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How to apply bitumen paint

Updated: 21 October 2026

You have a tin of black bitumen paint, and the usual mistakes are one thick coat, a closed shed, and emulsion over it next weekend. How to apply bitumen paint, for this set, is two thinner coats on a clean dry surface, with ventilation, left black. Peter F. used the Bartoline and Sika sheets and HSE solvent guidance behind the [Bitumen paint](/hub/flooring-tools-and-accessories/bitumen-paint) comparison. Dry times belong to the named tin. Tin size is in the [bitumen paint buying guide](/hub/flooring-tools-and-accessories/bitumen-paint/sub/bitumen-paint-buying-guide). A purchase through our links can earn a commission at no extra cost to you. Posts are on [bitumen paint for fence posts](/hub/flooring-tools-and-accessories/bitumen-paint/sub/bitumen-paint-fence-posts). Which tin to open is on [best bitumen paint](/hub/flooring-tools-and-accessories/bitumen-paint/sub/bitumen-paint-best).

You have a tin of black bitumen paint, and the usual mistakes are one thick coat, a closed shed, and emulsion over it next weekend.

Our top picks

Bartoline Bartoline Bitcote 5 litre

Best overall

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
Bird Brand Bird Brand black bitumen paint, 1 litre

Alternative

Bird Brand Bird Brand black bitumen paint, 1 litre
5.3/10about £14.79
View offer
On this page
  1. 1.Before you open the tin
  2. 2.Prepare the surface
  3. 3.Two coats, and when you may thin
  4. 4.Brushes, white spirit, and paint on top

Before you open the tin

The surface should be sound and dry, inside the maker's window. Sika's UK sheet gives about 5°C to 40°C for application, and about −20°C to 50°C once the film has cured. Bartoline's sheet puts the flash point at 38–40°C and says not to use the paint where the surface can exceed 70°C. Do not start if rain will arrive before the first coat can touch-dry. HSE's sheet CIS27 says ventilate, and it prefers a brush when a brush will do, because spraying raises the vapour. If an employer is paying for the work, somebody treats it under COSHH. Keep flames and a hot exhaust away from the wet film and from solvent-wet rags. Bartoline classes the product as UN 1999, Class 3. Stir the tin before you decide it is too thick.

Prepare the surface

Loose rust, dust, and oil sit between the bitumen and the metal. Wire-brush loose scale, and do not paint over grease. A chassis rail wet with engine oil needs that oil off first. Existing felt can take a maintenance coat when it is still stuck down. A soft deck or water that ponds is a different job. Do not wire-brush a sheet that may be asbestos cement. If the roof might be asbestos, stop. Timber should be dry before you start.
Bartoline Bartoline Bitcote 5 litre

Testsieger

Bartoline Bartoline Bitcote 5 litre
8.7/10about £28.50
View offer

Two coats, and when you may thin

Thinning is not one rule for every tin. Bartoline's 10% white spirit is for spray only, and Sika says do not thin. Stir a thick tin before you add solvent. A second thin coat beats one heavy coat that skins and stays soft. Coverage tells you whether the second coat is still in the tin. Bartoline states 9–13 m² per litre. Sika's sheet, not the unitless Amazon field of 12.5, says about 4–6 m² per litre on porous surfaces and about 11 m² on non-porous surfaces, per coat. If the first coat has emptied a 2.5 litre tin, buy more. Do not stretch the second coat until the timber shows through.

Brushes, white spirit, and paint on top

Use an old brush you can throw away, plus gloves. Keep used rags outside in a lidded metal tin until the solvent has gone. Solvent-soaked cloth is a fire risk while it is wet. Do not put ordinary emulsion or gloss over the black film. Bartoline's sheet says not to. Sika's sheet says bitumen may bleed through later paints. A forum tip about an aluminium sealer is someone else's experiment, not an instruction for these tins. If you need another colour, use a system whose maker names a primer for bitumen, or leave the film black. The gloss dulls in sunlight. That chalking is normal. It is not a cue to overcoat the film the same week. None of these ASINs shows a current WRAS number.

Common questions

Do I need two coats?
Yes where the sheet says so. Bartoline asks for a minimum of two, the second at right angles. Sika's UK sheet also says two coats, even though the 2.5 litre Amazon bullets leave that out. One heavy coat on porous timber looks black and still leaves the end grain thin. Bird Brand's listings here do not state a coat count, so do not copy Bartoline's number onto that tin.
How long do I wait?
Name the tin. Bartoline's listing gives a touch-dry of 4–8 hours. Sika's sheet gives about 4–6 hours, with about 2–4 hours between coats on the application page. Cold, still air pushes you to the long end. Bird Brand states no hours. If rain is due before the coat is touch-dry, wait for another day.
Can I thin it?
Only as Bartoline allows: no more than 10% white spirit, and only for spraying. Brush coats on that sheet stay unthinned. Sika says ready to use, do not thin. Bostik says do not thin as well. Stir a thick tin before you add anything. A buyer who found Sika thinner than an old tin should not correct it with more solvent.
Brush, roller, or spray?
Prefer a brush. HSE's solvent guidance treats spray as the option that raises vapour, and it says ventilate. Bartoline's 10% white spirit limit is for spray, not a licence to atomise the tin in a shed. A roller can lay a thin maintenance coat on flat felt if you still do two coats. Reviewers describe the paint as sticky. An old brush matches that better than a good household brush you hope to save.
How do I clean the brush?
Use white spirit, which Bartoline and Sika both name, or the wipes Sika names. Expect a fight. Some Sika reviewers bin the brush. Do not wash solvent into a drain. Let rags dry outdoors in a lidded metal container, away from flames, before you throw them away. The wet film and the wet rag are the flammable part of the job.
When should I stop and call someone?
Call a roofer when the deck is soft, the felt has split, or water ponds. Do not wire-brush possible asbestos cement. Do not coat the inside of a cistern or a mains fitting with these tins. A workplace spray or a confined space needs a COSHH assessment. A dry, sound outside surface is the job this page describes.

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

Bitumen paint for fence posts: coat the buried end

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)