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How Should a Downstairs WC or Cloakroom Be Designed in London?

A London downstairs WC needs minimum 1.2×1.5m (1.8m²); comfortable 1.5×1.8m (2.7m²). Spec: wall-hung WC with concealed cistern (saves 150mm depth), compact basin or counter-mounted bowl, mirror, hook, mechanical extract 8 L/s (Building Regs Part F). No window required if extract present. Cost £3,500–£9,500 turnkey. Adds value at sale — non-negotiable for any 3+ bed family home in London.

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01

Size and layout

Minimum: 800×1,500mm (1.2m²) — Building Regs accept this, but feels cramped. Useful minimum: 1,200×1,500mm (1.8m²) — door swings inward into corner, WC + corner basin fit. Comfortable: 1,500×1,800mm (2.7m²) — room for vanity unit, full mirror, hooks for coats. Door swing matters: outward-opening preferred but space-dependent; inward-opening must clear WC. Pocket door (slides into wall cavity) saves 800mm of swing — premium option. Under-stairs WC very common in London terraces (4–6m² triangular space) — wedge layout with WC at deepest end, basin and door at shallow end.

02

WC and basin selection

Wall-hung WC with concealed cistern (Geberit Duofix or Roca In-Wall frame £180–£385): cistern hidden behind 120–150mm partition, saves floor depth, modern look. Close-coupled WC (cistern visible on pan): £180–£385 supplied, simpler install but bulkier — fine for under-stairs where space is unusual. Compact basin: corner basin 350×350mm (Roca Senso, Vitra Mia £85–£185); counter-mounted bowl on small vanity 500–800mm wide; wall-hung basin saves floor space. Tap: lever mixer (one-finger operation for users with wet hands).

03

Ventilation and finishes

Extract: 8 L/s minimum (Part F intermittent), humidistat-controlled, ducted to outside (not soffit/loft). Permitted to omit window if extract present. Lighting: single recessed downlight + sconce above mirror; warm 2,700K for evening guest use. Floor: porcelain tile (any pattern — small format fine here), or LVT/vinyl. Walls: paint to ceiling in moisture-resistant emulsion; tile splashback above basin (300×500mm tile or marble splash). Mirror: medicine-cabinet-style mirror cabinet (Burgbad, Roper Rhodes £180–£385) hides hand-soap and spare loo-roll. Door: solid-core 35mm, privacy lock with coin override. Coat hooks behind door — useful for guests.

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Does a downstairs WC need a window?

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No — Building Regs Part F allows mechanical extract at 8 L/s in lieu of opening window. Most under-stairs WCs have no external wall, so window is impossible. Extract via plastic ducting to nearest external wall or roof vent. Window if available is desirable for natural ventilation and light, but not required.

Where should the downstairs WC go?

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Under-stairs is the classic answer in terraced houses — wasted volume becomes useful. Off the entrance hall (so guests don't have to ask the way upstairs) is the comfortable answer. Off the kitchen/utility is a third option but compromises both. Don't locate directly adjacent to dining or living without acoustic isolation (solid-core door + acoustic seal at threshold).

Does adding a downstairs WC add value?

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Yes — typically £15,000–£28,000 of resale value uplift in London family-home market against a £3,500–£9,500 install cost. Among the highest ROI improvements in any London renovation. Mortgage valuers list 'downstairs WC' as a value-positive feature on 3-bed+ properties.

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