Specifying cladding? There’s a lot to remember – safety regulations, fixings, finishes … at least eight things, in fact. Barbour Index and Scott Brownrigg tell you what they are
1 - General points
- Ensure a specialist supplier manufacturer is consulted as early as possible in the design.
- If specifying glass, take extreme care over glass selection and performance.
- Obtain information from three independent sources.
- Attention to detail is paramount if the building is to be durable and weathertight.
2 - Health and safety
- CDM Regulations require that a cladding system is designed to minimise risk for manufacturers and installers.
- Care should be taken in the handling of glazing units and cut edges of framing sections. Correct safety equipment must be used on site to prevent falls during the fixing phase.
- A method statement should be obtained from the installer to demonstrate the safe fixing of the product.
3 - Curtain walling selection
This will rely on the type, complexity and budget of a particular project. Many manufacturers will discuss projects in early stages and arrange visits to workshops and sites. Specifiers must ensure that the manufacturer has sufficient information to give informed advice and realistic prices.
- Standard system: Designed, manufactured and tested by curtain walling manufacturers. The manufacturer must ensure that the system meets the project’s requirements, and provide performance and test data.
- Modified standard system: As above, but with a few modifications to suit a specific project. Again testing may be required to prove that the system is suitable.
- Bespoke system: This would be custom-designed, manufactured and tested by the manufacturer. Standard components will be used where possible. The manufacturer must produce test reports for inspection and approval, following full-scale testing in a laboratory.
4 - Fixings
The main structure of the building will determine the type and positioning of fixings to be used. All should be capable of not less than about 25 mm of adjustment in three dimensions. Fixing details should be agreed before commencement of the work on site, prototyped if at all unusual and worked through with the other trades to ensure complete understanding.
5- Sealed double-glazing units
Sealed double glazing units generally have a manufacturer’s assumed life expectancy in the order of 10 years. Guarantees vary but a minimum of 10 years should be expected from the supplier. Research shows that more than 25 years is easily achievable but not yet offered by the trade. Life expectancy is far shorter than it is commonly assumed by clients.
6 - Aluminium finishes
It is difficult to get paint to adhere to aluminium. The paint will easily chip leaving bright metal showing through. Specifiers must choose from the following suitable finishes:
- Polyester powder coating: This is a factory-applied spray finish that achieves a very consistent finish in texture and colour. It provides good UV resistance with excellent gloss and colour retention. It can be finished in gloss or satin. Minor scratches in PPC can be repaired on site.
- Anodising aluminium: Anodising is an electrochemical process that alters the surface of the metal to produce a tough oxide layer on its surface. During the anodising process, the oxide layer is porous, and at this point it’s possible to introduce a dye. The smallest defects in the surface of the aluminium may telegraph through the anodising and may provide unacceptable results.
7 - Toughened glass and spontaneous fracture
It is unsafe to use ordinary toughened glass in overhead or high situations where glass particles could fall on people below. The use of heat-soaked toughened glass is recommended and must be certified by the processor, stating details of the treatment provided and applicable standards complied to either DIN 18516-4 or prEN 14179-2.
Toughened glass could fracture for many reasons, such as incorrect installation, handling or impact. Although it disintegrates into particles when broken, fragments can still cause significant injuries when falling from a height.
8 - Composite wall cladding
- Composite wall cladding and roof sheeting materials usually consist of the following: A sandwich of two sheets of flat or profiled material separated by and factory bonded to a plastic foam-type insulating core material.
- Usually the strength of the composite laminate is taken into account in assessment of the overall strength for purposes of permissible loadings (dead, imposed or wind), fixings or deflection.
- Consider whether the composite is capable of fulfilling life expectancy requirements for walling and roofing. The structural stability of the system will rely on the durability and integrity of the foam core; the flatness of the outer panel may rely on the bond of the metal to the foam core.
- Consider the extremes of temperature differences between outer and inner sheets and their possible effects on movements to be accommodated by the foam core.
- Use only systems with foam formulations, which have been assessed by the British Board of Agrément. Discuss all the above points with the client before making your decision, and record your conclusions.
Subject guides similar to this are available from Barbour Index as part of its Construction Expert and Specification Expert services.
For further information contact Barbour Index on 01344-899280 or visit www.barbour-index.co.uk
- American Architectural Manufacturers Association, publications 603.8-92 and 605.2-92
- Barbour Index Construction Expert (see left)
- Building Regulations Part B (2004 Edition)
- BSRIA tests 3290 Part 1 & Part 2
- Centre for Window and Cladding Technology Standard and Guide to Good Practice for Curtain Walling
- Galvanizers’ Association
- Glass and Glazing Federation
- Steel Construction Institute Interfaces, Curtain Wall Connections to Steel Frames (publication 101)