What is the safest way to remove bottom paint from a boat?

The safest practical method is to remove failing antifouling with a vacuum scraper, then smooth the surface with an orbital sander connected to suitable dust extraction. Leave sound primer and gelcoat intact, collect all debris, and avoid chemical stripping and wet sanding for this approach.

Check the coating and hull

Start with a clean, dry hull. Inspect the waterline, the turn of the bilge, the area around the keel and any patches where paint is lifting. Establish whether loose antifouling covers sound primer, the coating has failed more widely, or there is damage beneath the paint. This determines how far to strip.

There is no need to remove every layer as a matter of course. Sound, compatible paint may need only local scraping and preparation to the new antifouling manufacturer's instructions. Strip thick layers that crack, curl or detach in sheets back to a firm foundation.

• Sound primer: leave it in place wherever possible.
• Rust on an iron keel: treat this as a separate corrosion and primer repair.
• Blisters beneath the gelcoat: arrange an assessment before proceeding with ordinary paint removal. Blisters in the paint alone do not establish osmosis.

These instructions mainly suit conventional antifouling on fibreglass hulls. Timber, steel and aluminium need preparation specific to the substrate. Silicone foul-release coatings require their own removal procedure.

Contain debris and protect yourself

Ask the yard where stripping is permitted and whether it hires out vacuum scrapers and extraction equipment. Lay a tough tarpaulin beneath the working area, extending beyond the hull. Put up screening where wind or nearby boats make spreading debris a risk.

Wear a properly fitted respirator with P3 particulate filters, sealed eye protection, gloves and disposable coveralls. Work only beneath a boat securely supported by the yard. Never move props or cradle pads yourself.

Connect the vacuum scraper and every powered stripping or sanding tool to an extractor suitable for hazardous fine dust. A household vacuum is unsuitable. Check the extractor's specified dust class, filters and bagging arrangements against the coating's safety data sheet and the yard's requirements.

Keep other people away from the work area. Avoid chemical strippers and wet sanding for this method. Strippers introduce chemical handling and contaminated sludge; wet sanding produces contaminated water that must be contained.

Scrape first, then sand lightly

Try a small patch before tackling the whole hull. A vacuum scraper usually removes heavy paint build-up faster than sanding alone, with much less material escaping into the surroundings.