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External Wall Insulation and Verge Trim

What is Verge Trim?

A Verge Trim is a thin strip of plastic or metal that sits at the top of the wall where the insulation meets the either the roofline or the window sill. Our Verge Trim are made from 1mm powder coated aluminium, and each come in various widths to house different thicknesses of insulation. Verge Trim is suitable for most situations where the external wall insulation requires capping, whether around window sills or at the top of the system to extend the roof line. Its main purpose is to redirect water away from the EWI system and prevent any moisture penetrating behind the insulation boards.

As we know, water ingress can be extremely detrimental to an EWI system. Water has a direct effect on the insulating properties of the external wall insulation, because water reduces the ability of the insulation to slow heat transfer. Water ingress can also be really dangerous for the structural integrity of the EWI system; continuous water ingress will eventually wear away the adhesive which holds the insulation boards to the wall. This will eventually cause the insulation boards to become insecure and even fall off the wall, potentially causing injury. This is why technical design is so important – at EWI Store, we always stress that installations need to be done properly by fully trained installers such as those that we have trained ourselves.

UK properties tend to vary depending upon the type of roofs they have. Some roofs have a wide enough soffit to allow the insulation to sit underneath, and so in this case good quality beading will be sufficient to create a seal with the soffit board – water ingress should never be a problem here because the water will simply run off the side of the roof. However, not all roofs have a wide enough soffit to accommodate the insulation, so in these cases a Verge Trim will be required.

Verge Trim – Creating a Waterproof Seal for EWI

Where there is a fascia board, it is possible to tuck the Verge Trim behind it or up under the roof line. Here at EWI Store, we offer different types of Verge Trim for a range of areas, so no matter the project we’ve got everything you need! 

Over-Sill Verge Trim:

The Over-Sill is intended to extend the length of an existing window sill. The idea is to ensure that the extended window sill overhangs the insulation so that water runs straight off.

over-sill verge trim

Dropdown Verge Trim:

For use when fixing from below, the Dropdown fits under sills and soffit boards and effectively ensures that water falls away from the system while also minimising the need for expanding foam tape and other sealants.

dropdown verge trim

Upstand Verge Trim:

When fixing from above, the Upstand is ideal. Used in areas such as the connection to a flat roof or where the Upstand can slide up behind the fascia board, the Upstand creates a waterproof seal which again minimises the need for foam tape.

upstand verge trim

Additional Items…

Verge Trim Connectors and End Caps:

Verge Trim Connectors are used to secure the joint where continuous lengths of Verge Trim are installed, while End Caps come in pairs and are designed to create an aesthetically pleasing finish. Both the connectors and the end caps ensure effective waterproofing around all joints.

verge trim connectorsverge trim end caps



One thought on “External Wall Insulation and Verge Trim

  1. I would like to know more on the joining of verge trims to ensure they are as watertight as the join to soffit or facia

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