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Mastic Asphalt Repair


Mastic asphalt repair is the process of repairing or restoring damaged or deteriorated mastic asphalt. These repairs are frequently carried out on mastic asphalt roofing, flooring, and waterproofing applications. Mastic asphalt is an easy material to repair. It is highly durable and made from a mixture of asphalt cement and fine aggregates. It known is widely called “The King Of Waterproofing” and is renowned for its weather resistance, durability and longevity. Mastic asphalt repair involves identifying damaged areas, including; cracks, blisters, or worn-out sections. Then removing the defective asphalt and then applying fresh mastic asphalt.

The new asphalt is normally heated to a molten state and poured or troweled onto the damaged area. The asphalt is finished with a seamless and watertight repair. Mastic asphalt repair helps extend the lifespan of the surface, maintain its integrity, and prevent water infiltration. The ease of repairing mastic asphalt membranes make it a cost-effective waterproofing solution.


At RJ Evans we offer a full range of asphalt repair services. This service covers all applications in mastic asphalt from roof and floor repairs through to steps and balconies. Our highly-experienced team of asphalt specialists cover the whole of London and the South of England. If you would like a quotation or any advice about an asphalt repair please get in touch with us or call us now on 01277 375 511.

One of the best things about mastic asphalt is the ease of carrying out asphalt repair work. This makes asphalt a very cost effective choice of waterproofing membrane across a variety of applications.

Common Asphalt Repairs Needed

Below we look at some of the common mastic asphalt repairs needed on various applications:

Asphalt Roof Repairs

The most common faults you find in an asphalt roof which need repairing are as follows:

• Cracks in the Asphalt Surface

This is normally caused by water ingress, where the moisture tries to escape through the surface causing a blow to develop. A crack develops when the blow finally gives way and splits. Another way in which cracks can occur is, cold shock cracking. This is where an extreme drop in temperature causes an asphalt roof which is not protected by solar reflective paint to crack. This is where an extreme drop in temperature causes an asphalt roof, normally one which is not protected by solar reflective paint to crack. The occurrence of asphalt cracks are extremely rare.

Crack repair can be carried out by using the hot poultice method on problem area, and then removing the defective patch. Next, the joints should be warmed and cleaned around affected area. If the area below the asphalt patch is damp it will be dried out with a blow torch, then primed. Then new coats of asphalt can be laid bringing the nominal thickness to match the rest of the roof. Once the asphalt is laid the old asphalt will be heated to bring the bitumen to the surface and to create a fusion joint between the old and new asphalt.

• Blows in the Asphalt Surface

Asphalt blows are caused by trapped moisture trying to escape through the asphalt. These are commonly referred to as bumps and blisters. If not repaired these asphalt blows will eventually split causing a crack in the waterproofing membrane meaning the roof will be vulnerable to further problems with water ingress. As with crack repair the way to remedy blows is to use the hot poultice method around the affected area, remove the defective area and re-make the asphalt.

• Impact Damage

Asphalt can be damaged by heavy objects being dropped on to it's surface. If the roof is used as a service deck this can be caused by heavy delivery items being dropped on to the surface. The asphalt is especially vulnerable to impact damage on cold days. The damage normally looks like a dent and in most cases does not effect the integrity of the roof as it does not penetrate the asphalt membrane.

• Oil Damage

A common problem on asphalt roof is oil damage. Oil damages asphalt by leaching into the mastic asphalt coating and over time slowly breaking down the bituminous content of the mastic asphalt.

This is normally caused by vehicle leaking oil on loading bays and service decks on by tradesman work on plant machinery on an asphalt roof. With tradesman working on asphalt roofs the oil damage is done completely innocently as they unknowingly let oil come into contact with he asphalt surface.

• The Asphalt Pulling Away From The Brickwork

Another common problem with an asphalt roof is water ingress caused by the asphalt roof separating from the brickwork. There are a number of reasons this can happen. As the roof experiences thermal movement the joint between the asphalt upstand or flashing and the brick work will experience pressure. If this joint has deteriorated it will need to be re-made. It is important to point the joint between the brickwork and the flashing or asphalt in sand and cement mortar. If this joint is pointed in silicon rather than sand and cement it will give way sooner.

• Faulty Upstands

Asphalt upstands can become defective in a number of ways. They can be of an insufficient height, not inserted into a chase cut in to the brickwork, suffer slumping from sun exposure, or not being pointed with sand and cement mortar.

You can learn more about asphalt roof repair here: Asphalt Roof Repair

Asphalt Floor Repair

Damage to asphalt flooring is most commonly caused by water ingress causing blows in the asphalt surface or from impact damage such as a heavy item being dropped on the surface.

• Blows in the Surface of An Asphalt Floor

Blows in the asphalt are caused by water trapped in the asphalt trying to outgas. As this water tries to escape it pushes against the asphalt causing a lump. Over time these bumps will crack causing the waterproofing membrane to be compromised. The way to fix asphalt blows in flooring is to use the hot poultice method to heat around the affected area. Then the permitted of the affected area is cut and removed with a pick. The joints are cleaned out and new asphalt is laid to the same level as the rest of the floor. Once this is done the old asphalt is joint with the new asphalt to create a fusion joint. Once this is done the asphalt flooring is repaired. It is important to survey the whole flooring area to identify if there is an obvious point where water has got underneath the asphalt. When this is found it must be rectified to prevent further problems.

• Impact Damage To The Floor

Just like with an asphalt roof there is no damage to the waterproofing membrane if impact damage does not penetrate the surface. However, if the surface is penetrated it is wise to get an asphalt patch repair as soon as possible due to the waterproofing membrane being compromised.

Asphalt Step Repair

Most of the time asphalt step repairs are only identified when a leak is identified coming into the room below them. Any problems with asphalt steps can be put into one of these three categories: Water Ingress, Sun Damage or Impact Damage. Below we look at some of the common causes of these problems.

• Lack of Solar Reflective Paint

As the sun shines on asphalt steps it is draws the bitumen out of the surface. This causes steps to look worn and faded before there time. This is especially common on south facing steps. Aside from the aesthetic damage this does it also causes something called slumping. This is where the continuous baking of the asphalt in the day causes the asphalt to soften, then as the temperature cools the asphalt contracts. Over time, this expansion and contraction can cause cracks in the asphalt which allows for water ingress. By applying solar reflective paint the asphalt is protected from reaching such high temperatures meaning the asphalt doesn’t have to ensure as extreme temperate fluctuations. Which in turn makes cracks from expansion and contraction less likely to occur.

• Asphalt Blows

Asphalt Blows occur when water gets trapped under the asphalt surface and tries to escape. As mentioned above the most common fix for this problem is to cut out the affected area and re-make the asphalt.

• Impact Cracks

This happens when an object is dropped on the asphalt and damages the asphalt surfece. Surface cracks more likely in cold conditions as the asphalt has less give in it. Asphalt crack repair involves cutting out the affected area using the hot poultice method, cleaning the joints and re-making the asphalt.

• Upstands Not Cut into Wall

The upstands on asphalt steps should be set inside a chase cut into the brickwork of the wall. If this is not done, water ingress is likely to occur. To fix this problem the upstand will have to be removed and a chase cut into the brickwork. Once the chase has been cut the asphalt will need to be reapplied.

• Upstands Not High Enough or Incorrectly Finished

Another problem which can occur with asphalt upstands is they are not finished to a sufficient height. Asphalt upstands should be at least 150mm high and finished with a termination bar or sand and cement mortar. If the upstand is too short it will have to removed and a new one applied. And if the upstand is not correctly finished this will have to be rectified. Silicon finishing is unacceptable. Both the problem of poor finishing and insufficient height of upstands are likely to lead to water ingress.

You can learn more about asphalt step repair here: Common Problems with Asphalt Steps

Asphalt Car Park Repairs

Asphalt is an extremely popular material for car parks due to the ease of carrying our repairs making it a very cost effect choice of waterproofing membrane in the long run. Below we look at some of the common repair needs of an asphalt car park.

• Small Leaks

The most common causes of small leaks found in asphalt car parks are as follows; bay joints opening up, upstands becoming stressed and cracking, oil contamination from vehicles and expansion joints becoming defective. All of these problems can be fix with simple asphalt repair work which can be carried out without having to shut the whole car park.

• Damp Patches On The Car Park Ceiling Or Walls 

In most cases this problem is caused by a defective membrane on the level above. Here the problem area will need to be identified with a survey. Once the problem has been identified the necessary asphalt repair work will need to be carried out to remedy the problem and to prevent the water seeping through the membrane and appearing as a patch in the ceiling or walls below.

• Cracks or Blows On The Car Park Deck.

Cracks and blows are often caused by trapped moisture below the asphalt trying to gas out. The way to remedy this is to use the hot poultice method and cutting out the affected area. To complete this asphalt repair the joints will have to be cleaned out and new asphalt applied with the new asphalt being made good with the existing asphalt by finishing with a fusion joint.

• Impact Damage.

Heavy objects may be dropped on the surface of the car park. Which can cause hairline cracks. As water seeps into these hairline cracks freezing temperatures can cause these cracks to grow larger. Also, water can get underneath the asphalt and cause blows as the moisture tries to escape.

• Oil Damage.

Oil damage is a common cause of damage to an asphalt car park. Oil damages asphalt by leaching into the mastic asphalt coating and over time slowly breaking down the bituminous content of the mastic asphalt. Due to cars sometimes having oil leaks, a parked car with an oil leak is often the cause of oil damage to the asphalt surface.

• Sun Damage.

If the asphalt is exposed to sunlight damage such as slumping can occur. This is caused by the asphalt expanding and contracting with the different temperatures. The way to prevent this problem is with a coat of solar reflective paint.

Other Types Of Mastic Asphalt Repairs

Other types of mastic asphalt repairs which are often needed work include:

• Pavement Light Repair

• Bridge Expansion Joints

Asphalt Balcony Repair

Rainwater Outlet Repair

Need Some Advice Or A Quotation From Some Asphalt Repairs?

If you would like a quotation or any advice about an asphalt repair please contact us with us or call us now on 01277 375 511.


Mastic Asphalt Repairs