Exterior Window Sills

Combining Weather Protection and Aesthetic Style into one Composite Construction Element

Exterior Window Sills

Apart from the window itself, external sills significantly determine the look of a building's facade. The various decorative possibilities, such as flowerpots, for example, make them popular elements for exterior decoration. They can be fabricated from different materials and come in a variety of colours to match the selected window. Yet, such a sill is not only a means of decoration on the outside, it also provides weather protection for windows and other construction elements.

Installation and Function

The main purpose of an external window sill is weather protection. Due to the predetermined thickness of the wall and the windows installed in it, a part of the facade is almost always exposed to the weather. This exposed part needs to be protected by an external window sill.

Water entering the masonry from the outside can damage the window's frame, its seals as well as the wall itself. Sills are typically installed with a slight slope and a so-called drip edge - this serves as a water drainage measure to allow proper drainage, preventing stagnant bodies of moisture from forming inside the masonry.

The overall construction depth of an external window sill is based on the thickness of the walls and the available space between the exterior edge of the reveal and the position of the window frame. Adding plaster to the edges of an external sill provides additional protection for the masonry.

Different materials and their characteristics

The selection of materials suitable for an external window sill is limited by the fact that these construction elements have to face a variety of weather conditions. Ultraviolet light, heavy rain, wind and dirt can affect their condition and lifespan significantly. However, the available selection of suitable materials for the external sill allows for a great measure of individualisation. While wood might better match the design of your facade, it also requires more maintenance than ashlar. The most common materials currently used in this area of fenestration are:

  • Aluminium
  • Ashlar
  • Timbers
  • uPVC
  • Marble

In addition to the classic materials, such as ashlar, wood and marble, modern fenestration mainly employs aluminium for the manufacture of external window sills. The light metal is often used for both the interior and the exterior.

Classic Materials for your Sill

In the past, external window sills were fabricated from wood. However, as solid wood tends to require special maintenance - to prevent the harm that inclement weather can cause the premium material - nowadays highly compressed wooden fibre cores with a resign binder material are much more commonly used. However, even these models are almost exclusively suitable for internal window sills only.

A marble sill, meanwhile, tends to be slightly more expensive than one made from timbers, but in return, it provides an eye-catching look for any home. This beautifully grained stone enhances the visual appearance of any building's facade and can be used as a central element to the visual style of any house. Marble that is used on the exterior can quickly lose its lustre, and thus requires a significant amount of maintenance, just like wood. In addition, potting soil and water can result in unsightly discolorations and pose a serious problem for an external sill made of marble or ashlar.

Ashlar is the more affordable alternative to marble. It is a low-maintenance material and highly resistant to the influence of inclement weather, but the options for customising building elements made of ashlar are actually rather limited. Neither an ashlar nor a marble sill allows you to choose the design of the drip edge. The relative weight of stone materials should also be taken into consideration, as lighter materials are much easier to transport and install by yourself. This means that lighter external window sills can usually be installed without any extra help and within a smaller timeframe. Especially in regards to installing exterior sills, less weight significantly facilitates the work process.

The Aluminium External Window Sill - an all-around Solution

Aluminium is a particularly popular manufacturing material for external window sills in modern fenestration. This is because, apart from its very affordable price, the material stands out due to a number of positive characteristics:

  • Various designs thanks to a variety of possible shapes for the drip edge
  • Noise suppression tape muffles the sound of raindrops hitting the surface
  • Full RAL colour range allows for individual customisation
  • Easy maintenance

One significant overall advantage is the fact that, thanks to the material's low weight, its modern fabrication and the available additional equipment, aluminium sills can also be installed by laypersons. That being said, it is imperative to make sure that all thermal insulation measures are installed properly. This includes sealing all joints properly to prevent your window from supporting the formation of thermal bridges. If insulating the sill is not done properly, even the highly beneficial Uw-values of a high-end window can suffer.

Custom Design

An external aluminium window sill can benefit from a wide selection of available colours as well as different designs for drip edges. Particularly the choice of different edge shapes can lead to a highly individualised facade and a distinctive exterior appearance for your house. Not only is the full RAL colour range at your disposal, but also a variety of foil-based decors showing marble, granite or wooden grains, which can be used to provide your home with a particularly classy appearance.

Aluminium as a construction material also guarantees the colour steadfastness of your external sill. The selected colour does not fade, reliably staying vivid until you decide to change the colour or design.

Starting a beautiful Day - every Day

Noise suppression tape can help ensure that you are not woken early by the impact noise of heavy rain. The maintenance of an external aluminium sill only requires minimal effort. Simply wipe it with clean water or a combination of water and mild household cleaner to remove dirt caused by rain. The plaster edges on the sides create a continuous edging, facilitating the effortless maintenance of an external window sill.

Tasteful Sills for your Home

The external aluminium window sill also shows advantages in regards to installation. Due to its low weight, it can be easily transported and installed into plastered and non-plastered facades. With suitable tools and a trusty installation manual at hand, you can install the external sill yourself. If you want to be extra careful with the installation, you can always get the help of a professional.

Thanks to the favourable characteristics of the various materials and the multitude of options for customisation, you can choose from a wide range of products when purchasing your next external window sill.

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