Frequently Asked Questions


What are the U values?

There are no u values on cavity closers. The calculation required to meet part L building regulations is the path of thermal resistance. Closers must meet a minimum of 0.45m2KW – all closers from Subframes UK meet this criterion

Do the cavity closers have the required European CE mark?

Unlike windows and glass, CE marks do not apply to cavity closers.

Are all cavity closers fully insulated?

Not all cavity closers are fully insulated. Whether or not a cavity closer is insulated depends on the design of the cavities within the closer. Some cavity closers, including closers from Duraflex, do not require full insulation as long as they meet the 0.45m2KW path of thermal resistance calculation. This means they comply with Part L regulations.

Which is the inside and the outside of the closer?

In general, there is no inside and outside of a closer. As a result, it does not matter with a fully insulated closer. If one lip is longer than the other, the longer side goes to the inside face. However, if only partially filled, then the insulated side of the closer should go to the outside face

How quickly can they be delivered?

Cavity closers can usually be delivered within 7 to 10 Working days, although some products may require longer lead times. For an accurate delivery time, get in touch with the team at Subframes UK. We would be delighted to assist you and answer any questions you have.

What cavity sizes can we supply?

Subframes UK supplies a range of cavity sizes, from 50mm up to 300mm.

Are standard cavity closers fire rated?

In general, standard cavity closers are not fire-rated. However, at Subframes UK we do offer fire-rated cavity closers. For more information, get in touch with our team.

Do you supply 1-hour fire-rated closers?

Yes – Cavalok FlameBlok are available from Subframes UK.

Do you supply closers for steel frame builds (including Metsec)?

Subframes UK do supply steel frame builds, including Metsec. For more information, get in touch with our team. We would be delighted to assist you.

Do you supply closers for timber frame builds?

Subframes UK supplies both standard and fire-rated cavity closers for timber frame builds.

What do you do if it’s a split lintel design?

For split lintel design, Subframes UK recommends a 4-sided cavity closer.

Can windows and doors be fixed directly into a closer?

Windows and doors cannot be fitted with standard closers. However, at Subframes UK, we can supply structural closers which are mainly used for front doors and will meet this requirement.

What if the product I want is no longer available on the market?

Unfortunately, the following products are no longer available; however, Subframes can offer suitable alternatives:

  • Spectus
  • Spectus F751
  • Spectus F752 – 30mm upstand
  • Spectus F753 – internal fit
  • Spectus F574 – 75mm check
  • Spectus F101F – flat
  • Spectus F102F – 30mm upstand
  • Spectus F103F – internal fit
  • Spectus F104F – 100mm check
  • Winfit F105F – 100mm internal fit with outer bead
  • Duraflex
  • Duraflex headvent 9107 OHV
  • Duraflex 9072 – upstand 75mm
  • Duraflex 9073 – flat 75mm
  • Duraflex 9074 – check 75mm
  • Duraflex 9002 – upstand 100mm
  • Duraflex 9003 – flat 100mm
  • Duraflex 9004 – check 100mm
  • Duraflex 9010 – 150mm flat
  • Duraflex 9011 – 125mm flat
  • Duraflex 9013 – 125mm check
  • Duraflex 9006 – EP structural flat
  • Duraflex 9008 – EP structural check
  • Kingspan Kooltherm Plus – all sizes – 50-150mm

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

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