W20 Windows

Suitable for internal, commercial and heritage windows

W20 is the traditional heavy-duty framing system,32mmwide with 5mm thick flanges, originally developed for commercial and industrial applications, and which was introduced in the early 1960s to consolidate the various commercial steel window ranges available at that time (most notably the Small, Medium and Heavy Universal ranges). It accommodates single and insulating glass units up to 16mm thick in the same profiles simply with a change of bead. All glazing, whether in fixed lights or casements, is in the same plane. It can be divided into small panes with tee glazing bars, having a table face width of no more than 29mm. Opening windows are weather-stripped using integral gaskets. Hinged casements, hung at top, bottom or side, and swing windows pivoted horizontally or vertically, can all be constructed from the same kit of profiles. Elemental coupling is achieved with simple slender transoms and mullions.


W20 windows are the natural replica replacement product for Universal Range windows installed between 1922 (introduction of mild steel windows) up to the early 1960s (when Universal ranges were withdrawn in favour of W20). W20 windows are, therefore, ideal for windows in recognised historic or aesthetically sensitive buildings or areas as they offer a near-exact sightline match for the existing and may, therefore, be exempt from Building Regulations Document L (Conservation of Fuel and Power). If you require fully compliant double and triple glazed commercial replacement steel windows, please refer to our W40 range.

Exemptions are likely (subject to gaining the necessary permissions from the relevant governing authority) to include buildings that are:
- Listed
- In a designated conservation area
- A scheduled ancient monument
- In a designated building of architectural or historic interest
- In a national park or area of outstanding natural beauty
- Buildings of traditional construction with permeable fabric that both absorbs and readily allows the evaporation of moisture.

A large range of quality modern or traditional face-mounted ironmongery can be fitted, in addition to restrictors, background trickle ventilators and security locks. All available with a range of attractive finishes in addition to standard finishes of satin chrome plate or RTD RotoTone Dark bronze lacquer. Main ironmongery, comprising handles and stays, are generally solid brass.

A key part of BS 6510, adhered to by Steel Window Services, is positive protection from rust. Frames of hot-rolled solid steel are hot-dip galvanized after fabrication to BS EN ISO 1461. During this process, the windows are thoroughly cleaned and then dipped in a bath of molten zinc. The zinc reacts with the iron in the steel to form alloy layers, which are then covered with pure zinc as the window is withdrawn. This combination of soft zinc over hard alloy layers produces a highly durable protective coating that will not flake or peel. In the event of accidental damage, the galvanized coating will corrode in preference to the steel which prevents rusting.

Galvanized steel windows do not require painting for protection but their appearance is enhanced by the addition of a factory-applied polyester colour coating. Polyester coatings have a life expectancy of at least 15 years and a comprehensive range of colours is readily available, with the matt finish proving most popular because of its surface enhancing properties.

A small selection of the extensive RAL colour choices for powder coating new steel windows

The durability and high performance of steel windows can be enhanced even further if good maintenance practices are observed.

Frames should be cleaned at regular intervals using a mild, non-alkaline detergent in warm water, applied with a soft cloth or sponge.

Glazing and perimeter sealants should be inspected on an annual basis and appropriate maintenance action should be taken.

Galvanized steel windows, which are not factory finished with a polyester colour coating, are manufactured with clearances to allow for up to three or four coats of paint on the meeting surfaces. When the repainting programmed has exceeded this, the paint should be stripped off all meeting surfaces prior to repainting.

All hinges, pivots, handles, stays and other mechanical parts should be checked for operation, kept free of excessive paint build-up and lightly lubricated.

Full O & M Manuals (Operation and Maintenance Manuals) are supplied by Steel Window Services upon request on any new window project.


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