Please see the headings below to find out about building regulations –

The following sections show a brief outline of how the Regulations apply to extensions, and which elements will require inspection by your Building Control Officer. For a more detailed guide to extensions, please see the LABC Guide to Extending Your Home

Foundations

The foundations are one of the most important parts of an extension. The design of foundations can vary for each project, dependent on factors such as ground conditions, nearby trees, topography of the site, or existing and proposed drains or sewers.

 

For domestic extensions, traditional trench-fill or strip concrete foundations are most common. These must be taken down to firm natural ground. Your Building Control Officer will be able to assist you on site to determine the nature of the ground conditions, or the impact of nearby trees and drains, and therefore advise you on the recommended depth or width of foundations.

 

Where conditions on site are not suitable for traditional foundations, more specialist solutions may be required (e.g. reinforced raft foundations, piled foundations). In these circumstances you will need to employ a qualified structural engineer to provide a design for your foundations.

Ground Floors

The ground floor of an extension needs to be structurally adequate and robust, but should also provide protection against damp penetration, and thermal insulation. There are several options for ground floor construction, depending on factors such as site conditions and existing construction, as well as financial and practical preferences.

 

A ground-bearing concrete floor is a layered construction, with a firm and compacted sub-base of suitable hardcore material, damp proof membrane, layer of insulation, and solid concrete slab at least 100mm thick, finished with a level screed.

 

In some circumstances, such as where the floor is significantly higher than ground level, or where ground conditions are not suitable for a concrete floor, a suspended floor may be more appropriate. These can be either of timber or concrete construction, with thermal insulation is generally provided between the joists on a timber floor, or above a suspended concrete floor . A void beneath the suspended floor, ventilated to outside air, provides the necessary protection from damp.

Walls

The walls of an extension must carry the structural loads of the upper floors and roof, keep the weather out of the extension, and provide thermal insulation. External walls can be either masonry cavity wall construction, or timber frame construction.

 

Cavity walls are usually of brick or block construction, with an insulated central cavity. The two skins of masonry are held together with steel ties to ensure stability. Where openings are provided for doors and windows, a suitable lintel, generally of steel or concrete, is required over the opening. Damp proofing is provided by a horizontal damp proof course at least 150mm above ground level.

 

Timber frame construction comprises an insulated structural timber stud wall, with protection from the weather being provided either by an outer skin of brick, or by hung tiles or weatherboarding. This type of construction may need to be engineer designed, and where built adjacent to a boundary with a neighbour, may also require additional layers of fire resisting material to prevent spread of fire.

Upper Floors

Where the proposed extension is more than one storey, the upper floors will generally be of timber joists spanning between loadbearing walls. Suitable flooring is provided above the joists, and a plasterboard finish below to form a ceiling. While thermal insulation is not required to internal floors, suitable insulation is required to provide sound resistance between levels.

Roofs

The roof of an extension is designed to keep out the weather, provide thermal insulation, and to bear the load of the roof coverings, light storage to loft spaces, and occasional build-up of snow. Domestic roofs will be either of flat or pitched roof construction.

 

Flat roofs can be a relatively simple, practical and economical solution for extensions. They are generally constructed of a timber joists spanning between loadbearing walls, with a plywood or similar roof deck above, finished with roofing felt or other alternative material for weatherproofing. Insulation is either provided between the roof deck and the felting to form a warm deck, or is added between and below the timber joists to form a cold ventilated roof.

 

Pitched roofs can either be a traditional cut timber roof, or can come as pre-formed engineer designed roof trusses from a specialist manufacturer. While truss roofs are made and delivered to order, a cut roof is usually designed by a architect or engineer, then cut and pitched on site by a carpenter. Most modern roofs are overlaid by a breathable membrane (although traditional roofing felt is still acceptable), and then covered by overlapping tiles or slates for weather resistance. Where a flat ceiling is provided inside, insulation is provided by loft quilt rolled between and over the ceiling joists. For a vaulted roof, insulation may be cut between and below the rafters.

 

With the exception of warm deck roofs, all roofs will require ventilation between the underside of the roof deck and the insulation, to prevent build-up of damp and condensation. This is provided via breathable roofing felts, and through additional ventilation grilles at the eaves and ridge.

Drainage

For any extension, drainage for surface water must be provided to discharge rainwater water from the new roof. If the extension includes new kitchens, bathrooms or utility rooms, then new foul drainage runs will also be required. The foul and surface water systems should be kept separate wherever possible, and allow drainage to discharge to a suitable final disposal point. It is worth identifying existing drain locations and planning drainage layouts at the earliest possible stage, as they can have an impact on the design of other elements such as floors and foundations.

 

All drainage systems must be laid with a suitable fall to allow gravity to carry the water and effluent downstream, and must be provided with adequate ventilation, and ideally in straight runs with access points for rodding at change of directions. All below ground drainage should be laid in suitable granular fill, and capped with concrete where cover is shallow.

 

Foul water should discharge to a mains public foul sewer, or to a treatment plant or cesspool. Surface water should discharge to a public surface water sewer, adequate soakaway, or natural water course. A surface water connection should only be made to a foul or mixed public sewer where there is no reasonable alternative, and where the expressed permission of the local water authority (e.g. Southern Water) has been obtained.

Fire Safety

It is very important to consider fire protection when designing and planning an extension. Domestic fires pose a serious risk to life, and the most dangerous can occur at night when people are asleep. It is important fire safety is considered as early as possible, as it may have a significant impact on the proposed design and layout of your extension.

 

In order to provide adequate early warning, smoke detection should be installed on each storey of the house, and should be mains powered and interlinked to the relevant British Standards.

 

As well as early warning, adequate provision should be allowed for means of escape from habitable rooms. This can be via access to a suitable protected escape route, via hallways and landings to a final exit door. Where the ground floor is open plan, or where inner rooms are present, escape from ground and first floor can be via a suitable emergency egress window.

 

Further advice on the above is readily available, and your Building Control officer will be happy to discuss fire safety measures with you before and during your project.

Windows and Ventilation

The Building Regulations require that adequate ventilation be provided to new buildings and extensions. This can generally be achieved easily in domestic extensions through provision of windows with an openable area at least 1/20th the area of the floor in each room, with background ventilation provided by trickle vents fitted to the head of windows and doors.

 

New windows and doors should achieve minimum standard for thermal performance as required by the Regulations, usually through use of double glazed low-e units.

 

Any glazing provided in critical areas, such as doors, window panes adjacent to doors, and windows with a cill height below 800mm should be provided with suitably robust toughened glass. Windows above ground floor level, where the bottom of any opening is below 800mm, should also be provided with guarding or restrictors to prevent danger from falling.

 

It should also be remembered that certain windows may need to be suitable for means of escape in case of fire. Please see guidance above on Fire Safety for further details.

 

Where the extension includes a new bathroom, WC, kitchen or utility room, it you should also install mechanical extraction fans to ensure removal of excess moisture from the house, and prevent condensation and mould. Your Building Control officer can advise you on the required extraction rates appropriate for each location.

Heating and Electrical Services

Any new electrical works or heating services installed during extension works should be carried out by a qualified installer, who is registered with the relevant Competent Persons scheme, such as NAPIT or NICEIC for electricians, GASSAFE for gas central heating and boiler installations, OFTEC for oil fired boilers, or HETAS for solid fuel burning stoves. The installer will provided you with an installation and commissioning certificate for the works carried out, a copy of which will need to be provided to Building Control prior to completion of works.

 

Where any fuel burning appliance is provided inside the house, it is necessary to provide carbon monoxide detection adjacent to the appliance.

Most houses will include a loft space or attic, which may be an ideal opportunity for expanding your home and providing extra space. Not all lofts are suitable for converting, so before starting it is a good idea to carry out a survey of the loft, to ensure there is adequate space to accommodate the new room. This will likely require raising the level of the floor, as well as installing a new staircase, additional windows or roof lights, and possibly moving chimneys or services already present in the loft. Loft conversions can be complex and difficult jobs, so it is worth obtaining professional advice, such as from an architect or structural engineer.

 

If your loft is suitable for conversion, the following sections offer some brief advice on elements of the conversion which should be considered at the planning stage. For additional details, please see our downloadable Guide to Extending Your Home.

Roof and Floor Structure

Your roof is likely currently designed to bear the load of the roof itself, together with occasional weather related loading from wind and snow, and light storage on the loft floor. The new conversion will require alteration to a number of structural elements, as significantly different loadings will be imposed on the structure. It is likely that all but the simplest loft conversions will require a structural engineer’s design, to detail the new loadings and structural alterations which are required.

 

Your existing roof will either be a pre-formed trussed roof, or a cut and pitched timber roof. A trussed roof is a precisely engineered construction, and should not be altered without a structural engineer’s design, as inappropriate alterations can have serious consequences for the structural stability of the roof.

 

A cut and pitch timber roof will comprise a system of timber rafters, struts, purlins and ceiling joists, spanning between loadbearing walls. These are more straightforward to convert, but will likely require engineer designed beams to support the new floor, as well as roof purlins and rafters. The existing ceiling joists will likely be inadequate for bearing the new floor loadings, so new floor timbers are usually required, which will mean raising the level of the floor in the loft.

Access to Loft Rooms

In order to convert a loft, a new staircase must be provided to access the loft room. This is often one of the most critical parts of a loft conversion, and should be carefully considered before commencing works, to ensure access is practical and feasible.

 

It is usually easiest to provide a new stair in the existing landing stairwell, as this not only provides continuity within the property, but can be important for means of escape (see section on Fire Safety). The staircase can be no steeper than 42 degrees pitch, and should be provided with safe and regular steps as detailed in the appropriate guidance. A minimum headroom of 2 metres is also required above the stairs, and a safe landing should be provided at the head and foot of the stairs. Suitable balustrading must also be provided at a minimum height of 900mm above the floor or nosing of the stairs.

Fire Safety

House fires pose a serious risk to life, and the most dangerous can occur at night when people are asleep. It is important fire safety is considered as early as possible, as it may have a significant impact on the proposed design and layout of your extension. This is particularly important in loft rooms, as unlike first floor bedrooms, the additional height above the ground will usually mean safe escape to the outside from a window is impossible.

 

In order to provide adequate early warning, smoke detection should be installed on each storey of the house, and should be mains powered and interlinked to the relevant British Standards.

 

As well as early warning, adequate provision should be allowed for means of escape from habitable rooms. For most loft conversions, this can only be provided via access to a suitable protected escape route, via hallways and landings to a final exit door. You may also need to provide new doors throughout the escape route, as all doors to habitable rooms should be suitable fire doors.

 

It is also a requirement that the floor/ceiling separating the first floor from the new loft room should provide 30 minutes fire resistance, to protect against fires stating below the loft room. Your Building Control officer can advise on whether the existing ceiling would be acceptable for fire resistance. If the ceiling is lath and plaster or other non-suitable construction, then upgrades will be required, such as adding fire resistant insulation from above between the floor joists, or by over-boarding the ceiling below with fire resistant plasterboard.

 

Further advice on the above is readily available, and your Building Control officer will be happy to discuss fire safety measures with you before and during your project.

Bathrooms and Drainage

If you plan to include a bathroom or en-suite as part of your loft conversion, it is worth considering the location of the bathroom carefully. Ideally, a bathroom should be placed above the existing bathroom below, as this will allow any new drainage to be connected to the existing system with the minimum of new pipework.

 

Any new bathroom must also be provided with a mechanical extractor fan (see Windows and Ventilation) to remove excess moisture.

Windows and Ventilation

The Building Regulations require that adequate ventilation be provided to new habitable rooms. This can generally be achieved easily in domestic loft conversions through provision of windows with an openable area at least 1/20th the area of the floor in each room, with background ventilation provided by trickle vents fitted to the head of windows and roof lights.

 

New windows and doors should achieve minimum standard for thermal performance as required by the Regulations, usually through use of double glazed low-e units.

 

Any glazing provided in critical areas, such as windows with a cill height below 800mm should be provided with suitably robust toughened glass. Where the bottom of any opening is below 800mm, guarding or restrictors should also be provided to prevent danger from falling.

 

Where the conversion includes a new bathroom or WC, you should also install mechanical extraction fans to ensure removal of excess moisture from the house, and prevent condensation and mould. Your Building Control officer can advise you on the required extraction rates appropriate for each location.

Thermal and Sound Insulation

In order to meet the requirements for conservation of fuel and energy, as well as provide a comfortable living space, the roof of the loft conversion will need to be insulated to provide adequate thermal performance. This is usually achieved by providing high performance insulation boards between and under the rafters.

 

It should be noted that a ventilation space will be required between the insulation and the roof felt or membrane, to prevent build-up of interstitial condensation. You may also need to provide additional ventilation to the roof, via ridge vent tiles or eaves ventilators.

 

Insulating the roof in this way will also lower the height of the ceiling in the room, which should be considered at the design stage. Specialist products are available, such as insulation multi-foils, which may help reduce the loss of headroom.

 

The new floor will also need to be insulated, not for thermal performance, but to resist passage of sound. This is usually achieved through sound resisting quilting laid between the floor joists.

Heating and Electrical Services

Any new electrical works or heating services installed during extension works should be carried out by a qualified installer, who is registered with the relevant Competent Persons scheme, such as NAPIT or NICEIC for electricians, GASSAFE for gas central heating and boiler installations, OFTEC for oil fired boilers, or HETAS for solid fuel burning stoves. The installer will provided you with an installation and commissioning certificate for the works carried out, a copy of which will need to be provided to Building Control prior to completion of works.

 

Where any fuel burning appliance is provided inside the house, it is necessary to provide carbon monoxide detection adjacent to the appliance.

Structural alterations in the building will require building regulations although some may require more work than others due to the installation of certain elements to support what is being removed.

You may wish to consult an architect or a structural engineer before putting in for building regulations to see if the works you would like to undertake are feasible.

Removing Walls

When removing a wall you would first need to find out if it is a load bearing wall. The load bearing wall requires the installation of a steel beam or a lintel.

If you need to install either of these to support the structure after the wall is removed, you will need to consult with a structural engineer to create calculations for the steel beam to make sure it can hold the weight.

The Beam will then need to be fire boarded before plaster.

Knock through of walls or openings

Knocking through a wall or creating an opening in one is considered a structural alteration and would require building regulations.

If you have an existing masonry garage attached to your property, it may be suitable for converting. It is worth considering if the garage is a unusual construction, or has any known structural problems, whether the garage is large enough to provide the space you require, how access can be gained from within the house, and of course where you can park your vehicle once the garage is no longer available.

 

Although appearing relatively simple compared to an extension or loft conversion, garage conversions can be surprisingly complicated. Careful planning is essential, and you may wish to seek professional advice from an architect before commencing.

 

If your garage is suitable for converting, the following technical advice will provide some guidance on the common technical issues you will need to consider when planning your garage conversion.

Infilling the Garage Door

However the existing opening to the garage door is in-filled, it will need adequate support. It will necessary in the first instance to dig a small trial hole to the front of the garage door, to establish whether any foundation is present. If an existing foundation is present, and to the satisfaction of your Building Control Officer, you will be able to build off this foundation.

 

If no foundation is present, then there are several options available. You can dig a new excavation to minimum 1m depth, or the same depth as the existing house (whichever is deeper), and provide a new concrete trench fill foundation. This should be founded on firm virgin ground, and be inspected by your Building Control Officer prior to pouring concrete.

 

For a standard single garage door opening, it may be possible as an alternative to bridge the gap with a suitably deep lintel, at least 150mm deep, bearing into the loadbearing structure on each side. This should be agreed with the Building Control Officer on site before installing.

 

Once the firm footing is provided, you can infill the garage either wit standard masonry cavity wall construction, or with timber frame construction and suitable external weathering. This will often depend on personal preference, or the existing construction, as to which is most appropriate for your project. You may also wish to include a new window or door. Whichever option you choose, it is important the infill provide adequate resistance to weather and rising damp, and suitable thermal insulation performance.

Raising the Floor Level

A garage floor will usually be lower than the existing house, and may slope towards the main door. The floor will therefore need to be raised to match the level of the house. This is also a good opportunity to provide additional damp proofing and floor insulation.

 

One common method is to lay a damp membrane on the existing floor and use insulation boards to build up the floor level. This can then be brought up to the level of the existing house using concrete, or a sand and cement screed.

 

As an alternative, you can lay a damp proof membrane, then install treated timber bearers, with insulation in between the timbers, and tongue-and-groove flooring above. It should be remembered that if installed as a suspended floor, this will need to be cross ventilated to prevent build-up of damp and condensation.

Most door and window installations are covered under a competent persons scheme such as:

These governing bodies are able to certify installers to be able to issue their own certification on works that they install.

For works that are not done by a Fensa or Certass registered installer, you would be required to submit a building regulations application to us and one of our surveyors will come and inspect the works as they progress and sign them off with a certificate when complete.

Any new electrical works or heating services installed during extension works should be carried out by a qualified installer, who is registered with the relevant Competent Persons scheme, such as NAPIT or NICEIC for electricians, GASSAFE for gas central heating and boiler installations, OFTEC for oil fired boilers, or HETAS for solid fuel burning stoves. The installer will provided you with an installation and commissioning certificate for the works carried out, a copy of which will need to be provided to Building Control prior to completion of works.

 

Where any fuel burning appliance is provided inside the house, it is necessary to provide carbon monoxide detection adjacent to the appliance.