Product catalogue
Westbury Conservatories
10.1 Building regulations
When making your order, ventilation, glazed area, mobility, heat loss, safety glass and escape need to be taken into consideration. We have included some useful extracts from the regulations for dwelling houses of which there are five main areas of concern.
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| Part L (Heat Loss) |
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| Part M2 (Mobility) |
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| Part B1 (Escape) |
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| Part N (Safety Glazing) |
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| Part F (Ventilation) |
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Document L1
Conservation of fuel and power in dwellings (2002)
1.8 The requirement would be met if the average U-value of windows, doors and rooflights matches the relevant figure in Table 1 and the area of the windows, doors and rooflights together does not exceed 25% of the total floor area.
1.9 The average U-value is an area-weighted average for the whole dwelling, and depends on the individual U-values of the glazed components and door components proposed and their proportions of the total area of openings.
Table 1: Elemental Method: U-values (W/m2K) for construction elements
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| Exposed element | U-value |
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| Windows, doors and rooflights1 (area-weighted average), glazing in wood or PVC frames2 | 2.0 |
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| Windows, doors and rooflights1 (area-weighted average), glazing in metal frames2 | 2.2 |
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| Notes to Table 1: 1 Rooflights include roof windows 2 The higher U-value for metal-framed windows allows for additional solar gain due to the greater glazed proportion. |
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Historic buildings
2.9 Historic buildings include -
A. Listed buildings.
B. Buildings situated in conservation areas.
C. Buildings which are of architectural and historical interest and which are referred to as a material consideration on a local authority's development plan.
D. Buildings of architectural and historical interest within national parks, areas of outstanding natural beauty and world heritage sites.
2.10 The need to conserve the special characteristics of such historic buildings needs to be recognised. In such work, the aim should be to improve energy efficiency where and to the extent that it is practically possible always provided that the work does not prejudice the character of the historic building, or increase the risk of long-term deterioration to the building fabric or fittings. In arriving at the appropriate balance between historic building conservation and energy conservation, it would be appropriate to take into advice of the local planning authority's conservation officer.
2.11 Particular issues relating to work in historic buildings that warrant sympathetic treatment and where advice from others could therefore be beneficial include -
A. Restoring the historic character of a building that had been subject to previous inappropriate alteration. (e.g. replacement windows, doors and rooflights).
B. Rebuiliding a former historic building (e.g. following a fire or filling in a gap site in a terrace).
C. Making provisions enabling the fabric of the historic buildings to 'breathe' to control moisture and potential long term decay problems.
Document B1
Fire Safety (2000) (2002 Amendments)
2.7 Except for kitchens, all habitable rooms in the upper storey(s) of a house served by only one stair should be provided with a window (or external door) which complies with paragraph 2.11.
2.11 Any window provided for emergency egress purposes and any external door provided for escape should comply with the following conditions.
A. The window should have an unobstructed openable area that is at least 0.33m2 and at least 450mm high and 450mm wide (the route through the window may be at an angle rather than straight through). The bottom of the openable area should not be more than 1100mm above the floor.
Note: Approved document K Protection from falling, collision and impact specifies a minimum guarding height of 800mm, except in the case of a window in a roof where the bottom of the opening may be 600mm above the floor.
B. The window or door should enable the person escaping to reach a place free from danger from fire. This is a matter for judgement in each case, but in general a courtyard or back garden from which there is no exit other than through other buildings would have to be at least as deep as the dwelling is high to be acceptable.
Document M
Access to and Use of Buildings (2004)
Access into the dwelling
Design considerations:
6.19 There the approach to the entrance consists of a level or ramped approach (see paragraphs 6.13 - 6.15), an accessible threshold at the entrance should be provided. An accessible threshold into entrance level flats should also be provided.
6.20 In exceptional circumstances where the approach to the entrance consists of a stepped approach (see paragraph 6.16), it would still be reasonable to provide an accessible threshold. If a step into the dwelling is unavoidable, the rise should be no more than 150mm.
6.21 If the approach to the dwelling or block of flats consists of a level or ramped approach, requirement M1 will be satisfied if an accessible threshold is provided into the entrance. The design of an accessible threshold should also satisfy the requirements of Part C2: 'Dangerous and offensive substances' and Part C4: 'Resistance to weather and ground moisture''.
Note: General guidance on design considerations for accessible thresholds has been published separately by The Stationery Office as 'Accessible thresholds in new housing: guidance for house builders and designers'.
Entrance doors
Design considerations:
6.22 The provision of an appropriate door opening width will enable a wheelchair user to manoeuvre into the dwelling.
Provisions:
6.23 Requirement M1 will be satisfied if an external door providing access for disabled people has a minimum clear opening width of 775mm.
Note: For dwellings, the clear opening width is taken from the face of the door stop on the latch side to the face of the door when open at 90° (i.e. no change from the 1999 edition of ADM).
Document N
Glazing (1998)
Critical Locations:
1.1 The following locations may be considered 'critical' in terms of safety:
A. Between finished floor level and 800mm above that level in internal and external walls and partitions (see Diagram 1).
B. Between finished floor level and 1500mm above that levelin a door or in a side panel, close to either edge of the door (see Diagram 1).
Reducing the risks:
1.2 Glazing in critical locations should either
A. Break safely, if it breaks (see paragraph 1.3), or
B. Be permanently protected.
Safe breakage:
1.3 Safe breakage is defined in BS 6206: 1981 Specification for impact performance requirements for flat safety glass and safety plastics for use in buildings: clause 5.3, and is based on an impact test which requires the result of the impact to be limited to creating:
A. A small clear opening only, with a limit to the size of the detached particles, or
B. Disintegration, with small detached particles, or
C. Breakage resulting in separate pieces that are not sharp or pointed.
In terms of safe breakage, a glazing material suitable for installation in a critical location would satisfy the requirements of Class C of BS 6206 or, if it is installed in a door or a door side panel and has a pane width exceeding 900mm, the requirements of Class B of the same standard.
Glazing in small panes:
1.4 In the context of this approved document, a 'small pane' may be an isolated pane, or one of a number of panes contained within glazing bars, traditional leaded lights or copper lights.
1.5 Small panes should have a smaller dimension not exceeding 250mm and an area not exceeding 0.5m2 each measured between glazing beads or similar fixings. Annealed glass in a small pane should not be less that 6mm nominal thick, exceptin traditional leaded or copper lights in which 4mm glass would be acceptable, when fire resistance was not a factor.
Document F
Ventilation (1998)
1.2 The performance will be achieved if the following provisions are made in accordance with Table 1:
A. For rapid ventilation, one or more ventilation opening with some part of the ventilation opening at high level (typically 1.75m above the floor level), e.g. an opening window; and
B. For background ventilation, a ventilation opening (or openings), e.g. trickle ventilators, air bricks with a 'hit and miss' ventilator, or where appropriate, suitably designed opening windows. The ventilation opening(s) should be reasonably secure, adjustable and located (typically 1.75m above the floor level) so as to avoid discomfort due to cold draughts and to prevent rain ingress.
Table 1: Ventilation of rooms containing openable windows (i.e. located on an external wall)
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| Room | Rapid ventilation | Background ventilation |
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| Habitable room | 1/20th of floor area | 8000mm2 |
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| Kitchen | Opening window (no minimum size) | 4000mm2 |
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| Utility room | Opening window (no minimum size) | 4000mm2 |
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| Bathroom (with or without WC) | Opening window (no minimum size) | 4000mm2 |
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| Sanitary acco- mmodation | 1/20th of floor or mechanical extract of 6 litres/second | 4000mm2 |
Full building regulations are accessible online at www.odpm.gov.uk. Please note that regulations may vary form district to district and most certainly in Wales and Scotland.
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