Designing and Fitting a Utility Room in a London Extension or Refurbishment

**Minimum and ideal dimensions:** A utility room can function at a minimum of approximately 1.8m × 2.0m (3.6m²) — this will accommodate a washing machine and dryer stacked or side-by-side, a sink, and a small base unit run. However, a more usable utility room has a minimum dimension of 2.0m × 2.4m (4.8m²), and an ideal utility room is 2.0m × 3.0m (6.0m²) or above — the extra depth allows for a generous worktop run, full-height storage, and room to move.

For a side-return extension, the utility room is commonly formed from the infilled side return passage (typically 900mm–1200mm wide), which, when combined with a new outward extension, can produce a workable 2.0m × 2.5–3.0m space. In a rear extension, the utility room can be created as a separate room off the main extension volume or as a return off the rear extension at the side of the main kitchen area.

• **Standard appliance dimensions:**
• The primary appliances that drive the dimensional requirements are:
• •Freestanding washing machine: 600mm wide × 600mm deep × 850mm high (standard)
• •Tumble dryer: 600mm wide × 600mm deep × 850mm high (or ventless heat-pump dryer, slightly larger at 630mm depth)
• •American fridge-freezer (if relocated from kitchen): 900mm wide × 700mm deep × 1800mm high
• •Utility sink (butler's sink or inset single bowl): 400–600mm wide, typically set in a 600mm deep base unit
• •Worktop run: allow minimum 600mm clear worktop either side of sink

**Stacked vs. side-by-side washer/dryer:** In a narrower utility (under 2.4m wide with a run along one wall only), stacking the dryer on top of the washing machine on a stacking kit saves 600mm of width and allows more worktop run alongside. In a wider utility, side-by-side allows both to be under a continuous worktop, which is neater.

**Door swing:** Utility rooms are often accessed from the kitchen or rear lobby. The door should swing into the utility room (away from kitchen traffic) or be a sliding/pocket door — a utility room door swinging into the kitchen is a constant inconvenience. A half-glazed door or full-glazed door panel helps reduce the enclosed feel of a utility room with limited natural light.

• **Plumbing supply:**
• A utility room requires:
• •Cold water supply to the washing machine and sink (15mm or 22mm copper or plastic pipe from the main rising main or the kitchen cold supply)
• •Hot water supply to the sink (15mm supply from the domestic hot water cylinder or combination boiler)
• •For the washing machine: standard 15mm hot and cold supplies with service valves, connecting to the machine's fill hoses, is the norm for a freestanding machine; or a single cold fill supply for a cold-fill-only machine (most modern washing machines are cold-fill-only)

• **Drainage:**
• Drainage from the utility room requires:
• •Waste from the washing machine: typically connects to a 40mm diameter standpipe (open waste with an air gap, not directly connected to the trap), which drains to a 40mm branch drain running to the main soil stack or an external back-inlet gully
• •Waste from the sink: 40mm or 32mm trap (P-trap or bottle trap) running to the same branch drain as the washing machine or to a separate branch
• •The washing machine and sink drain must be within reach of the soil stack or a below-ground drainage channel; the maximum horizontal branch drain run is limited (typically 3m at 1:40 gradient for a 40mm waste, depending on the appliance); if drainage is an issue, a waste pump can pump from a lower point

**Ventilation:** A utility room requires adequate ventilation for two reasons:

1. **Condensation from tumble drying:** A vented tumble dryer (less common now, but still specified) must be ducted directly to outside — a 100mm duct through the wall is required. A heat-pump (condenser) dryer recycles heat internally and produces condensate into a collection drawer — no external duct required. A heat-pump dryer is significantly more energy-efficient and the preferred specification for a new utility room.

2. **General moisture and odour ventilation:** An extractor fan to outside (continuous running low-speed with boost, or intermittent) is required. A background trickle vent (or a window) can supplement this.

• **Boiler or water cylinder in the utility room:**
• If the boiler is to be relocated into the utility room (a common rationalisation when the kitchen layout changes), note:
• •A floor-standing boiler or water cylinder requires space planning — typically 600mm wide × 600mm deep for a combi boiler wall-hung, but a system boiler + cylinder requires significantly more space (cylinder 450–500mm diameter × 1100mm high or taller)
• •A boiler in a utility room with an internal wall requires a balanced flue through the external wall or roof — allow for the flue position in the layout design

**Storage design:** The utility room is the service hub of the house and should be designed with practical storage in mind:

• •**Full-height pantry unit or tall cupboard**: For cleaning equipment (vacuum, mop, broom), ironing board, and general household storage. Minimum 600mm wide, 600mm deep, full height.
• •**Base units under worktop**: For bin storage, under-sink storage, cleaning products. Standard kitchen base unit carcasses (600mm wide × 600mm deep) are cost-effective in a utility room — paint doors to match or use a contrasting colour from the kitchen.
• •**Open shelving**: Practical for everyday utility items (detergents, spare bulbs, first aid). Open shelving above the worktop between wall units is cheaper than wall units and easier to access.
• •**Coat hooks and boot/shoe storage**: In a combined utility/boot room, a bench with integrated shoe storage below and coat hooks above is a popular addition at the entry point from the garden.

• **Worktop specification:**
• The worktop in a utility room can be a lower specification than the kitchen:
• •**Laminate worktop** (£20–£50/m supply): Durable, low maintenance, available in stone or solid colour finishes. Practical and cost-effective for utility use.
• •**Solid timber worktop** (£50–£100/m supply): Adds warmth; needs oiling and maintenance; not ideal immediately adjacent to the sink.
• •**Compact laminate** (Formica Axiom or similar, £40–£80/m supply): Highly durable, post-formed edge, water-resistant — a good choice for utility rooms adjacent to the sink.

**Flooring:** LVT or porcelain tile is the practical choice for a utility room floor — fully waterproof, easy to clean, and durable under heavy traffic and potential washing machine leaks.

• **Indicative utility room costs:**
• •Basic utility room (plumbing, drainage, extraction, no units or appliances): £3,500–£6,000
• •Utility room with flat-pack base units, laminate worktop, butler's sink, LVT floor: £6,000–£10,000
• •Fitted utility room with bespoke joinery, quality worktop, butler's sink, boot room bench: £10,000–£18,000
• •These costs are for the fit-out only — if the utility room is within an extension project, the shell costs (walls, roof, floor slab) are included in the extension cost
• •rcbGroup standard terms: second-fix materials (units, worktop, sink, taps) are client-supplied