Pothole repair FAQs
A guide to using cold-lay tarmac

Potholes, cracks and defects in tarmac or bitumen can cause a headache when they occur. Rather than digging out and relaying the tarmac or bitumen, they can be repaired with ease with cold-lay tarmac. Find out the best cold-lay tarmac to fix your path, driveway, car park or road with ease, how to apply this packed asphalt and other pothole repair frequently asked questions.

What causes potholes?

Potholes are caused by the expansion and contraction of water. Basically, water will infiltrate the tarmac of a pavement or road through narrow cracks. As the water freezes, it expands and will cause the tarmac to weaken and crack. 

During the colder months, this freezing process can happen many times over, further weakening the surface. When heavy cars or lorries pass over the weaker spots of the road, parts of the tarmac will further break down from the weight, creating larger and deeper potholes each time. 

Potholes vary in size and shape. They can be seen in footpaths, roads, driveways and carriageways.

How much does the UK spend on potholes each year?

In 2021 the UK government expects to give local councils around £500 million to fix the estimated 10 million potholes found on local roads across the country. 

What is cold-lay tarmac?

Cold-lay tarmac is a ready mixed, bitumen-based asphalt which comes in a small tub or bag. Quick and easy to use – and very cost-effective – cold-lay tarmac is the ideal choice for repairing and filling potholes in paths, driveways, roads and carparks. 

Quality cold-lay tarmacs such as Ultracrete Instant Road Repair and Permanent Road Repair are approved by the Highways Authority Product Approval Scheme, which is known as HAPAS in the industry. Following the strict, rigorous and independent testing that comes with HAPAS approval, these products offer instant and permanent pothole repairs when used correctly.

What is cold-lay tarmac made from?

Cold-lay tarmac is typically made from minerals and graded aggregates such as Portland cement, sand, gravel and stone chippings mixed with a bitumen. This mixture creates a cold-lay surfacing material that is ideal for fixing potholes.

What colours does cold-lay tarmac come in?

Cold-lay tarmac typically comes in black or red.

Does cold-lay tarmac come in a bag or tub?

Cold-lay tarmac or pothole repair products come in either a 25kg reinforced plastic bag or a 25kg resealable tub.

What size does cold-lay tarmac come in?

Ultracrete cold-lay tarmac is called Instant Road Repair and is available in 25kg units – in either a reinforced plastic bag or a resealable tub.

What area will a tub of cold-lay tarmac cover?

A 25kg tub or bag of Ultracrete Instant Road Repair (cold-lay tarmac) will cover an area of approximately 1 metre square, filled at a depth of 12–15mm when fully compacted. This estimate does depend on the surface of the repair.

What is cold-lay tarmac used for?

Cold-lay tarmac, also known as packed asphalt or pothole repair, is used for the permanent reinstatement of potholes in the surface of roads, pavements, driveways, carriageways and carparks.

How does cold-lay tarmac work?

When applied correctly, the aggregate and bitumen within the cold-lay tarmac compact together to set within the pothole and create an impenetrable and solid reinstatement. A compacted cold-lay tarmac reinstatement prevents water from entering into any narrow cracks within the surface of the road, driveway or path. It prevents another pothole from forming, or from the tarmac breaking further apart to create wider and deeper potholes. 

What temperatures can cold-lay tarmac be used at?

Cold-lay tarmac, such as Ultracrete Instant Road Repair or Permanent Pothole Repair, can be used in all weathers. For the best results, we do not recommend using these cold-lay tarmacs during freezing temperatures or during spells hotter than 30oC. 

If the conditions are very wet, so much so that the pothole is filling up with rainwater during application, we do advise using Permanent Pothole Repair Wet. This Ultracrete product has been specifically formulated to offer more durability when applied in wet conditions. 

Can I use cold-lay tarmac or pothole repair in the rain?

Most quality cold-lay tarmac or pothole repairs can be used in all weathers. However, the Ultracrete Permanent Pothole Repair Wet is specially formulated to be applied during wet weather and still offer the same exceptional durability as other Ultracrete products.  

How long does it take for cold-lay tarmac to harden?

When used correctly, cold-lay tarmac products harden instantly. The benefit of using the HAPAS approved Ultracrete range of products – including Instant Road Repair (IRR), Permanent Pothole Repair (PPR) and Tough Patch – are an instant, first time permanent reinstatement to potholes. When compacted with a tamp or wacker plate, these areas can be trafficked by vehicles and pedestrians immediately.

How quickly can you walk on cold-lay tarmac?

A correctly prepared and reinstated cold-lay tarmac for repairing potholes can be walked or driven on immediately.

How do you apply cold-lay tarmac?

Following these steps to permanently fill and fix a pothole with cold-lay tarmac: 

  1. Remove any debris, dirt or ponded water from the pothole 
  2. Use a circular saw to cut-out a ‘picture frame’ around the edge of the pothole
  3. Clean-out the loose tarmac or aggregate 
  4. Use a cold joint spray such as Ultrascape SCJ to seal the edges and surface 
  5. Gently loosen the cold-lay tarmac to warm it
  6. Add the cold-lay tarmac to the pothole
  7. Tamp the cold-lay tarmac thoroughly with a tamp or wacker plate – apply more tarmac if needed
  8. Seal edges with a bitumen tape such as Ultracrete Instaband ECO   

What depth of pothole can I fill with cold-lay tarmac?

Different cold-lay tarmac products are available for different sized holes. For example, Instant Road Repair 6mm contains smaller aggregates that can fill holes up to 60mm deep. Typically used on roads and carriageways, Instant Road Repair 10mm includes asphalt repair material with larger aggregates that can fill potholes up to 100mm deep.

How long does cold-lay tarmac take to cure?

Cold-lay tarmac cures instantly. After repairing the pothole and tamping it down correctly, the area is immediately ready to be driven or walked over.

Why is my cold-lay tarmac still soft?

There are two reasons why your cold-lay tarmac is still soft after application: 

  • Extremely hot weather can soften the binder within the tarmac
  • If you have used a contractor, they may have ‘thinned’ the pothole repair by mixing it with a little solvent such as petrol

Cold-lay tarmacs such as Instant Road Repair and Permanent Pothole Repair are both designed to be used straight from the tub, without the need for any additives. You can use both products in all weathers. For the best results, we recommend not applying them during extremely hot spells when temperatures are above 30oC. 

Why has my pothole popped out or developed surface cracks?

A filled pothole can pop out or develop surface cracks if it is not correctly prepared. We strongly recommend using a circular saw – with a diamond blade – to cut-out the area that is to be filled with cold-lay tarmac. Next, remove any debris and asphalt, apply Ultrascape SCJ cold joint spray to seal the edges and then fill with cold-lay tarmac. Always compact the area fully with a tamp or wacker plate. 

If the cold-lay tarmac has simply been poured into the hole, water will penetrate the pothole again. Over colder months, the cracks will widen and deepen and the tarmac will pop out.

Why is my cold-lay tarmac hard?

If a bag of cold-lay tarmac has been stored on a pallet, particularly at the bottom, it may have hardened and be firm to the touch. Apply a light amount of pressure to return the material to its normal consistency. Rolling your knee over the edge of the bag works well. 

What is the difference between pothole repair, packed asphalt and cold-lay tarmac?

Generally speaking, there is no difference between pothole repair, packed asphalt and cold-lay tarmac. They are all common names used for cold-lay tarmac which comes in a pre-mixed tub, for easy and economical pothole repairs. Recommended products include Instant Road Repair, Permanent Pothole Repair and Tough Patch, all from Instarmac. 

These cold-lay tarmacs – also known as macadams – can cure in two different ways. A reactive macadam, such as Tough Patch, cures through a chemical reaction within the product. Whereas a non-reactive macadam, such as Instant Road Repair and Permanent Pothole Repair, both cure when the product is compacted. 

What are the different types of tarmac?

Hot-lay and cold-lay tarmac are the two main types of tarmac. As the name suggests, hot-laid tarmac must be heated at a production facility before being transported to site to be laid. 

Cold-lay tarmac does not need to be heat-treated prior to application. Also known as pothole repair or packed asphalt, cold-lay tarmac is pre-mixed, easy to use and ideal for permanent pothole fills and fixes.

What are the different grades of cold-lay tarmac?

There are two different grades of cold-lay tarmac, either containing smaller aggregate or larger aggregate. Which one you choose depends on the size of the pothole and the required strength or finish of the tarmac.  

Smaller aggregate cold-lay tarmac (typically 6mm) is often used for residential driveways as it gives a smoother surface appearance. A cold-lay tarmac containing larger aggregate (typically 10mm) is commonly used for roads and carriageways. As a rule of thumb, the larger the aggregate, the stronger the tarmac.

Can tarmac be repaired?

Yes, tarmac on paths, driveways and roads can be repaired by using either a hot-lay or cold-lay method. Which method you choose depends on the scale of damage.

Minor or shallow potholes can easily be reinstated using a pre-mixed and ready-to-use cold-lay tarmac. For a permanent fix, we strongly recommend using a circular saw to cut vertical, straight edges around the hole, removing all debris and sealing the area with a cold joint spray. After applying the tarmac, thoroughly tamp it down for an instant and long-lasting repair. 

With severely damaged tarmac or large potholes, we recommend removing the top 6mm layer of the damaged tarmac and laying a new 6mm topping. The new layer will then bond more easily to the surface below. 

If you are unsure about the best way to fix a pothole, give our team a call on 0845 862 1099 (Mon-Fri, 8.30am-5.30pm) for some expert advice.

Will my tarmac pothole repair be permanent?

Pothole repairs are permanent when you follow the instructions on the bag or bucket. For example, when using Ultracrete Instant Road Repair, you will need to: 

  1. Remove any debris from the pothole
  2. Saw-cut a ‘picture frame’ around the pothole using a circular saw
  3. Clean-out the loose tarmac
  4. Seal the edges and surface with a cold joint spray
  5. Add the cold-lay tarmac or pothole repair material to your hole
  6. Tamp cold-lay tarmac thoroughly
  7. Seal the edges with a bitumen tape 

Can I use cold-lay tarmac for my driveway?

Yes, you can use cold-lay tarmac, pothole repair, cold-lay macadam or cold asphalt to repair a driveway.

Can I repair a tarmac driveway myself?

Yes, you can repair a tarmac driveway yourself using a tub of cold-lay or pothole repair tarmac. We recommend using either Instant Road Repair (available in either red or black) or Permanent Pothole Repair.  

How do I repair a tarmac driveway?

You can use a cold-lay tarmac to repair a pothole in a tarmac driveway. We recommend using either Instant Road Repair or Permanent Pothole Repair. 

Follow these steps to permanently fix potholes of up to 100mm deep: 

  1. Clear any dirt, debris or ponded water from the pothole
  2. Use a circular saw with a diamond blade to cut a neat ‘picture frame’ with straight edges around the repair or reinstatement area
  3. Use a brush to remove any loose bits of tarmac or debris 
  4. Seal the vertical edges and base of the hole with a cold joint spray to stop any water ingress (we recommend Ultracrete SCJ) 
  5. Remove the tarmac in its plastic wrapping from the tub and apply gentle pressure to the edge of the bag to soften it
  6. Pour the first layer of cold-lay tarmac to a depth of approximately 45mm and compact with a tamp to around 30mm 
  7. Reapply the cold joint spray to the vertical edges of the hole before adding another layer of cold lay tarmac and compacting again 
  8. On the final layer, compact well to provide the final surface course
  9. Apply an overbanding tape (Ultracrete Instaband Eco works well) around the edge of the reinstated pothole for added protection and to prevent any water ingress 

Note: use Instant Road Repair 6mm for potholes of up to 60mm deep. Instant Road Repair 10mm can be used for potholes up to 100mm deep. Always apply in a maximum of 45mm layers (compacted to 30mm) for the best results.

How do you fill a pothole?

Follow these eight simple steps to fill a pothole: 

  1. Clear the area of dirt and debris
  2. Cut a neat, vertical ‘picture frame’ around the pothole using a circular saw
  3. Remove loose tarmac from the hole
  4. Seal the edges with a cold jointing spray
  5. Pour pothole repair into the hole and tamp down
  6. For larger holes, spray more cold joint spray into the hole, and add an additional layer of pothole repair
  7. Thoroughly tamp down your final surface course
  8. Once fully compacted, the pothole can be driven or walked over immediately

Can you fill a pothole yourself?

The simple answer is yes. To get started, clean any debris away from inside the hole, saw-cut a picture frame around the hole and remove all of the new loose tarmac. Next, seal the inside with a cold joint spray and add your pothole repair or cold-lay tarmac. Finally, fully compact with a tamp or wacker plate. Job done!

What can I use to fill holes in my driveway?

Cold-lay tarmac offers a quick, easy and cost-effective solution to filling holes in a driveway. It is the ideal alternative to having the whole driveway dug out and hot-lay tarmac reapplied.

Our paving experts recommend Ultracrete products for cold-lay paving. For repairing a domestic driveway, consider using either:

  • Instant Road Repair 6mm: for light traffic driveways and holes 15–100mm deep
  • Permanent Pothole Repair: for heavily traffic driveways and holes 10–100mm deep
  • Permanent Pothole Repair Wet: heavily trafficked & applied during wet weather
  • Surface Defect Repair: for minor or shallow holes and defects up to 45mm deep

How long does cold-lay tarmac last?

The shelf life of cold-lay tarmac or pothole repair macadam, stored in an unopened bag or tub with the seals unbroken, is six months from the date of manufacture.

How should I store my cold-lay tarmac?

Store unopened bags or tubs of cold-lay tarmac in a cool and well-ventilated place. Ideally they should be stored on a pallet or above the ground, and away from drafts, cold air and frost.

Where does the name tarmac come from?

The original tarmac name derived from John Loudon MacAdam, who was a Scottish Civil Engineer and road-builder by trade. MacAdam was the inventor of “macadamisation” in the early nineteenth century and is considered to be the father of the effective and economical method of constructing our roads and carriageway networks. 

MacAdam found that naturally occurring tar could hold small stones together to form a material that creates a smoother surface area for – at the time – horse and carriages to travel over.  The name ‘tar macadam’ was born, which was later shortened to the trademark name ‘Tarmac’. 

These days, the binding agent for the stones and aggregates to form tarmac is bitumen rather than tar. As a by-product of the oil refining process, tarmac is often referred to today as bitumen. 

Which type of cold-lay tarmac is recommended?

The type of cold-lay tarmac you choose depends on what type of surface you are repairing, the size of the pothole and the weather conditions at the time of application.

Cold-lay tarmac can be used to repair driveways, pathways, cycle tracks, car parks and roads. Our paving experts recommend Instarmac’s Ultracrete products for the ease of application and the permanent repairs they provide.

See which product is ideal for repairing your potholes:

Product nameIdeal for repairing potholes on…
Instant Road Repair 6mmFootpaths & cycle lanes (15–100mm deep)
Instant Road Repair 10mmRoads, Types 3 & 4 (30–100mm deep)
Permanent Pothole RepairRoads, driveways & carparks (10–100mm deep)
Permanent Pothole Repair WetTrafficked areas & during wet weather (10–100mm deep)
Tough Patch 6mmAll areas, especially heavily trafficked & during wet weather (up to 60mm deep)
Tough Patch 10mm*All areas,  especially heavily trafficked & during wet weather (up to 100mm deep)
Surface Defect RepairMinor or shallow holes & defects (up to 45mm deep)

*Tough Patch 10mm is only available on order. Call us on 0845 862 1099 to make an order.

Which Ultracrete cold-lay tarmac product is best for pothole repairs?

Ultracrete offers three main types of cold-lay tarmac that are ideal for fixing and filling potholes with ease: 

  • Instant Road Repair (IRR)
  • Permanent Pothole Repair (PPR) 
  • Tough Patch

Instant Road Repair and Permanent Pothole Repair are bitumen and solvent based products. As such, they harden after compaction when the solvent evaporates. Both of these pothole repair products gain their strength from the physical interlocking of the stone during compaction, and they cure over time. They are both ideal choices for general pothole repairs and tend to be more cost-effective. 

Tough Patch works very differently. This type of cold-lay tarmac contains an innovative reactive binder that is activated by adding water. When water is sprinkled across each layer during application, this speeds up the Tough Patch curing process and hardens the material within an hour. Tough Patch is ideal for heavily trafficked areas, and especially areas where point loading or turning are common. Highly skid-resistant, Tough Patch is another ideal choice for potholes at cross roads or junctions. It is also resistant to scuffing and rutting.  

The aggregate and stone sizes within each of the cold-lay tarmacs determines their ideal application. PPR 3mm and IRR 6mm are both ideal choices for fixing paths, cycle tracks, car parks, domestic driveways and private roads with small amounts of traffic. Whereas IRR 10mm is more suited to high-traffic roads and carriageways. 

If you are planning on carrying out any pothole repairs and wet weather is forecast, look for the products with ‘Wet’ in the title or use Tough Patch as they have been specifically formulated for these conditions. Permanent Pothole Repair Wet contains a greater level of anti-wash agent, which prevents the binder from being washed out if it is raining, and Tough Patch contains a special binder so can also be used in the WET, and in any conditions.

Still have a question about pothole repair?

If you still have a burning question about repairing potholes and cold-lay tarmac, contact our expert team on 0845 862 1099 (weekdays, 8.30am–5.30pm). We’re here to help you make the best choice for your domestic or commercial project.

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