In the second of our series on technical advice from specialist suppliers, Effi Wolff of www.balconette.co.uk talks about the design of privacy screens:
“Privacy screens” are what is often requested by local authorities. This is stipulated by them if your terrace, balcony or part of them only overlooks a neighbour’s property. It is requested so that your use of this balcony area does not invade or compromise their privacy.
Privacy screens are usually requested to be 1.8m high and use a glass that cannot be seen through – i.e. an opaque glass.
The subject of privacy screens and their height requires extra consideration for wind loadings and the subject of wind loading is not a simple calculation as there are many variables that need to be considered.
The loads on privacy screens are a lot larger than on regular glass balcony rails and will require stronger posts with bigger base plates.
Therefore the structural design of 1.8m high screens is governed by wind loading. For sites in the UK wind loading is calculated in accordance with British Standard 6399-2: 1997 Code of practice for wind loads. The basic wind speed for different geographical locations is obtained from Figure 6 of BS 6399-2. The basic wind speed varies from 20m/sec in an area around Oxford to 30m/sec in the North Scottish Islands.
The basic wind speed is adjusted by various factors to allow for differences in site conditions. These include the site altitude and topography, whether the site is in a town or in the country, distance from the sea, and height of the building.
In order to properly design a safe privacy screen there are some things to ascertain:
1) The area the job is in in terms of basic wind speed. On each calculation there is a map of the UK with basic wind speeds.
2) Altitude of site
3) Effective height of the building
4) Site distance from the sea.
The design must take into account the fixing method and structure being fitted to. Some areas in the UK are subject to gale force winds and the design must take these things well into account.