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1a-Visual Quality
Roof Glazing
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Slope Glazing

The Glass and Glazing Federation and other industry glazing bodies, such as The BSI, make clear recommendations that both panes of glass should be adequately supported within the glazing system.

From previous correspondence the following points would support this previous statement:-

  1. The GGF issued a document entitled “System Design and Glazing Consideration for Insulating Glass Units”, Section 4, May 1995. Section 7 refers to setting blocks and distance pieces and states quite clearly in 7.1:- “In order that both panes of glass are supported, the width of the setting block should, in general, be equal to the sum of the unit thickness plus the back face clearance”. This statement also applies to distance pieces.

  2. The NHBC refers to “glazing to relevant standards” in its document NHBC Standards Chapter 6.7. Also that blocks should be of a suitable resilient material.

  3. British Standards’ Workmanship on building sites Part 7. Code of practice for glazing. (BS8000 : Part 7 :1990) states clearly in Section 3.1.2 that the width of the block should be equal to the width of the unit plus the back face clearance or the thickness of the unit if using load bearing tapes.

All IG Sealant manufacturers would recommend units should have both panes of glass supported in accordance with good glazing techniques. It is also recommended that if there is any exposed sealant at the sealant to glass bond area it should be protected from the effects of Ultra Violet Light. In stepped units, in slope glazing, where this bond area is likely not to be enclosed within the glazing system the usual practice is to use 12 mm flat self-adhesive lead strip to mask the visible sealant.

There is also a European Standard in preparation. I believe prEN 12488 refers to Glass in Building - Glazing requirements – Assembly rules, whilst the requirements for glazing blocks are laid down in prEN ISP 14439. Further information may be available from The GGF and/or The BSI.

Extract from document supplied by Cen Solutions Limited
Unit 3 Penkridge Industrial Estate,
Boscomoor Lane, Penkridge,
Staffordshire ST19 5NZ