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Bitumen paint for fence posts

Updated: 21 October 2026

You are setting a post or a sleeper, and you want the buried end drier than bare timber in wet soil. Bitumen paint for fence posts is a black film on the end grain, the buried length, and a short band above the soil. It sheds water. It is not a preservative, and it is not creosote. Peter F. used the [Bitumen paint](/hub/flooring-tools-and-accessories/bitumen-paint) listings, Sika's UK sheet, and the HSE creosote decision. No listing here shows an added service life. Brushing is on [how to apply bitumen paint](/hub/flooring-tools-and-accessories/bitumen-paint/sub/bitumen-paint-how-to-apply). Tin size is in the [bitumen paint buying guide](/hub/flooring-tools-and-accessories/bitumen-paint/sub/bitumen-paint-buying-guide).

You are setting a post or a sleeper, and you want the buried end drier than bare timber in wet soil. Bitumen paint for fence posts is a black film on the end grain, the buried length, and a short band above the soil.

Our top picks

Bartoline Bartoline bitumen paint, 2 × 2.5 litre

Best overall

Bartoline Bartoline bitumen paint, 2 × 2.5 litre
6.3/10about £45.36
View offer
Bartoline Bartoline Bitcote 5 litre

Rank 2

Bartoline Bartoline Bitcote 5 litre
8.7/10about £28.50
View offer
Sika Sika Black Jack 901, 2.5 litre

Best value

Sika Sika Black Jack 901, 2.5 litre
7.3/10about £22.14
View offer
On this page
  1. 1.Where fence posts fail
  2. 2.What bitumen paint does on timber
  3. 3.Which tin in this set
  4. 4.Coating the buried end

Where fence posts fail

A timber post usually fails at the soil line and in the end grain, not halfway up the arris rail. Coating only the visible fence and leaving the buried 400 mm bare misses the part that rots. A wood-care note says coat the buried part and about an inch, roughly 25 mm, above finished ground. That band is a rule of thumb from that note, not a measurement we made. If the base is already soft, replace the post, then coat the new one before it goes in the hole. One United Kingdom review of Sika Black Jack 901 describes painting 56 posts and calling it a messy day. A Bartoline review compared the smell on buried wood with creosote. The smell is the solvent, not a biocide. Coat the timber on the ground.

What bitumen paint does on timber

The film is a water-shedding barrier. On porous wood, Sika's UK sheet gives about 4–6 m² per litre per coat, against about 11 m² on a non-porous surface. End grain is the thirsty end of that range. The paint is not authorised as a GB biocidal wood preservative. A seller who writes "years of extra durability", as Clarke Fencing does when selling Black Jack for posts, is making their own claim. A forum comment that treated sleepers still rotted in about six years is one garden, not a typical life. A fencer's habit of gravel under the post, so the end is not in a sump, is practice, not a trial. If the hole is clay that holds water, a black film is only half the job.
Bartoline Bartoline bitumen paint, 2 × 2.5 litre

Testsieger

Bartoline Bartoline bitumen paint, 2 × 2.5 litre
6.3/10about £45.36
View offer

Which tin in this set

Bartoline Bitcote, 5 litres, was £28.50 on 19 October 2026, £5.70 a litre. Six United Kingdom texts include a shed and buried wood. Sika Black Jack 901, 2.5 litres, was £22.14, about £8.86 a litre. Posts, sleepers, and end grain dominate the first 50 United Kingdom texts. Use the sheet's 4–6 m² per litre on porous wood, per coat, because the Amazon coverage field is 12.5 with no unit. The twin pack is dearer per litre and does not state two coats. The single 5 litre Bitcote tin is the top pick on best bitumen paint when price per litre matters.

Coating the buried end

Cut the post to length first, so the end grain you seal is the end that will sit in the hole. Stir the tin. Brush the bottom, the faces that will be buried, and about 25 mm above where the soil will finish. Work the first coat into the end grain. Let it dry before the post goes into damp soil. A post dropped into a wet hole the same afternoon has not had a second coat. If the visible fence should stay a timber colour, stop the black band just above the soil, because bitumen can bleed through emulsion and gloss. Gloves and an old brush match the reviews. The paint will not reverse rot in a soft base.

Common questions

Do I coat the whole post or only the buried end?
Coat the buried length, the end grain, and about 25 mm above the soil, which is the band in the wood-care note used here. Coating the whole post black makes a later coloured paint risky, because bitumen can bleed through. Leave the visible rails alone if you want a timber finish. Paint the post while it is still out of the hole.
How many coats on end grain?
Two. Bartoline states a minimum of two, the second at right angles, after a 4–8 hour touch-dry. Sika's UK sheet also says two coats and do not thin, even though the 2.5 litre Amazon bullets omit the coat count. End grain is the thirsty face. Let the first coat dry before the post goes into damp soil.
Will it stop the post rotting?
It sheds water at the soil line. It does not promise a rot-free post, and these listings contain no trial that adds a number of years. One comment about sleepers failing in about six years is that garden, not a typical life. A soft post needs replacing. Gravel under the post is common practice from fencers, not a test result.
Is it a replacement for creosote?
No. Creosote is a separate biocide. From 1 April 2026 the HSE limits its renewal to professional uses such as railway sleepers, transmission poles, and safety-critical fencing. A garden post is not that list. Bitumen paint is a solvent-based coating, even if the smell reminds a reviewer of creosote.
Which tin in this set names timber?
Bartoline Bitcote names timber, and the 5 litre listing also states two coats and 9–13 m² per litre. Sika Black Jack 901 names wood, and UK reviewers use it on posts and sleepers, though the Amazon coverage field has no unit. The twin Bartoline pack names timber at a higher price per litre. Bird Brand's bullets do not name timber. Everbuild's bullets do not either.
Should I coat sleepers for a raised bed the same way?
Coat the faces that will touch soil, and the cut ends, with two coats, before you build the bed. Sika reviewers mention sleepers and planters. The film sheds water. It is not a preservative, and it is not a drinking-water approval. Do not use these tins to line a water butt. A vegetable bed is timber against soil, not a cistern.

Related pages

Bitumen paint or a roof coating

Bitumen paint

Best bitumen paint: the 5 litre and 2.5 litre tins

Bitumen paint buying guide: coverage and tin sizes

How to apply bitumen paint: two coats and a solvent

Sources

Public UK sources and the amazon.co.uk listing lines saved on 19 October 2026. No laboratory test.

  1. Bartoline Bitcote technical data sheet (retrieved 19 October 2026)
  2. Bartoline black bitumen paint (retrieved 19 October 2026)
  3. Sika Black Jack 901 UK product data sheet (retrieved 19 October 2026)
  4. Drinking Water Inspectorate — bitumen products FAQ (retrieved 19 October 2026)
  5. WRAS approvals directory, section 5021 (retrieved 19 October 2026)
  6. HSE CIS27 — solvents (retrieved 19 October 2026)
  7. Bird Brand black bituminous paint (retrieved 19 October 2026)
  8. HSE — creosote ministerial decisions (retrieved 19 October 2026)