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Beading and Verge Trims – YouTube Series Episode 4

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 4 will focus on the next stage of the installation which is the beading and verge trims which are both crucial parts of the EWI system. Certain areas of your property are highly susceptible to water ingress and dampness. Window reveals, wall corners, and window sills are the major stress points, and our products can help prevent them from being an issue by creating a watertight envelope. 

Verge trim regulations are a hot topic in the EWI community due to PAS2035. The new regulations dictate that a secondary waterproof membrane is required during the verge trims stage. We have discussed how this fits into EWI systems in a previous blog.

Beading is used in EWI systems to reinforce areas prone to impact and is most commonly made from PVC for its anti-rust properties. We are going to take a closer look at 7 types of beads. Some of these will be required in all EWI projects, whereas others will be only required for certain facades.


  • Corner beads – All 90° exterior building angles require beads. Corner beads are ideal for reinforcing these angles in a building structure. They fit directly onto the insulation board and are easy to install, especially those with included mesh. Beads themselves dont require any fixings. Instead, secure them by embedding the mesh during the basecoat layer stage. Some corners on a building will be wider or narrower than 90 degrees, in which case youll want a flexible corner bead. These beads can wrap around the corner irrespective of the angle while providing the same strength.
  • Window reveal beads – This bead provides a professional finish around window and door frames. It’s designed to make direct contact with the frame and comes with an adhesive strip to hold it in place before it’s embedded. As a result, the reveal is protected from water ingress. Unlike other options, this method requires no silicone sealant which can sometimes look messy and will perish over time
  • Window head drip bead – Used at the top of the window and door reveals. The bead helps the system to resist impacts and prevents water ingress from tracking back along the underside of the window reveal and back towards the window itself. 
  • Movement beads – If your facade is in excess of 12m, movement beads are crucial in preventing cracks and ensuring stability. These beads are embedded parallel with the longest edge and within the basecoat layer to provide strength.
  • Flexible arch beads – Flexible arch beads are a great option for strengthening curved 90-degree edges, such as an arch. This bead flexes to fit the profile of the curve, giving you a smooth and durable finish.
  • Clip-on profile – These beads are specifically designed to work with an aluminium starter track. The drip nose ensures rainwater cannot travel back towards the wall and create damp issues.

Verge trims

During an EWI project, the external walls of a property are extended with insulation. Once completed with basecoat, mesh and render, the exterior walls can protrude as much as 250mm, depending on the thickness of your insulation. This can often be beyond the existing roofline and will need correcting to seal the system. 

The best long-term solution is extending the roofline by adding timber battens and a secondary layer of tiles. This will increase the width of the roofline and allow the insulation to tuck in under the tiles. However, this can often cost upwards of £1000 which is not affordable in most cases.

In this scenario, we recommend a verge trim. This is a thin strip of metal that sits at the top of the wall where the insulation meets the roofline. A lip sitting up against the wall prevents moisture from going down the back of the insulation. Ultimately, this creates the watertight seal which is so important and prevents moisture from penetrating the system. Whilst this alternative is much more affordable and easier to install, current PAS guidelines insist that verge trims have two measures of weather seal protection. This will likely be a piece of protective membrane or flashing. We also recommend some silicone sealant along the top edge. Be sure to use high-quality silicone sealant that will bond with the brick and the metal trim. It’s worth mentioning that even the best silicone sealant will perish over time and will therefore need to be maintained.

Window sills

As we mentioned earlier, EWI work increases the thickness of exterior walls. This can present issues not only for the roofline but also for windows, as it may extend beyond the existing window sill. The obvious solution would be to replace the windows before you begin your EWI work. For those of you that are considering this, we recommend requesting extended sills from the window manufacturer, ready to house the additional depth of insulation. Each sill should hang 40mm over the face of the render. Involving the window company in this way will always look the best. However, we understand this is not always possible for everyone, in which case, powder-coated window sills will be a good alternative.

The EWI Store sells these in a range of colours and is designed to extend the existing sill in a more cost-effective way. This method will also require silicone sealant as an extra protective measure. In either case, the extended sill will direct rain to run off, therefore preventing it from seeping into the insulation below. Bear in mind a minimum of 15 degrees is needed for the rain to runoff.

If you have any other questions, drop us a message!

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