Since ancient times, man has settled civilizations near permanent water bodies to meet his needs of irrigation, transport, and to sustain life. Early man used to take shelter in caves to avoid getting drenched in rain. Slowly they started making temporary shelters until they reached a point where the permanent settlement was possible. The architecture of mankind has always revolved around rain drainage. The control and successful management of water had an important impact on early society.
Be it early housing at Harappa and Mohenjodaro or Buddhist caves in Kanheri (Maharashtra), our ancestors have built marvelous examples of drain drainage lines that exemplify the excellence of the water management system of those times. These examples are almost perfect in terms of their functionality and therefore they set the basic rules of architecture when it comes to water drainage. Times have changed and we have mended architecture according to our needs but, the basic purpose of shelter remains the same.
Let us now discuss the Principles of Rain Drainage in Architecture which are the outcomes of learning from the past.
1. Roof design
The basic function of any roof is to offer protection from harsh weather conditions. As per the function of the building, different roof forms are adopted to avoid rainwater or snow inside the structure. According to the changing geography, certain parameters are considered before designing a roof form.
The slope in the roof let the water, snow, and ice flow off the roof with the help of gravity. The placement of the slope and the degree of the angle is often based on the size of the home.
Even the flattest roof needs to have some amount of slope to avoid the accumulation of water since it can lead to leakages.
3. Overlapping plates
Any roof material, be it terracotta, bamboo, slate, G.I, or wood must be fixed by overlapping on top of each other to prevent water from reaching any structural member, as it may rust/spoil or weaken the strength of it. The shallower the slope, the more they need to be overlapped. There is a possibility of capillary seepage between the objects, so a tight seat between overlaps is important.
For a flat roof structure, a parapet wall is the utmost essential. They hold back roof snow/rain from falling and prevent the decaying of walls. They also act as a guide for water to reach drainage pipes. It is good practice to provide overflow drains for parapets, particularly if the roof is low-slope or flat. These overflow drains might be scuppers, which are simply holes in the parapet and channels that pour out onto the landscape below.
On a flat or low slope roof, corners like behind the chimney or the boundary edges are most prone to leakages. To prevent the damage, plaster, china mosaic tiles with white cement, or small pieces of metal are used to create flashing. The small curved surface between the junction of the vertical wall and the horizontal surface is called flashing.
6. Gutter systems
A rain gutter is a very important component of a water discharge system for a building. It is essential to direct the falling water to a suitable disposal site where it will not damage the building. Typically a metal piece is shaped round or rectangular and fixed at the end of the slope. These systems of pipes across the roof have several exits as down sprouts from where the water is carried down to a safe location where it can not damage the foundation.
Vertical metal pipes on the facade may look aesthetically unpleasing if it gets repeated many times. As an alternative to it, metal chains are used at regular intervals to carry the water down. These chains don’t splash water, they create a pleasing sound and look pretty on a picturesque landscape.
7. Rainwater harvesting
Rather than allowing the rainwater to run off, it can be collected and stored in tanks for future use. Rainwater harvesting ranges from collecting roof water in tanks to collecting stormwater on site. A system of gutters on the roof channelize water to a single or more downspout which takes it to a storage tank. After storage, a filtration process may take place before directing it towards the domestic tank for domestic, flushing, or landscape use.
8. Rain screen/wall system
Rainscreen cladding is a double-wall construction that uses a surface to help keep the rain out, as well as provide an inner layer that offers thermal insulation and prevents excessive air leakage. Additionally, it also carries the wind load on the structure. As the inner layer reduces energy losses, the surface breathes just like skin.
In hot climates, rain screens can assist with cooling and In cold climates, they allow walls to dry without compromising the integrity of the siding. It also creates a lower pressure zone which reduces the force of windblown rain.
Once the water reaches away from the building, then what? The entire site needs planning for water drainage. The soil around the building must be sloped outward. A system of the stormwater channel with a metal screen on top needs to be laid out on-site to direct water towards municipal mains. Porous pavers shall be used to allow the seepage of water. If the site is small and the chances of the foundation getting damaged are high, water must be channelized away from the site in a practical way.
Renowned Architects like Le Corbusier, Tadao Ando, B.V.Doshi, Louis Khan, Frank Llyod Wright, etc have used the gutter system as intricate elements of their design. Depending on the perspective or visualization of the architects, water has been interpreted in many forms.
Valley formed between two vaults is converted into a gutter that carries rainwater to a water body in the landscape which promotes the flow of cold air.
Colline Notre Dame du Haut, also known as ronchamp chapel,France, by
A downspout takes the form of a gargoyle that throws water away from the walls of the chapel in a dramatic way. Waterfalls in a basin that channelizes the water away from the foundation of the building.
Eliminating typical metal pipes, these concrete gutters are beams that support the wall and roof of the structure. The same beam is protrude outwards to form a gargoyle that throws away water into the landscape and in a water body in the courtyard.
Water is a precious source. One must save ourselves from the damage it can cause but at the same time, it should be treated respectfully. Local building codes and laws must be followed ethically. Once, water was considered primarily for buildings and construction. Today, we take for granted the efficiency with which one can just connect a pipe to city utilities and get whatever we want. It is important to connect ourselves back to the primacy of nature.