Fence Paint Calculator

Fence paint or stain coverage depends on the product and the condition of the timber. Most fence paints cover 4 to 6 m² per litre on rough-sawn timber, which absorbs more, and 8 to 10 m² per litre on smooth or previously painted wood. Water-based fence paints dry in 1 to 2 hours, while solvent-based treatments take 4 to 6. Two coats are the sensible default on bare or weathered timber, and one is usually enough for maintenance.

The calculator measures total fence area as panel height multiplied by the total run length multiplied by the number of painted sides, which is usually one or two. Closeboard and overlap panels carry more surface than their outline suggests, because the overlapping boards add area, so 15 to 20% goes on to cover it. Posts and gravel boards are counted as additional area. Enter the dimensions, the sides and the number of coats and you get the area, the litres and the tin sizes, since most UK fence paints come in 5 L and 9 L tins.

A worked figure makes the scale clear. A run of 12m at 1.8m high, painted on 2 sides, is 43.2 m², and 2 coats means covering 86.4 m². At 9 m² per litre that needs 9.6 L of paint. Larger tins are better value, with 5L own-brand tins at £25 to £50 and branded ones at £30 to £60. Ronseal Fence Life Plus sells at £25 to £35 for 5L, Cuprinol Garden Shades at £20 to £30 for 2.5L, and Sadolin Superdec at £40 to £60 for 5L.

Choosing the base type sets the repainting cycle. Water-based products are easy to clean up after, low in odour and breathable, and last 7 to 10 years. Solvent-based stains penetrate more deeply and last 10 to 15 years, at the cost of a strong smell. Oil-based finishes are the traditional option and repel water best, on a 5 to 8 year cycle. Decorative coloured stains from Cuprinol and Sadolin come in a wide colour choice and are semi-transparent, while solid colour fence paint is opaque and hides imperfections. Check the product is specified for sheds and fences, as garden furniture stains are often a different formulation.

Weather is the constraint that catches people out. You want dry, warm conditions between 10 and 25°C with no rain forecast for 24 to 48 hours, which in practice means April to May or early September. Hot direct sun makes the paint dry too fast, freezing temperatures ruin adhesion and wet timber will not bond at all. New timber needs 4 to 6 months for its moisture to escape before it takes a coating. After that, expect to repaint every 3 to 5 years with water-based products and every 5 to 7 with a premium solvent-based one.

Preparation is short but not optional. Brush off dirt, moss and algae, treat any mould with a specialist cleaner such as Cuprinol Mould Remover, and sand smooth where the fence has been painted before. A brush suits textured surfaces, a roller is faster on smooth panels, and an HVLP sprayer is fastest of all but messy, so cover the planting first. Two thin coats beat one thick one, and allow 2 to 4 hours between them. A 30m² fence painted on both sides takes one person 3 to 5 hours plus drying time.

Cheap paint is rarely cheap over the life of a fence. Budget paint at £20 for 5L lasts 3 to 5 years, while premium at £50 to £60 for 5L lasts 7 to 10. Over 20 years on a 12m fence that is roughly £100 in materials across 5 repaints, each taking 3 hours, against £180 across 3 repaints, so 15 hours of work against 9. The premium option usually wins on both lifetime cost and labour. Ronseal Fence Life Plus, Cuprinol Ducksback with its 5 year guarantee, and Sadolin Superdec with 10 years on suitable timber are the names to look for.