How Much Does Mastic Asphalt Cost?

How These Ranges Were Checked

The £60–£90 per m² installed figure for roofing comes from Swift Surfacing’s dedicated mastic asphalt pricing guide (30 January 2026), which quotes it as a general installed range covering roofs, balconies, walkways and industrial floors together, rather than a separate figure per application. As a cross-check, MyJobQuote’s flat roof construction cost guide prices “asphalt and roll-on” materials alone at £40–£70 per m²: adding typical roofer labour of £250–£350 per day (also from MyJobQuote) is consistent with the £60–£90 installed range once that labour is spread across a normal job size.

The by-thickness flooring figures come from Heritage Asphalt (trading as Mastic Asphalt Contractor), a specialist UK mastic asphalt contractor that publishes rates for flooring laid horizontally to a new substrate: £40–£60 per m² at 20mm, £50–£70 at 25mm and £70+ at 30mm, plus £25 per linear metre for upstands and skirtings at any height up to 500mm. These sit inside, and then above, Swift Surfacing’s general band as thickness increases, which is the pattern you would expect: thin floors undercut it, the thickest, heaviest-duty lay-up exceeds it.

Mastic Asphalt vs Felt, EPDM and GRP

On these figures, mastic asphalt is not the cheapest material to buy and lay, but it is usually no more expensive up front than felt, EPDM or GRP, and it is often cheaper than the top of those ranges. For materials only (no labour), our own flat roof felt and membrane guide gives roughly £8–£25 per m² across torch-on felt, EPDM and GRP; that is a different, materials-only figure and should not be compared directly against the installed prices above.

The Mastic Asphalt Council, the UK trade body for the material, argues the real gap opens up over time rather than on day one: it states that alternative membranes typically last 15–20 years against mastic asphalt’s roughly double that lifespan, and cites an independent Building Performance Group study concluding mastic asphalt was “the most cost effective waterproofing option on the market” over a 60-year building life, with alternative systems costing 12–21% more across that period. Treat this as an industry body making its own case, not a neutral comparison, but the underlying point (fewer replacement cycles) is consistent with mastic asphalt’s typical 25–30+ year service life on a well-detailed roof.

Specification: Primer, Underlay and Edge Details

Roofing-grade mastic asphalt to BS 8218:1998 is laid in two coats to a total thickness of 20mm on horizontal surfaces up to and including a 10° pitch, over a separating (isolating) layer of sheathing felt laid loose with 50mm lapped joints. Where the fall is less than 1:80, or the roof will be “buried” under a roof garden, ballast or a reservoir, the standard steps up to three coats at a total of 30mm over a separating layer of glass-fibre tissue.

• Primer: if the concrete deck is damp or dusty, a cold-applied bitumen-based primer is used to seal and prepare the surface before the underlay goes down (RJ Evans Roofing specification guidance). On a dry, sound deck a primer is not always needed
• Underlay: sheathing felt or fibreglass tissue laid loose beneath the asphalt, isolating it from movement in the deck below
• Upstands and skirtings: to a height of 300mm, multiple coats to 13mm thick; above 300mm, three coats to 20mm (two coats is acceptable in protected areas such as tank rooms), per Heritage Asphalt’s BS 8218-based specification
• Surface finish: typically solar reflective paint, or stone chippings bedded in a bitumen-based adhesive, both of which also protect the asphalt from UV and foot traffic
• Insulation and vapour control: on a warm-deck build-up, a vapour control layer sits beneath the insulation per BS 6229, ahead of the asphalt itself; see our roof insulation guide for current Part L thicknesses

Why Tanking Has No Simple Per m² Price

Mastic asphalt tanking to BS 8102 is laid in three coats to 20mm on vertical surfaces and 30mm on horizontal surfaces, and the asphalt then needs a protective render or sand-and-cement screed at least 50mm thick applied straight away to stop it being damaged before the structure is backfilled or the floor is finished. Every specialist tanking contractor we checked (Heritage Asphalt, RJ Evans Roofing, and a dedicated London tanking specialist) quotes this work against a site survey rather than publishing a per m² rate, because the price depends heavily on ground-water pressure, access, and whether the substrate is sound enough to bond to. We could not verify a current, independently sourced mastic asphalt tanking rate, so we have left it as a qualitative estimate rather than inventing a number. As a general point of reference, our own basement waterproofing cost guide prices the more common cementitious tanking (Type A) at £30–£60 per m² and cavity drain membrane (Type C) at £80–£150 per m²; expect mastic asphalt tanking to sit above the cementitious figure given its thicker, three-coat build-up and the protective screed, but get a specialist quote rather than budgeting from a generic range. Use the basement waterproofing calculator to size the job first.

What Moves the Price

• Region: both Swift Surfacing and MyJobQuote note London and the South East run higher than the Midlands, North and Scotland; MyJobQuote’s general roofer day rate of £250–£350 sits towards the top of that range in London
• Access and scaffold: a flat roof over an extension or garage that needs a scaffold tower or hoist adds a separate cost on top of the m² rate; mastic asphalt is also hot-applied from a gas-fired boiler (the “kettle”), which needs safe, level access for the equipment
• Substrate condition: a damp, uneven or friable deck needs primer, screeding or repair before the asphalt goes on, all of which add cost beyond the base rate
• Thickness and specification: two-coat 20mm work costs less than the three-coat 30mm buried or tanking specification, both because of the extra material and the extra labour to lay a third coat
• Project size: small, bespoke areas (a single balcony or bay window, for example) carry a higher cost per m² than a full roof, because mobilising the kettle and crew is a largely fixed cost regardless of area

Figures cross-checked against Swift Surfacing (swiftsurfacing.co.uk, 30 January 2026), Heritage Asphalt / Mastic Asphalt Contractor (masticasphaltcontractor.co.uk), MyJobQuote (myjobquote.co.uk), Nationwide Roofing Specialists (nationwideroofingspecialists.co.uk, April 2026), the Mastic Asphalt Council (masticasphaltcouncil.co.uk) and RJ Evans Roofing specification guidance (rjevansroofing.com), all checked July 2026. Guide prices only, not quotes: get at least two or three itemised quotes from mastic asphalt specialists before budgeting. Last updated: July 2026.