Introduction

Converting your loft into a useable living space is a cost-effective way of developing your home without using additional space from your plot of land.

Although not recommended for really heavy loads, such as lots of gym equipment, loft conversions are an excellent way to create an additional bedroom, bathroom or office.

A loft conversion can add a considerable amount of floor space to your home, but bear in mind that some of the walls and ceilings will usually be sloping to fit beneath the roof, so you will not have full head height across the whole room. Most commonly, the available standing area is increased with the inclusion of a dormer or mansard window, although a very large loft space may not require this and instead simply has skylights inserted flush with the roof.

Planning permission

• The volume of the property is not changing; windows will only be in the form of skylights.
• No part of the new building projects above the highest point of the original building.
• Where a dormer or mansard is to be added to a terraced propery, the volume of this addition is less than 50CuM (1,767 cubic feet) or less than 10% of the volume of the original building, whichever is the greater, subject to a maximum of 115CuM (4,064 cubic feet).
• Where a dormer or mansard is to be added to a semi-detached or detached property, the volume of this addition is less than 70CuM (2,474 cubic feet) or less than 15% of the volume of the original building, whichever is the greater, subject to a maximum of 115m3 (4,064 cubic feet).
• No dormer or mansard window is to be installed such that it overlooks a highway (public road, footbath or bridleway).
• The original building is not listed or in a conservation area.

• Bear in mind that the volume of the original building is not necessarily the same as the volume of the current building, which may already have been extended and therefore will have used up some of the ‘permitted development limit’.

Building regulations

All loft conversions will have to meet the latest building regulations and be certified by the local Building Control Officer. This is because the loft is being turned into ‘habitable space’ which must therefore have suitable levels of health and safety. With this in mind, the following areas are particularly important:

• Regulations & permissions for extensions

• Structural strength of the current top floor must be sufficient to support another habitable level. This will usually require at least two new RSJs (rolled steel joists) to be inserted into the walls of the top floor. In addition, the existing joists in the roof void are likely to measure 102mm x 51mm (4in x 2in) which will not support a new floor. New fire-resistant joists measuring at least 153mm x 51mm (6in x 2in) will have to be installed.
• Your loft conversion will more than likely turn your home into a building with three or more stories, in which case certified fire doors, with self-closing mechanisms, will need to be fitted to staircases, escape routes and communal areas.
• A fire exit must be provided from the roof. This will most often be in the form of a window, glazed with safety glass and with a minimum openable area of 0.33m2 (3½ sqft).
• Adequate ventilation must be provided to loft room by means of one or more windows, which must be glazed with double-glazing that has a U-value of 2.0 or less.
• The loft walls and ceiling must be suitably insulated to be energy efficient.
• All electrics and plumbing must be safely installed.

• Fire doors
• Window requirements of the building regulations

If your home is terraced or semi-detached, the additional RSJs required to support the new loft room will invoke the Party Wall Act 1996, and you should be sure to gain written consent from your adjoining neighbours for work to proceed.

• The party wall act

Loft beams

The construction of your current roof will determine whether you can convert the space in a decent room.

Firstly, you should measure the height of your roof void at it tallest point. If this measurement is less than 2.3m (7ft 6½in), you will not easily create a decent loft room. If you’re prepared to go to the extra expense and planning permission, you can actually raise the roof!

Secondly, take a look at your existing roof trusses. If they are of the rafter variety, they will require a great deal more strengthening in order to support the weight of the conversion, and this will increase the cost and complexity of the project. If you have a trussed roof, any loft conversion company is capable of converting this space.

Types of loft conversion

There are several types of loft conversion, largely determined by the location of any windows:

A dormer conversion is usually developed when additional full height space is required in the loft room. These extensions to the roof line can be flat roofed or gabled and of various sizes. If you plan to put a dormer window on the front of your home, or overlooking a highway, you will need to apply for planning permission.

A mansard conversion adds a considerable amount of space to a loft room, usually at the back. With a flat roof, the walls slope into the room at an angle of 72^o while the windows are built into small dormers. Planning permission will usually be required for this type of conversion.

Staircase

In order to be considered as a habitable room, a loft conversion must be accessed by a staircase; loft ladders don’t comply with Part K of the building regs.

You should therefore consider where this staircase will be accommodated in your existing building. Where landing and vertical space is limited, it is not unusual for the smallest bedroom to be sacrificed in order to position a staircase up to the new loft room(s).

• Building Regulations: Part K

In summary the building regulations stipulate that a staircase must have the following attributes:

• Maximum step height of 220mm (8¾in).
• Maximum tread depth of 220mm (8¾in).
• Minimum headroom of 1.9m (6ft 3in) at the centre of the stair width, and not less than 1.8m (5ft 11in) at the edge of the stair width.
• Staircase cannot be steeper than 42^o.
• The staircase must be guarded where the sideways drop is greater than 600mm (24in).

• Note that alternate tread stairs and spiral staircases will not be accepted unless there is absolutely no space to accommodate a normal staircase.

Soil pipes

If you are planning to put a bathroom or toilet into the loft conversion, you should consider its position carefully. Waste water is most conveniently carried away in a large bore soil pipe, which are often situated at the back of the property. If you plan to position your bathroom at a distance from the soil pipe, you will need to use a toilet that includes a macerator which will prepare the waste to be carried away by a small bore soil pipe.

• Adding an additional toilet with a macerator

Water tanks

Don’t forget that most heating and hot water systems include water storage tanks in the loft. You will need to plan where these will be moved to, and how access will be gained to them should they need any attention in the future.

Further information and useful links

• Guide to conservatories
• Guide to basements
• Making structural changes to your property
• More building works topics
• Walls & ceilings topics

• Find a Loft Conversion specialist near you
• Find an Architect near you
• Find a Chartered Surveyor near you
• Find a Builder near you