architectural products limited

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Design Considerations

Choice of Glazing Bars

Architectural Products range of glazing bars have been developed over the years and feature five different styles:

  • APC40 Range – Inverted stalk patent glazing bars for both double and single glazing.
  • APC40 Box Range – Box roof glazing bars for both double and single glazing.
  • PRW Range – Period type external stalk patent glazing bars for single glazing replicating the old lead clothed bars.
  • APR Box Range – Period type box roof glazing bars for both double and single glazing giving the internal appearance of architrave timber.
  • APSG Range – A system of structural glazing for flat top rooflights.

All glazing bars and aluminium components are extruded from aluminium alloy complying with BS 1474, designation 6063 T6. They can be supplied in mill finish, natural anodised to BS 3987, or polyester powder coated to BS 6496 in a wide range of colours.

Choice of Infilling

A wide range of transparent, translucent and opaque infill material is now available and may be incorporated in a patent glazing installation. A variety of plastics, metals and other panels may be considered though glass remains the universal choice of infill material.

Laminated Glass – Suitable for use where safety glass is required in overhead glazing and is preferred by Architectural Products in a single glazed application to canopies as it remains in-situ if broken. Laminated glass is available clear, tinted or obscure.

Toughened Glass – Has good impact strength, with high resistance to mechanical and thermal stress. On fracturing toughened glass breaks into small pieces without sharp edges. Toughened glass is available both clear, tinted or obscure.

Double Glazed Units – Architectural Products recommend the use of 6.4mm laminated glass inner pane and 6mm toughened glass to the outer pane in the build up of a double glazed unit. With the ever-increasing need for energy conservation and changes to document L of the building regulations, choosing the most efficient and cost effective make up of a double glazed unit can be a highly specialised task. We highly recommend that you contact our office to discuss this fundamental aspect of a patent glazing project.

Supporting Structure

Our patent glazing systems are designed to withstand combinations of self-weight and loads imposed by wind and snow but no load must be imposed by the structure to which the patent glazing is attached.

Whilst patent glazing can accommodate structural tolerances better than framed systems, the accuracy of the supporting structure will influence the appearance of the completed installation so recommended tolerances are given in BS 5516. As a general rule, it is recommended that the supporting structure is within plus or minus 5mm of the design dimensions.

Bar Spacings

Patent Glazing achieves a traditional elegance through the balance of slender glazing bars and proportionately sized pane widths. As a design guide, 2.5m2 is the generally recommended maximum pane size, with a width of between 600mm to 700mm. Although wider bar spacings and larger panes can be achieved future maintenance difficulties should be considered as once a project is complete, the cost of replacing large panes can be high.

Weather tightness

Patent glazing is designed to allow the maximum admission of daylight whilst preventing the ingress of water. The design recommendations of BS5516 will ensure weather resistance and dispersal of water through the provision of suitable pitches, overhangs and glazing bar water channels. In general, the recommended pitch is 15 degrees, although lower pitches can be achieved special consideration needs to be given to flashings, caps and other weatherings.


Regular cleaning of patent glazing is all that is usually necessary to maintain the appearance and performance of the installation. Safe efficient means of access to internal and external surfaces should be considered at the design stage as part of the requirements under the CDM regulations.

Architectural Products systems are designed to shed water simply and quickly so as not to impede the natural flow of surface water. Exposed joints are easily accessible, if necessary, for the replacement of any defective seals.