Antifouling FAQs – What, Why, How and When

Whether you’re a seasoned professional, a cautious novice, or somewhere in between, antifouling is a significant part of the maintenance of your boat and something you need to know about.

If you didn’t already know, antifouling is a type of paint that is used to protect your boat’s hull against a variety of marine growth which can affect the performance of your boat along with fuel efficiency.

Despite the persistent snow and ice over the past 8 weeks, we’ll soon be coming out of winter and into boating season again so it’s time to start thinking about preparing your boat.

To help with this, we’ve answered some common questions regarding antifouling to get you ready for another successful season.

Feel free to click on the links below to jump to the question you’re interested in reading an answer to:

1. When should I apply antifouling?
2. How often should I apply antifouling?
3. What antifouling paint should I use?
4. How much antifouling paint do I need?
5. How do I apply antifouling?
6. How do I remove antifouling?

1. When should I apply antifouling?

The optimal time to apply antifouling is in dry weather (accounting for the extra time required for multiple coats and drying times) when it is above 12 degrees.

uk map

In the UK, it can be difficult to get long stretches of dry and warmer weather so you may need to wait for the best time of year, depending on where you store your boat.

If you’re in the Highlands of Scotland, April to October offers the right temperature. For the Lowlands of Scotland, this stretches out to between March and November while the weather in the east and west coasts of England may allow you to start work as early as February, also lasting into November.

It is also worth noting that freshly painted boats release their biocides better so it’s best to antifoul your boat a maximum of 12 weeks before launch.

2. How often should I apply antifouling?

This really depends on the type of antifouling that you use and how often you use your boat throughout the year, along with where you store it. Generally, it’s advised that you apply it once a year though some may last for two years. See question 4 for further information.

3. What antifouling paint should I use?

The type of antifouling paint you use should align with the type of sailing you do so it’s important to pick the right antifouling for you.

gael-force-antifouling

Some antifouling performs better than others in high fouling areas. For example, International Micron Optima, Micron Extra 2 and Interspeed Ultra 2 perform particularly well in these waters.

At the same time, certain types of antifouling are more suitable for a high-speed craft. For example, Cruiser Bright White and Trilux 33, while Micron Extra 2 and Cruiser Uno EU supports speeds up to 25 knots.

International has a wide range of antifouling with Gael Force offering its own brand too.

4. How much antifouling paint do I need?

The amount of antifouling you will need is dependent on the size of your boat and how long you want the antifouling to last.

The practical coverage of antifouling is approximately 9 square metres per litre, though specific brands and types of antifouling may vary.

It would be advised to apply 2-3 coats if you want it to last a single season while 3-4 coats will often last two seasons.

International also has a useful guide to working out how much you need, if you’re still unsure.

5. How do I apply antifouling?

You can apply antifouling with either a large width brush (for quick application) or a roller (takes longer but is less labour intensive).

antifouling-image-2

Before applying antifouling, check for any indication that existing paint is not in good condition. If it’s in poor condition, i.e. antifoul is cracked, peeling or showing signs of detachment – see question 6. If it is in good condition, high-pressure wash it to remove loose antifouling and allow the area to dry.

Next, mask off the area that will be painted, repair any damage, and inspect GRP for gelcoat damage. Check the recommendations on the tin to find out about drying times and overcoating intervals, along with compatibility (using a primer if necessary).

Paint should be mixed thoroughly with a stirring stick to allow any settlement to be mixed in, applying it evenly to the correct thickness.

Multiple coats may be required and it is worth noting that areas with more ‘water turbulence’ such as the waterline, trim tabs, outdrives, keels and rudders may need an extra coat.

6. How do I remove antifouling?

Antifouling should be removed from your boat before applying new antifouling if it is in poor condition.

To remove old antifouling, you can use an antifouling stripper such as International Interstrip which has been specially formulated to remove this paint without causing damage to your boat.

Application of the paint stripper should be with an old brush, applied liberally, according to the application guidelines on the tin. When the appropriate amount of time for the stripper has passed, remove old antifouling with a blunt scraper while it is still soft.

We advise wearing all necessary health and safety equipment such as safety goggles, nitrile rubber gloves and overalls when carrying out this work. Remember to sand and prime the hull before applying fresh antifouling.


The British Coatings Federation (BCF) launched a DIY antifouling initiative in 2017 to “inform and educate boat owners with regard to the hazards associated with antifouling their boats.”

bcf-antifouling-dos-donts

Download their handy leaflet of Do’s and Don’ts for antifouling or visit their website for more information.

N.B. Due to the strict carriage of dangerous goods regulations, Gael Force can only dispatch antifouling to addresses in the UK.

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