Cavity Closer fitting guidelines

There are two ways to fit a cavity closer – either first or second fix, both are detailed below.


When building cavity closer into the brick/block work using a timber former or window.

Products: TF1000, TF2000, TFR1000, TFR2000, TF Multi – Standard and Check Reveal.

  1. If using a timber former, make an accurate timber template the same size as the structural opening.
  2. Cut closer to the size of the sill and jamb adding a minimum of 50mm run on at the base of the jambs.
  3. Tack/nail the cavity closer to the window or former along the sill and jamb ensuring the run on is at the base of the jamb.
  4. Remove the relevant flanges on the run on so you are left only with the cavity width portion.
  5. If building in the window, position the frame with 30mm overlap of cavity closer from the inside of the outer skin. (For Check Reveal installations position the closer flush with the outside of the window, with the closer’s single flange projecting to the inside).
  6. Build the inner and outer skins up to the sill level.
  7. Position the window/former with the cavity closer attached onto the sill in the required position.
  8. Ensure the timber window/former is level and upright then prop up in position.
  9. Build up the two skins ensuring that they butt up tight to the closer.
  10. Use a Dacatie fixing tie every 225mm alternating between the two skins as you build up to the height of the window/former.
  11. For check reveal installations, build inner skin up to the inside flange of the cavity closer and butt to the outer skin – allowing for the required check reveal overlap.


Used where the cavity is already formed eg. Refurbishment work.

Products: SF, SF Multi, SF Flexi, SFR, TF Multi, XFR2000 – Standard and Check Reveal (first fix products can also be installed using this method).

  1. Follow stages 1a. and 1b. to cut the closer to size.
  2. When using a multi width cavity closer, cut the insulation to cavity size.
  3. Push fit the closer into the jamb cavity opening ensuring the orientation is correct (exposed insulation points towards the internal skin).
  4. Push fit the sill section in place, ensuring the correct orientation. Check the closer butts up to the jambs.
  5. To secure in place, use galvanised or non-ferrous nails or screw through the flange into masonry.
  6. For check reveal installations, cut to size as mentioned, ensure the single flange sits on the internal skin, and the front butts up against the inside of the external skin.

If you require further installation guidance please visit the website or call 0161 627 4222.

Please note: above guidelines are based on 3 sided window installations for 3+ sides please contact Dacatie. The guidelines have been produced to aid the installer, Dacatie cannot be held responsible for the installation of their products on site.

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