Home
1 Welcome
1.1 Contact us
1.2 What’s changed
2 Introduction
2.1 The Standards and Technical Requirements
3 General
3.1 Concrete and its reinforcement
3.1 Figure reference table
3.1.1 Compliance
3.1.2 Provision of information
3.1.3 Storage of materials
3.1.4 Site-mixed concrete
3.1.5 Ready-mixed concrete
3.1.6 Concrete specification
3.1.7 Admixtures
3.1.8 Special types of concrete
3.1.9 Design of reinforced concrete
3.1.10 Installation of reinforcement
3.1.11 Blinding concrete
3.1.12 Formwork
3.1.13 Before concreting
3.1.14 Casting
3.1.15 Curing
3.1.16 Testing
3.1.17 Glossary
3.1.18 Further information
3.2 Cold weather working
3.2 Figure reference table
3.2.1 Compliance
3.2.2 External conditions
3.2.3 Materials
3.2.4 Concreting
3.2.5 Masonry
3.2.6 Rendering, plastering and screeding
3.2.7 Admixtures
3.2.8 Painting
3.2.9 Further information
3.3 Timber preservation (natural solid timber)
3.3 Figure reference table
3.3.1 Compliance
3.3.2 Durability
3.3.3 Sitework
3.3.4 Protection and storage
3.3.5 Treatment of cut surfaces
3.3.6 Compatibility with metal
3.3.7 Further information
4 Foundations
4.1 Land quality – managing ground conditions
4.1 Figure reference table
4.1.1 Compliance
4.1.2 Initial Assessment – desk study (all sites)
4.1.3 Initial Assessment – walkover survey (all sites)
4.1.4 Initial Assessment – results
4.1.5 Basic Investigation (sites where hazards are not identified or suspected)
4.1.6 Detailed Investigation (sites where hazards are identified or suspected)
4.1.7 Managing the risks (sites where hazards are found)
4.1.8 Unforeseen hazards
4.1.9 Documentation and verification
4.1.10 Guidance for investigations
4.1.11 Further information
4.2 Building near trees
4.2 Figure reference table
4.2.1 Compliance
4.2.2 Provision of information
4.2.3 Building near trees
4.2.4 The effects of trees on shrinkable soils
4.2.5 Foundations in all soil types
4.2.6 Excavation of foundations
4.2.7 Foundations in shrinkable soils
4.2.8 Design and construction of foundations in shrinkable soils
4.2.9 Foundation depths for specific conditions in shrinkable soils
4.2.10 Heave precautions
4.2.11 New drainage
4.2.12 Method of assessment of foundation depths using charts
4.2.13 Method of assessment of foundation depths using tables
4.2.14 Worked example
4.2.15 Further information
4.3 Strip and trench fill foundations
4.3 Figure reference table
4.3.1 Compliance
4.3.2 Provision of information
4.3.3 Ground conditions
4.3.4 Hazardous ground
4.3.5 Setting out
4.3.6 Services and drainage
4.3.7 Safe transmission of loads
4.3.8 Sloping ground and stepped foundations
4.3.9 Excavations
4.3.10 Reinforcement
4.3.11 Concrete
4.3.12 Movement joints
4.3.13 Construction joints
4.3.14 Further information
4.4 Raft, pile, pier and beam foundations
4.4 Figure reference table
4.4.1 Compliance
4.4.2 Provision of information
4.4.3 Site conditions
4.4.4 Hazardous ground
4.4.5 Services and drainage
4.4.6 Safe transmission of loads
4.4.7 Construction
4.4.8 Engineer checks
4.4.9 Compressible materials
4.4.10 Reinforcement
4.4.11 Concrete
4.4.12 Movement joints
4.4.13 Resistance to moisture
4.4.14 Further information
4.5 Vibratory ground improvement techniques
4.5 Figure reference table
4.5.1 Compliance
4.5.2 Provision of information
4.5.3 Hazardous sites and ground hazards
4.5.4 Desk study and site investigation
4.5.5 Confirmation of suitability for treatment
4.5.6 Suitability of ground conditions
4.5.7 Compatibility of the ground, design and treatment
4.5.8 Acceptable methods
4.5.9 Materials for use as fill
4.5.10 Granular material
4.5.11 Sitework
4.5.12 Adjacent excavations
4.5.13 Verification of completed treatment
4.5.14 Further information
4.6 Engineered fill
4.6 Figure reference table
4.6.1 Compliance
4.6.2 Provision of information
4.6.3 Hazardous sites and ground hazards
4.6.4 Desk study and ground investigation
4.6.5 Suitability of ground conditions
4.6.6 Materials for use as engineered fill
4.6.7 Design and specification of earthworks
4.6.8 Compatibility of fill with foundations, infrastructure and external works
4.6.9 Acceptable methods of earthworks filling
4.6.10 Site work
4.6.11 Adjacent excavations
4.6.12 Verification of engineered fill
4.6.13 Reporting
4.6.14 Further information
5 Substructure, ground floors, drainage and basements
5.1 Substructure and ground-bearing floors
5.1 Figure reference table
5.1.1 Compliance
5.1.2 Provision of information
5.1.3 Transfer of loads
5.1.4 Ground conditions
5.1.5 Services and drainage
5.1.6 Ground below fill
5.1.7 Fill below floors
5.1.8 Infill up to 600mm deep
5.1.9 Materials used for fill
5.1.10 Harmful or toxic materials
5.1.11 Regulatory solutions
5.1.12 Walls below the DPC
5.1.13 Durability
5.1.14 Mortar
5.1.15 Wall ties
5.1.16 Blinding
5.1.17 Ground floor slab and concrete
5.1.18 Laying the ground-bearing floor slab
5.1.19 Damp proof course
5.1.20 Damp proofing concrete floors
5.1.21 Thermal insulation
5.1.22 Installation of insulation
5.1.23 Further information
5.2 Suspended ground floors
5.2.1 Compliance
5.2.2 Provision of information
5.2.3 Contaminants
5.2.4 Proprietary systems
5.2.5 Transfer of loads: concrete floors
5.2.6 Reinforced concrete
5.2.7 Construction of suspended concrete ground floors
5.2.8 Transfer of loads: timber floors
5.2.9 Thermal insulation and thermal bridging
5.2.10 Damp proofing and ventilation
5.2.11 Floor finishes
5.2.12 Floor decking
5.2.13 Further information
5.3 Drainage below ground
5.3 Figure reference table
5.3.1 Compliance
5.3.2 Provision of information
5.3.3 Preliminary work
5.3.4 Foul and surface water disposal
5.3.5 Drainage system performance
5.3.6 Groundwater drainage
5.3.7 Design to avoid damage and blockages
5.3.8 Durability
5.3.9 Septic tanks and cesspools
5.3.10 Septic tank outputs
5.3.11 Surface water soakaways
5.3.12 Component requirements
5.3.13 Excavation
5.3.14 Protection of pipework
5.3.15 Laying pipework
5.3.16 Protection of work
5.3.17 Drainage under buildings
5.3.18 Testing
5.3.19 Further information
5.4 Waterproofing of basements and other below ground structures
5.4 Figure reference table
5.4.1 Compliance
5.4.2 Provision of information
5.4.3 Waterproofing
5.4.4 Ground conditions
5.4.5 Structural stability
5.4.6 Design considerations
5.4.7 Waterproofing systems
5.4.8 Handling, storage and protection
5.4.9 Buried podiums
5.4.10 Further information
6 Superstructure (excluding roofs)
6.1 External masonry walls
6.1 Figure reference table
6.1.1 Compliance
6.1.2 Provision of information
6.1.3 Structural design
6.1.4 Fire resistance
6.1.5 Acoustic resistance
6.1.6 Exposure
6.1.7 Thermal insulation
6.1.8 Concrete blocks
6.1.9 Bricks
6.1.10 Stone masonry
6.1.11 Construction of masonry walls
6.1.12 Lintels
6.1.13 Materials suitable for mortar
6.1.14 Mortar
6.1.15 Render
6.1.16 Cladding
6.1.17 DPCs and cavity trays
6.1.18 Wall ties, bed joint reinforcements and windposts
6.1.19 Handling materials
6.1.20 Protection of the works during construction
6.1.21 Further information
6.2 External timber framed walls
6.2 Figure reference table
6.2.1 Compliance
6.2.2 Provision of information
6.2.3 Design checking and certification
6.2.4 Load-bearing walls
6.2.5 Fixing the frame
6.2.6 Nails and staples
6.2.7 Sheathing
6.2.8 Differential movement
6.2.9 Fire resistance
6.2.10 Protection from moisture
6.2.11 Timber preservation
6.2.12 Air and vapour control layers
6.2.13 Breather membranes
6.2.14 Wall ties and fixings
6.2.15 Insulation
6.2.16 Further information
6.3 Internal walls
6.3 Figure reference table
6.3.1 Compliance
6.3.2 Provision of information
6.3.3 Supporting load-bearing internal walls
6.3.4 Masonry walls
6.3.5 Load-bearing timber walls
6.3.6 Fire resistance
6.3.7 Sound insulation
6.3.8 Partitions: internal non load-bearing
6.3.9 Construction of timber partitions
6.3.10 Construction of steel framed partitions
6.3.11 Construction of proprietary systems
6.3.12 Plasterboard
6.3.13 Damp proof courses
6.3.14 Components
6.3.15 Further information
6.4 Timber and concrete upper floors
6.4 Figure reference table
6.4.1 Compliance
6.4.2 Provision of information
6.4.3 Upper floor design
6.4.4 Fire spread
6.4.5 Sound insulation
6.4.6 In-situ concrete floors and concreting
6.4.7 Precast concrete
6.4.8 Timber joist spans
6.4.9 Timber joist performance
6.4.10 Construction of timber floors
6.4.11 Joists supported by intermediate walls
6.4.12 Joists connected to steel
6.4.13 Joists into hangers
6.4.14 Timber joist and restraint strap
6.4.15 Strutting
6.4.16 Joists and openings
6.4.17 Multiple joists
6.4.18 Notching and drilling
6.4.19 Floor decking
6.4.20 Floating floors or floors between homes
6.4.21 Further information
6.5 Steelwork
6.5 Figure reference table
6.5.1 Compliance
6.5.2 Design guidance
6.5.3 Steel grade and coatings
6.5.4 Installation and support
6.5.5 Padstones
6.5.6 Connections
6.5.7 Examples
6.6 Staircases
6.6 Figure reference table
6.6.1 Compliance
6.6.2 Provision of information
6.6.3 Fire precautions
6.6.4 Lighting
6.6.5 Glazing
6.6.6 Structural design
6.6.7 Headroom and width
6.6.8 Design of steps
6.6.9 Landings
6.6.10 Guarding
6.6.11 Handrails
6.6.12 Staircases made from timber and wood-based products
6.6.13 Concrete staircases
6.6.14 Steel staircases
6.6.15 Proprietary staircase units
6.6.16 Protection
6.6.17 Further information
6.7 Doors, windows and glazing
6.7 Figure reference table
6.7.1 Compliance
6.7.2 Provision of information
6.7.3 In-service performance
6.7.4 Coupled door and window frame assemblies
6.7.5 Glazing
6.7.6 Security
6.7.7 Timber doors and windows
6.7.8 Non-timber doors and windows
6.7.9 Ironmongery
6.7.10 Material storage and protection
6.7.11 Installation
6.7.12 Completed work
6.8 Fireplaces, chimneys and flues
6.8 Figure reference table
6.8.1 Compliance
6.8.2 Provision of information
6.8.3 Solid fuel – fireplaces and hearths
6.8.4 Solid fuel – combustion air
6.8.5 Solid fuel – flue pipes
6.8.6 Solid fuel – chimneys
6.8.7 Solid fuel – outlets and terminals
6.8.8 Gas – fireplaces and hearths
6.8.9 Gas – combustion air
6.8.10 Gas – flue pipes
6.8.11 Gas – chimneys
6.8.12 Gas – outlets and terminals
6.8.13 Liquid fuel – fireplaces and hearths
6.8.14 Liquid fuel – combustion air
6.8.15 Liquid fuel – flue pipes
6.8.16 Liquid fuel – chimneys
6.8.17 Liquid fuel – outlets and terminals
6.8.18 All – fireplaces and hearths
6.8.19 All – fireplace surrounds
6.8.20 All – flue pipes
6.8.21 All – flue liners
6.8.22 All – flues
6.8.23 All – chimneys
6.8.24 Masonry
6.8.25 Mortar
6.8.26 DPC
6.8.27 Flashings
6.8.28 Terminals
6.8.29 Flue testing
6.8.30 Further information
6.9 Curtain walling and cladding
6.9 Figure reference table
6.9.1 Compliance
6.9.2 Provision of information
6.9.3 Certification
6.9.4 Loads
6.9.5 Support and fixings
6.9.6 Durability
6.9.7 Interfaces
6.9.8 Insulation
6.9.9 Damp proofing and vapour control
6.9.10 Installation and tolerances
6.9.11 Electrical continuity and earth bonding
6.9.12 Maintenance
6.9.13 Glazing, gaskets and sealants
6.9.14 Cavity barriers and firestops
6.9.15 Ventilation screens
6.9.16 Handling and storage
6.9.17 Curtain walling
6.9.18 Rainscreen cladding
6.9.19 Insulated render and brick slip cladding
6.9.20 Further Information
6.10 Light steel framed walls and floors
6.10 Figure reference table
6.10.1 Compliance
6.10.2 Provision of information
6.10.3 Structural certification
6.10.4 Structural design of load-bearing floors and walls
6.10.5 Structural design of infill walls
6.10.6 Roofs
6.10.7 Steel and fixings
6.10.8 Detailing of steel joists
6.10.9 Restraint
6.10.10 Construction of load-bearing walls and external infill walls
6.10.11 Interfaces with staircases
6.10.12 Fixing floor decking and ceilings
6.10.13 Other design issues
6.10.14 Behaviour in relation to fire
6.10.15 Acoustic performance
6.10.16 Moisture control
6.10.17 Insulation
6.10.18 Air and vapour control layers
6.10.19 Breather membranes
6.10.20 Cladding, lining and sheathing boards
6.10.21 Wall ties
6.10.22 Services
6.10.23 Further information
6.11 Render
6.11 Figure reference table
6.11.1 Compliance
6.11.2 Provision of information
6.11.3 Weather conditions
6.11.4 Backgrounds
6.11.5 Accommodation of movement
6.11.6 Mixes
6.11.7 Detailing
6.11.8 Render onto board backgrounds
6.11.9 Finishes
6.11.10 Further information
7 Roofs
7.1 Flat roofs, terraces and balconies
7.1 Figure reference table
7.1.1 Compliance
7.1.2 Provision of information
7.1.3 Flat roof, terrace and balcony general design
7.1.4 Drainage
7.1.5 Flat roof, terrace and balcony structural design
7.1.6 Timber structure and deck
7.1.7 Concrete decks
7.1.8 Profiled self-supporting metal roof decks
7.1.9 Profiled self-supporting metal roofing
7.1.10 Thermal insulation and vapour control
7.1.11 Waterproofing layer and surface treatments
7.1.12 Green and biodiverse roofs – including roof gardens
7.1.13 Blue roofs
7.1.14 Raised and buried podiums
7.1.15 Detailing of flat roofs
7.1.16 Accessible thresholds and upstands
7.1.17 Metal balcony decking systems
7.1.18 Parapets and guarding to terraces and balconies
7.1.19 Further information
7.2 Pitched roofs
7.2 Figure reference table
7.2.1 Compliance
7.2.2 Provision of information
7.2.3 Design of pitched roofs
7.2.4 Protection of trusses
7.2.5 Durability
7.2.6 Wall plates
7.2.7 Joints and connections
7.2.8 Restraint
7.2.9 Bracing for trussed rafter roofs
7.2.10 Strutting for site formed attic trusses and cut roofs that form a floor
7.2.11 Support for equipment
7.2.12 Access
7.2.13 Dormer construction
7.2.14 Underlay, sarking boards and sheets
7.2.15 Ventilation, vapour control and insulation
7.2.16 Fire-stopping and cavity barriers
7.2.17 Battens
7.2.18 Roof coverings
7.2.19 Fixing tiles and slates
7.2.20 Weathering details
7.2.21 Valleys and hidden gutters
7.2.22 Drainage
7.2.23 Fascias and trim
7.2.24 Spandrel panels in cold roofs
7.2.25 Roof cassette systems
7.2.26 Solar roof panels
7.2.27 Further information
8 Services
8.1 Internal services
8.1 Figure reference table
8.1.1 Compliance
8.1.2 Provision of information
8.1.3 Water services and supply
8.1.4 Cold water storage
8.1.5 Gas services
8.1.6 Electrical services
8.1.7 Meter boxes
8.1.8 Hot water services
8.1.9 Unvented storage systems
8.1.10 Internal soil and waste systems
8.1.11 Further information
8.2 Electrical generating technologies
8.2.1 Solar photovoltaics (PV)
8.2.1 Figure reference table
8.2.1.1 Compliance
8.2.1.2 Provision of information
8.2.1.3 System design
8.2.1.4 Building integration
8.2.1.5 Fixing
8.2.1.6 Access
8.2.1.7 Electrical installation requirements
8.2.1.8 Handling and storage
8.2.1.9 Sequence of work
8.2.2 Wind turbines
8.2.2 Figure reference table
8.2.2.1 Compliance
8.2.2.2 Provision of information
8.2.2.3 System design
8.2.2.4 Building integration
8.2.2.5 Fixing
8.2.2.6 Access
8.2.2.7 Electrical installation requirements
8.2.2.8 Handling and storage
8.2.2.9 Sequence of work
8.3 Space heating systems
8.3.1 Space heating
8.3.1.1 Requirements
8.3.2 Gas heating appliances
8.3.2.1 Compliance
8.3.2.2 Provision of information
8.3.2.3 System design
8.3.2.4 Building integration
8.3.2.5 Fixing
8.3.2.6 Access
8.3.2.7 Electrical installation requirements
8.3.2.8 Handling and storage
8.3.2.9 Sequence of work
8.3.3 Heat pumps
8.3.3 Figure reference table
8.3.3.1 Compliance
8.3.3.2 Provision of information
8.3.3.3 System design
8.3.3.4 Pipes, insulation and protection from cold
8.3.3.5 Ground collectors
8.3.3.6 Building integration
8.3.3.7 Fixing
8.3.3.8 Access
8.3.3.9 Electrical installation requirements
8.3.3.10 Handling and storage
8.3.3.11 Sequence of work
8.3.4 Biomass
8.3.4 Figure reference table
8.3.4.1 Compliance
8.3.4.2 Clean air act
8.3.4.3 Fuel storage
8.4 Ventilation
8.4.1 Mechanical ventilation and heat recovery (MVHR) systems
8.4.1 Figure reference table
8.4.1.1 Compliance
8.4.1.2 Provision of information
8.4.1.3 System design
8.4.1.4 Acoustics
8.4.1.5 Building integration
8.4.1.6 Ductwork
8.4.1.7 Fixing and jointing of ductwork
8.4.1.8 Access and operation
8.4.1.9 Electrical installation requirements
8.4.1.10 Handling and storage
8.4.1.11 Commissioning and balancing
8.4.1.12 Sequence of work
8.4.2 Mechanical extract ventilation systems (MEV)
8.4.2 Figure reference table
8.4.2.1 Compliance
8.4.2.2 Provision of information
8.4.2.3 System design
8.4.2.4 Acoustics
8.4.2.5 Building integration
8.4.2.6 Ductwork
8.4.2.7 Fixing and jointing of ductwork
8.4.2.8 Access and operation
8.4.2.9 Electrical installation requirements
8.4.2.10 Handling and storage
8.4.2.11 Commissioning and balancing
8.4.2.12 Sequence of work
8.5 LZC hot water systems
8.5.1 Solar thermal hot water systems
8.5.1 Figure reference table
8.5.1.1 Compliance
8.5.1.2 Provision of information
8.5.1.3 System design
8.5.1.4 Safe discharge
8.5.1.5 Building integration
8.5.1.6 Fixing
8.5.1.7 Access
8.5.1.8 Electrical installation requirements
8.5.1.9 Handling and storage
8.5.1.10 Handover requirements
8.5.1.11 Sequence of work
8.6 Installation and commissioning
8.6 Figure reference table
8.6.1 Compliance
8.6.2 Installation
8.6.3 Insulation to services
8.6.4 Insulation performance
8.6.5 Testing and commissioning
8.6.6 Handover requirements
9 Finishes
9.1 A consistent approach to finishes
9.1 Figure reference table
9.1.1 Compliance
9.1.2 External walls
9.1.3 Internal walls and ceilings
9.1.4 Doors and windows
9.1.5 Floors
9.1.6 Glazing
9.1.7 Ceramic, concrete, terrazzo and similar tile finishes
9.1.8 Fitted furniture
9.1.9 Joint sealants
9.1.10 Paint finishes
9.1.11 Sanitary ware
9.1.12 Other surfaces and finishes
9.1.13 Pitched roof coverings
9.1.14 Garages
9.1.15 External works
9.1.16 Further information
9.2 Wall and ceiling finishes
9.2 Figure reference table
9.2.1 Compliance
9.2.2 Provision of information
9.2.3 Plastering
9.2.4 Dry lining
9.2.5 Ceramic wall tiling
9.2.6 Further information
9.3 Floor finishes
9.3 Figure reference table
9.3.1 Compliance
9.3.2 Provision of information
9.3.3 Insulation
9.3.4 Screed
9.3.5 Ceramic, concrete, terrazzo and similar tile finishes
9.3.6 Wood finishes
9.3.7 Flexible sheet and flexible tile finishes
9.3.8 Asphalt finishes
9.3.9 Staircase finishes
9.3.10 Further information
9.4 Finishes and fitments
9.4 Figure reference table
9.4.1 Compliance
9.4.2 Provision of information
9.4.3 General provisions – cupboards and fitments
9.4.4 Finishings and internal trim
9.4.5 Joinery
9.4.6 Airing cupboards, cupboards, worktops and fitments
9.4.7 Ironmongery, prefabricated items and other materials
9.4.8 Protection and handover
9.5 Painting and decorating
9.5.1 Compliance
9.5.2 Provision of information
9.5.3 Storage
9.5.4 Conditions for painting and decorating
9.5.5 Timber
9.5.6 Steel
9.5.7 Walls
9.5.8 Wallpapering
9.5.9 Other surfaces
9.5.10 Completed painting and decorating
10 External works
10.1 Garages
10.1 Figure reference table
10.1.1 Compliance
10.1.2 Provision of information
10.1.3 Garage foundations
10.1.4 Garage floors
10.1.5 Garage walls
10.1.6 Resistance to fire spread
10.1.7 Security
10.1.8 Doors and windows
10.1.9 Garage roofs
10.1.10 Permanent prefabricated garages and carports
10.1.11 Services
10.2 Drives, paths and landscaping
10.2 Figure reference table
10.2.1 Compliance
10.2.2 Provision of information
10.2.3 Stability
10.2.4 Freestanding walls and retaining structures
10.2.5 Guarding and steps
10.2.6 Drives, paths and landscaping
10.2.7 Materials
10.2.8 Garden areas within 3m of the home
10.2.9 Garden areas
10.2.10 External decking
10.2.11 Landscaping
11 Modern Methods of Construction
11.1 MMC Systems
11.1 Figure reference table
11.1.1 Compliance
11.1.2 Certification
11.1.3 System Manual
11.1.4 Quality management
11.1.5 Site management (handling, storage, and protection)
11.1.6 Structural design
11.1.7 Structural design checking and certification
11.1.8 Temporary stability, robustness, and integrity
11.1.9 Installation
11.1.10 Verification
11.1.11 Handover requirements
11.2 Closed Panel Systems
11.2 Figure reference table
11.2.1 Compliance
11.2.2 Provision of information
11.2.3 Structural design
11.2.4 Structural design checking and certification
11.2.5 Behaviour in relation to fire
11.2.6 Acoustic performance
11.2.7 Differential movement
11.2.8 Protection from moisture
11.2.9 Insulation
11.2.10 Junctions and interfaces
11.2.11 Cladding
11.2.12 Doors, windows, and glazing
11.2.13 Air and vapour control layers
11.2.14 Breather Membranes
11.2.15 Sheathing boards
11.2.16 Wall ties
11.2.17 Services
11.2.18 Further information
11.3 Volumetric systems
11.3 Figure reference table
11.3.1 Compliance
11.3.2 Provision of information
11.3.3 Structural design
11.3.4 Structural design checking and certification
11.3.5 Behaviour in relation to fire
11.3.6 Acoustic performance
11.3.7 Differential movement
11.3.8 Protection from moisture
11.3.9 Insulation
11.3.10 Junctions and interfaces
11.3.11 Cladding
11.3.12 Doors, windows, and glazing
11.3.13 Staircases
11.3.14 Air and vapour control layers
11.3.15 Breather membranes
11.3.16 Sheathing boards
11.3.17 Wall ties
11.3.18 Services
11.3.19 Further information
NHBC Standards 2025
