Is My Loft Suitable for a Conversion? The Checks to Make

What to look for in your loft

Start with five checks on the loft and the house. The rafter, height, floor and pitch rows come from Checkatrade’s suitability guide, and the stair rows from Approved Document K and the Planning Portal’s stairs guidance.

Check	What you find	What it means
Rafter shape	An M shape, common in homes built before 1965	A traditional roof, generally easier to convert
Rafter shape	A W shape, standard after 1965	A trussed roof, more complex and costly to convert, but not ruled out
Height at the highest point	2.2m or more from the floor	At least 1.9m of finished headroom, on Checkatrade’s guide
Height at the highest point	Less than 2.2m	A roof lift can add headspace, subject to the planning office
Usable floor	Areas under 1.2m from the floor to the eaves, the stairwell and chimney breasts	Deduct them from the usable floor area
Roof pitch	Over 30 degrees	Tends to work better, with more usable space
Space for a stair	Room for a stair with 2m of headroom, or 1.9m at the centre and 1.8m at the side	Stair headroom that meets Approved Document K
Space for a stair	No room for a full traditional stair	A space saving stair may be possible, but a retractable ladder is not normally acceptable

Traditional roofs and trussed roofs

Roof type is the biggest factor in whether a house suits a loft conversion. Traditional roofs, common in homes built before 1965, have rafters forming an M shape and are generally easier to convert.

Trussed roofs became standard after 1965, and their rafters form a W shape. A trussed roof is more complex and costly to convert, because the frame typically needs replacing, but it does not rule a conversion out.

How much head height a loft needs

Checkatrade looks for at least 2.2m from the floor to the highest point of the loft, which allows for at least 1.9m of finished headroom once the flooring and insulation are added.

If the loft measures less than 2.2m, a roof lift can create more headspace, subject to the local planning office. Checkatrade says a roof lift is unlikely to be approved in a conservation area.

Usable floor space and roof pitch

When it works out the usable floor, Checkatrade’s guide deducts any area where the height from the floor to the eaves is under 1.2m, the space for the new stairwell, and obstacles such as chimney breasts.

A steeper pitch means more usable space, and a pitch over 30 degrees tends to work better. The space you have also narrows the type of conversion. A roof light conversion fits windows into the existing roofline with no structural alteration and no added floor space, so it needs a loft that already has the room, while a dormer adds headroom and floor space with a box structure and vertical windows.

Room for a new stair

Building regulations approval is required to convert a loft into a liveable space, and among the things the regulations make sure of are safely designed stairs to the new floor and a safe escape from fire.

The loft room needs a new stair for fire safety, and the Planning Portal says retractable ladders or stairs are not normally acceptable. Where a full traditional stair will not fit, a space saving stair may be possible.

Approved Document K asks for 2m of headroom over the flights and landings of a stair, and a pitch of no more than 42 degrees for a private stair. In a loft conversion without space for 2m, 1.9m at the centre of the stair and 1.8m at the side is satisfactory. An alternating tread stair is allowed only where there is not enough space for a stair meeting the normal guidance, and only to reach one habitable room, plus a bathroom or WC that is not the only WC in the home.

Fire safety and the escape route

Checkatrade’s guide says turning a two-storey house into three storeys generally needs a protected escape route from the new floor to the final exit. It can affect the layout, so raise it with the architect or building control at the planning stage.

On a typical loft conversion to a two-storey house, the Planning Portal’s fire safety guidance calls for new fire-resisting doors, and sometimes partitions, to protect the stairway, plus mains powered, interlinked smoke alarms in the stairway at each level. Escaping through a window is too dangerous from a floor above first floor level.

When a loft may not be suitable for conversion

A trussed roof or a low ceiling does not always stop a conversion, but Checkatrade says a loft may not be suitable in these cases.

• The ceiling is too low, and raising the roof is not possible or permitted.
• The home is a listed building, or is in a conservation area, where structural alterations are not allowed.
• You do not own the freehold for the loft space.
• The cost of the conversion would exceed the value it adds.

A loft conversion on a flat is possible but uncommon, and you need the freehold for both the flat and the loft space.

Measure your loft before you call a company

Set against Checkatrade’s figures, your own measurements tell you early whether the loft is worth a company’s visit.

Among the loft conversion companies we rank in and around Nottingham, XL Lofts does truss roof conversions and has converted bungalows and detached, semi-detached and terraced houses. Roof Rooms supplies full working plans and structural calculations, and Premium Home Conversions’ own architects offer a free initial consultation at your home.

Put your measurements in the first message, so every company answers the same question.