EPS on wall

EPS insulation is a fantastic product designed to insulate external buildings, whilst at the same time providing a robust and long term solution. The EPS for external wall applications is retailed is packs of varying thicknesses and can be cut and shaped to size depending on the requirements of the customer. Hopefully after going through this blog, you will see how easy it is to actually work with the expanded polystyrene (EPS) on external wall applications.

How is the EPS supplied to the installer?

Depending on your requirements the EPS can be cut to any level of thickness (20mm to 200mm+), but the standard external wall insulation products are packaged with the following thicknesses of the boards:

  • 20mm
  • 50mm
  • 70mm
  • 90mm
  • 100mm

If you are insulating a solid wall property and you would like it to meet the current building regulations for energy efficiency (a u-value of 0.3 or better), then using a thickness of 90mm+ is what you will be after.

20mm and 50mm insulation boards are normally used to already supplement an already insulated wall (usually a cavity wall) where space is at a premium.

20mm insulation is also thin enough to use on the window reveals and where you want to provide a nice even substrate to apply the layer of render. Note: the 20mm EPS is too thin to drill in the mechanical fixings.

How is the EPS handled during the installation process?

The good news is that EPS is very easy to cut – you can simply use a saw or a hot knife. When using a saw you will have to be really careful because the cutting process will cause debris to scatter around the site. We recommend doing it in a sheltered area or under the netting that is placed around the scaffolding.

If you would really like to have the best piece of kit for this process, then we recommend using the hot wire cutter. As mentioned above, using a saw or knife can lead to a jagged edge or messy finish, with bits of polystyrene flying around the install area, the wire cutter slices through the EPS like a hot knife through butter, leaving minimal waste and providing a precise accurate finish!

The EPS boards themselves need to be installed in a staggered formation, as illustrated in the EWI Pro Installation Manual. Additional diligence needs to be applied when going around openings and corners – please refer to the relevant installation diagrams.

When the mechanical fixings are installed, ensure you minimise the thermal bridging between the anchors and the EPS material itself. Best way to do this to insert the EPS caps on top of the fixings – fixing them into position using the foam adhesive OR simply use the EcoDrive fixings, which don’t have such limitations.

Rasping the EPS to provide a nice and even substrate

The surface of the grey (platinum) EPS can get pretty oily and needs to be rasped before the basecoat is applied on top. You can use a flat trowel or the angled for different applications. The angled one works very well for corners and the flat trowel is perfect for all other EPS surfaces.

Rasping can be quite a messy process with the EPS bits potentially flying around to all parts. Best to have netting around the scaffolding or the area you are working on – ideally you will have an industrial vacuum, so as you rasp the debris are sucked up and cleaned before it becomes an issue.

Storing your EPS safely

Although the EPS is fairly robust, it works best when it is not exposed to the external elements for a period of time. To ensure the EPS remains a robust product it needs to be stored away from direct sunlight and shielded from rain and wind.

The best bet is to work with the EPS behind a layer of netting – this will keep away direct sunlight. When you are not working on site, ensure that you store the EPS in a dry place away from the elements. Try to use protective sheeting and potentially store in a shed or garage to avoid extremities in temperature.

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