Cavity Closers

What are cavity closers and how do you install them?

If you’re in the process of completing a renovation project or are in the throes of building a new home, you may have come across the term cavity closer. From preventing mould and condensation to creating a fire barrier, cavity closers are a crucial component of your property’s construction.

Here at Subframes, our professional team have years of combined product knowledge and industry experience when it comes to cavity closers. We can give you the advice and guidance you need to complete your insulation project to the highest standard.

But first, what is a cavity closer and do you install them?

What is a cavity closer?

The cavity closer acts as a seal, preventing heat from being lost through any gaps as well as preventing external moisture from entering the cavity wall. Cavity closers can be utilised in masonry, timber frames and steel frame systems, among other types of construction.

When windows and doors are installed, a cavity closer should be fitted within the cavity wall. Buildings require cavity closers for a variety of reasons, such as guarding against moisture, damp and condensation, as well as preventing the loss of heat. As a result, the cavity closers within your home help to maintain heightened levels of energy efficiency and keep your property dry and comfortable throughout the year.

A cavity closer also assists in improving a building’s fire safety, especially if it is a fire-rated cavity closer. Depending on the product you select, fire-rated cavity closers can stop the spread of fire for 30 minutes to an hour. Fire-rated cavity closers also guarantee your property complies with local fire-safety regulations.

How are cavity closers installed?

Cavity closers can be installed before a wall has been constructed (first fix) or after the wall is constructed (second fix). Every cavity closer installation will differ significantly depending on the manufacturer. When a product is purchased, a cavity closer installation guide should be included in the packing.

The size of the cavity closer you’ll need will depend on the width of the cavity wall. With the flange against the inner leaf wall, the cavity can be sealed off completely. The brick ties should be inserted into a brick tie slot on the cavity closer and the key should be inserted into the mortar bed alternating between the outer brick skin (every 6 bricks) and the inner blockwork (every other block). A tight fit of the closer is required, leaving no gaps between it and the walls, with a minimum 20mm overlap between the flange and the masonry skin.

A head closer section is not required if an insulated lintel is utilised. The closer jamb parts should be butted up against the lintel.

Types of cavity closer

Here at Subframes, we only supply cavity closer systems from a selection of the best cavity closer manufacturers and brands.


Eurocell is the UK’s number one for uPVC. They are a leading manufacturer, distributor and recycler due to their precision extrusion, excellent customer service and continued product innovation.

Since 1974, Eurocell has been committed to developing products that meet the changing needs of architects and specifiers as well as fabricators and installers to ensure that energy efficiency, sustainability and aesthetics are integral to all developments using their products. It is their window, door, conservatory and roofline products that have established them as the nation’s number one. Their acquisition of Merritt Plastics recycling and Cavalok also fully entrenched them as a marketing leader for recycling and sustainable products.

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Dacatie Building Solutions

Dacatie Building Solutions is the manufacturer and supplier of the original range of Insulated Cavity Closers for the UK construction market.

As a market leader, the Dacatie Building Solutions brand gives specifiers and building contractors the assurance of the essential Building Regulation compliance in the construction of cavity walls in the area of reveals around windows and doors.

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Duraflex is one of the largest extruders of uPVC profile for the Window Industry in the UK. They supply Householders, Builders, Developers, Local Authorities and Housing Associations through a nationwide network of window fabricators and installers.

Backed by over twenty-five years of uPVC extrusion experience in the window and door sector, Duraflex create the ideal environment for innovative product design, quality production, reliable logistics and all the necessary customer support services.

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Kingspan Kooltherm® Cavity Closer is a uPVC extrusion with a rigid thermoset insulation core, manufactured with a blowing agent that has zero Ozone Depletion Potential (ODP) and low Global Warming Potential (GWP). It is manufactured in thirteen sizes from 50–150 mm. Jointing clips extend the range further by allowing the Kingspan Kooltherm® Cavity Closer sections to be joined to suit cavity widths of up to 300 mm. It is suitable for use with timber, metal or uPVC window frames and can also be supplied to order in curved sections.

This is only available as a bar length product

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Timloc Building Products has been serving the building industry for over 50 years. Part of the Alumasc Group Plc, the brand is based at their 90,000 sq. ft. manufacturing facility in Howden, East Yorkshire.

They are committed to sustainable manufacturing and 75% of products are made from recycled plastics. Their products are designed for use throughout the lifespan of a building and are recyclable at the end of the building life.

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Titon Vents

Trimvent Select XS13 & XS16 are semi recessed clip fix plastic slot ventilators that fit into an 18mm slot in a window overhead section (Vented Head) and provide an Equivalent Area (EA) of 4600mm² (XS16) or an EA of 4400m²(XS13) when fitted with a pair of GS18 grilles.

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Custom Cavity Closer

At Subframes, we can offer you a choice of custom cavity closer profiles for your property. We can serrate most profiles to facilitate fitting into almost any structure.

Custom Cavity Closers

Structural Door Packs

Our range of cavity closers seal up gaps in your masonry efficiently and effectively, whilst also improving the thermal efficiency and retention of your home.  They also give the ability to direct fix through the outer door frame into the cavity closer, removing the reliance on strap fixings removing any movement that may occur once the door has been installed.

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Cavity closers at Subframes

If it’s making sure your house is well insulated or adding a layer of protection from water or fire damage, Subframes’ cavity closers systems are the perfect solution.

Subframes Ltd is the United Kingdom’s leading manufacturer of cavity closer systems. Our uPVC cavity closers are perfectly insulated and are designed to fill any cavity between your windows, doors and walls.

For quotations, product information or technical support please give our team a call on 01773 590100 or email [email protected].

For quotations, product information or technical support please call us on 01773 590100 or email

Further Information

Cavity closers for all frames

Subframes UK manufactures cavity closers to suit all makes and types of doors and windows suitable for brick and block, timber frame, Metsec or any other build type.

We offer a bespoke service designed to meet unique specifications from architect design to site approval with samples supplied.

Our cavity closers can be manufactured as 2, 3 or 4-sided frames supplied with or without vented heads, as circles, arches, ovals, mosques or as a combination of T or P-shaped flags.

Supplying Cavity Closers to Manufacturers

At Subframes UK, we supply cavity closers for all parts of the industry, including window and door manufacturers. For this reason, we use a fleet of unmarked vehicles which deliver nationally on a daily basis.

High-quality Cavity Closers

We are the UK’s leading manufacturer of cavity closers. Our uPVC cavity closers are insulated perfectly and designed to fit between any cavity around your windows, doors and walls.

At Subframes UK, we supply the highest quality cavity closers from a number of brands to provide a solution to every type of window and door insulation.

An experienced team

We only supply cavity closers. Our team of industry experts are experienced in cavity closers and is on hand to help with any quotations, product information or technical support you may need when purchasing your cavity closers.

If you are interested in bespoke designed cavity closers, please speak to a member of the team who can arrange this for you. We offer a choice of cavity closer profiles from the majority of the UK’s major suppliers. We can also modify most profiles to facilitate fitting into almost any structure.

When placing your order please ensure that you provide the following information:

  • Circular Frames – The diameter size.
  • Combination Frames & Stand Frames – A simple sketch with dimensions.
  • Arches – A simple sketch with dimensions & spring point.

Supplying Cavity Closers

We supply cavity closers to window and door manufacturers from our base in the East Midlands. For this reason, our cavity closers are delivered daily by our fleet of unmarked vehicles. To order cavity closers from Subframes UK, please get in contact with us via our telephone number or contact form. If you are ready to buy your cavity closers and you know what you would like to order, please see our online order form and our team will endeavour to get back to you within 24 hours; however, if it requires a take-off from drawings, this may take longer.


What is a cavity closer?

A cavity closer fits the gap within a cavity wall, where windows and doors are fitted. The cavity closer acts as a seal to prevent water vapour and damp from entering the cavity wall. This prevents damp problems as well as stops heat from being lost through the gap.

Cavity closers are made from a number of different materials. At Subframes we manufacture our uPVC cavity closers using a range of products from manufacturers such as Cavalok, Duraflex, Dacatie and more.

There are many types of cavity closers, and we offer a range of cavity closers from a number of manufacturers to suit most builds. However, if you need a bespoke cavity closer, we can manufacture these from your architect’s designs.

Why do you need a cavity closer?

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

For window and door installations, cavity closers are essential. Most window and door manufacturers rely on cavity closers from a specialist cavity closer company such as Subframes UK. As a leading market supplier, we offer a wealth of knowledge about cavity closers so that our customers can make informed decisions to support their state-of-the-art products.

How to install Cavity Closers?

Cavity closers can be fitted either before or after the brick wall has been built. If fitted before, it is known as the ‘first fix’. If cavity closers are fitted after the brick wall has been built, it is known as the ‘second fix’.

The installation process may vary depending on the manufacturer. At Subframes we offer a handy installation guide with instructions and video for simple installation.

Is Subframes UK registered by any independent bodies?

We are a registered ISO 9001-2000 company and members of the chamber of commerce. All standard (non-fire) profiles have current BBA certificates and are manufactured to the highest standard in our Tibshelf factory. We produce our cavity closers to UK fire regulations.

It is important to note that cavity closers are not measured by U Value ratings. The calculation required to meet part L of building regulations is the path of thermal resistance. The cavity closer forms part of this calculation. Our cavity closers meet this requirement.

What size are the cavity closers that Subframes UK supply?

Profiles can be supplied in 6m or cut lengths. All standard (non-fire rated) profiles are BBA certified and meet part L of building regs. We offer a wide range of profiles from some of the country’s leading extrusion houses.

Subframes UK manufactures cavity closers to suit all makes and types of doors and windows suitable for brick and block, timber frame, Metsec or any other build type.

We offer a bespoke service designed to meet unique specifications from architect design to site approval with samples supplied.

Our cavity closers can be manufactured as 2, 3 or 4-sided frames supplied with or without vented heads, as circles, arches, ovals, mosques or as a combination of T or P-shaped flags.

We can offer solutions for cavities between 50 & 300mm. We can potentially offer some solutions outside of this range on special request.

Where do cavity closers go?

Typically, a cavity closer fits within a cavity wall, between the outer brickwork and inner blockwork where windows and doors are to be fitted. The cavity closer gives a solid framework that the bricklayer can build up quickly and easily to form the structural opening required for windows and doors.

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