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Window Fitting Guide in 7 Steps

Step 1 - Protection

Leave manufacturers protection in place on prefinished and preglazed windows unless it interferes with the integrity of the DPC and seals.More care is necessary when fitting prefinished units.Treat any timber cut during the course of instalation with a compatable preservative.

Step 2 - Forming Openings

Tight fitting of adjacent materials should be avoided as there is a danger of distorting the frame. Side tolerances should not exceed 10mm on each side. When not building in opening should be made 10mm to 20mm larger than the actual window size. In exposed areas consideration should be given to the use of a rebated check reveal.

Step 3 - Fitting

DPC can be either fixed to the frame prior to building in or fitted to the structure when making preformed openings. It is ofen convenient to use a wider DPC than needed and trim it after fitting. Avoid forming a cold bridge.

Step 4 - Support

Support with durable packings at a max of 150mm from each jamb and under mullions. Keep the window level and plumb. When building in the cill can be set on a continuous motor bed. Side packings should be located where fixings occour. Minor distortions can prevent movement of sashes. Check operation before final fixing.

Step 5 - Fixings

Side fixings should be situated 150mm from top and bottom and at a maximum of 450mm centers. If the width execeeds 1800mm or is made from 2 or more units fixing should be positioned in the head and sill. Use internally fixing clips nylon frame fixings or a proprietary screw which enable ajustments to be made on the screw fixings.

Step 6 - Sealing

The gap between the window and the wall should be sealed. A polythene backed sealing strip can be fitted prior to building in or expanding foam seal or mineral wool can be fitted after building in. An additional seal can then be provided by a silicone or polysulphide sealant. Or cover strips can be fitted. This strip should be cut 10mm short of the sill to allow moisture to escape.

Step 7 - Decoration

Finishing should be carried out in dry weather, useing good materials in accordance with the manufactures's instructions.

You Will Need

  • Tape measure
  • Pencil
  • Preservative
  • Packing
  • Drill
  • Level
  • Fixings
  • Hammer
  • Square
  • Screw Driver
  • Silicone
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Adapted from an article by the BWF