Key points
- This guide covers visual screens only. Acoustic screens are a separate specialist design, and Koyda does not supply them.
- Wind load is calculated to BS EN 1991-1-4 and its UK National Annex. It depends on location, height, terrain and how solid the screen is.
- Agree the free area (open percentage) with the M&E designer, so the plant can still take in and exhaust air.
- If the screen also acts as edge protection, it must be designed as a barrier as well.
Planning
Screens are often required by a planning condition. Many conditions need the details approved before installation, so allow time to submit drawings and get the condition discharged. See the government's guidance on planning conditions.
Screen types
- Vertical bars or blades (steel or aluminium)
- Horizontal louvres
- Perforated or expanded mesh panels
Design inputs
- Wind: to BS EN 1991-1-4. Rooftop screens see higher wind speeds than screens at ground level, and corners and edges carry the highest pressures.
- Free area: the M&E designer confirms how much open area the plant needs for airflow.
- Height and line: set from the planning drawings, so the plant is hidden from the agreed viewpoints.
- Access: doors or removable panels for maintenance and plant replacement.
Fixing to the roof
There are three options: posts fixed to the structure, a steel frame spanning between structural points, or a ballasted system. Every penetration through the roof needs a detail agreed with the roofing contractor, so the waterproofing warranty is not affected. Check that ballasted systems are stable against overturning and sliding in wind.
Finishes and earthing
Hot-dip galvanising to BS EN ISO 1461 with a powder coat suits steel screens. Aluminium can be powder coated or anodised. Metal on a roof may need bonding to the lightning protection system, so check with the lightning protection designer (BS EN 62305).
Checklist
- The planning condition and the approved drawings
- Wind design basis and who does the calculations
- Free area agreed with the M&E designer
- Fixing method and roof interface details
- Access doors; finish and colour (RAL)
- Visual screening only: acoustic performance is excluded
Sources
- Use of planning conditions (GOV.UK planning practice guidance)
- BS EN 1991-1-4 Wind actions and UK National Annex (BSI)
- BS EN ISO 1461 Hot-dip galvanized coatings (BSI)
- BS EN 62305 Protection against lightning (BSI)
General guidance only, not design advice for a specific project. Check the current edition of each document.