First fix: what good looks like

32 mm

32mm waste pipe support

Independent 32mm polypropylene discharge or waste pipes, conforming to relevant British Standards such as BS 5254 or BS EN 1451, must be adequately supported with pipe clips throughout their run to the soil stack or manifold

75 mm

Clearance from combustible materials

Appliances that generate heat, such as solid fuel burners, must maintain a minimum separation distance of 75mm from any combustible materials to prevent fire

125 mm thick, at least 840 × 840 mm on plan, extending 500 mm in front of the appliance and 150 mm each side

Constructional hearth thickness and extent

Solid fuel appliance on a constructional hearth

750 mm

Ductwork Fixing and Condensate Management

MVHR ductwork must be securely fixed at appropriate intervals to prevent sagging, typically no more than 750mm apart, or as per manufacturer guidelines

100 mm

Electrical accessory spacing

Electrical socket outlets and switches should be installed with a minimum spacing of 100mm between their centres to ensure adequate access and compliance with wiring regulations

75 mm

Exceptions to combustible material clearance

Exceptions to the standard 75mm clearance from combustible materials are permitted under specific conditions

150 mm

Fixing Plywood to Battens

Plywood sheets fixed to battens require 10-gauge nails or screws, placed at 150mm centres along perimeters and 300mm centres on intermediate supports

250 °C

Flue liner requirements for new builds

Flue liners must be selected based on the expected flue gas temperature; for temperatures unlikely to exceed 250°C, requirements for gas flues apply, while for higher or unknown temperatures, solid fuel flue pipe standards are used

18 to 90 mm per metre for a 75 mm or 100 mm branch

Gradient of a branch discharge pipe

Measured along the branch from the appliance to the stack

2000 mm, reducing to 1900 mm at the centre of a loft conversion stair and 1800 mm at the side

Headroom over a stair

Stairs and landings within a dwelling

6 m

Maximum length of a WC branch to the stack

For a 100 mm branch serving a single WC, with no more than 90 mm/m fall

60 °C

Minimum Hot Water Storage Capacity

Domestic hot water storage systems must provide a minimum capacity to adequately supply hot water at a target temperature, typically 60°C

Notches: max depth 0.125 x joist depth, only between 0.07 and 0.25 of the span. Holes: max diameter 0.25 x joist depth, on the centreline, between 0.25 and 0.4 of the span, at least 3 diameters apart

Permitted notches and holes in floor joists

Solid timber floor joists — engineered joists follow the manufacturer's zones instead

1 mm

Protection of gas pipework through timber

Gas pipework that penetrates timber studs or joists must be protected by steel plates, typically 1mm thick, to prevent accidental damage from screws or nails during subsequent fit-out

25 mm

Screed Cover for Buried Pipes

A minimum of 25mm screed cover is required over pipes and insulating material, and where pipes cross, a duct may be necessary to maintain this cover

25 mm

Separation of flues from combustible materials

Flues must be adequately separated from combustible materials to prevent fire hazards, typically requiring a minimum clearance of 25mm

Within 7.5 m of the door to every habitable room, within 3 m of every bedroom door, and at least 300 mm from any wall or light fitting

Smoke alarm siting distances

Ceiling-mounted mains-powered alarms on circulation routes

550 mm

Stair rise and going relationship

Staircases must be dimensioned such that the relationship between the rise (R) and the going (G) falls within prescribed limits for safety and comfort, typically expressed as 2R + G between 550mm and 700mm