Flat window installation

Flat Window Installation

Offer the window into the aperture, bedding in the appropriate manner as illustrated on the following page, temporarily wedging it into position making sure it is level & plumb. Ensure perimeter clearances are retained by using appropriate fixing packers. Mechanical fixings should be made through the packers. The packers themselves must be made of a non-degradable material (e.g. plastic).
Fix the window into the aperture using either fixing brackets or by drilling and fixing through the outer frame. Fixing locations should be no closer than 150mm from corners and intermediate transoms/mullion joints and at max. 600mm centres elsewhere (see Fig 1.) Windows over 1800mm wide should be fixed centrally at both head and cill.
A minimum of 2 fixings per jamb must be achieved.
The use of polyurethane foam is permitted where it is impractical to achieve mechanical fixing in the normal way. The manufacturers guidelines must be followed for application. Foam fixing will not be accepted as a sole means of fixing a frame.
If it is necessary to fix through the bottom member of the outer frame, where water can collect, adequate sealing over screw heads is recommended. Where possible, fixing brackets should be used for this application.
Re-fit any of the glass units you have removed, making sure they are sitting on the necessary glazing blocks.
Re-fit the glazing beads taking extreme care not to damage the glass.
Re-fit sash or sashes you have removed.
Check the window for correct operation before proceeding with the mastic seal or making good.

Drainage

It is essential that our recommendations for securing the glass in place are followed. Specifically, care must be taken to ensure that glazing blocks or spacers do not obstruct drainage of the water from the glazing rebate.

The details contained in “Limiting thermal bridging and air leakage : Robust Construction details for dwellings and similar buildings” (TSO 2001) are applicable to new build applications under Building Regulations ( Approved Document L) but also make good practice on replacement work where possible.

Frame fixings should penetrate a minimum of 25mm into timber and 40mm into plugged brick or block work. Separate fixing details apply when fixing to timber kit framing, steelwork and thin gauge metal pressings. In all situations the facility for PVCU frames to expand and contract must be provided.

Details shown below provide further examples of fixing PVCU frames.