How to plan your loft conversion

  • We earn a commission for products purchased through some links in this article.
  • Convert your loft to create a new playroom, office or bedroom with en suite

    Need more space? The loft is often the simplest and least disruptive space to convert, and it’s certainly less expensive and stressful than moving house.

    According to the Royal Institution of Chartered Surveyors (RICS), the cost of the average loft conversion equates to one third of the cost of moving to a property with an extra room, and the addition of a loft room can increase the value of your home by up to 25%.

    Practical considerations

    As a rule of thumb, if you can measure 230cm from the floor to the roof at the tallest part, you have sufficient head height for a conversion. To make for a comfortable bedroom or living room, at least half the loft space should be this tall.

    Pre-war buildings with steeply pitched roofs are often the easiest to convert, but there will always be structural considerations when turning this space and most lofts need additional support from steel beams to strengthen the floor and roof.

    Building regulations stipulate that if the loft is to be turned into a bedroom, bathroom, study or playroom, it must have a permanent staircase. The stairs leading to it need not be as wide as the steps on the lower flights. The most minimal arrangements resemble a fixed ladder and a spiral staircase offers an attractive solution where space is tight.

    When weighing up the pros and cons of converting, look at the space you will lose on the floor below to accommodate the new stairs, and check in particular the head height available.

    Time and budget

    How long will it take?

    A simple loft conversion can be completed in 4 to 5 weeks and is the least disruptive type of
    extension. Scaffolding is used for access until the staircase linking the loft to the rest of the house is installed, so no materials are hauled through the house and waste can go directly down a chute into a skip outside. The work will be noisy, but won’t create as much mess as a ground-floor extension.

    Budget for the unexpected

    Installing extra electrics and plumbing is the main area where extra expenses arise, so much so that many reputable firms insist on a qualified electrician running checks before giving a quote.

    Plumbing and waste for a bathroom can be re-routed from below and the soil pipe extended on the exterior, but your old boiler might not be able to cope with the new demands. A Saniflo system that stands separately from the rest of the plumbing offers one possible solution.

    Windows and insulation

    Window options
    Choosing the right windows is crucial for any conversion, as the joy of such a space is the availability of daylight.

    Dormer windows offer extra headroom as well as light, as the glazed units are normally set parallel to the facade of the house, and a section of the pitched roof raised to accommodate them. Because dormer windows change the exterior appearance of a house, planning permission is sometimes required. Skylights or rooflights are simple to install flat into the

    Part L of the building regulations insists on a good standard of insulation as loft spaces can be subject to extreme temperatures, getting very hot in summer and feeling extra chilly in winter.

    For walls and ceilings, specialists generally use a rigid insulation such as Celotex insulation boards while a fibre blanket such as Gyprock Rockwool is often used between floor joists. This insulation should be 150-250mm thick in order to satisfy building regulations for thermal, sound and fire insulation. Soundproofing is also advised.

    Safety considerations

    Fire regulations should be incorporated in your earliest plans. Building materials must comply with standards of fire resistance; you will find the latest information online at You will need to fit a smoke detector in the hallway; any building with a floor more than 7.5m above the ground should have a sprinkler system.

    In a two-storey home, internal doors around the staircase must be replaced with fire doors to create a protected path from the attic down to the ground-floor exit; original doors can be upgraded by companies such as Envirograf.

    If there are several rooms in your conversion, you need to provide an emergency exit to the roof. The easiest, most attractive option is to fit a fire-escape window large enough to climb through in each space. Purpose-designed windows are available from Velux.

    All the latest from Ideal Home