When it comes to window sills, most homeowners choose materials that provide great durability, particularly for exterior use. And though modern aluminium or uPVC window boards offer excellent durability and low maintenance, many people still choose a hardwood window sill over synthetic materials. The reasons are simple: durable hardwood provides great longevity in combination with elegant traditional timber aesthetics; while such a sill may require slightly more maintenance, its benefits are undeniable.

Timber Window Sills

In modern fenestration, the choice of material is of great importance and greatly influences things like weather resistance, strength and of course appearance. This is as true for windows as the sills themselves. Nowadays, modern window sills are typically manufactured using:

Various types of timber (hardwood or softwood)
Unplasticised polyvinyl chloride (uPVC)
Aluminium
Composite materials

However, the requirements for window sills are a bit different than the windows themselves. As the sill is not responsible for thermal insulation, the U-values of the various materials are irrelevant - meaning that hardwood, softwood and uPVC lose their main advantage in relation to metal. At the same time, window sills also play no role in terms of security meaning the strength of metal compared to uPVC is also unimportant.

What to Look for in a Window Sill

Ultimately, the main purpose of the window board is two-fold, depending on its place of installation. When mounted as an external sill, it is meant to protect the window reveal from accumulating rainwater and from constant exposure to sunlight. On the other hand, mounted as an internal sill, it must provide a homely ambiance and a safe place to put decorative items such as potted plants.

Hardwood is the only available material that excels both as an interior and exterior sill, being both highly robust and aesthetically pleasing.

Hardwood Compared to Aluminium

Thanks to the complex internal fibre structure of hardwood, only aluminium can compete with this type of timber in terms of sheer strength and longevity. However, while wood generally needs to be re-painted regularly in order to protect it against water, timbers are able to minimise the effects of exterior damage much more easily than aluminium. After all, re-painting a hardwood window sill is much easier than re-anodising a metal sill after its surface has been scratched.

uPVC as an Alternative Material

In terms of prices, unplasticised PVC is easily the most inexpensive choice for a window sill, certainly when compared to hardwood such as oak or Meranti, almost all of which are derived from trees which are known to grow particularly slowly. Thus, hardwood is the material of choice for homeowners who are willing to choose premium materials, focussing on elegant, traditional wood aesthetics and immense robustness. For anyone that may prefer uPVC, the wide range of colours and decorative wood-grain foils allows the synthetic material to mimic timbers - in purely visual terms, at least.

The Differences between Types of Timber

As their names suggest, the main differences between hardwoods and softwoods lie with their respective strength and hardness characteristics. This means that most hardwood sills are more resistant to damage, while the production of a softwood sill is less expensive because the materials are easier to process. Even though hardwoods and softwoods often differ quite drastically in terms of density, this has almost no bearing concerning their usefulness as a material for sills.

Anyone planning to install their sills without professional help should keep in mind that hardwood is much harder to cut to size without specialised equipment such as high-powered tools.

When it comes to the topic of engineered woods, the differences become even more pronounced. Hardwood is generally much more robust, denser, but also more expensive than MDF, plywood or chipboard. Thus, the question of whether to manufacture a window sill from premium hard- and softwood or more economic engineered woods turns into a cost-effectiveness trade-off.

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