Cold Lay Asphalt

What is cold lay asphalt?

Cold lay asphalt is a bitumen-bound or resin-bound surfacing material that is supplied ready to use and laid without heating. It is applied direct from the bag, tub, or pre-packaged kit, compacted by hand or with a small plate, and left to cure under ambient traffic and air temperature. Cold lay asphalt is also sold and specified under several other names: cold lay tarmac, cold lay macadam, cold mix asphalt, and cold patching. The material class and the way it is applied are broadly the same across those names; the differences sit in product formulation, aggregate grade, and whether the product holds a BBA HAPAS certificate.

Cold lay is the alternative to hot-lay asphalt for small-area, reactive, and specialist reinstatement work where a planer, paver, and hot box are not practical. It is widely used for ironwork reinstatement around manholes and gullies, for emergency and planned pothole repair, and for utility cut reinstatement on footways and carriageways.

How cold lay works

Cold lay asphalt cures through one of two chemistries. Bitumen-bound products set through the evaporation of solvent and the interlocking of aggregate under compaction. MMA (methyl methacrylate) products cure through a chemical reaction between a base and a hardener, forming cross-links that set the material without compaction. The choice between them depends on the use case and the specification.

Setting time and trafficability

Bitumen-bound cold lay hardens through compaction and ambient solvent evaporation. The material is trafficable as soon as it is fully compacted, which is one of the main reasons highway teams use it: a lane can be reopened immediately rather than waiting for a hot-lay patch to cool. Full cure, where the patch reaches final strength, takes days to weeks depending on temperature, traffic, and layer depth. MMA products cure much faster. PermaFyx L273, the Meon UK MMA surface-course product, is trafficable in around 30 minutes from mixing with no compaction required. That speed is why MMA is the preferred choice for ironwork reinstatement where the road cannot be closed for long.

Why DIY bags and HAPAS products behave differently

Not all cold lay is the same material at a different price point. Builders-merchant cold lay bags, sold under names like Tarmac Cold Lay Macadam and supermarket private-label cold lay, are formulated for light-use repair: homeowner driveways, shallow pothole infill, occasional path patches. The manufacturers are clear in their own documentation that these products are intended for temporary repair. HAPAS-certified cold lay, the product class used by highway contractors, is a different formulation: high-PSV interlocking aggregate, polymer-modified bitumen, and independent performance testing under the Highway Authorities Product Approval Scheme run by the BBA. The same bag label might say “cold lay” on both; the BBA HAPAS certificate number on the contractor product is the thing that makes it a permanent repair under SROH.

When cold lay is used

Cold lay asphalt sits inside the wider surface reinstatement work that utility contractors and local authorities do under the duty to reinstate set out in the New Roads and Street Works Act 1991. The Act requires that any excavation in a highway is reinstated within defined time limits, to a specification set out in HAUC’s Specification for the Reinstatement of Openings in Highways. Cold lay is one of the material classes SROH permits, subject to product and use-case conditions. Three use cases dominate.

Ironwork reinstatement around manholes and gullies

The single biggest contractor use of cold lay is sealing the surface around ironwork: manhole covers, gully gratings, stop valve and hydrant surrounds, and frame-and-cover reinstatement after utility works. This is the area where HAPAS-certified cold lay and MMA surface products outperform hot lay: the gap between the frame and the carriageway is too narrow for a paver, the repair depth is shallow, and the road needs to reopen quickly.

Permanent pothole repair on live roads

Cold lay is used for reactive pothole response on live highways where a hot box and surfacing crew are not economic. HAPAS-approved products compact to a permanent, trafficable repair without the road closure a hot-lay patch would need. Councils with seasonal pothole programmes and framework contractors delivering pothole response on carriageway contracts both rely on HAPAS cold lay as their material of choice.

Footway reinstatement after utility works

For footway reinstatement, the SROH section is S8 (footpaths, footways and cycle tracks). Cold lay formulations graded for footways (Meon PatchMaster H575 is the footway-grade product) deliver a patch that matches the surrounding surface tolerance without the compaction energy a heavy plate would put into a narrow footway. The material is used for both utility cut reinstatement and small-area planned repair.

Is cold lay asphalt permanent, or only temporary?

This is the single most confused question on the product. The short answer is that cold lay asphalt can be either, and the difference is the product specification, not the technique.

HAPAS-approved permanent cold lay

HAPAS-certified cold lay is a permanent repair material under SROH. The BBA HAPAS scheme, run by the British Board of Agrément on behalf of National Highways and the devolved administrations, is the certification path for products used in UK highway maintenance. A HAPAS certificate for a cold lay asphalt means the product has passed independent road trials and laboratory testing, is audited at the manufacturing plant every six months, and carries a three-yearly re-assessment. HAUC SROH section S11.5 permits HAPAS-certified materials for reinstatement around ironwork, and sections S6.5.6 to S6.5.10 specifically name polymethyl methacrylate (PMMA, also called MMA) as the recommended material for high-stress areas such as braking and turning zones.

Builders-merchant temporary cold lay bags

Builders-merchant cold lay bags, sold under names like Tarmac Cold Lay Macadam and supermarket private-label cold lay, are a different product class. They are formulated for shallow, light-use repair: homeowner driveways, pothole infill on private ground, occasional path patches. The manufacturers describe these products as “temporary” in their own documentation. The materials do not hold HAPAS certification, and using them on live highway or utility reinstatement work will not meet the SROH performance standard the highway authority is signing off against.

The practical test: if the bag carries a BBA HAPAS certificate number, the material is permanent under SROH. If it does not, the product is fine for a residential driveway patch and is not the right choice for ironwork reinstatement or live road repair.

The Magma Ironworks System

The Meon UK Magma Ironworks System is one of two HAPAS-certified ironwork reinstatement systems in the UK market. It covers the full stack: a bedding mortar for the frame, a backfill concrete around the chamber, a movement joint strip at the carriageway junction, and a cold-applied surface course that goes either side of the frame. McFadden operatives are trained and certified under the Meon UK Magma Approved Installer Programme, which covers the installation sequence, compaction, curing, and sign-off standards the system depends on.

The McFadden kit within the Magma range includes:

• PatchMaster H570, a HAPAS-approved permanent cold lay asphalt designed for highway surface reinstatement
• PatchMaster H575, a HAPAS-approved cold lay formulation graded for footway reinstatement and utility works
• UltraCrack L270, an MMA cold-pour crack sealant used for overbanding and crack infill around ironwork surrounds

The alternative HAPAS ironwork system in the UK market is Instarmac’s UltraCrete range (Envirobed bedding mortar, M60F backfill, Instant Road Repair cold lay asphalt, Instaband ECO overbanding). Both are BBA HAPAS certified. Both are used by tier-1 and regional contractors on SROH reinstatement work. The differences sit in installation sequence, cure times, and which installer programme the crew holds certification under.

Both systems do the same job. McFadden crews run the Magma system. If a client is tied to the UltraCrete system under an existing framework specification, the technique and the SROH compliance are equivalent, the products and installer training differ.

Common mistakes with cold lay

Five failure modes account for the bulk of cold lay work that does not last. All are avoidable.

1. Feather-edging. Tapering cold lay down to a thin edge at the patch boundary leaves the material without a contained shoulder. Within weeks, the edge cracks, water gets underneath, and the patch breaks out. Product data sheets specify a minimum compacted depth (typically 15mm); patches thinner than that are a rework.
2. Skipping the primer. Cold lay relies on an edge seal between the vertical faces of the existing surface and the new material. Bitumen-bound products need a tack-coat spray (SCJ or equivalent); MMA products need their own primer coat. Without it, water tracks in through the cold joint within a season.
3. Wrong grade for depth. 6mm graded cold lay is for shallow patches. 10mm grades are for deeper lifts and heavier traffic. Using a fine-grade 6mm product for a 100mm pothole means the aggregate cannot interlock and the patch deforms.
4. Ironwork not re-bedded. Applying cold lay around a frame that is loose in its bedding, or sitting off-level, does not fix the problem. The frame has to be re-bedded and set level first. Skipping the bedding step is the most common reason ironwork reinstatements fail within a year.
5. Cold-weather application. Bitumen-bound cold lay slows its cure in cold weather and the patch ruts under traffic before it hardens. Most products are not recommended below 5 to 10°C ambient. HAPAS and MMA products are more weather-tolerant but still temperature-dependent.