Why a Bay Window Deserves a Bespoke Seat

A bay window is one of the loveliest features in a British home, yet it is also one of the most awkward. All those angles and sills eat into floor space, and most people end up dumping a plant pot and a dying fern in there. A built-in window seat changes that entirely. Instead of a dead corner, you get a proper place to sit with a mug of tea, watch the street, and read while the rain does its worst outside.

The real magic, though, is what goes underneath. A bespoke bench over a bay gives you somewhere between 150 and 250 litres of hidden storage, depending on the depth of your recess. That is a whole winter's worth of blankets, board games, wellies, or the ever-growing pile of children's toys. On top you get a seat. Below you get a cupboard. Few pieces of joinery work that hard for the money.

Measuring the Bay Before You Commit

Bays come in three main shapes: the canted or angled bay (three sides, the most common in Victorian terraces), the square bay (a rectangular projection), and the curved or bow bay. Each needs a slightly different approach, so start with a proper survey rather than a rough sketch.

• Measure the width at the back wall, then at the front of the recess, and again at the widest point. On an angled bay the front face is usually the shortest, and the two angled returns taper inwards.
• Check the sill height. Standard sills sit around 750–900mm from the floor. This is the maximum comfortable seat height, so if your sill is low you may need a slimmer base.
• Mind the radiators. Many bays have one tucked underneath. If yours does, either leave a vented gap behind the bench or relocate the radiator before you build — trapping heat behind MDF is a recipe for warping.
• Look at the skirting and any pipework. Wrapping the bench around existing skirting looks neater than cutting it out, but it costs you 15–20mm of depth.

Draw the footprint to scale on graph paper, treating the bay as a trapezoid. That plan will tell you whether a single lift-up lid is practical or whether you need to break the storage into sections.

Building the Base and Adding Hidden Storage

The frame is straightforward carpentry, even for a confident beginner. Build a plinth from 50 x 50mm timber battens, fixed to the floor and to the wall, then clad it in 18mm moisture-resistant MDF. Prime the cut edges twice — MDF drinks paint and cut edges show every brushstroke otherwise.

For access, you have two realistic options:

• A lift-up lid. The whole seat top hinges along the back edge. This gives the largest single opening, ideal for long items, but you must lift the cushion off every time you want in.
• Drawer fronts. Three or four shallow drawers on the front face are far more convenient day to day. Use 400mm full-extension runners and allow a 3mm gap around each front.

A good compromise is a mix: drawers in the straight back section and a lift-up lid over the angled corner where drawers would jam. Line the inside with a wipe-clean painted finish rather than fabric, and add a discreet vent or two — trapped damp air in a cold bay will make everything smell musty by February.

Comfort, Cushions and the Seat Top

A window seat is only as good as its cushion. A hard MDF top with a thin pad is fine for a minute and miserable after ten. Aim for a foam cushion at least 75mm thick, and go to 100mm if it is a seat you will use daily. Medium-density foam with a soft top layer gives the best balance of support and squish.

Choose a fabric that can cope with sunlight, because a south-facing bay will bleach anything delicate within a season. Tight weaves, linen blends, and washable covers in a mid-tone are the sensible choices. If you can, have the cover made with a zip so it can go in the machine. A fitted box cushion with piping looks smart, but a simple piped pad that sits loose is far easier to live with.

For the seat top itself, 18mm MDF is fine, but 25mm plywood is stiffer and less likely to bow over a long span. If your bench runs beyond about 1.2 metres unsupported, add a central leg or a mid-panel. It will save you a sagging seat in two years' time.

Styling a Small Space Around the Seat

The whole point of a window seat is that it earns its footprint, so keep the surrounding area calm. A bench that runs wall to wall with built-in storage replaces the need for a side table, a toy box and a blanket basket.

• Choose one or two cushions in a colour drawn from the room, not five in competing patterns.
• Add a slim wall light or a rechargeable lamp on the return wall — lamps on a sill block the view and are easily knocked.
• Fit a Roman blind rather than curtains if space is tight; blinds sit within the recess and do not steal the seat's corners.
• Use the under-seat space honestly. One category per compartment beats a mystery box you never open.

Paint the joinery the same colour as the wall to make the bay feel wider, or go a shade darker for a snug, cocooning effect. Either way, the bench should look like it was always meant to be there — which, once it is finished, it will.