How to Choose the Right Cavity Closer for Your Project
Cavity closers are key components in any building project, creating a barrier in cavity walls to keep out damp, improve insulation and add structural support around window and door reveals. With numerous options available to suit different construction types, installation stages and performance needs, choosing the correct cavity closer means understanding the specific requirements of your project. Overlooking details like cavity width, fire safety or material compatibility can lead to non-compliance or even costly rework down the line.
So, what do you need to look for to make sure your build is up to standard and built to last?
What to Consider When Selecting a Cavity Closer
Are the Closers Being Installed at First or Second Fix?
The type of cavity closer you’ll need depends on the installation stage. First fix refers to the primary construction phase when the building’s structure is still going up and windows haven’t been installed. For this stage, pre-formed cavity closers are ideal as they integrate directly into the wall, bonding with brickwork and mortar to create a lasting, secure seal. Pre-formed options also help guide bricklayers, keeping window and door openings consistent and accurate, which can speed up construction.
In second fix installations, where the building work is already complete and openings are being prepared for final fittings, pre-formed closers aren’t suitable. Instead, multi-width cavity closers or cut lengths are better suited, as they can be trimmed to fit the specific cavity width and easily inserted into the cavity. These options are secured with grab adhesive or tacks, providing a solid seal that maintains the integrity of the finished wall.
What is the Size of the Cavity?
Determining the cavity width—the measurement from the inner to the outer leaf of masonry—is essential for selecting a properly fitting cavity closer. Since cavity widths vary based on the building’s design and insulation requirements, an accurate measurement is essential for a snug fit. An incorrect cavity closer size can lead to poor insulation and dampness, impacting both the building’s durability and energy efficiency.
For standard cavity sizes between 50-300mm, pre-sized closers in fixed dimensions simplify installation without the need for on-site adjustments. However, for non-standard or unique dimensions, multi-width cavity closers with pre-cut grooves allow for easy trimming to the exact size needed on-site.
What Materials are Used in the Building Structure?
The materials used in your building’s structure are an important factor when choosing a cavity closer. Different construction types—like brick and block, timber frame or steel frame—may require specific cavity closers to ensure a secure fit and reliable performance.
- Brick and block walls typically work well with a wide range of cavity closers because they provide a stable, solid base that allows closers to fit securely and form an effective barrier against moisture and draughts.
- Timber frame constructions benefit from insulated cavity closers, as timber is more vulnerable to moisture. These closers help prevent damp from affecting the timber, improving the structure’s longevity and energy efficiency.
- Steel frame builds require cavity closers that address thermal bridging, as steel can conduct heat. Closers designed for these builds help manage heat transfer, reducing the risk of condensation and maintaining the structure’s energy efficiency.
Does the Project Require Fire-Rated Cavity Closers?
Fire-rated cavity closers are designed to prevent the spread of fire and smoke through cavity walls for at least 30 minutes, providing critical protection in multi-storey buildings and certain high-risk structures. This type of cavity closer is typically required by law under Building Regulations Approved Document B, which sets out fire safety standards for residential and commercial buildings.
These regulations specify that buildings over 18 metres tall, or those with higher occupancy and fire risk, should use fire-rated materials in cavity barriers for sealing cavities around window and door openings. Choosing a cavity closer with a certified fire rating to meet your architect specified requirements, means you’ll be meeting these safety standards and adding an important layer of safety to your build.
Explore Our Range of Cavity Closers
Subframes UK is proud to be the largest trade supplier of welded and mechanically jointed cavity closers in the UK, offering some of the best products to meet the needs of modern construction projects—from small renovations to large-scale commercial builds. Our commitment to quality and compliance is reflected in the trusted brands we partner with, including Cavalok, Dacatie, Kingspan, Timloc and Titon Vents.
Alongside these partnerships, we also manufacture our own high-quality cavity closers in our Midlands-based factory. With a focus on precision and durability, every product we make meets stringent building regulations and offers exceptional thermal efficiency and structural integrity. Our in-house range is ideal for both commercial and domestic properties, ensuring you find a solution for your specific project requirements.
