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Avon Timber Merchants is now closed for the festive holidays until our return on Friday, 2nd January 2026, reopening at 8:00 AM.

 

All orders placed on our website will be processed and delivered as soon as possible after our return in January 2026.

The quoting system remains available to use, however, it will not be monitored during the closure. Requests will be reviewed and processed promptly upon our return.

We would like to take this opportunity to wish all our customers a very Merry Christmas and a Happy New Year. Thank you for your continued support.

Warm regards,
The Website Administration Team

Avon Timber Merchants – Stock Take

Please note that we will be closed on Friday 29th May 2026.
We will be open as normal on Saturday 30th May 2026.

Warm regards,
The Website Administration Team

Oak

Oak Window Boards

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A window board, also known as a window sill, not only frames the base of the window itself but also acts as a shelf which can be used to display decorative accessories, store important possessions or brighten up the home.

For UK homeowners who want to upgrade to oak window boards as part of a renovation project or decorating project, knowing what makes a high quality and durable timber is key.

Here at Avon Timber, our solid oak window boards are made to measure and available in two different finishes - enabling designers, developers and DIYers to select the finish which best compliment the style of the surrounding space.

Oak Window Sill Finishes

Bullnosed window sills

Bullnosed window sills boast a subtle curve on the outer edge of the sill which softens the aesthetic and creates a more traditional look and feel. An ideal way to tone down the angular corners of modern living, bullnosed window boards are also well suited to family homes thanks to the high quality machined finish which helps to soften the sharp corners.

Square Edged window sills

A square edged oak window board is a modern and stylish addition to the home which suits a very neutral decorated space with minimal furnishings and lots of angular corners and edges. The choice of solid oak in particular lends itself to this simple but durable window sill being naturally decorative and the perfect feature for just inside of your interior windows.

2 Products

Oak Windowboard FAQs
Is oak the best material for internal window sills?

Here at Avon Timber, we believe that oak is not only one of the best materials in terms of durability but also with regards to quality, aesthetic value, and the sustainability of kiln dried oak.

Why is oak good for a window sill?

The natural grain of solid oak really comes to life when used to create oak window board structures, thanks to the proximity to the natural light source.

In addition, oak compliments all manner of different interior styles and UK home designs, making it a versatile choice for any homeowner.

What size wood do you use for window sill?

As our oak window structures are bespoke products, once you have selected your ideal finish (bullnosed edge or square edge) we will ask you for the dimensions of your window in terms of ideal length and width. We recommend to all customers that the dimensions they provide us with include adequate length for the horns of the window structure - that is, an extension of the sill along the front which strengthens the joint between the sill and the edge of the window. The horn is both aesthetic and structural, adding strength to the sill and ensuring it blends neatly into the surrounding wall.

This information should be provided in millimetres as per the order pages, so that the window board can be made to the right size for your property.

Is it correct to say window sill or window cill?

Both sill and cill are used in English, though sill is the standard modern spelling in most contexts, including architecture and joinery, so window sill is the correct form. The variant cill is more commonly encountered in historical or engineering contexts, particularly in reference to canal locks, where it refers to the horizontal ledge at the base of the lock gate. Despite the different applications, both terms describe horizontal structural elements.

Let Avon Timber help you find the perfect oak window board for your home, pairing our expert advice with your vision of how you'd like your oak window boards to look.

Why install a window board?

A windowboard serves several important functions in a home:

1. Aesthetic Enhancement: Provides a finished, polished look and integrates the window into the room’s design.

2. Practical Surface: Creates a usable space for plants, photos, or décor.

3. Protection: Protects walls from condensation and wear.

4. Insulation: Helps reduce drafts and improves energy efficiency.

5. Structural Support: Helps maintain stability around the window opening.

Can you supply bespoke sizes?

Yes, all of our window boards are machined in-house to customer specification, allowing us to produce custom sizes to suit your project. Our online formula allows you to adjust width, length (up to 3m) and edges. If you’d like further customisation or longer lengths than 3m, please feel free to contact us via [email protected], and we’ll be happy to help out.

How much should a window board overhang?

How much your window board overhangs is your own design choice. We’d usually recommend between 20mm to 50mm overhang at the front and 50mm side overhang (horns) on each side – adding 100mm to the full width of the board.

The amount a window board overhangs is largely a design preference and may vary depending on the style of the property and installation requirements.

As a general example, some installations use approximately 20mm–50mm front overhang, with side overhangs (horns) of around 50mm on each side. This would increase the overall length of the window board by approximately 100mm.


Side horns are typically left longer and trimmed on site by the installer to suit the wall conditions and achieve the desired appearance. This also allows for a more accurate fit, particularly where walls may not be perfectly square.

We recommend confirming requirements with your installer prior to ordering, as preferences and site conditions can vary.

What thicknesses are available?

Our standard thickness is 26mm, as this best suits our rounding cutter. However, we can provide thicknesses from 18mm upwards.

Please note:

Below 25mm, the bullnosed/returned end window board will not be fully rounded and will have a more pronounced curved profile.

Above 27mm, the edges are typically rounded on the top and bottom with a flatter front face.

Are the window boards fully finished?

Our hardwood window boards are supplied freshly machined but unfinished as standard, while our MDF window boards are supplied pre-primed. This means they are ready for painting, staining, or varnishing on site.

Are the window boards suitable for kitchens and bathrooms?

Yes, however we recommend moisture-resistant MDF or hardwoods where appropriate. Proper sealing and finishing is advised after installation.

What is meant by returned ends?

When the ends are returned, it means they are rounded. On a bullnosed edge window board, the front edge profile is continued around the ends for a clean, finished appearance. Returned ends also help conceal any exposed end grain and provide a more professional finish once installed.

Do you cut out the horns?

No, we do not cut out the horns prior to supply. Boards are supplied square so installers can cut them on site for a precise fit.

How are the window boards packaged?

We take care to package window boards securely with bubble wrap, shrink wrap, and end protection to minimise damage in transit.