Outdoor Kitchen Calculator — Block Plinth, Worktop & Foundation

Build a three-sided block plinth on a concrete foundation (C25, 150mm deep). Use 100mm dense concrete blocks or engineering bricks, laid to courses with 10mm mortar joints. The standard worktop height is 900mm (approximately 4 courses of blocks on a slab). The plinth must be level with falls for drainage. Leave openings for service connections.

Granite and porcelain slabs are the most popular choices for UK outdoor kitchens — both are frost-proof, heat-resistant and low-maintenance. As a 2026 guide, granite is roughly £270-600/m² supplied and fitted (around £435/m² average). Porcelain large-format slabs are lighter and can be bonded directly to the plinth, with material around £250-450/m² (more once fitted). Avoid marble (stains easily) and timber (maintenance-heavy) in the UK climate. Prices vary by stone grade, region and edge/cut-out work — always get a templated quote.

Most garden outdoor kitchens fall under permitted development if they are single-storey, not in front of the principal elevation, and the total area of outbuildings doesn't exceed 50% of the garden. However, gas and electrical installations must comply with Building Regulations and should be done by qualified Gas Safe and Part P registered tradespeople.

A sink needs a 40mm waste pipe connected (via a trap) to the foul drainage system, not surface water. Per Approved Document H the sink branch waste should fall 18-90 mm/m (roughly 1:55 to 1:11; ~1:40 is a good practical target) — the shallower 1:80 minimum only applies to the 100mm underground foul drain at peak flows over 1 l/s (1:40 below 1 l/s). Use our Drainage Fall Calculator to set gradients. Lay the paving and worktop with a 1.5-2% fall away from the building, and fit a trapped gully for any wash-down areas.

Yes, but both must be installed by qualified professionals. Gas must be installed by a Gas Safe registered engineer with outdoor-rated fittings and an isolation valve. Electrical supply must comply with BS 7671 (Part P) with RCD protection, weatherproof sockets and an isolator switch. Budget £500-1,500 for gas and £300-800 for electrical installation.