6.7 Doors, windows and glazing
SCOPE
DESIGN STANDARDS
Design that follows the guidance below will be acceptable for doors, windows, and glazing.
STATUTORY REQUIREMENTS
Design should be in accordance with relevant Building Regulations and other statutory requirements.
ENVIRONMENTAL FACTORS
Items to be taken into account include:
(a) noise control
Where noise levels are very high, for example near airports or motorways, it may be advisable to install sound-insulating windows, usually of special design and construction.
(b) planning requirements
Local planning authorities may impose limitations on the shape, size and choice of materials for windows and doors, for example in conservation areas.
(c) climatic conditions
Climatic conditions, especially wind speed, together with the required level of window performance (eg in relation to air tightness), may govern the size of glass panes and opening lights in exposed locations.
SECURITY
Items to be taken into account include:
DWELLINGS
The main entrance doors of individual dwellings should be fitted with one (or more) securely fixed lock and keep which complies with BS 3621 or has:
- at least 1000 differs, and
- a fixing which, if burst open, would not pull out without breaking the door or its frame, and
- a hardened steel bolt or inserts to prevent sawing, and
- latch and deadlocking facility
and is preferably openable on the inside by a single simple manual operation not requiring the use of a key.
Any glazing which, if open or broken, would permit release of the snib by hand or arm entry should be laminated.
Multipoint locking systems (espagnolettes) are alternatives to conventional locks provided they meet with the above requirements.
FLATS AND MAISONETTES
Locks to entrance doors of individual flats and maisonettes of three or more storeys should be openable from the inside by a single simple manual operation not requiring the use of a key.
To avoid the possibility of the door becoming locked during a fire while one of the occupants is outside the dwelling the lock should not have a self locking latch.
A securely fixed opening limitation device should be fitted to main entrance doors.
Opening limitation devices should be fitted to the entrance doors of individual flats and maisonettes.
In sheltered accommodation opening limitation devices should be of a type capable of being disengaged from the outside with a key.
There should be a means of giving a wide angle view of the area immediately outside the main entrance door of individual dwellings. Acceptable ways include:
- a through-door viewer
- clear glazing either to part of the door or a convenient window
- closed circuit television.
Secondary external access doors including sliding patio doors should have:
- a 5-lever lock fixed securely
- bolts fixed securely at both top and bottom of the door on the internal opening edge.
Where multipoint locking systems (espagnolettes) are used bolts may be omitted.
External sliding doors should be designed to prevent the doors being forced along their tracks, being opened by lifting the door off the latch, and fitted in such a way that the doors cannot be lifted from their frames from the outside.
Connections between door and/or frame components which can be easily released from outside should not be used. This includes accessible screw connections.
Ironmongery for windows should be supplied as follows:
- hinges and fastenings of opening lights of windows should be of a type which prevents them from being opened from the outside when in the closed position
- opening lights on all ground floor windows and others which are readily accessible from the outside may be fitted with lockable devices which cannot be released without a key
- where the windows are required by Building Regulations to have background ventilation they may be fitted with trickle ventilators or some other means of providing ventilation which is controllable and located to avoid undue draughts. Windows with 'night vent' positions are not accepted as meeting these recommendations.
Key operated locks should not be used on any windows above ground floor level which are controlled by the Building Regulations for escape purposes; push button release window latches may be used.
Restrictors on escape windows above ground floor level should be readily released without the need to operate more than one mechanism or use a key.
IN SERVICE PERFORMANCE
Items to be taken into account include:
Windows and external doors exposed to wind-driven rain may need particular protection to ensure they remain weathertight.
BS 6375 contains recommendations for the classification of window components according to their resistance (under test) to air and water penetration, and wind pressure. A similar classification is used by BBA for certification of windows.
Water penetration may occur not only between frame and opening leaf or light, but also between the frame and the surrounding structure. Vertical and horizontal dpcs should be provided around the frame in accordance with Chapter 6.1 'External masonry walls' (Design and Sitework).
In Scotland, Northern Ireland and other locations of Very Severe exposure, rebated reveal construction should be sealed with an appropriate sealant.
Reference should be made to Chapter 6.1 'External Masonry Walls' Appendix 6.1-A for categories of exposure to wind driven rain.
In all locations where weathertightness is likely to be a problem, additional precautions may be needed, such as:
- setting the frame back from the facade
- fixing the frame behind a rebate in the structural opening (sometimes known as a 'check' reveal)
- fixing weather boards and water bars to external doors but ensuring threshold is accessible where appropriate
- building a projecting porch
- rain check grooves to inward opening external door frames
- a combination of the above.
Where metal windows are to be used, designs should incorporate a thermal break.
Trickle ventilation is covered in Clause D4.
Mechanical ventilation is covered in Chapter 8.1 'Internal services' (Design).
Fire resisting doors should be fitted with a positive self-closing device.
Any door between a dwelling and an attached or integral garage should be a half-hour fire resistant door and frame.
Door frames and windows and their fittings should be adequate to withstand operational loads. Structural loads should be carried on lintels, beams or some other structural element. If frames are required to carry structural loads, they should be designed accordingly.
Doors and windows should be designed and selected to avoid significant distortion, such as twisting and bowing during use. Timber shrinkage should be allowed for.
To reduce twisting, doors should be hung on hinges as follows:
| Type of door | Hinges |
| External | 1½ pairs x 100mm |
| Fire door | 1½ pairs* x 100mm |
| Airing or cylinder cupboard | 1½ pairs x 75mm |
| Other internal | 1 pair x 75mm |
* 1 pair where rising butts are used
Window boards may be wetted by condensation. Materials other than natural timber should be moisture-resistant.
Where doors to rooms containing a bath or WC have a securing device, it should be of a type capable of being opened from the outside in an emergency.
In sheltered accommodation, additional special provisions may be needed for all door locks, limiters and other fasteners, to enable wardens to gain access to dwellings when necessary.
RESISTANCE TO DECAY
The following elements of timber doors and windows should be of naturally durable timber or timber pre-treated against fungal decay:
- external door frames
- windows
- timber surrounds to metal windows
- external doors, other than flush doors.
For detailed information, reference should be made to Chapter 2.3 'Timber preservation (natural solid timber)' (each section).
GLAZING
(a) resist wind loads
The quality and thickness of normal window glass should be specified to suit the design wind load for the location, in accordance with BS 6262 and relevant data sheets issued by the Glass and Glazing Federation.
(b) minimise risk of injury
Where there is a high risk of accidental breakage, the glazing should be designed and selected to comply with the safety recommendations for risk areas specified in Approved Document N for England, Wales and the Isle of Man, Technical Booklet V in Northern Ireland and BS 6262 in Scotland. Where there is a particular risk, such as at door side panels, 'low level' glazing and where fully glazed panels can be mistaken for doors, toughened or laminated glass, or other materials, such as acrylic or polycarbonate, may be needed.
(c) ensure adequate performance
DRAINED AND VENTED SYSTEMS
- These systems should allow any moisture that enters the glazing channel between the frame and the edge seal of the insulating glass unit to be drained away. The system should prevent long term moisture contact with the edge seal.
A gap of at least 5mm should be provided between the frame's lower rebate and the edge seal of the insulating glass unit. Adequate drainage and ventilation should be provided by holes, slots or channels.
Insulating glass units 1m2 or greater in area should have a drained and vented glazing system, whether they are factory glazed or site glazed.
Suitable systems and installations are shown in the relevant parts of BS 8000, BS 6262 and BRE Digest 453. The system should provide adequate protection of the edge seal of the insulating glass unit.
FULLY BEDDED SYSTEMS
- Factory glazed methods should be in accordance with the relevant parts of BS 8000, BS 6262 and BRE Digest 453.
Fully bedded systems (acceptable for factory glazing only) rely on no gaps being left around the perimeter of the insulating glass units. Moisture that can reach these areas will lead to the breakdown of the edge seal.
Site glazing may incorporate fully bedded systems on the top and sides of the insulating glass unit but the rebate platform requires a drained and vented bottom bead.
INSULATING GLASS UNITS
- Insulating glass units should comply with the requirements of BS EN 1279, be CE marked and the subject of a third party certification scheme (e.g. Kitemarking).
Insulating glass units should normally have a dual seal, or single seal if of hot melt butyl, together with desiccant in at least one long and one short section of the spacer bar.
BEADS
In external situations the bottom bead should project slightly over the rebate edge, and be bedded to the rebate platform.
PROVISION OF INFORMATION
Ensure that design and specification information is issued to site supervisors and relevant specialist subcontractors and/or suppliers.
