Designing an Efficient Surface Water Drainage System for Roofs

Designing an Efficient Surface Water Drainage System for Roofs

Drainage systems are a necessary and often overlooked aspect of civil design and engineering for architects Warrington. Essential in the removal of excess water on the surface or sub-surface of roofing, without a properly designed and installed drainage system you can encounter waterlogging of soil and indoor flooding. There are many big and small specifications to consider when developing drainage systems, especially surface water drainage systems.

Architects Warrington know that even minimal amounts of rainwater not being appropriately drained can quickly lead to dampness and damage to the building and roofing system. This is why we’ve outlined some of the key considerations when designing a surface water drainage system, along with some of the basics of the installation and successful maintenance.

The Two Types of Drainage to Consider

The two main types of drainage systems are subsoil drainage and surface water drainage, both with their particularities and difficulties when considering their drainage properties. Surface drainage is the most commonly considered type of drainage as it is easily visible. From roofing drainage to paved areas, both require different methods of drainage.

However today we’re focussing on surface water drainage, and how to design the right system depending on the surface and specifications present. The main subsets of surface water drainage are roofing drainage and paved area drainage, each with very different methods and requirements architects Warrington consider when designing.

Roofing Drainage Design and Required Fall

In keeping with the Building Regulation’s Approved Document H, roofs must be designed with a minimum amount of fall and subsequently drain into either a surface water collection channel or gutter. If draining to a gutter, surface water must eventually reach vertical rainwater pipes that connect and deposit to the drainage system.

Depending on the roofing material you’ll have a different requirement of fall for the roof design. The average recommended falls for various materials are listed below:

Aluminium – 1:60

Copper – 1:60

Lead – 1:120

Mastic asphalt – 1:80

Roofing felts – 1:60

Roofing Drainage Considerations Regarding Guttering and Downpipes

Most roofs will typically use internal rainwater outlets and downpipes or a system of gutters or hoppers. No matter what kind of system, two drainage points are always recommended as a minimum in case of possible blocking or malfunction with one of the points. Not only must all pipes have leak-proof joints, but roofing should extend into and below the tops of any gutters to prevent water from being blown away from the drainage system and onto any eaves or other buildings.

Call Architects Warrington Today for More Information

While we’ve outlined a few of the basic considerations when building surface water drainage systems for roofs, there are many more particularities that should be considered when designing and constructing any kind of roofing. If you want to read more about drainage systems, we’ll be covering other surface and subsurface drainage systems in depth throughout our next few blog posts.

If you have any questions in the meantime, our team of expert architects Warrington are always available and happy to help with any construction or civil engineering design consulting you might need. Call us at 0151 321 1986 today to talk to us about whatever building or constructions questions you might have.