Michael Holmes tips on how to convert a loft

With the recent warning from surveyors that house prices will rise six per cent a year until 2019 due to the lack of properties on the market, people looking to buy a new home might consider staying put and renovating their current properties. Michael Holmes, editor in chief of Homebuilding and Renovating Magazine believes that a cost-effective and straightforward way to add extra living space and value is to convert your loft. He provides his top tips below:

Is it possible?

The usable space in your loft is the area with headroom of 2.2m or above between the top of the ceiling joists and underside of the rafters. By the time the floor is strengthened and the ceiling insulated, this will give around 2m of headroom and above. Headroom below this level where the roof slopes down to the floor starts to get tighter but is still useful for positioning furniture, storage, beds, a bath etc.

If there is little or no room in the loft because the roof slope is low you would need to alter the roof to get an additional storey. If there is space but it is limited you can expand it by altering the roof design.

Structural alterations

The lofts of pre-1960s houses are typically easy to convert because the roof was usually cut to size on site and assembled with relatively large timbers with lots of clear space. Often only relatively minor alterations are required to create the clear space needed for a loft conversion. Post-1960s homes built with modern prefabricated roof trusses – a web of thin timbers typically with W-shaped struts held together by metal plates – require more work as the roof structure needs to be altered to strengthen it, but it is still possible to convert, usually with the additional of steel or aluminium beams.

Energy efficiency

A loft conversion will require the roof to be insulated to meet the current building regulations by placing insulation between and under the rafters, or if the roof is being stripped or rebuilt, between and over the rafters. Either way, a house with a loft conversion is likely to be significantly more energy efficient if the existing roof is not insulated, as 25% of energy is lost through the roof.

A loft conversion is also an opportunity to upgrade the existing boiler, heating and plumbing to a more energy efficient system, such as a condensing combi boiler, or condensing boiler and mains pressure cylinder. This will also eliminate the need for the header tanks in the attic for gravity fed plumbing systems, freeing up more space. Other obstacles like TV aerials, or even redundant chimneystacks can be removed.

Converting the loft can also be a good time to add renewables, such as solar panels.

The design route

For a loft conversion you have three main options:

1) You can commission a local architect to design your conversion produce drawings and get planning permission and building regulations approved. These drawings will then be sent out to builders to find the best value price. You will also need a structural engineer to oversee some of the more technical aspects of the job.

2) You can hire a design and build contractor that specialises in loft conversions to be in charge of the whole project. This might limit the architectural choices for your conversion, however this type of company will be able to deal with planning permission, building regulations and engineering on your behalf. In addition, this route will offer you a fixed price package from the design stage, so you know what to expect.

Finally, you can opt for a pre-fabricated loft conversion which is made in a factory and then craned onto your roof, fitted and made weather tight within two days. This is known in the industry as the “remove and rebuild” option. It is ideal for urban sites where site space is limited.

Types of conversion.

All loft conversions are different and will largely depend on the type of roof you have.

  • Rooflight conversion: This is the most cost-effective as is involves converting just the existing loft space with no additions and there is very little alteration to the roof space apart from the addition of roof windows set into the slope of the roof, insulation and strengthening of the floor etc.
  • Dormer conversion: This is the most common type of loft conversion. Dormer windows are added to increase the volume of the roofspace with full headroom. Dormer windows are usually added to the rear, side or both.
  • Gable-to-gable conversion: This is a variant of the dormer roof conversion where the dormer window stretches the full width of the house, from gable end to gable end and tends to look more sympathetic than a very large ‘box dormer’. Sometimes it involves building up the gable end walls to ‘bookend’ the new space at either side.
  • Hip-to-gable conversion: This involves one or more of the hips (where the roof slopes in from the side(s) as well as front and back) being replaced with a gable wall. The roof is then extended over these gables to add extra space with full headroom.
  • Mansard conversion: This involves one or both slopes of the roof being replaced with a new structure with very steep sloping sides (almost as steep as the walls) with an almost flat roof over the top. This design is used where the original roof had little or no headroom and creates sufficient volume for an additional storey.

Floor joists

The floor of your new loft conversion will have previously been the ceiling for the storey below and so will need to be strengthened to take the additional weight. The alterations to the roof structure will also need to be calculated to ensure the roof remains strong enough to withstand all weather conditions. You will need a structural engineer to design this detail and produce drawings and calculations to comply with the building regulations.


A space efficient staircase design is key to making a loft conversion work. A single room loft conversion can have a loft ladder or space saver staircase, but larger conversions with more than one room require a full staircase. The minimum ceiling height above the stairs is set at 1.9 metres (1.8 metres at the centre under a sloping roof) and this often dictates where the new staircase can be positioned to ensure there is sufficient headroom. The ideal location is within the existing hall or landing area so space is not lost from existing rooms.

Planning permission

Most loft conversions do not require a planning application providing the design complies with the rules for permitted development (these do not apply in ‘designated areas’ such a conservation areas or National Parks so always check with your local authority). The rules allow 50m3 of additional space to detached or semi detached house and 40m3 to a terraced house, providing the additions do not face the highway or are any taller than the existing roof. You can also add roof windows to the front elevation.

Listed buildings may still have permitted development rights, but listed building permission is required for any material alterations. Larger loft conversions, or those with dormers to the front, or in designated areas can still be converted subject to grant of planning permission.

Fire safety

Any habitable rooms in the loft conversion where the floor level is more than 4.5m above external ground level will require a window large enough to get in and out of in the event of a fire and the whole structure, including a staircase route to an external door, must be able to resist for 30 minutes to allow safe escape. You will also need a hard wired smoke alarm system.

For open plan houses where the stairs land in a room as opposed to an enclosed hallway, a fire suppressing sprinkler or misting system can make a loft conversion viable without having to change the open plan layout.

How much will it cost?

The cost of a conversion will vary depending on the type you choose, the level of work involved, and the cost of materials and fittings. For a simple rooflight renovation you can expect to pay around £1,000-1,250/ m2 plus VAT. Average costs for a dormer conversion are higher at £1,200-1,400/m2 plus VAT. The more alteration work is required to the roof the higher the cost, so a new mansard roof conversion would cost £1,400-2,000/m2 plus VAT.

For further advice from Michael Holmes, visit The National Homebuilding and Renovating Show at the NEC Birmingham from 27-30 March 2014. Standard tickets are £12 if booked before 3pm on 26 March 2014 or £17 on the door (a £1.75 transaction fee applies). Children under 16 go free. Tickets also allow entry into both The National Homebuilding & Renovating Show and the new Home Improvement Show, taking place in the same hall. For more information on seminars, masterclasses, features and tickets, visit www.homebuildingshow.co.uk and www.improveyourhomeshow.co.uk