Raise the roof with a loft conversion

A loft conversion is a great way to turn unused space in your home into another useful room or rooms.

A good loft conversion can add up to 30% more living space to your home and up to 20% to the value of the property. It’s usually less stressful than moving and less disruptive than a ground-floor extension. Yet it still involves considerable organisation and cost, what with floor reinforcements, skylights, extra insulation, the new staircase, electricity, lighting, heating and fire safety etc.

Whatever your reasons for converting your loft, you need to make sure you do it well and safely - without damage to your home.

Where to start

The first thing to check is that your loft is big enough to be converted. There are three key measurements: 

•Internal height - ideally at least 2.5m -  but a minimum of 2.2m

•Pitch or angle of roof, which will dictate head height 

•Floor area - ideally at least 5.5 m wide (including any chimney) and 7.5 m front to back 

You must have a minimum of 2m headroom for the stairs and landing area. If you don’t, you might be able to replace part of the roof with dormer windows or even raise the whole roof - but this will be expensive and you’ll need planning permission to do so.

Once you know the size of your loft space, you can plan how to use it. 

You might need to think creatively here. In most domestic loft conversions, space is limited and the angle of the roof restricts movement. Even if you have lots of room and want to install a bath or shower room, you’ll need to consider how that will connect to the existing drainage system.

You then have two main choices. An architect or architectural technologist can prepare drawings and designs, and arrange relevant approvals. They might also recommend a structural engineer and builder, or manage your project for you.

Alternatively, you can appoint a specialist loft conversion company to oversee the design, approvals and work for an all-inclusive price. It is advisable to get quotes from at least three potential companies, and ask friends and family for their recommendations. 

How much will it cost?

As a rough guide and dependent on where you live, a very basic loft conversion package can start at as little as £25,000, but is usually higher, when you start to add on other features .  This will include floor reinforcements, skylights, extra insulation, staircase, electricity, lighting, heating and fire safety.

Add a minimum of £5,000 to this if you also want to install dormer windows for extra light and space.

If you have insufficient headroom in your existing loft (the minimum is 2 m), you’ll need to raise the roof structure. This is likely to cost at least £40,000 in itself, not including planning permission and building regulations application fees.

Fire safety in loft conversions 

A key element of building regulations, especially with loft conversions, is fire safety and the means of escape in the event of fire. 

If you are converting the loft of a single-storey house, such as a bungalow, all habitable rooms at first-floor level need an escape window fitted. These should measure at least 450 x 450 mm, with a clear opening of at least 0.33 m2 and hinges that allow the window to fully open. 

Escape windows are not permissible where you convert the loft of a two-storey house. Instead, the main stairway forms the means of escape and so requires adequate fire protection. All doors that open on to the stair should be fire rated to at least 20 minutes, and the stair should end in a hall with a door leading directly outside. 

Alternatively, you may wish to consider a “fire engineered solution”, such as a mechanical smoke ventilation system.

If your house already has three storeys and you wish to add further floors, loft conversions become much more complicated from the perspective of fire safety. You will probably need a sprinkler system or possibly a second escape stair. These types of loft conversion need specialist design from an architect or structural engineer to minimise risks from fire. 

Creating an eco-friendly loft

There are many ways to incorporate eco-friendly aspects into your loft conversion.  The loft itself will be maximising potential existing living space, and where previously the space may have been poorly insulated and leaking heat into the atmosphere, this will no longer be the case.

You could consider use of sustainably sourced materials, such as:

• Timbers - check for the Forest Stewardship Council (FSC) logo

• Roofing materials, reuse existing tiles where possible and check reclamation yards for second hand tiles to match or consider recycled rubber and wood fibre shingles 

• Rain water run off and plumbing and guttering - could you collect rainwater into a tank to flush the toilet?

• Lighting - look at LED light bulbs and maximise light from your loft windows. Central pivot roof windows are usually cheaper and therefore more popular. Windows need to be A+ rated and double or triple glazed

• Insulation - is essential to the success of a loft conversion, ensuring the space is neither too hot nor too cold. Sheep fleece, hemp and flax products, wood fibre and cellulose products (made from newsprint) are iust a few of the alternative insulators on the market

• Interior design - nowadays there is more and more choice of non-toxic, natural paint, recycled wallpaper and FSC cladding as well as ideas for upcycling furniture.

Planning permission 

Planning permission is not normally required for loft conversions unless you extend the roof space or if you live in a conservation area or listed property. However, should always check with your local planning authority to understand what you are allowed to do before any works commence..

Most loft conversions are viewed as permitted developments, as long as they don’t exceed 50 m3 in a detached or semi-detached house, or 40 m3 in a terraced house. The conversion should also be lower than the highest part of the existing roof and set back as far as possible.  The Planning Portal has more detailed information about when planning permission is required.

You’ll need to consider the materials you use, so that they are in-keeping with those already used in your home. Side-facing windows may need to use opaque rather than transparent glass and be non-opening.

Building regulations 

Building regulations apply because a loft conversion is classed as a “material change of use”. The regulations ensure that the structural strength of the new floor will be sufficient and that the stability of the existing structure is not endangered. 

Stringent fire safety rules also apply - see above. 

A loft conversion may also be subject to the Party Wall Act, under which you must give adjoining property owners notice of any works before you start. (Building control does not have any involvement in the Party Wall Act.)

If you plan to convert your loft for habitable use, you will need to install a new staircase. Where possible, these stairs should continue from the existing stairwell to save space and maintain the natural flow of the building. If not, you will need to partition off a room to accommodate the new staircase. In some loft conversions where space is very limited and only one room is created, a steeper, more traditional staircase may be acceptable, but you will need to check this with your local authority building control team before any work starts. 

Building regulations also apply to a number of other elements related to loft conversions, including bathrooms, thermal insulation, sound insulation, heating, electrics, and windows and ventilation. For more about these matters, see the section on loft conversions in our Guide to Extending your Home. 

To make a building regulations application before you start work, visit the Planning Portal or contact your local authority building control team (see below) to discuss your project in more detail.


Further information on loft conversions and other home improvement projects is available here

Contact your local authority building control team here