Building a Simple Window Seat for a Bay Window

Why a Bay Window Seat Is Worth the Effort

Bay windows are a lovely feature of British homes, but they can also be awkward. Those angled walls and deep recesses often end up as dumping grounds for plants, paperwork or a lonely armchair that never quite fits. A built-in window seat solves that problem. It turns wasted floor space into a cosy perch, adds valuable storage beneath, and frames the view like a stage. Whether your bay is a Victorian three-sided affair or a simpler square bay, a timber frame with a cushioned top can be tailored to fit. The project is achievable for a confident DIYer with basic tools, and the result feels bespoke without a bespoke price tag.

Measuring the Bay and Planning Your Seat

The first job is to make an accurate template of the bay floor. Cardboard or thin hardboard works well. Press it into the corners, trace the angles of the walls, and cut it to shape. Don’t assume the bay is symmetrical. Measure the width at the back, the width at the front, and the depth at the centre and at each side. Note the height of the window sill and any radiators. A comfortable seat height is usually around 450mm from floor to the top of the cushion, so allow for your chosen foam thickness. If a radiator sits in the bay, you’ll need to leave clearance or consider moving it, as blocking heat is both inefficient and bad for the timber.

Think about how you want to access the storage. A lift-up lid is simplest, but it needs clear space above to open. Drawers are more practical if you want to keep the top clear, but they require pull-out room. For a small bay, a combination of a fixed centre panel and hinged end sections can work well. Also check for skirting boards and picture rails. You may need to scribe the frame around them or remove a section of skirting to get a neat fit.

Constructing the Timber Frame and Storage

Use 44mm x 69mm CLS timber for the main frame. Cut a base frame to match your template: a front rail, a back rail and angled side rails. Fix them together with wood screws and PVA glue, checking for square as you go. Add vertical studs at the front and back to support the top, spacing them no more than 400mm apart. If you’re building a lift-up lid, create a shallow box with a hinged top made from 18mm MDF or plywood. For drawers, build a simple carcass with runners screwed to the sides.

Secure the frame to the wall using frame fixings or heavy-duty brackets. Don’t rely on the floor alone; a window seat takes weight and you want it solid. Clad the front and sides with 18mm MDF or plywood, scribing the panels to the walls and skirting. Use your cardboard template to cut the angled side panels accurately. Fill screw holes and joints with wood filler, then sand smooth. Prime and paint the frame before fitting the cushion, using an eggshell or satinwood that matches your woodwork.

For the storage base, line the inside with a thin plywood or MDF floor. If you’re using a lift-up lid, fit a piano hinge along the back edge and add a pair of gas struts to hold it open safely. Drill ventilation holes in the lid or base to prevent damp and musty smells.

Upholstering the Cushioned Top

The cushion is what makes a window seat truly inviting. Choose a medium-firm foam, around 50mm to 75mm thick, with a density of at least 25kg per cubic metre. Too soft and you’ll feel the timber beneath; too firm and it won’t feel cosy. Cut the foam using your template, but add a little extra to the front edge for a slight overhang. A serrated knife gives a clean cut.

For the cover, pick a durable upholstery fabric such as linen, wool, or a sturdy cotton blend. A removable cover with a hidden zip is worth the effort, as it can be washed. Add piping around the top and bottom edges for a crisp, professional finish. Before sewing, wrap the foam in a layer of polyester wadding to soften the edges and help the cover slide on. Attach the cushion to the lid or frame with hook-and-loop tape so it stays put but can be removed. If you have a lift-up lid, fix the tape to both the lid and the cushion so they open together.

Finishing Touches for a Cosy Look

With the seat built and cushioned, the fun part begins. Paint the frame in a colour that complements your walls—soft grey, sage green, or a classic off-white all work well in British homes. Add a couple of scatter cushions in contrasting textures: a chunky knit, a velvet, a linen. A small reading lamp on a side table, a stack of books in the storage below, and a throw for chilly evenings complete the picture.

If your bay has a radiator, make sure it’s not blocked by the seat. You could fit a slimline radiator or move it to an adjacent wall. A Roman blind or a pair of curtains hung at the edges of the bay will frame the window without crowding the seat. Finally, consider a small basket for blankets or magazines. The result is a warm, practical nook that makes the most of one of the best features of a British home.