Cavity closers are an essential part of any cavity wall, but what exactly are they and how do you fit a cavity closer? Here at Insulation Superstore, we are confident that we will be able to provide you with everything you need for your latest insulation project, and we are also able to offer product recommendations and installation advice.


What is a cavity closer?

A cavity closer fits within a cavity wall, where windows and doors are fitted. Cavity closers are required for a number of reasons within a building to protect it from various factors, including water ingress, damp, heat loss and condensation.

The cavity closer acts as a seal, preventing external water vapour and damp from entering the cavity wall and the building, whilst also preventing heat from being lost through the gap. Cavity closers can be used in a range of different constructions, including masonry, timber frame and steel frame systems.


Insulated cavity closers

Insulated cavity closers have the same features as most cavity closers, meaning there is a damp proof membrane to help prevent the ingress of moisture (which causes damp and condensation issues), as well as PVC extrusions and a flexible seal. However, an insulated cavity closer also features a layer of insulation, such as XPS insulation, to further increase the thermally insulating capabilities of the cavity closer. Insulated cavity closers are particularly useful in projects where sustainability, minimal energy consumption and insulation are key factors.


Which brands offer cavity closers?

Brands such as Timloc, Manthorpe, SuperFOIL and YBS Insulation offer cavity closers in a range of widths and specification. Single flange cavity closers, double flange cavity closers, multi-width cavity closers and fire rated cavity closers all feature in Insulation Superstore’s comprehensive range.


Why do you need a cavity closer?

Cavity closers have three main priorities when installed around a door frame or window frame within a cavity wall:

  • To prevent water ingress
  • To reduce heat loss
  • To improve fire safety

Prevent water ingress

Firstly, a cavity closer will prevent the ingress of water occurring around the edges of a window or door, acting as a damp proof course, reducing the potential for damp, condensation and mould from occurring. This is important to ensure the building complies with Building Regulations Part C (resistance to contaminants and moisture).

Reduce heat loss

Secondly, cold bridging commonly occurs around windows and doors, where heat transfer is much greater, significantly reducing thermal insulation. The cavity closer prevents thermal loss from occurring within uninsulated cavity walls, which is important for Building Regulations Part L (conservation of fuel and power) because it helps to reduce the amount of energy used to keep the building warm. Part L building regulations are becoming increasingly important as the drive to become more sustainable and conserve more energy grows.

Improve fire safety

Thirdly, a cavity closer will help to improve the fire safety of the building, particularly when the cavity closer is specifically a fire-rated cavity closer – fire rated cavity closers can prevent the spread of fire for 30 minutes or an hour, depending on the fire-rated product you choose. Fire-rated cavity closers can help to ensure your building is compliant with Building Regulations Part B (fire safety).


Cavity closer installation guide

Cavity closers can be fitted both before the brick wall has been built, known as the first fix, or after the wall has been built, known as the second fix.

As with all products, each cavity closer installation process will vary slightly depending on the manufacturer, but a cavity closer installation guide should be found within the packaging of each product when purchased. Check out the video below for a guide to installing Kingspan Kooltherm Cavity Closers, and to see more about how the cavity closer installation process works.


Unsure of which cavity closers are best suited to your project? Call our team of experts on 01752 692 206 or use the live chat in the bottom right-hand corner and we will be more than happy to offer product recommendations and advice.

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