Roof Drainage

Caskade® PREMIER

Caskade Premier

Well designed roof drainage is critical to the success of any building. The CA Building Products Caskade® PREMIER PVC pre-laminated membrane gutter has been developed to provide long term durability and efficient performance in removing rainwater from the roof quickly and effectively. With a complete portfolio of fully compatible accessories, full design and calculation service for gravity fed systems in accordance with BS EN 12056-3:2000 and classroom based or on-site training available, the Caskade® PREMIER system offers bespoke solutions to most rainwater management design issues. The membrane supplied within the system is pre-laminated under the most rigorous quality assurance conditions, allowing the entire system to be supplied complete with the CA Building Products up to 25 year guarantee. The membrane delivers the additional comfort of comprehensive BBA Agrément Certification and is highly puncture-resistant. Structurally designed to exacting requirements, the Caskade® PREMIER system utilises high tensile precision steels in its manufacture. Expansion and contraction issues…

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Truline Gutters

Truline Gutters

Suitable for most Cat. 1 roof drainage designs the Truline gutter systems can be a cost effective solution specifically designed to suit the project application. Truline external boundary gutters are typically manufactured from pre-coated steel including Colorcoat HPS200 Ultra® and Colorcoat Prisma®.  Post coating is also available using polyester powder coating and Syntha Pulvin® to match most colours…

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Roof Drainage Design

Aerial Gutters View

The design of any rainwater management system should achieve a balance between the cost of the roof drainage system and the frequency and consequences of flooding. The capacity of any roof drainage system should be adequate to dispose of intense rainfall that usually occurs in summer thunderstorms.

In accordance with BS EN 12056-3:2000 gravity and siphonic drainage systems are calculated based on categories of risk.  The risk equates to a probability of exceeding the chosen rate of rainfall during the lifetime of the building, this probability may be assigned a value between 0, representing assured safety, and 1, representing certainty that the rate will be exceeded.

Four Categories of design rate are proposed in BS EN 12056-3: 2000 as follows;

  • Category 1 has a return period1 of 1 year and is the minimum option that should be used for eaves (external) gutters and flat roofs
  • Category 2 is used on valley & parapet gutters or where the building or its contents should have an additional measure of protection, a return period of 1.5x anticipated building life should be used, corresponding to a probability of around 0.5.
  • Category 3 when a higher degree of security than that provided by category 2 is desired; a return period of 4.5x the anticipated building life is used, corresponding to a probability of 0.2.
  • Category 4 is used when there should be the highest possible security (probability approaching 0.0)

For each project the drainage system should be designed and constructed to comply with BS EN12056-3:2000 and based on the geographical location of the building, building design life (generally 25 years) and the risk protection category, producing the Rainfall Intensity RFI expressed as litres/second/m² (l/s/m²).

1 Return period is the likelihood of a storm of a similar intensity returning within that period of time (years).  For example, a return period of 1 year (Cat. 1) is less onerous that a return period of 37.5years (Cat. 2 – 25 year building life x 1.5 = 37.5 years), which is less onerous than 112.5 years (Cat. 3 – 25 year building life x 4.5 = 112.5 years).

CA Building Products Gutter Systems

Caskade® PREMIER

Caskade Premier

Well designed roof drainage is critical to the success of any building. The CA Building Products Caskade® PREMIER PVC pre-laminated membrane gutter has been developed to provide long term durability and efficient performance in removing rainwater from the roof quickly and effectively.

With a complete portfolio of fully compatible accessories, full design and calculation service for gravity fed systems in accordance with BS EN 12056-3:2000 and classroom based or on-site training available, the Caskade® PREMIER system offers bespoke solutions to most rainwater management design issues.

Caskade® PREMIER can be integrated into any roof drainage design, whether gravity or siphonic, click here for further information.

Truline Gutters

Suitable for most Cat. 1 roof drainage designs the Truline gutter systems can be a cost effective solution specifically designed to suit the project application.

Truline external boundary gutters are typically manufactured from pre-coated steel including Colorcoat HPS200 Ultra® and Colorcoat Prisma®.  Post coating is also available using polyester powder coating and Syntha Pulvin® to match most colours.

Rainwater Pipes and Accessories

Rainwater Pipes

Often an after-thought, rainwater pipes can provide a striking architectural feature as well as a fundamental function forming part of the rainwater management system.

Square or round rainwater pipes are available in a range of colours and finishes, manufactured in standard lengths up to 3 metres or bespoke to suit individual applications.

Circular pipes are generally manufactured from extruded aluminium, stainless or galvanised steel and can be post-coated in a range of finishes including polyester powder and Syntha Pulvin® to standard colours.  Square pipes are available in Colorcoat HPS200 Ultra® and Colorcoat Prisma®, as well as Plastisol and extruded aluminium.

A range of accessories are also available including collars, rodding eyes, swan necks, gully adaptors and pipe clips, all manufactured individually to meet client requirements. “Anti-Climb” and chain pipes are available on request.

Siphonic Systems

When specifying a siphonic system to be used in conjunction with the valley/boundary gutter systems supplied by CA Building Products it is important that the entire system including the gutters are designed in accordance with BS 8490: 2007 ‘Guide to siphonic roof drainage systems’, by a suitably trained and qualified person as siphonic systems usually are designed with two separate drainage runs; a primary system and a back-up secondary, to ensure the whole system does as intended.   However history has proven that certain clauses should be stipulated to aid in this design;

  • both primary and secondary siphonic systems should be provided, with both being connected to the storm drainage system. The primary system shall drain at least 50% of the design rainfall intensity (RFI), which equates to most rainfall and the secondary system must be designed to drain the balance, at peak rainfalls.
  • siphonic pipework must be firmly attached to an engineered continuous railing system, using appropriate pipe clamps.  It shall be securely fastened back to the main structure at a maximum of 2m centres, to provide adequate and proper restraint against thermal expansion and contraction plus vibration during operation.

Inspection and Maintenance

Badly Maintained Gutters
Badly Maintained Gutters

CA Building Products recommend that gutter inspection and maintenance is carried out on a regular basis to ensure you do not encounter problems, such as blockages, which impact on the drainage of the roof leading to water entering the building.

Gutters should be inspected more frequently than the roof and wall cladding systems and as a minimum we recommend a maximum of 12 month intervals.

When the gutters are connected to a gravity drainage system, ensure all pipework is inspected in accordance with BS EN 12056- 3:2000.  Section NE.5.1 states; “Gutters, rainwater pipes, outlets and gratings should be inspected and thoroughly cleaned once a year, or more often if the building is in or near to an industrial area or is near trees or may be subjected to extremes of temperature.”

When the gutters are connected to a siphonic drainage system, ensure the system (outlets, tailpipes, horizontal carrier pipes, etc) is inspected in accordance with BS 8490:2007. Section 12.1 states; “During the first year of operation, it is recommended that inspection, etc. should be carried out four times a year in order to establish an appropriate maintenance regime. The regime should take account of autumn leaf fall and the fact that intense rainfall tends to occur during summer storms.”

Friday, July 27th, 2012