No one likes to antifoul their yacht, but keeping a boat free of the harmful growth is vital. Adam Fiander shares how to get it right

How to antifoul your boat

No one likes the annual effort and cost of antifouling, but keeping the underside of a yacht free of the unsightly, costly and potentially harmful effects of aquatic fouling has challenged and vexed owners for decades.

Apart from a few exceptions where water is at its coldest, almost no matter where you keep your yacht in the UK, sailors are faced with some of the harshest and most virulent underwater fouling in Europe.

Green and brown seaweed, slime, kelp, sponges, sea squirts, worm casings, barnacles and mussels are vying to take hold and build an entirely natural but unwanted community on your hull and appendages.

This incurs lacklustre sailing performance, unresponsive handling and increased fuel burn.

Protective equipment is vital during the application of antifoul

Protective equipment is vital during the application of antifoul. Credit: Graham Snook

But it’s not just about keeping the hull and propeller clean.

If the risk of transferring harmful non-native species from one region to another wasn’t a good motive, then the fact that health and safety authorities are currently reviewing antifoul product approvals should be.

Since the Biocidal Products Regulation (528/2012) was introduced in 2012, European antifoul paint manufacturers have worked hard to maintain performance from a reduced list of approved active substances they can now use.

Some products have remained unchanged, others have been dropped from product lines completely, and others have received some ‘tweaking’.

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Correct procedures to protect the environment and personal safety risks to applying these paints are being considered at the same time.

If the process of applying those highly effective pesticides is not given approval for continued DIY use, then applying antifoul as a ‘professional-only’ application may become a reality.

Being seen to adequately protect yourself, the environment and those around you in the coming months is key.

The British Coatings Federation, trade body for the coatings industry, set up the Protect, Collect, Dispose campaign ( to educate boat owners in the correct procedures to follow, which, happily, will also help your new layer of antifoul adhere better and last longer.

Different antifoul types

The type of antifouling product to use depends upon your hull material, where you use your boat, how much money you want to spend on it and how often you plan to maintain the underwater coating.

By far the most common choice of DIY-applied paints are normally either a hard (self-polishing), or erodible (ablative) type.

Applied by either roller or brush, these types contain sufficient active ingredients – organic and non-organic compounds such as copper, zinc and booster biocides suspended in a resin or a solvent-based formulation that will last for one, possibly two, or even up to three seasons’ protection, depending upon boat use, quality, type and whether enough coats have been applied correctly to the required film-thickness.

Hi-tech solutions

Other ideas known to work well either as stand-alone solutions, or when used in conjunction with ‘traditional’ types, are sonic transducers that emit specific frequencies that prevent fouling from attaching.

Adam Fiander

Having sailed since the early 1990s, Adam Fiander cruised and raced a variety of yachts. He has years of experience working with antifoul products and produced the video for the BCF’s Safe Antifouling Initiative.

More well-known are long- term, copper-rich, durable solutions that have more lengthy application procedures, but offer up to 10 or more years’ protection, though these need to be applied under very controlled conditions and are normally professionally done.

Also having emerged in the last few years, vinyl-wrap coverings rely upon the slipperiness of the vinyl and can be easily peeled at the end of their life, though this raises questions about the use of disposable plastics.

Other coatings containing silicone, Teflon and PTFE are available, as are coatings using nanotechnology, but these are more geared towards high-end racing boats.

The science behind antifouling is changing all the time.

As copper is the predominant force in the majority of coatings, it’s important to check compatibility with the hull substrate you intend to antifoul.

Aluminium hulls, for example, require a different copper formulation to that found in the majority of copper-based antifouls.

Most existing coatings can be overcoated, but there are exceptions to this rule and those exceptions must be respected.

If you’ve recently bought a brokerage yacht, for example, and don’t know the make or type of the existing coating you have on, then a full barrier/primer coat is your best option.

Or if you want to be totally sure, full removal of the existing coating will give you that complete peace of mind.

How much antifouling paint will you need?

There’s nothing worse than realising two-thirds of the way in that you don’t have enough antifoul to finish the job.

Antifouls generally have a coverage-rate- per-litre on the label or technical data sheet, brochure or website.

Once you’ve established the surface area of your hull, keel and rudder combined, divide this number by the coverage rate for the product you have chosen, giving you the number of litres required per coat.

Some manufacturers offer a simple formula for you to work amounts out easily per each product based upon boat keel type.

For Yachting Monthly‘s editor Theo Stocker’s 29ft Sadler, we used 4.5 litres of antifoul for two good coats, which suggests that some manufacturers’ tables are a little too cautious in their estimates.

In any event, don’t forget to factor in some extra paint to cover areas such as where the supporting props have been.

And if you spill some paint, you’ll want to have enough to compensate.

Paint quality formula

Surface area = Waterline Length x(Beam + Underwater Depth) x 0.50 (fin keel) or x 0.75 (long keel) Total litres required = Total surface area (m2) ÷ Coverage rate of paint (m2/lt)

Before you start of antifoul

A man in PPE preparing to antifoul his yacht

Choose a still, dry day to apply the antifoul. Credit: Graham Snook

Antifouling contains biocides, so wearing personal protective equipment (PPE) is more than just a formality and it should be worn until the final clean-up procedure is complete.

You’ll need coveralls, eye- protection, a mask, a hat or hood, sturdy work boots and appropriate disposable gloves or sturdy reusable gloves.

Most antifouls contain solvents, so if you are working in a boatshed, ventilate the area as much as possible, take regular fresh-air breaks and use a respirator facemask with cartridge filters, as opposed to paper dust masks, which are fairly ineffective.

Even if you are working outside,a respirator mask with filters is still preferable.

Keep pets and children out of the working area and ensure you don’t eat or drink during the process.

Make sure you read and understand the paint labelling, data sheets and product information before starting.

Follow manufacturers guidelines and observe local health & safety recommendations.

You should antifoul outdoors in a safe and secure location and not in a busy or public place, such as a car park.

Locate your boat on a hard-standing, impermeable surface and use a suitable tarpaulin or cover to capture any washings or scrapings.

Weight the tarpaulin down, to avoid tripping up and so it doesn’t blow around in the wind.

Choose a dry day, not too cold or frosty and with as little wind as possible.

Avoid very early mornings or early evening when damp air, dew and condensation might be around.

Upon haul-out take some pictures to compare how your new paint works over the season, then get the hull pressure washed over a bunded catchment area to prevent antifouling entering the sea or ground water.

Surface preparation

The key to antifoul that lasts is ensuring the surface beneath is properly prepared

1. Wash off

A man pressure washing the hull of a boat ahead of antifouling

Pressure washing is effective but causes a lot of contamination run-off, which needs to be captured. Credit: Theo Stocker

Pressure washing is the easiest way to get the hull clean.

This should be done on a bunded wash-off area, where contaminated water will be collected and stored in a holding tank rather than running back into the sea.

If this isn’t possible, portable bunding is available, or use a tarpaulin to capture removed fouling and paint particles.

2. Scraping

A person scrapping old antifoul from a yacht ahead of a new coat of paint

Credit: Graham Snook

Loose or flaking antifoul and small blisters can be scraped.

For removing several layers of old antifouling, gelcoat- friendly chemical removers are useful, as is professional soda-blasting, but never use a blow lamp or heat gun.

If using a scraper, round off the corners to avoid gouging.

3. Keying the surface

A MAN In PPE sandpapering the hull of a yacht

Credit: Graham Snook

Lightly wet-sanding the surface with 60 or 80 grit wet-and-dry paper wrapped over a sanding block will provide a key and help the antifoul to adhere well.

Dry-sanding is not recommended because of the dust it puts in the air which can be inhaled, or get onto other boats’ hulls and decks.

Scrub the waterline and then rinse the hull thoroughly with fresh water.

4. Hull fittings

A anode on the bottom of a yacht

Credit: Graham Snook

Protect anodes and skin fittings, exhaust outlets, heater vents and other fittings by wrapping with aluminum foil or taping over and sealing off.

If your anode is due to be replaced, this could be a good time to remove it, but protect the studs from paint.

5. Masking off 

A man masking off the side of a yacht ahead of applying antifoul

Credit: Graham Snook

Proceed by masking off the waterline, press the tape down hard to prevent paint or rainwater ingress and ensure a clear masked space around stern gear.

Avoid domestic decorating tape which will leave residue and invest in a good quality, waterproof masking tape – the blue kind will last outside for several weeks if necessary.

6. Patch prime

Patch priming during antifouling

Credit: Graham Snook

When you’ve finished rubbing back, bare patches can be ‘patch-primed’ with a suitable primer or barrier coat.


A man in PPE applying antifoul to the hull of a yacht

Credit: Graham Snook

A slap-dash approach simply won’t do it – it’s all in the preparation

1. Paint preparation 

Use an old towel to prevent splashback when opening a tin of antifoul

Credit: Graham Snook

Ensure the antifoul is kept at room temperature so it flows and mixes well, (store in your car, or boatshed with the lids on).

Standing a tin in a bucket of warm water beforehand will do the same job.

Cover the tin completely with an old towel and open the lid carefully to prevent splashbacks from pressure build-up.

2. Stir and pour 

Stir your antifoul pain before application

Credit: Graham Snook

Stir well as the contents, particularly the active ingredients and heavy metal particles, settle and it’s important to achieve a homogenous coating.

Pour into a roller paint tray, or a sturdy paint pot and always re-secure the lid of the tin as solvents will evaporate quickly.

3. Choose your roller carefully 

A roller

Credit: Graham Snook

To ensure a suitably thick coating is applied, use a medium-pile simulated mohair or sheepskin roller, which will avoid slipping across the hull.

Foam rollers disintegrate more quickly, and can slip, causing patches of thin paint.

Don’t spray antifouling paints from a gun – this practice is best left to professionals inside a shed.

If you need a break, cover the roller in cling film to stop it drying out

4. Film thickness 

Use a wet film thickness gauge to test antifoul film thickness

Credit: Graham Snook

Load the roller or brush generously and use a small brush where you need a higher degree of accuracy, such as on the waterline.

Try and achieve a minimum dry film- thickness per coat of no less than 60 microns (approx. 120 to 150 microns wet).

Use a Wet Film Thickness Gauge to measure by placing one edge flat on the wet antifoul.

A natural-fibre roller should give roughly the right thickness.

5. Second coat

It is a good idea to apply a second coat of antifoul

Credit: Graham Snook

For the second and successive coats, follow the same procedures as before and observe the correct drying interval times between coats, and the safe-to-relaunch period indicated on the tin.

Make sure you apply extra coverage where friction is greater, such as at the bow and the leading edge of your keel and rudder or skeg, and just beneath the waterline

6. Get the masking off

Peel of the masking when the paint is still tacky when antifouling

Credit: Graham Snook

While the paint still feels tacky, peel back the masking tape for a sharp line that doesn’t stand proud.

Remove the temporary coverings over the anode and skin fittings, and congratulate yourself on a job well done.

Once it’s dry you can mask up again to refresh the boat top if it needs it.

Correct antifoul clean-up

Dispose of antifouling chemicals carefully

Any large spillages should be contained and collected with non-combustible absorbent materials such as sand or earth and disposed of properly as hazardous waste.

All PPE, apart from goggles, should be disposed of in appropriate hazardous waste collection bins.

Contaminated water after antifouling

Contaminated water needs to be poured into a bunded drain. Credit: Graham Snook

Scrapings from your tarpaulin can be emptied into an old tin and disposed of likewise.

Dirty water from washing down the hull should be disposed of in bunded catchment drains.

Please don’t casually discard this in a hedgerow or scatter it across the boatyard as the biocides will leach into the groundwater.

Two men carrying tarp out from underneath a yacht

Waste material is gathered up and put into hazardous waste. Credit: Graham Snook

Don’t take any contaminated equipment, half-used tins of paint or soiled PPE off-site.

In particular, don’t retain these in your car and then drive off because the paint and solvent fumes may impair your ability to drive safely, or will at least give you a thumping headache by the time you get home!

The results

After a season in the water, this coat of antifoul on the editor’s boat had lasted much better than the previous year’s application.

Granted, she had sailed fewer miles, but there were no patches of undercoat showing through on the keel, no rust bubbling up on the keel, and no more than a thin slime on the hull, with no serious weed, barnacles or algae.

A boat which had been freshly antifoul painted

Freshly painted, the antifoul looked smart. After a season in the water, there was some slime but no significant growth. Credit: Theo Stocker

Theo realised he had missed painting one of the spots where the props had supported the boat before it was dropped in the water, and this was much more coarsely fouled.

The propeller did not fare quite so well and had been colonised by a thin layer of coral worm and weed, despite the silicone-based antifoul, though it did come off with the pressure washer without much complaint.

Painting in other locations

Not everyone will be antifouling in a fully kitted out boatyard.

Those with boats on more basic hard standings, using scrubbing posts, or cleaning off between tides will need to take responsibility for reducing risk to themselves, others around them and the environment.

To prevent toxic paint waste entering the sea, groundwater, or general environment, a full-length tarpaulin is essential, or for clubs where bunded drainage isn’t available, portable bunding – a tarpaulin with edges and a means to collect waste water – is an inexpensive alternative.

Some of the products needed to antifoul your boat

Plan where you will dispose of hazardous waste. Credit: Graham Snook

Clearly signpost the area to keep passers-by from coming close.

A few cones and ‘hazardous area’ protection tape would be a good idea.

Plan beforehand how and where you are going to dispose of your hazardous waste including paint chips, antifoul residue, used paint tins and brushes, either at a nearby marina, or a council recycling centre, though check beforehand which ones accept hazardous waste.

Scrubbing posts

Using scrubbing posts is cheaper than lifting out, but makes it harder to antifoul safely and effectively

Using scrubbing posts is cheaper than lifting out, but makes it harder to antifoul safely and effectively. Credit: Alamy

Many places around the UK still offer scrubbing grids on which you can dry out between tides, either against freestanding posts, or against a harbour wall, although some harbours are considering doing away with this facility because of the difficulty in preventing antifouling run-off from entering the water.

If you are going to use scrubbing posts, here are a few tips to follow:

  • Check the posts are suitable for your boat and at what tidal heights you’ll need to get onto the scrubbing grid. Don’t just use a harbour wall as the base is unlikely to be firm enough to support your boat.
  • As the tide ebbs, make sure the boat leans towards the posts with a line from the masthead to a strong point ashore. Lash the boat firmly to the posts fore and aft, and untie only as the tide reaches the waterline.
  • You can scrub or scrape your hull clean, but pressure washers are not permitted due to the amount of run-off.
  • Use just enough pressure to clean the hull; if the water runs blue beneath the boat, you’re pressing too hard.
  • Use a tarpaulin to catch as much debris as possible. Laying a rope around the edge will catch some of the smaller fragments and sediment.
  • Applying antifoul between tides is not ideal as the hull needs to be completely dry, and the paint needs time to set properly. If you are doing it, doing so over the course of two tides may give you more time, but the performance of your antifoul may be reduced.

Antifoul top tips

  • Don’t forget to patch in where the prop supports were when the boat is in the slings on the way to the water, or ask if the boat can be held in the slings overnight.
  • Use masking tape to seal off where your coveralls leave your wrists exposed – antifoul has a nasty habit of finding its way on to any areas of exposed skin, including face, neck and ears!
  • Take the opportunity to inspect the hull for any obvious signs of wear and treat any serious issues such as osmosis professionally before proceeding.
  • This is also a good time to repair any surface defects. If you have a cast iron keel there may be some surface pitting, which can be filled with epoxy – car body filler epoxy is a good cheap option. Race boats will invest a lot of time ensuring their keels are fared to a perfect, symmetrical aerofoil shape.
  • Use a workmate bench or similar – scrabbling around on the floor opening and stirring tins is uncomfortable and encourages spills and accidents
    to happen.
  • Invest in a proper flat-bladed paint stirrer – a thin screwdriver to stir heavy antifoul paint won’t work well enough.
  • Wrap masking tape across a new paint roller, then remove it to take off loose hairs that would otherwise come off on to your fresh paint film. Allow yourself enough time and avoid rushing the job at all costs.
  • If it is going to rain when antifouling, use the widest blue masking tape to make a gutter. Stick some balls of tape just above the waterline and then stretch the tape across the supports. It will keep the coating below dry while it cures.
  • Keep some dermatological hand- wipes or purpose designed cleansers close by, so that the splashes can be dealt with quickly before they are allowed to dry. Should antifoul encounter skin, wash immediately with warm soapy water and don’t use a solvent or paint thinner.

Teamac Antifouling D Plus

We used a navy-blue, self-polishing antifoul from Teamac called Antifouling D Plus, priced at £89.93 inc VAT for 2.5 litres.

This high copper-oxide product with added co-biocides is for sailing yachts and powerboats up to 30 knots speed.

Two good coats gave us a smooth finish and this should last for between 18 to 24 months reliable fouling protection.

Buy Teamact Antifoulung D Plus from Amazon (UK)

For more information visit: The Green Blue, and the British Coatings Federation

*Yachting Monthly is not paid by manufacturers for our recommendations. If you click through and buy an item, we may receive a small amount of money from the retailer, at no cost to you.*