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Insulation, Adhesive, and Fixings – YouTube Series Episode 3

To run alongside our new YouTube series, we have a dedicated series of blogs detailing the processes described in the series. We will cover every single step of the installation process, from an unprepared substrate, all the way to the aftercare stage. This includes customer and system aftercare. The series is broken up into the following steps:

  1. Starter Track
  2. Priming
  3. Insulation, adhesive, and fixings
  4. Beading and verge trims
  5. Basecoat and mesh
  6. Topcoat (priming and rendering)
  7. Tips and aftercare
  8. Our other services

Episode 3 will focus on the insulation, adhesive, and fixings. All three stages are intrinsically linked as insulation boards should be fixed with both adhesives and fixings. Some installers will choose dry or wet fix options, however, we always advise that using both dry and wet fixings is the best policy. This ensures maximum security and stability. The holes required for insulation fixings may cause repeating thermal bridges. However, we have a solution for this in the form of EPS dowel caps.

Adding insulation to the walls of your home provides several benefits; boosting thermal comfort, reducing energy bills, and building fabric protection – all with zero impact on internal floor space.

Choose an adhesive

EWI Pro produce a range of dual-purpose basecoat adhesives that are designed to provide you with the best results for your project. For those of you insulating with EPS board, we recommend using EWI-220 EPS Basecoat. For heavier insulation such as Mineral Wool and Kingspan K5, we recommend our best-selling EWI-225 Premium Basecoat.

Prepare and apply adhesive

Both adhesives come as a dry mix in 25kg bags and should be combined with just under 6 litres of clean, cold water per bag. To do this, use a heavy-duty mixer on a slow setting for a few minutes. Most importantly, the freshly mixed adhesive should be left for approximately 5-10 minutes and then re-mixed before being used. This is where its strength comes from. Once it’s been remixed, the Bucket life is roughly 1 hour, although, like a lot of timings, this is will depend upon the weather conditions.

When it comes to applying the adhesive to the insulation board, we typically recommend the ‘dot and dab’ method. Using a trowel, apply the adhesive evenly around the edges of the board (3-4cm wide track), then dot and dab adhesive spots inside of this perimeter (approximately 3 of them). The adhesive should cover at least 40% of the back of the board.
On the other hand, It’s equally valid to apply a layer of the adhesive to the entirety of the board, something we call complete coverage. This method is better suited to completely flat walls.
Either way, the amount of adhesive used by either of these methods should be similar.

Typically, each 25kg bag has a coverage rate of around 5m², although this will vary depending on the quality of your substrate. A flat wall will require less adhesive

Fit insulation

The insulation boards should always be attached in a staggered formation. When it comes to the corners, you do this by interlinking the insulation from the two sides.
When installing the insulation around window and door frames, cut your insulation boards in an L-shape. You must check the joints between the boards are not in line with the frame edges. This will be crucial in preventing cracks from appearing in the future.

Levelling and filling

With the boards on the wall, it’s now time to align the insulation as best you can. This is the perfect time to do this given the adhesive is still soft. Using a spirit level, make sure all the boards are level both horizontally and vertically.

If there are any gaps between the boards that are wider than 2mm, you should fill these with strips of off-cut insulation or expanding foam tape. A common mistake is to fill these gaps with adhesive, but this can lead to cold bridges, which, put simply, are passages that allow heat to escape out of the property. Beyond cold bridging, cracks will also appear between the joints if they are not corrected properly.

Adding fixings

Once the adhesive has been left to dry for a couple of days, it’s time to begin drilling the mechanical fixings. All our insulation systems require the use of mechanical fixings and help to make the system completely secure.

We recommend installing 5 per board or 7 per m2. Depending upon the fixing that is used, they can either be hammered into place or driven straight into the insulation using a power tool. If you are using metal fixings, it’s really important to recess the fixing into the insulation board and insert a dowel cap.

We have two approved fixing patterns which can be seen below.

Smoothing and levelling the façade

Now that the fixings are in place, the surface of the insulation boards must be flat and level throughout. This step will really benefit you when it comes to applying to render later on. If you’re using EPS, all uneven areas can be made good using a rasp. Not only that, but the rasp will also take off the natural oils that rest on the surface of EPS and encourage bonding with the basecoat layer. Be sure to run the rasp over any dowel caps if needed.

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