How to correctly specify cavity closers & cavity barriers - Quantum Profile Systems (TA Dacatie)


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Specifying Cavity Closers & Cavity Barriers

For this ondemand CPD, Dacatie (Quantum Profile Systems) look at the building regulations around the specification of cavity closers and cavity fire barriers.

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My name is Tim Hayes and I’m the marketing manager of Dacatie. We are the world's original manufacturer of cavity closers and have been going for over 50 years.

Manufactured from our site in Oldham, all our products are made in the UK and carry our own "made in Britain mark".


Learning Aims

The agenda, We are looking at objectives and introductions. Then we will move onto legislation and industry standards, then specification of the correct cavity closer and cavity fire barrier and explain the differences, then we will move onto summing up and extras then a bit about us at the end – The CPD itself should take around 30 minutes.

Firstly the objectives and introduction. The aim of today is to understand the what, where, why, and how cavity closers and fire barriers. Including building regulations.

And by the end of today you will know how to specify the correct cavity closer or cavity fire barrier in your project.


So where should a cavity closer and cavity fire barrier go?

Well anywhere with a cavity that you need to close off if it’s around reveals or internal such as party wall junctions you need to close those cavity with some form of barrier. So traditionally you’d have your traditional brick and block builds, but also cladded tower block systems you should be using cavity fire barriers. Also, in the more popular and ever-growing timber frame construction within the residential sector.


What is a Cavity Closer.

An insulated profile, closing off the cavity at reveals acting as a DPC, use with standard brick construction, timber frame better than a block return. The image you see in the bottom right is your traditional block return or DPC. The image on the left is a cavity closer that is a push fit. The DPC only offers a damp proof membrane where as the cavity closer offers multiple benefits including a fire rating which acts as a fire barrier. However not all cavity barriers are at reveals.

Some cavity barriers such as the image below are at a party wall junction between different sections or between the roof and eaves. So cavity barriers as in approved document B state in the building regulations, fire safety defines a cavity barrier as a construction other than a smoke curtain provided to close concealed spaces against the penetration of smoke and flames, the restriction of movement of smoke and flames within such a small space. And so what you are trying to do with specifying cavity barriers is to stop smoke and flames spreading within a cavity. I have some examples of where they have failed or have not been there, within this CPD.


Next How are Cavity Closers fit?

Cavity closers come in two standard makeups, they are either push fit as it sounds they are pushed to fit, compression fit gives you your fire rating or are built in as the brick work goes up this gives you slightly more security as you’re building. Push fit is for the retro fitting only, where as first fix ties can either be built into new builds or retro fit.

There are two ways that cavity closers can come. Standard or check reveal. The Image at the top you see is a standard finish where as the brick and block work are the same heights and the cavity closer sits on top of that, this is what you see most commonly in England. The other option is check reveal you usually see this in Scottish and Welsh constructions and this is where the brick work is slightly larger than the block work and the window is pushed from the inside.

The reason to build check reveal is if you are trying to build in a very severe exposed area where you need a severe weather rating, that’s when you should look to specify a check reveal for closers.

The other option you have to specify is when you are doing a window is to specify frame formers. These are cavity closers that are made up to frames for the windows to fit to. You send your window schedule to a company and they’ll manufacture the frames and they will get delivered to site. They can only be used in new builds, the benefit to frame formers is that it give the brick work contractor something to build around and therefore it means that the window arrives on site the windows fit to the frames that are already installed.

As mentioned before not all cavities that need closing are at reveals, so other cavities include party wall junctions, wall plate junctions as you enter the eaves. Also in the timber frames and SIP construction where you have cavities that require closing off you can use fire sock products, something that is compression fit with a fire rating to stop fire spreading into different areas of a building – these can be installed retroactive or in new builds.


And so why is it so important?

Building control may want to see proof of what cavity closer you have used and fire barrier you have on site. Obviously we will come onto part B within this CPD, but building control may want to see if you have the right products installed on site.

Also it’s important, when it comes to cavity closers to think about heat loss and cold penetration. Water and air penetration, to comply with building regulations and also to create a fire barrier which this CPD will go through in more detail.

Just to touch on a case study here, this is a hotel in Ireland that burnt down a couple of years a go in 2017 the fire doors internally and the fire safety was correct but what they didn’t have was cavity barriers. So what happens is the fire got into the cavity and spread extraordinarily quickly brought the building down much quicker than anyone had anticipated because it spread through the cavity and it acted almost like a chimney to draw the fire through the building. The one that everyone is aware of is Grenfell Tower, one of the findings was that no cavity barrier was installed.

Part B has always stated that you should section off different levels with a cavity barrier and this wasn’t the case with Grenfell. One of the failures with Grenfell was that the fire got into the cavity and was drawn up the building and there was nothing breaking each section, each floor, each flat space, from the next one. So that is why it is important to get the specs right because if you don’t the cost can be and is human lives.


Legislation and Industry standards

So what does the Legislation and Industry standards say. So legislation and industry standards can trace their way back to part L 2013 which is about conservation of fuel and power. Part C2 resistance to moisture. Part B was updated in 2017. And also BS5350 and Robust Detail 262 which will be touched upon as to what they mean to the actual specification process.

Breeam and the green guide we often get asked about. Cavity closers and the Cavity fire barriers do not actually come under Breeam or the green guide. We know there are changes going on there all the time, what we can say at this point the products we make have 0 Ozone depletion potential and 0 Global warming potential and a high percentage of recycled compounds where possible.

We also get asked about EPC cavity closers and cavity barriers although they have thermal properties they don’t count towards it as it is only a visual check.

All of our cavity closers have a BBA Certification copies can be found on and on the BBA website.

There are also wider environmental considerations. The life cycle of a good insulated cavity closer. Once you install the cavity closer there is zero maintenance, there is zero maintenance, they will last the life of the build. What I would say with that is if you are doing a refurb and you are taking the windows out it is worth considering replacing the cavity closer, because technology has moved a long way since more than likely the cavity closers if there was any installed, you can also improve the thermals greatly by switching out to improved product will also improve fire safety.

All of our products are made from part recycled compound. All of our mineral wool is non pollutant. No formaldehyde. They are manufactured to ISO9001 and ISO14001 standards. We are also a lean manufacturer which we will touch on a little later.


Specifying the correct cavity closer and cavity fire barrier, what are the key considerations?

Firstly what is the width of the cavity? How wide should the cavity be? Is there a maximum and minimum?

When it comes to the widths of a cavity closer we have seen anything from 40mm all the way up to 200/300mm as the size of the cavity. It goes the bigger the cavity the better the thermal values however there will be additional costs. With insulation improving with time we have seen the cavity reveal coming down to around 150mm. Now we can offer a fire rated cavity closer to 170mm and fire rated cavity sock type barrier to 300mm when you are specifying your build you specify the cavity at the same size as the cavity, so if the cavity is the 100mm you specify your cavity to 100mm, the barrier or closer will come slightly bigger and you push it in and that is where you achieve that fire rating from. All of our cavity closers are available at 5mm increments and all of our fire barriers are available at 10mm increments.

So that is widths, of a cavity closers. So now onto heat loss and part L. The images you see on the screen one is showing the heat escaping out the eaves and the other into the eaves. The second is showing cavity barrier failure. What is this? Why does this happen? It is through something called cold bridging, heat inside the building is warmer than that outside especially at night so the building tries to equalise with the temperature outside. The cavity is quite a good insulator, the window and glazing has improved drastically in recent years. So the temperature will try to equalise over the cavity closer because this is the easiest place for thermal bridging to happen. Cavities should be closed off around window and door reveals with a closer which will provide a minimum thermal resistance path MTRP of at least 0.45m2K/W. If you specify this as a minimum you will achieve part L. which is conservation of fuel and power.


BBA Documentation

How is that worked out (we are often asked)? This is set out in BBA Documentation. It is worked out with the window being set back 30mm, The sum on the screen is how it is calculated. The higher the number, the higher the thermal value.

So in our pocket guide we show all of our products and all of their thermal values. If you look at the XFR2000 this has nearly three times the thermal resistance path, so this Is a great product if you want to increase the thermals of a property but all of our products meet the minimum requirements of part L.

Part C2 is water ingress, the picture you see on your screen now is where water has travelled across the cavity closer and not only does it look bad but it causes health issues. When people see it, they often blame the window. This is because they cannot see the cavity closer. So how do you prevent this from happening. When you write your specification you need to be writing into it that the window is set back at least 30mm into the reveal. A recognised sealant used internally and externally and the cavity closer you specify should have grooved flanges on it. So little castellations on the profile. What this means is that when the water comes into contact with the cavity closer the water is drawn down the closer and into the cavity as apposed to across the closer. By doing this you will meet part L.

I touched on earlier BS520 Robust Detail 262 The biggest thing to know is you are also meeting part L and C2 you are also meeting BS5250 and robust detail 262.

Moving onto Fire Safety and part B, why is it important? Fire has always been dangerous and can cost people their lives. So it is important to get it right. Fires can lay undetected in cavities for large periods of time. There is a need to protect and allow people to escape also. What is the best solutions for cavity reveals. Window and door reveals should be closed off with a barrier with a fire integrity of at least 30 minutes. We offer a range of cavity closers with 30 minutes, we have the XFR with an hour and we test these both burn in, so the fire is coming in from outside the cavity and burn out, so he fire is inside the cavity and trying to get out. It is important to specify this. The windows and doors are the escape roots, so if there is a fire in the cavities then you want to make it safe for as long as possible.

All Dacatie fire closers are fire tested at Warrington Certification and come with a fire rated tape so they can be easily identified on site. All Dacatie fire tests are certified in BBA  Certification.

Going to run over a couple of detailing examples, it is a check reveal formation, it’s a 100mm cavity. So you want to specify XFR200, check reveal as that is the formation

Specification number 2 very similar just a slightly more complex drawing, XFR200. 100mm check reveal.

Next one so say you have something slightly more complex which is a module build, you want to stop the fire spreading under the module build. You want to specify a dacatie firesock 200mm, which is push fit, compression fit to the size of it 175mm. Compression fit is where you get the fire rating from. And something slightly bigger in different levels of a building, as you build up you want to put a fire sock in between each floor, this is a wider cavity so 200mm wide.

Detailing example 3 when it comes to firescocks, this is Dacatie Firesock 20mm Extra Wide, this is where you want to block off the top of your eaves. This area is often overlooked in new build residential what will happen is the roof will go on and people will forget to put a fire break in at the top of the brickwork. This is one of the more crucial because what happens if the fire is in the cavity and races up towards and gets into the roof, the roof is made from timber. That can allow the fire to spread extraordinarily quickly, it’s an important fire break to put in.


Summing up and extras.

So that was how to specify, a cavity closer, cavity barrier. It isn’t that complicated. It is important that you et it right and section off each part of the building. You need to make sure you are specifying fire rated.

Specification of the correct product, Cavity widths, specify a cavity closer, cavity barrier which is the same size as the cavity. It will come slightly bigger and is compression fit, that is how you get the fire rating.

Prevent the heat loss, you need to specify a cavity closer with a minimum thermal resistance path of 0.45.

How to prevent Water Ingress or cold penetration? Make sure that it is specified 30mm set back and the cavity closer has castellations so that the water runs down into the cavity and you want to use a recognised sealant internally and externally.

Fire protection, you want to be specifying a minimum of 30 minutes fire integrity for all cavity closers.

Sustainability, as mentioned BREEAM does not directly affect the cavity closer choice, but specifying a closer with green credentials which will enhance the environmental aspects of any construction. It is worth thinking about.

Just to sum up -

The reasons for a cavity closer are to minimise heat loss from a building, to minimise cold penetration, minimise water ingress, to act as fire protection and make sure that they are right when specified.

The reasons to specify a cavity fire barrier, is simply to stop the fire spreading, so a cavity closer if fire rated is a cavity fire barrier, but a cavity fire barrier isn’t necessarily a cavity closer.



Sustainability is an ever growing issue and always important to consider.

The future – part L was open for consultation is now closed we can see tighter thermal resistance paths going up to 1. Also as people try to achieve passive house and passive house plus, that’s what people are going to think of more and more, thermals.

Just a few case studies, we supply to Bovis Homes, Persimmon and Morgan Sindall. The reason we do is because we are reliable, a British Manufacturer, we are safe in the knowledge of our compliance. We also supply quality product to our supply chain partner through builders merchants.

All of our products are easy to specify, if you go to our website, services and to NBS. You will get to the NBS+ listings for our different products and product details.

Take away from today, Specify Daccatie for all you cavity closers and fire cavity barrier needs. Get peace of mind by specifying Dacatie fire rated product throughout a project. If you have any concerns or questions, Dacatie are here to help, email for same day response.

A bit about us, we make a wide range of cavity barriers, insulated cavity barriers and also insulated DPC. We are part of a bigger group, this is our factory in Oldham. Quantum Profile Systems and we have been going over 50 years in the PVC, uPVC extrusion industry.

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We make the largest range of PVC contract flooring accessories, including: stair nosing, matting, transition profiles an skirting profiles. We have two CPDs, one on Matting and one on specifying a safe stairway.

We make the widest variety of cavity closers, fire rated barriers and fire barriers, under the brand of Dacatie. We also manufacture under the Qwood brand a range of products that go into the joinery market, eight out of ten joinery use our profiles in their windows. Timber windows are beautiful, the small profiles that go on to timber windows have a habit of moving. Qwood looks like timber, acts like timber, paints like timber but without the small timber profile.

We also make profiles in Qlean, where we supply into the offsite marketplace. Bespoke PVC and uPVC extrusions.

Just touching on QWood, it enhances the performance of windows, will not bow, crack or rot timber, all of the beauty none of the trouble.

QPSL are Lean, Green, Safe and Clean, these are our principles.

To create value for customers, generate flow to eliminate job queues, let customer pull decide what is made, strive for perfection, and never be satisfied, always learning to be better.

We don’t have an order book we wait for the phone to ring, get it on the system, manufacture it that day and then ship it out that night.

We are green, we are heading towards a 0-waste site, we have environmental sustainability in all we do. We are ISO14001 certified. Its more than that, it’s a culture, we do waste walks and turn bins upside down to see what is in them and question everything in there.

We are safe, if you were to come here you will be looked after, we will keep you safe and are committed to keeping all stake holders safe.

Clean and transparent in our reputation, we have a complete RIBA CPD.

Further Information, are you currently working on any projects? We are always happy to help. The options to contact us are,, where you can find our CAD Drawings, profile guides and datasheets for all of our products. We also have an app and a telephone number.

Thank you for your time today, I have been Tim Hayes and should you have any further questions please email or call 0161 627 4222.

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