washer running and the yard already billing you for a lift. Adding anodes, seacocks, cutless bearings and a transducer swap to a bottom job costs a fraction of what those jobs cost individually, because the expensive part is the lift and the stands, not the parts.
This is the single most useful habit an owner can adopt, and it applies far beyond bottom paint: batch yard work, then leave the boat alone for three years.
Frequently asked questions
- How much does it cost to remove boat bottom paint?
- Soda or media blasting runs roughly $40 to $75 per foot in 2026, so $1,600 to $3,000 on a 40-footer, before fairing and repainting. Chemical stripping is cheaper per foot but far more labour and rarely quicker in practice.
- How many coats of antifouling can a hull take?
- There is no fixed limit, but most yards start recommending removal somewhere between fifteen and twenty-five accumulated coats. The tell is cracking and flaking rather than the count, because failing paint takes new paint off with it.
- What is soda blasting and why is it used on boats?
- Blasting with sodium bicarbonate, which is soft enough to strip paint without cutting into gelcoat the way sand or grit would. It is the standard method for fibreglass hulls precisely because it removes coating and stops.
- Should I ask about bottom paint history before buying?
- Yes, and ask for the last three haul-out invoices. They show what was applied, how often, and whether anyone has ever stripped back to gelcoat. A hull that has been repainted annually for twenty years with no strip is carrying a bill you will inherit.
