Can You Fit Cavity Closers After Windows?

Understand the importance of cavity closers for your project and why it’s ideal to fit them before windows and doors are installed.

When installing windows in a new build or renovation, ensuring the cavity around the aperture is properly sealed is essential for thermal efficiency and preventing issues like damp and mould. Cavity closers, which are insulated sections that slot into the open cavity, play a crucial role in reducing cold bridging - where cold surfaces cause internal condensation that can lead to mould growth.

Typically, cavity closers are installed before windows and doors, forming a three-sided frame that is braced at the top. However, if windows are already in place, can cavity closers still be fitted effectively? This article explores the challenges and best practices for retrofitting cavity closers after window installation.

Is It Possible to Fit Cavity Closers After Windows?

Yes, it is possible to fit cavity closers after windows, but it presents additional challenges. Retrofitting cavity closers require careful cutting and fitting to ensure they fully seal the cavity while maintaining a secure fit around the window frame. This process is more labour-intensive than pre-installation, as working space is limited, and additional insulation or sealing may be required.

Considerations When Retrofitting Cavity Closers

Access and Fit – The cavity closer must be cut to fit the available space, ensuring it fully seals the cavity without obstructing the window frame.

Thermal Performance – Proper installation is essential to prevent gaps that could lead to heat loss and condensation issues. Expanding foam or additional insulation may be needed to compensate for a less-than-perfect fit.

Building Regulations Compliance – UK building regulations require effective insulation and airtightness around openings. A poorly fitted cavity closer could compromise compliance.

Best Practices for Retrofitting Cavity Closers

Use a rigid insulated cavity closer designed for retrofitting to make installation easier.

Apply expanding foam or sealant to fill any small gaps and ensure a complete seal.

Consider removing and refitting the window if the existing cavity is too difficult to access for proper insulation.

While fitting cavity closers after window installation is possible, it is not the ideal approach. Proper planning and pre-installation ensure a more effective and compliant seal. If retrofitting is necessary, careful installation and additional insulation can help maintain energy efficiency and prevent cold bridging.

At Dale Joinery, we offer cavity closers as standard for all projects to ensure your property meetings building compliance and the necessary regulations. To learn more about our cavity closers, contact our teamtoday or browse additional resources below:

Streamlining Building Projects with Cavity Closers

Hassle-Free Cavity Formers from Dale Joinery