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London Asphalt are based in Islington, North London N7. We are a specialist mastic asphalt contractor with expertise in all areas of mastic asphalt. This includes installations and repairs of the following, flat roofing, car parks, asphalt steps, flooring, tanking, walkways and balconies. We have operatives who have in excess of 40 years experience meaning you can be assured your works will be carried out to a high standard. We provide full guarantees on any mastic asphalt services we install. If you require any mastic asphalt works whether it be domestic or commercial please get in touch today or call us now on 07739207726.
Asphalt roofing is one of the best waterproofing systems available for your roof. It is often referred to as ‘The King of Waterproofing’ due to its exceptional waterproofing qualities. This 100% recyclable carbon zero rated material has stood the test of time. It is one of the oldest roofing systems in existence and can boast a lifespan of more than 50 years.
As this waterproofing system is applied as a hot molten liquid it is perfect for complex detailing on flat roofs. The reason for this is it can mould perfectly around details such as soil vent pipes, ventilation units and upstands. This results in a 100% waterproof seamless roof.
Asphalt roofing can also be further customised for both heavy use and to prevent slipping. For example, an asphalt flat roof can be strengthened for the heavy traffic which you may find in loading bays or roof gardens by adding a layer of asphalt mixed with paving grit.
Mastic asphalt is made up of limestone aggregates bound together with either bitumen or modified bitumen. It may also contain Lake Asphalt from the famous asphalt lake in Trinidad. Mastic Asphalt which contains Lake Asphalt has better handling properties and performs better once applied. Once bounded mastic asphalt is a dense material which contains no voids which makes it perfect for waterproofing. It is not possible to compact mastic asphalt so it can only be spread using a specialist float or spatula.
Mastic Asphalt Type R988 (Roofing Grade Asphalt)
Type R988 roofing grade asphalt can come in different compositions. The most commonly used compositions are as follows:
1) Type R988 B. This asphalt is composed of 100% bitumen.
2) Type R988 T25. This asphalt is composed of 75% bitumen and 25% lake asphalt.
3) Type R988 T50. This asphalt is composed of 50% bitumen and 50% lake asphalt.
Roofing grade asphalt is not just used in asphalt roofing but can be used in all types of asphalting to provide a waterproofing layer. The only type of asphalting you will not see roofing grade asphalt used is for basement tanking.
As you can see in the compositions of the R988 Roofing grade asphalt above some have an increased amount of Lake Asphalt. This Lake Asphalt comes from the famous ‘Asphalt Lake’ in Trinidad discovered by Sir Walter Raleigh discovered in 17921.
By increasing the amount of lake asphalt in the R988 the asphalt becomes both easier to handle and performs better. The reason for this is Lake Asphalt has a silky texture. This is because of the extremely fine particles of clay present in the Lake Asphalt. The result is a thixotropic characteristic2 which makes the mastic asphalt smoother and easier for the asphalter to apply to the roof.
The presence of Lake Asphalt in a mastic asphalt mix brings a much faster weathering time than asphalt mixes which do not contain lake asphalt. Like all mastic asphalt the finished surface will have a bitumen rich skin which will need to be rubbed with coarse sand to weather it. But mastic asphalt comprising of lake asphalt will weather much faster.
Another difference of mastic asphalt which contains Lake Aspahlt is the surface colouring upon application. For example, asphalt roofing which is made up of R988 B, all bitumen will look a lot darker than asphalt roofing applied in a mix such R988 T50 which contains a mixture of 50% bitumen and 50% Lake Asphalt. The reason for this is mastic asphalt which contains more Lake Asphalt dilutes the bitumen content in the mix. A higher percentage of bitumen means a darker colour of asphalt roof upon completion.
Over time asphalt roofing in any composition will start to look the same colour as the bitumen is pulled out.
Modified Mastic Asphalt
In recent times, modified mastic asphalt has become the asphalt of choice across applications. This type of mastic asphalt is created with polymer modified bitumen. This type of asphalt allows for easier handling and improved performance of asphalt across applications. To tailor for different specifications the polymer in these modified asphalts can be adjusted. Popular suppliers of modified mastic asphalt for roofing and other surfaces include Guaranteed Asphalt3 and IKO.
Before you lay an asphalt roof it is extremely important to prepare the roof you are going to lay. First the roof must be completely clean of all debris. This can be done by thoroughly brushing the whole substrate.
Once the whole roof is clear of debris the next step is to apply primer around the skirtings. Then to set out the required battens and the separating layer.
A separating layer is normally made from sheathing felt. In applications where very heavy traffic will be endured the separating layer is sometimes made from glass tissue paper.
The separating layer serves a dual purpose. The first is to isolate the mastic asphalt from any joint movement in the substrate. And the second is to prevent the asphalt from contacting in cold weather.
This separating layer is laid entirely loose with lap joints of 50mm. When laying the separating layer for an asphalt roof it is vital to ensure the separating layer does not adhere to the substrate. The separating layer is prone to adhering to some substrates such as pre-felted and bituminous ones (another problem with bituminous substrates is the bitumen contaminating the asphalt).
If you are laying on one of the substrates mentioned previously you can prevent problems by using at least one layer of building paper under the separating layer.
Once the separating layer the mastic asphalt is ready to be applied to the roof. The asphalt will arrive on site via lorry and will come in blocks. These blocks will be unloaded and stacked up close to the asphalt mixer. Once the mixer is ready to take asphalt a block will be taken from the stack and broken up using a sledgehammer of a club.
The broken-up asphalt block will be placed into the asphalt mixer and once alight will begin to melt. Once melted the asphalt must be constantly agitated for it not to burn. At a temperature of approximately 220° the asphalt is ready to be laid on the roof. At this point it is important to keep the temperature of the mixer constant. Suppliers of polymer modified asphalt IKO believe if the asphalt is cooked at a higher temperature the product loses elasticity.
There is one problem you can encounter with polymer modified asphalt. That problem is transporting the asphalt from the mixer to the roof without the temperature dropping off too much. In situations where it takes time to get from the mixer to the roof a mix of R988 may be more appropriate.
For the best results the asphalt roofing must be carried out at a temperature of 220°.
To get the asphalt from the mixer to the roof, the molten asphalt is poured into metal buckets duster with cement. The reason the buckets are sprinkled with cement is to ensure the asphalt does not stick to the sides when the asphalt is poured out on to the roof.
When the bucket reaches the roof to be waterproofed the content of the bucket is poured out onto a 2metre area. The asphalter will use his wooden float to evenly spread the first layer of mastic asphalt across the bay he set out with battens. This first coat of asphalt will be 10mm thick.
The same process will be repeated with another coat of asphalt which will be 10mm thick. This will bring the nominal thickness of the roof to 20mm. The only difference with the second coat is the perimeter will be 100mm inside the perimeter of the first coat.
Next coarse sand is tipped over the mastic asphalt and is rubbed in by the asphalter. The reason for this is to weather the asphalt and remove the bituminous skin. The time it takes to weather the asphalt roof will depend upon the bitumen content in the mix.
Finally, the roof can be finished with a coat of solar reflective paint. This solar reflective paint acts as extra protection to the asphalt against the sun. The benefit of this is it prevent the roof raising to as high temperatures and minimises the intensity of contractions in the roof’s surface temperatures as it reduces the variance between the roofs highest and lowest daily temperature.
An important detail when it comes to solar reflective paint is to ensure the paint goes on to the asphalt underneath lead flashings and on top of the lead flashing itself. The reason for this like asphalt, lead conducts heat. When the lead gets hot it heats the asphalt underneath and can produce slumping.
Solar reflective paint should be re-applied at least once every 5 years to give the roof the longest possible service life.
• Asphalt is Carbon Zero Rated.
• Asphalt is Environmentally Friendly and 100% Recyclable.
• Mastic Asphalt is 100% Waterproof and is often referred to as ‘The King of Waterproofing’.
• Asphalters undertake a rigorous apprenticeship ensuring a high standard of work.
• Asphalt is a Time Tested Waterproofing System.
• Asphalt Roofing is low maintenance and are easy to repair if there is ever a problem.
• Asphalt is laid as a hot molten liquid allowing it to seamlessly mould around complex detailing.
• Aggregates or specialist polymers can be added to provide properties to prevent slipping or to endure heavy traffic.
• Solutions such as IKO Permascreed4 improve the speed of installation eliminating the need for waiting for sand and cement to cure.
John and his team did a fantastic job with the asphalt roofing repairs they carried out. Very polite team and left everything very tidy. Very impressed.
Mr K Singh, Holloway, London
The mastic asphalt flat roof looked very good when finished. The team completed everything as promised. I couldn't have asked for any more. Would use again.
Mrs E Smith, Islington, London
My asphalt roofing was leaking. John diagnosed the problem very fasted and explained to me everything very clearly. He let me know there was no need for a replacement roof as I first feared. And my best course of action was a roof repair. The cost to solve my problem was a lot less than I anticipated and all works were completed to a high standard.
Mr M Roberts, Ladbroke Grove, London
The steps outside my house were suffering from some large bumps and I had a leak going through to my basement. One of the operatives from London Asphalt diagnosed the problem was due to my asphalt steps failing. They came and repaired my steps in a very professional manner.
Mr S Lucas, Balham, London
My asphalt balcony was leaking and had numerous cracks in the surface. London Asphalt repaired everything at a very reasonable price. The team who carried out the work were very polite and tidy.
Mrs A Vincent, Hackney, London
