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What is the Importance of Window Sills?

By: Dr. H.C. Mario Schmidt, Lingel Windows & Doors Technologies Private Limited

Window sills are an integral part of any building’s structure. The building envelope is the outside part and has to face many weather conditions or the fury of nature. We protect the outer skin by having different kinds of claddings; for example, stone cladding, marble cladding, etc. In some areas, we fix tiles or wooden cladding or go for special plastering, so that the area of the outer structure looks presentable and is protected against the weather condition.

But in India, that window sill area is completely neglected. Outer walls by default are vertical. So when the rainwater hits the wall, it will flow down. But the window sill area, where usually the windows are fitted in the centre, has a 2 to 4-inch horizontal plain area. So eventually in this area the rainwater and dust may also collect. If a mason does not make the slope towards the outer wall, the water will collect towards the window. In monsoon, there are chances of water leakage and the water will enter inside the house.

What are the options to consider?

Option 1: You can have a stone cladding at the sill area but even then care should be taken that there is one inch of overlap so that the water flowing out from the window sill is actually going down and not hitting back to the outer surface of the wall.

Option 2: This is widely used in Europe where the window sills are made out of aluminium. You can choose colour options to match it with the colour of the window. You could go in from lighter shades to darker shades to match the outer walls.

The rainwater hitting the glasses will drain down on the window sill. As the window sill will have a slope angle of 5 to 8 degrees, the water will completely drain out. If the window sill is around 50 mm in front of the building, then the rainwater will drop down hitting the surface of the building. This will ensure there is complete water tightness. So in the monsoon when the water comes through the glass, it will immediately drain out. At the sides where the Aluminium sill is attached to the wall, end caps are connected. This will assure complete water tightness and it provides the perfect connection to the wall.