When you buy a new build home, the doors, windows and glazing are some of the most visible and most-used components of your property. They affect how warm your home stays, how secure it feels, how it looks, and how easy it is to live in day to day. The NHBC Standards set out the technical requirements that builders should follow when designing, specifying and installing them, and Chapter 6.7 of the 2026 edition is dedicated entirely to this subject.
This article walks through Chapter 6.7 section by section, summarising each sub-chapter in plain language so you can better understand what should be expected of your new home. Where helpful, we mention how a snagging inspection may help identify issues, although it is worth remembering that a snagging inspection is a thorough visual and operational check rather than a full structural survey or factory test.
6.7.1 Compliance
This sub-chapter sets the headline requirement: doors, windows and glazing must comply with the NHBC’s Technical Requirements. In practice, this means that following the guidance laid out throughout the rest of the chapter will generally be enough to satisfy the standard. Compliance underpins everything that follows.
6.7.2 Provision of Information
Designs and specifications must be produced in a clear and understandable format, contain all the relevant information, and be distributed to everyone who needs them, including site supervisors, specialist subcontractors and suppliers. Without good information flowing to the people doing the work, even a well-specified product can be installed incorrectly.
6.7.3 In-Service Performance
This section sets out how doors and windows should perform once installed. The four key areas covered are weathertightness, minimising thermal bridging, accommodating thermal movement, and operation and strength.
6.7.3.1 Weathertightness
Doors and windows must keep wind and water out, with classifications appropriate to the exposure of the site. Higher levels of performance are typically needed for medium- and high-rise buildings where remedial work is harder. Sills should project at least 25mm beyond the wall face, and detailing around the frame should be robust and easy to inspect. Checked rebates are required in Scotland, Northern Ireland, the Isle of Man, and other areas of severe driving rain. Issues such as draughts, water ingress around frames, and missing or poorly applied seals are commonly picked up during snagging inspections.
6.7.3.2 Minimising Thermal Bridging
The interface between the door or window and the surrounding wall must be designed to limit heat loss and the risk of condensation. This typically involves insulated cavity closures in masonry walls and careful positioning of frames so that the insulation layer remains continuous. A standard snagging inspection that includes thermal imaging can help reveal cold spots and gaps in insulation around frames that would not be apparent to the naked eye.
6.7.3.3 Accommodating Movement
Frames expand and contract with temperature changes, so a perimeter gap is needed between the frame and the structural opening. The recommended gap depends on the frame material and the size of the opening, ranging from 8mm for a small steel frame up to 22mm for a large non-white PVC-U frame. The gap should be sealed with a material that resists water and air infiltration whilst still allowing for movement. Poor or missing perimeter seals are a frequent finding during snagging.
6.7.3.4 Operation and Strength
Doors, windows and their fittings must be strong enough to handle everyday use, with performance classes defined in Annex A of BS 6375-2. In practical terms, this is about windows that open and close cleanly, latches that engage properly, and doors that do not sag or bind, all of which are routine checks during a snagging inspection.
6.7.4 Coupled Door and Window Frame Assemblies
When several doors or windows are joined together to form a larger glazed wall within a single storey, additional considerations apply. Larger assemblies that span more than one storey or are not contained between a structural floor and ceiling fall under Chapter 6.9 instead.
6.7.4.1 System Design
Coupled assemblies should be supplied as a complete proprietary system, using only the components designed and detailed by the system manufacturer. Mixing components from different sources can compromise performance.
6.7.4.2 Weathertightness
Coupling joints should follow the principle of two lines of defence, with flexible inner and outer seals and a drained cavity between them. Weathertightness must be proven by laboratory testing through a UKAS accredited test laboratory, with no leakage onto the inner face of the system at any point.
6.7.4.3 Structural Integrity
The assembly must support its own weight and resist wind loads without excessive deflection. The recommendation is that the main structural members satisfy class B, allowing a maximum deflection of span/200 under design wind load.
6.7.4.4 Movement Accommodation
Larger assemblies move more than individual windows, so coupling joints and the interface with the surrounding structure must be designed to accommodate that movement whilst remaining weathertight.
6.7.4.5 Thermal Bridging
Coupling joints, brackets and fixings can create heat-loss paths and cold spots. Thermal breaks should be used where appropriate, and a thermal assessment should confirm that condensation will not form on visible interior surfaces under normal operating conditions.
6.7.4.6 Site Testing for Watertightness
To check that installation has not compromised performance, on-site watertightness testing using the CWCT hose test method should be carried out by a UKAS accredited lab. At least 5% of critical coupling joints should be tested, with a minimum of two installations on developments using the same assembly.
6.7.5 Glazing
This section covers the glass itself and the systems used to hold it in place.
6.7.5.1 Standards
Glazing should conform to the relevant British Standards covering insulating glass units, soda lime silicate glass, laminated glass, thermally toughened safety glass, and coated glass.
6.7.5.2 Performance Requirements
The type, thickness and size of glass should be appropriate to the design loads and the intended use. Safety glass in critical locations should be marked with the manufacturer’s trademark, the relevant standard, and an impact performance classification under BS EN 12600. During a snagging inspection, the inspector can check for these markings on glass installed in critical locations such as low-level windows and doors.
6.7.5.3 Insulating Glass Units
Insulating glass units should be CE or UKCA marked, hold appropriate third-party certification such as the BSI Kitemark, and use the correct seal types around the spacer bar. Visible signs of failure such as misting between panes are clear indicators of a problem and would be flagged in a snagging report.
6.7.5.4 Glazing Systems
Two main systems are recognised. Drained and vented systems are used for site-fixed units and any IGU larger than one square metre, providing minimum edge clearances, edge cover, and properly fixed beads so water can escape and the glass can expand without contacting the frame. Fully bedded systems are only acceptable for factory glazing of smaller units.
6.7.5.5 Condition Before Installation
Before installation, IGUs should be stored out of direct sunlight, kept dry, and supported to prevent bowing. Each unit should be visually checked for water between panes, edge damage and scratching.
6.7.5.6 Site Glazing
Site glazing should follow the frame design and be carried out by trained installers familiar with good practice. Drainage and ventilation slots must be clear of obstructions, edge clearance should be at least 5mm, and gaskets must fit tightly at the corners.
6.7.6 Security
Doors, frames, windows and locks should be specified and installed to resist unauthorised entry, in line with the relevant Building Regulations. A snagging inspection can confirm that locks operate correctly and that ironmongery is fitted as expected, although verifying compliance with specific security ratings such as Secured by Design is outside the scope of a standard snagging visit.
6.7.7 Timber Doors and Windows
Timber components must be of suitable quality, and either naturally durable or treated against decay.
6.7.7.1 Quality Assurance
Manufacturers of timber doors and windows should hold appropriate third-party certification confirming the fitness and quality of their products.
6.7.7.2 Classification and Use
Timber windows should conform to BS 644 and have at least a 15mm rebate where double glazing is fitted. External doors should be at least 42.5mm thick (44mm nominal). Planted stops on external door frames are not permitted in England, Wales, Northern Ireland or the Isle of Man.
6.7.7.3 Drying Shrinkage
When fitted, the moisture content of joinery should not exceed 17% for windows and external frames, with lower limits for internal joinery in heated spaces (down to 9% near a heat source). Excessive shrinkage of timber components, leading to gaps or splitting, is something that may become apparent in the months after handover and is often picked up at a later snagging visit.
6.7.7.4 Preparation and Finish
External timber components should be naturally durable or pre-treated against fungal decay. Items to be painted should be primed before fixing, and items to be stained should have the first coat applied before delivery to site. Compatibility between treatments, primers, sealants and finishes is critical and should be confirmed with the manufacturer.
6.7.8 Non-Timber Doors and Windows
For PVC-U, aluminium, steel and composite products, similar quality and standards rules apply.
6.7.8.1 Quality Assurance
Manufacturers of non-timber doors and windows should hold appropriate third-party certification.
6.7.8.2 Standards
Non-timber doors and windows should conform to the relevant British Standards, including BS 4873 for aluminium, BS 6510 for steel, BS 7412 and BS EN 12608-1 for PVC-U, BS 7414 for white PVC-U with heat-welded joints, and BS 8529 for composite doorsets.
6.7.9 Ironmongery
Hinges, locks, handles and door closers should be suitable for their intended use and conform to the relevant British Standards. Window hinges and fastenings should prevent opening from the outside when in the closed position, trickle vents (rather than night-vent positions) are required where background ventilation is needed, and locks on bathroom and WC doors must be openable from outside in an emergency.
6.7.10 Material Storage and Protection
Joinery, doors and windows should be properly protected from damp and damage on site.
6.7.10.1 Storage
External joinery should be stacked off the ground on bearers and covered with a waterproof material, while internal joinery should be stored under cover. Wetting during unloading should be avoided.
6.7.10.2 Cut Ends
If pre-treated joinery is cut or adjusted on site, the freshly exposed surfaces should be re-treated with a suitable preservative in line with the manufacturer’s recommendations. This is not visible once installed, but premature decay further down the line can suggest it was missed.
6.7.11 Installation
This section covers how doors and windows should be fitted on site.
6.7.11.1 Construction Tolerances
Tolerances for openings, doors and windows should follow Chapter 9.1 of the NHBC Standards, which deals with consistent finishes.
6.7.11.2 Workmanship and Fixing
Doors and windows should be installed plumb, square and free from twist, racking or distortion. Fixings should follow Table 7 of the standard, with corner fixings typically 150 to 250mm from the external corner and intermediate fixings no more than 600mm apart for most materials. Internal door frames should match the wall thickness, be securely fixed to prevent curling, and architraves should be neatly mitred or scribed with even margins.
6.7.11.3 Hanging Doors and Opening Lights
Doors and opening lights should hang square within their frame and fit neatly with minimal gaps. If a flush door is reduced in height, the bottom rail should be replaced where necessary. Doors that bind, rub on carpets, drop on their hinges, or fail to latch cleanly are routine snagging items.
6.7.11.4 General Ironmongery
Hinges should be neatly housed flush with the surface and supplied with a full set of matching screws. Locks should turn easily, not be too tight in their mortises, and have keyholes that are properly aligned.
6.7.11.5 Door Hinges
To reduce twisting, external doors should be hung on one and a half pairs of 100mm hinges, internal doors on a single pair of 75mm hinges, airing or cylinder cupboards on one and a half pairs of 75mm hinges, and fire doors in accordance with the manufacturer’s recommendations.
6.7.11.6 Window Boards
Window boards should have a flat and level top surface, be fixed close to the frame, and be adequately secured against twisting or sloping back towards the frame. Where MDF is used, it should be of a moisture-resistant grade.
6.7.11.7 Bay Windows
Bay windows should be properly supported and secured to the structure to prevent sagging or twisting, and should be properly linked to the damp-proof courses at the reveals.
6.7.12 Completed Work
The finished installation should be free from damage and presented to a standard appropriate for the trades that follow. During construction, internal doors should be kept covered, frames protected with timber strips or plywood to at least one metre above skirting level, and thresholds and sills covered. Temporary protection should remain in place until handover. Damage to frames, sills and ironmongery is one of the easier categories of defect to identify during a snagging inspection.
6.7.13 Further Information
The chapter signposts the Glass and Glazing Federation’s guidance on safety and security glazing as additional reading for builders and designers.
How a Snagging Inspection Fits In
A pre-completion or post-completion snagging inspection cannot replace structural engineering checks, factory testing or specialist assessments such as a curtain walling test, but it is well placed to identify many of the everyday issues that fall within Chapter 6.7. Our inspectors routinely flag gaps in seals, doors and windows that bind or do not close cleanly, hardware that operates poorly, scratches and damage to glass, misaligned frames, uneven sills and window boards, and visible signs of failure in glazed units. On a standard snagging inspection that includes thermal imaging, cold spots and insulation gaps around frames can also be identified, giving your developer a clear list of items to address before or after you move in.
If you are buying a new build home and want an independent, expert assessment of your doors, windows and glazing alongside the rest of the property, our snagging inspectors are happy to help. Please get in touch to arrange your inspection.
