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Benefits of choosing Mastic Asphalt
to waterproof your stairway

The Process of Waterproofing Asphalt Steps

Close-up of black concrete stairs with waterproofing for added durability.

The first thing which needs to be done before waterproofing steps in mastic asphalt it to ensure that the substrate is actually suitable for asphalt to be applied.

Mastic Asphalt is an extremely durable time-tested waterproofing system which can last for over 30 years.
• Mastic asphalt is recyclable and has carbon zero status.
• When an asphalt mixer is used, no flame is needed for the works.
• Asphalt is suitable for intricate detailing.
• Solar Protective coating provides a neat finish and disperses heat from the
asphalt steps.

Removing The Old Asphalt Waterproofing

Any old asphalt will need to be removed. This will need to be carried out extremely carefully, the reason for this is to avoid any damage to the substrate. Any remaining asphalt on the substrate will need to be removed with an abrasive sanding machine to totally make sure all existing mastic asphalt is removed.
Next the substrate needs to be inspected to ensure the surface is completely flat and dry so the asphalt has something to bond too. If this is not the case the defects need to be remedied with rendering or concrete being poured. If repairs to the substrate need to take place it is important to ensure everything is completely dry and dust free before priming.

Priming The Substrate

Once it is certain the substrate is completely dry and dust free it is time to apply the primer. The substrate needs to be primed with a high-bond primer. The reason for this is if you use a bitumen primer, the heat in the summer months will cause the oil to rise to the surface and create one of the common problems seen in asphalt steps, blows. Once applied the primer will take 1-2 hours to dry.

Laying The First Coat Of Mastic Asphalt To The Steps

The first base waterproofing layer for asphalt steps is mastic asphalt. This is roofing grade mastic asphalt which as the name suggests is commonly used in asphalt roofing.
First this initial coating of asphalt is applied to the side stringers up to a thickness of between 7 and 8 mm. This coating to the stringers is tucked into the prepared chases for termination. Next the risers will receive their first coat of mastic asphalt.

Applying the Top Coat Of Mastic Asphalt To The Steps

Now it is time to apply the top coat of mastic asphalt to each of the treads on the steps we are waterproofing. The top coat for the treads on the steps is laid with a fine 3mm grit added to the asphalt. The reason the grit is added to the asphalt is to provide the extra grip and durability required to cope with foot traffic a set of steps takes over time.
A batten is fit to 12-15mm above the riser in each tread to mark out the height which the asphalt needsto be applied up to. Then the asphalt is laid out of the bucket up to the height which has been marked with the batten.Next coarse sand is thrown over the asphalt tread which has been laid. And this is rubbed into the mastic asphalt coating. This rubbing of sand is done once the whole of the tread is covered and the result is a coarse level finish. Now the team installing the asphalt steps will brush away all of the excess sand from the area and remove the battens which were fitted to ensure the coat was laid to the correct height of 15mm.

Applying The Top Coat To The Upstands

The upstands on any mastic asphalt staircase must be at least 150mm high go into the chase and be finished by pointing with sand and cement mortar. The top coat thickness of these asphalt upstands should be 7-8mm thick. Just like with the asphalt treads coarse sand will be rubbed into this top coat of mastic asphalt.

Angle fillets are used to join the horizontal to the vertical in an Asphalt Staircase

To complete the waterproofing of asphalt steps the vertical elements have to be joined to the horizontal earlier. As mentioned earlier the vertical of the risers asphalt was joined to the horizontal of the treads with a double angle fillet. To bond and fully waterproof the steps the same must be done between both the treads and risers with the upstands running along the strings of the staircase. The use of angle fillets completes the waterproofing of the asphalt steps. It also is the most decorative part of the staircase.

Finishing the Asphalt Steps with a UV Solar Reflective paint

Once a set of steps are complete it is important to add solar reflective paint to ensure the steps last for the longest time possible. The reason for this is that in the summer months, the sun heats the asphalt and can cause slumping. Additionally, the sun can draw the bitumen out of the asphalt leaving it looking grey and worn. Although this solar reflective paint does not completely prevent the effects of the sun upon the asphalt it greatly diminishes the effect it has. On a new set of asphalt steps, two coats of solar protective paint will need to be applied. This solar reflective paint is applied to the treads, risers and stringers. The finish of these solar protective paint is normally a light grey colour or white. It is an important part of maintenance to re-apply the solar reflective paint
every 5 to 7 years if you want to get the most lifespan out of your steps.

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