Building & Other Regulations / Restrictions

As a FENSA registered company, Installations 4u has been authorised to certify that installations of windows & doors comply with relevant Building Regulations. Non FENSA registered contractors & homeowners installing windows & doors on a DIY basis must first apply for Building Regulations approval from their local council.

For full details of the FENSA Scheme & also for the Non FENSA Requirements visit FENSA at:


Please note that the following information is intended only as a ‘Layman’s Guide’ to those parts of the Building Regulations that apply to the Replacement of Windows & Doors in Domestic Dwellings under normal circumstances.

Additionally, links are provided to enable contact to be made with the Statutory Authorities controlling Building Regulations & Planning Permission.

The following information has been reviewed and is correct as at 01/04/2002 (the introduction date of Approved Document L1 – Conservation of fuel and power in dwellings) & is based upon the Law as it pertains to England & Wales. Similar but different Regulations & Statutes apply in the Channel Islands, Eire, Northern Ireland and Scotland.

In all cases your first point of contact should be with your Local Authority.

In addition to Complying with the relevant Building Regulations, you must also check your Property Deeds for any Restrictive Covenants and, if you are a Leaseholder or your property is a Flat with a Shared Freehold, you must get the Freeholders Permission before undertaking any work. In the case of Flats with Shared Freeholds, you will almost certainly have to comply with restricted design & colour options (usually to match the originals) and sometimes with restricted material options, such as only using timber.

NB: Additional Regulations apply to the Replacement of Windows & Doors in Listed Buildings & Conservation Areas:

When a building has been Listed it is protected by Law and Listed Building Consent must be obtained before any changes are made to it. Carrying out unauthorised work to a listed building is a criminal offence punishable by a fine or a prison sentence and the local council can require you to put the building back as it was.

When a property is situated in an area that has been designated as a Conservation Area (covered by an Article 4 Direction) then Conservation Area Planning Permission must be obtained before the windows and or doors may be replaced. Carrying out work in a Conservation Area without planning permission may lead to the serving of an Enforcement Notice by the Local Authority. Should this happen and the work has been carried out in an acceptable manner then a retrospective Planning Application will usually be invited, without any further action being taken or penalty imposed. If the work is not acceptable then reinstatement, which is not usually practical or possible, or replacement with approved products, will be required. Once an Enforcement Notice has been issued failure to comply constitutes a criminal offence.

It is recommended that you always check with your Local Authority Building Control Department before undertaking work of this type because the Responsibility for Compliance lies with you, the Householder, not with the contractor!

To contact your local authority go to and search from there.

BUILDING REGULATIONS Summary Applicable to Replacement Windows & Doors

BUILDING REGULATIONS L1 – Conservation of fuel & power in dwellings

It is Approved Document L1, effective from 1st April 2002, that has introduced the new Requirement that all Replacement Window & Door Installations must have Building Regulations Approval from your local Council.

The main thrust of L1, however, is Compliance with strict new Legal Requirements for the conservation of fuel & power in dwellings.

This is achieved by limiting emissions (escape of heat) through windows & doors by requiring that they meet laid down levels of insulation (thermal transmittance). Thermal transmittance is a measure of how much heat will pass through one square metre of a structure (door or window) when the air temperatures on either side differ by one degree. This measurement is known as the U-value. The lower the U-value the better the level of insulation, and vice versa.

uPVC Replacement Windows & Doors must have a U-value of 2.0 or less.

BUILDING REGULATIONS N1 – Glazing safety in relation to impact

Approved Document N, Part N1, deals with Protection against Impact, defining areas of Critical (High Risk) Glazing & the Type of Glass to be used in those areas.

Glazing with which people are likely to come into (physical) contact whilst moving in or about the building shall;

  • if broken on impact, break in a way which is unlikely to cause injury; or
  • resist impact without breaking; or
  • be shielded or protected from impact

Areas considered to be High Risk are;

  • Windows where the bottom of the glass is within 800mm of floor level
  • All glass within Doors from floor level up to a height of 1500mm
  • All glass within Door Side Panels & Windows adjoining Doors from floor level up to a height of 1500mm & to a width of 300mm

Safe Breakage is defined in BS6206: 1981 ‘Specification for impact performance requirements for flat safety glass and safety plastics for use in buildings: paragraph 5.3.

In practise, Compliance is achieved by using Toughened or Laminated Safety Glass as specified in BS6206 in all Critical (High Risk) Areas

NB1 Although not specifically covered in Document N, locations such as windows next to baths or showers & windows on stairs or landings should also be considered as Critical Areas if there is any risk of impact.

NB2 Due to the manufacturing process Safety Glass may appear to be of a slightly different ‘tint’ to normal glass. Good Industry Practise is to install Safety Glass in all the panes of a Door or Window which Require any Safety Glass.

With regard to the above Sections of the Building Regulations, Replacement Windows and Doors must Comply. With regard to the following Sections of the Building Regulations, Replacement Windows and Doors must be no less suitable than the Existing Windows and Doors.


For a typical Domestic Dwelling (storeys not more than 4.5 Metres above ground level) Approved Document B Requires that all Habitable Rooms (living rooms & bedrooms but not bathrooms or kitchens) on and above the First Floor must be provided with Emergency Egress (escape).

In addition, rooms at Ground Floor level whose’ only Fire Escape is via another room are also required to be provided with suitable Escape Windows.

This means an External Door (above ground floor) or Window that Complies with the Specification contained at 2.11 of the Document: Any window provided for emergency egress purposes and any external door provided for escape should comply with the following condition;

The window should have an unobstructed openable area that is at least 0.33 Metres Square and at least 450mm high and 450mm wide. The bottom of the openable area should be not more than 1100mm above the floor.

In practise this is achieved by fitting an Egress Brand Fire Escape Hinge to a Designated Casement Opening in each Habitable Room on & above the First Floor.

NB Due to the original construction of some properties (particularly post war bay fronted houses) it is not always possible to comply with the 2.11 specification, which was introduced in 2000.

In answer to recent questions concerning the above topic, senior representatives of FENSA, GGF and BBA, have agreed on their understanding of the requirements.

Their understanding is as follows:

Where a window that has been used as a means of escape is replaced with the same proportional fenestration as previously existed (i.e. transom and mullion and sash layout is the same) and modern materials are used, it is possible that the casement openers may create a slightly smaller aperture due to the use of larger sections. Where these windows are replacing existing frames, it is the opinion of the above, that a window of this design will still be acceptable to FENSA as a form of fire-escape, provided it is fitted with modern, ‘fire-escape’ type hinge which allows for full opening of the window to 90ยบ.

This understanding of the requirements applies only to refurbishment work.

The three organizations listed above will be discussing this view with the appropriate authorities requesting that they accept this ‘understanding’ of the Regulations.


Approved Document F1 deals with the Requirements for the Means (type) and Volume (amount) of Ventilation.

In practise, replacing ‘like for like’ in terms of the amount & size of opening Casements, Top-lights & Sashes will usually Comply.

If Replacements are not ‘like for like’ and the amount &/or sizes of openings are being reduced then it will be necessary to take measurements and make calculations to ensure Compliance with the Table below.

Requirements F1 – ‘Means of Ventilation’

  • Room Rapid Ventilation
  • e.g. Openable window area Background Ventilation
  • i.e. Trickle vent units
  • Habitable room 1/20th of floor area of the room served 8000mm2
  • Kitchen & Utility room Opening window (no min size) 4000mm2
  • Bathroom & Shower room Opening window (no min size) 4000mm2
  • Bathroom & Shower room 1/20th of floor area of the room served 4000mm2

Where alterations are being made, such as removing a door and side window & replacing them with a Patio or French-Door, the provision of an Approved Type & Size of Trickle (background) Ventilator to the Head of the new Door will achieve Compliance. This is also the case if an existing Door which is being replaced provides the only ventilation in a room.

BUILDING REGULATIONS K2 – Protection from falling, collision & impact

The relevant part of Approved Document K for Replacement Window Installations Requires the fitting of Restrictor Stays to Limit the Opening of Casements & Sashes in Windows fitted above the Ground Floor where they are within 800mm of Floor Level.


The Requirements of Approved Document A, Structure (structural) will not usually apply to Replacement Window & Door Installations, however:

Installers must ensure that all work carried out meets with all relevant Building Regulations.

When Installing new Windows/Doors an assessment should be undertaken by the Contractor as to the Suitability of the Support/Lintel above the Replacement Window/Door.

Bay Window Replacements must not compromise the Load Bearing ability of the Bay. Therefore, all appropriate poles and spreader plates must be in place to ensure conformance.

NB Dependant upon the Original Construction & Current Condition of some Bay Windows the Head (top section of frame) should be propped and left in place during replacement to prevent Structural Movement or Collapse.

If there is a Structural Alteration, for example replacement of a Lintel, you will need to seek approval from your Local Authority Building Control Department.


During the course of all work being carried out Statutory Health & Safety Requirements must be complied with to ensure the Health, Safety & Welfare of Operatives, Customers and Members of the Public. This Requirement is without limitation but relevant examples would be:

  • Safe handling & removal from site of all debris especially broken glass
  • To protect passers-by when working above public thoroughfares by the provision of appropriate scaffolds, netting, signs & look-outs
  • When working above first floor to provide appropriate safety equipment such as harnesses, scaffolding, safety cradles & lifting devices


Windows and Doors for any New Construction must Comply with all of the above Regulations, including such projects as Extensions to existing dwellings and the Forming of New door or window Openings within the Original Building.

Planning Permission may be required and you will always need to seek approval from your Local Authority Building Control Department. To contact your local authority go to and search from there.

Copies can be obtained from HMSO at