Rain Drainage Principles in Architecture


Earlier, a building consisted of a roof and an assembly of wood, metal or masonry, but now, modern technologies have improved this effort. Use of roof material and water-shedding methods which are cheaper and easier to install are prevalent, nowadays. Most of the drainage systems aim at reusing the rainwater as greywater for landscaping. This article contains some architectural aspects to modern-day rain drainage system design. Roof design and Gutters are the main components of an effective Rain Drainage Principal in architecture. Both of them are discussed in detail in further sections. 

Rain Drainage Principal

Source: roofingrepairoptions.com

Also Read: 6 Practical Landscape Design Tips for a Functional Outdoor Living Space

Roof Design

Rain Drainage Principles

Source: hudecheckroofing.com

A roof serves the purpose of keeping the natural element away from entering the house. A roof can be explicitly designed to allow small traces of skylight or sunlight to enter the inside of the house. A trellised roof can be designed to rain and snow to enter the interior. A roof design contains six primary components: slope, overlap, vapor barrier and ventilation, parapet, flashing, and skylights. All of these components are discussed briefly below. 

Slope: Gravity plays a vital role in shedding away precipitation. If a roof is steeply sloped, water will reach the ground more quickly. Buildings in areas that experience heavy snowfall require steeply sloped roofs because snow stuck on the roof takes time to melt. 6:12 Pitched Roof is typical in most of the cabins and snow resorts, and even the flattest roofs need some slope. 

Overlap: Roof materials should overlap in such a way that the uppermost piece is outside of the part that is at the underside. The installer begins by starting to put the slides at the bottom and goes upward. The overlap is used in chimneys and mechanical systems as well. The overlap is essential for a building which is exposed to natural elements. Shallower slopes need more overlap. 

Vapor Barrier & Ventilation: A waterproof layer is essential on the underside of the wall assemblies and the roof. Building codes domineer these moisture barriers to separate materials which should stay dry and the materials which should get wet. These barriers are significant because some moisture can build up due to temperature difference. Ventilation prevents the condensation of water. Modern roofs require some sort of ventilation to prevent water condensation. 

Parapet: Parapet roofs usually rise above the eave of the roofs to hold back roof snow from falling. Adequate drainage of parapet walls is vital, and thus, downspouts should be used more frequently. In general, downspouts are placed 20 ft of parapets and 40 ft. of eaves. Providing overflow drains for roofs and parapets is an excellent thing to do, especially in the case of low-slope roofs. These overflow drains can be small holes in the parapet and channels called scuppers. The drain hole size should be large enough to prevent clogs. 

Flashing: Flat areas on the roof should be avoided at all costs. Tight spaces like place behind the chimney leaks are prone to leakage. Building a cricket and surrounding the crickets and chimney flues with well-sealed metal flashings can avoid this problem.  Flashing, an anti-corrosive metal surrounds any penetration or transition and is sealed adequately to prevent all kinds of leakage. Flashing, combined with careful overlapping is necessary for best results. Snow may build up in tight areas and leach up the flashing. 

Skylights: Skylights, although great for daylighting are also a big culprit for roof leaking. Windows which come in contact with water can experience leaking and moisture condensation. The skylight should be sheltered as much as possible. Standing water should be avoided, and the rainwater should be allowed to drain away from the glass quickly. The material should be sealed and Adequate Ventilation and window thickness should be provided.


Rain Drainage Principles

Source: neiltortorella.com

Sizing: Roof gutters come in various shapes and sizes because the metal is simply bent into a rectangular or circular shape. Custom metals and shapes can add to the aesthetics of the building as well. Gutters, in general, are four to six inches tall and wide. However, larger areas with larger roofs require larger gutters. Gutters should be laid on a slight slope so that the water can pour quickly to a downspout. Internal gutters are also made that extrude down into the roofs. During the Gutter Installation, the metal side needs to be folded up the fascia and under the upper roof material.  If left undone, dripping water can get under the roof material. Gutters are commonly torn off from large rainstorms and snow. 

Gutter Screen: Gutter screens are used to keep away leaves, snow, and debris from the channels. While choosing the screen, the clinging nature of the water should be kept into consideration. The screen should make sure that the snow or debris that is accumulated melts off quickly. The gutter screen is also used to keep away pests if the downspout is also screened.

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