Swish Building Products - Rainwater & Roofline Profiles & Dimensions

Rainwater - UPVC - Roofline Cladding Profiles - Dimensions

Rainwater System

Swish Rainwater Systems are designed for application in most domestic properties throughout the UK. The following information is given to help specifiers determine the basic requirements of a gutter system. Swish Technical Services can provide further guidance as required. Tel: 01827 317238

Rainwater Run-off

The rainwater run-off from a roof during a storm event can be calculated by multiplying the rainwater intensity by the effective roof area.

Rainfall Intensity - BS EN 12056 suggests likely rainfall intensities for different areas of the UK, which may be experienced as unusual events of 2 minutes duration, once every year. It is sensible to design a system for a minimum intensity of 75mm/hour per m² or a flow rate of 0.021 litres per second.

Effective Roof Area - The area of roof (m²) that drains into any one gutter can be calculated in two ways (see diagram):–

• (H/2) + W x L
• L x W x Pitch Factor

A selection of pitch factors is shown below. For other pitch factors please contact Swish Technical Services.

Flow Capacity

Capacities shown above for Swish gutter systems have been independently assessed on a flow rig in accordance with BS EN 12056:2000. They are based on a ‘short’ run of gutter (ie 50 x height of water the gutter is capable of containing), the gutter being set straight and level (ie a fall of up to 3mm/m) with a storm event running at 75mm per hour per m² or 0.021 litres per second. Each capacity has been reduced by a ‘safety factor’ of 10%.

System Layout

The roof area to be drained should be compared with the maximum area that a gutter type is able to drain. If the figure is too low the designer may:

• Select a system with a higher capacity
• Increase the fall on the gutter. With a long gutter this has its limitations, as water coming off the tiles is more likely to overshoot the gutter at the lower end. With a shallow fascia this may not even be an option. In addition the greater volume of water in a long gutter will tend to reduce the speed of flow
• Move the outlet point to a central position to significantly increase the gutter drainage capacity
• The flow rate should be reduced by 15% if the run has a corner in it
• Larger valleys may require a dedicated outlet at the corner
• Where the roof discharges water rapidly or where low friction roof coverings are employed, a wider gutter may be required to avoid overshooting the gutter

Roofline System

The Swish Roofline range features all the necessary components for eaves and gable assemblies, including fascias, bargeboards, eaves soffits, as well as over fascia ventilation and protection. Matching PVC mouldings cater for all joints, corners and abutments.

Fascias

All fascia profiles are available in a wide range of sizes and feature a groove for the engagement of soffit boards by simple push-fit. They can also be used in ‘open eaves’ situations where there is no soffit.

Fixing Methods

Jumbo and 16mm boards do not require a supporting backboard. They provide support at the eaves for the roof covering at all roof pitches. Boards must be fixed to rafter ends at a maximum of 600mm centres using 2x65mm Trimtop nails. Fix gutter brackets directly to Jumbo and 16mm boards using A4 stainless steel screws which should penetrate the inner face of the board.

Coloured Roofline Profiles

16mm Square fascia boards are available in Mahogany, Light Oak, Rosewood and Black woodgrain effect finishes. Anthracite and Grey profiles with a self colour skin are also available. A range of matching ventilated soffits, flat board soffits, corners, trims and fixings is also available. Fixing centres for coloured profiles must not exceed 400mm.

Ventilation

Swish systems allow ventilation of the roof void in accordance with Building Regulations for England, Wales, Scotland and Northern Ireland. Swish ventilators meet the recommendations of the 1989 edition of BS.5250:1975.