Build a Window Bench With IKEA IVAR Cabinets in 8 Steps for 35% More Storage
Two IVAR 80x30 cabinets cost roughly £110 together and give about 120 litres of usable storage when laid on their backs. Add a 38mm worktop, proper wall fixings and a made cushion, and the window bench compares with a fitted seat quote at £700 to £1,100.
Choosing IVAR over KALLAX or a joinery quote
A UK joiner quoting a fitted window seat for a 1.6m run will usually land between £600 and £1,400, depending on whether the front is shaker or flat. Two IKEA IVAR 80x30x83cm pine cabinets come in near £110 before the top is added. The carcass is 18mm solid pine, while KALLAX uses melamine-faced particleboard inside, and that difference matters on a seat because the front edge takes knee load. Once the laminate on KALLAX splits, the exposed edge chips quickly.
IVAR arrives unfinished, which leaves the front treatment open. You can fit doors, keep open cubbies, or cut rattan inserts to the 80cm opening. At its standard 83cm height, the cabinet is too tall for a comfortable 45cm seat, so the usual build decision is whether to cut the carcass down or lay it on its back. Most builds use the second approach: the cabinet becomes a 30cm-deep, 30cm-high bench base, and the cushion brings the finished seat up to a usable 42cm to 45cm.
A laid-down 80x30 IVAR gives roughly 60 litres of open interior per cabinet. Two cabinets side by side give around 120 litres, compared with the 80 to 90 litres often available in a standard upholstered window seat with one shallow drawer.
The 8-step build
- Lay both IVAR cabinets on their backs with the open faces forward, tight against the wall below the window. Push the two boxes together so the centre seam reads as one line instead of a visible gap.
- Run a 600mm spirit level across both cabinets. Older floors near loft dormers and bay windows are rarely flat. Pack the low side with plastic shims under the base, because folded card compresses under seated weight.
- Bolt the carcasses together through the touching side panels. Use two M6x40 bolts with washers on both sides so the pair behaves as one unit and the centre seam cannot creep open.
- Anchor the back of each cabinet to the wall. A loaded bench can tip forward when a child stands on the end, and the wall fixing resists that movement.
- In masonry, drill 8mm holes, insert brown wall plugs rated for the substrate, and drive 5x60mm screws through the back rail into the plugs. Plasterboard alone will not hold a bench under load. Locate studs with a Bosch GMS 120 or similar and screw into timber, using spring toggles only as a last resort between studs.
- Cut the worktop. A 38mm laminate or oak-effect kitchen worktop should overhang the front by 30mm to 40mm, hiding the carcass edge and giving a lip your calves do not catch on.
- Fix the top from below with angle brackets into the cabinet top rails. Use 8 brackets across a 1.6m run so the top does not pop when someone drops onto the bench.
- Fit the front treatment, doors or open cubbies, then add the cushion last. That way the cushion is sized to the finished height, not to the drawing.
Seated weight goes down through the carcass sides into the floor, while tipping force travels back into the wall fixings. Once the plugs, screws and worktop brackets are doing their job, the rest of the project is finish work.
Wall fixings decide whether it holds
A 1.6m bench, two adults and a child standing on the end can put 200kg of dynamic load through the structure. The back-wall fixings carry the tipping moment. In a 1960s cavity wall, the inner leaf is often aerated block, where a standard brown plug can spin and pull. Use a frame fixing or sleeve anchor rated for lightweight block, and pre-drill at the exact bit size specified for the plug. An oversized hole of even 1mm can halve the grip.
Cushion, fabric and clearance around blinds
A 30mm to 50mm slab of high-density foam at around 35kg/m3 density will hold its shape under daily sitting. Cheap reflex foam can dish within months. Cut the foam to the worktop footprint minus 10mm so the cover seams sit neatly at the edge.
Designers Guild velvet cushions and seat pads look strong against pine, although velvet can mark where the pile crushes. On a bench, a flat-weave or tighter cotton velvet wears better than a long-pile upholstery velvet.
Cushions on window benches tend to slide forward. Two strips of hook-and-loop solve it: staple one strip to the underside lip of the worktop and sew the matching strip into the cushion base.
Loft window seats add a blackout problem. A loft window blackout blind mounted inside the reveal clears the cushion only when the bench top sits below the blind bottom bar. Measure the dropped blind position before fixing the worktop height, because a bench that fouls the blind has to come apart.
For the wall above the bench, picture ledge mounting brackets allow a shallow ledge without putting it in the way of seated heads. Keep the ledge at least 600mm above the finished cushion. Lower than that, people knock it when standing up.
Paint and oil for the pine
Raw IVAR pine scuffs and greys on the front edge within a season of use. Two coats of hardwearing eggshell hold up better than matt emulsion, which burnishes where knees and hands touch it. Mylands paint hallway colours, especially deeper greys and greens, suit this use because the eggshell sheen wipes clean and the pigment depth hides knee scuffing better than a pale flat finish.
Sand the pine to 180 grit, treat resinous knots with knotting solution, then prime. Without knotting, sticky brown halos can surface through the topcoat during the first warm spell as resin moves. If the worktop is real oak instead of laminate, oil it instead of painting it. Two coats of hardwax oil on the seating surface resist sweat and hand grease that a painted top would show.
Floors, hearths and awkward edges
A window bench changes how the base meets a stone hearth or hard floor. Where Karndean Korlok flooring installation runs wall to wall, the cabinet base sits directly on the planks. A 15mm skirting-matched plinth board across the front hides the carcass base.
Korlok is a click loose-lay or glue-down luxury vinyl. A heavy bench on a floating loose-lay run can pin the planks and stop the floor expanding. On loose-lay, either fix the bench to the wall only and let it float clear of the floor, or set the bench before the floor goes down.
A bench beside a fireplace also has to deal with the hearth edge. If the hearth is honed slate, sealing slate hearths Lithofin style with a slate-specific impregnator before the bench arrives avoids the problem of trying to seal a 50mm strip that is no longer reachable. The same applies to grouted stone behind the bench: do the messy sealing while the wall is open, before a 200kg unit blocks access.
Cost, litres and access
Two IVAR cabinets at roughly £55 each, a 1.8m worktop offcut at £40, fixings and brackets at £25, foam with a made cover at £90, and two tins of eggshell at £60 put the build near £325 for a 1.6m bench with 120 litres of storage. Several UK fitted-furniture firms quoted £700 to £1,100 for a made-to-measure upholstered window seat with one drawer over the same span, offering 80 to 90 litres.
The storage gain is 120 litres against roughly 88 litres, which is the 35% figure. That calculation holds if both IVAR interiors stay open and a drawer box with runners does not take away a third of the depth. Doors on 35mm clearance hinges keep the volume. Deep drawers give a useful pull-out action but hand part of the space back to the mechanism.
Access is the trade. A 30cm-deep cabinet under a fixed worktop means storage goes in and out through a low front opening, often from your knees. That makes 120 litres of low cubby storage different from 88 litres in a drawer that slides out toward you. Shoe boxes, spare bedding and folded seasonal clothes suit the low cubbies better than small objects that need sorting at arm’s length.
