Loft conversion plans in Hertfordshire

What do loft conversion plans show?

Loft conversion plans show how unused roof space becomes a room, and how it connects to the rest of the house. The drawings normally cover the existing and proposed floor plans, the roof shape from outside, a section showing head height and the line of the new stair, and the structural changes needed to carry the extra floor.

A structural engineer's calculations usually sit alongside the drawings, because the old ceiling joists were never designed to carry a bedroom.

Which type of loft conversion suits my house?

The roof decides. Common options are:

• rooflight conversions, where windows are set into the existing slope and the roof shape does not change
• dormers, which add a box at the back to gain floor area and headroom
• hip-to-gable conversions, which straighten a sloping side on a semi-detached or end-of-terrace house
• mansard roofs, which have a steep, near-vertical face and are more often found on terraces

A designer can look at the pitch, the ridge height and the position of the stairs before suggesting one.

Does a loft conversion need planning permission?

Often it does not. Many houses can use permitted development, which allows a roof extension up to a volume limit of 40 cubic metres for a terraced house and 50 cubic metres for other houses, counting earlier roof additions. Other conditions apply, including that it must not rise above the highest part of the existing roof or extend beyond the roof slope facing the road, and that side windows must be obscure glazed. The Planning Portal's loft conversion guide and the government's permitted development technical guidance give the full conditions.

Flats and maisonettes have no such rights. In a conservation area, roof extensions such as dormers need planning permission, and in a listed building you also need listed building consent. Your local council's planning department makes the decision.

Can I check this before I commit?

You can apply to the council for a lawful development certificate, which confirms that your proposed loft conversion counts as permitted development. It is optional, but it gives you written confirmation and is the sort of document a buyer's solicitor looks for later.

What do Building Regulations ask of a loft conversion?

Every loft conversion needs Building Regulations approval, even when planning permission is not required. The usual points are:

• floor strength, often with new beams
• a safe, permanent stair with enough headroom
• fire safety, which often means fire-resisting doors, a protected escape route down to the front door and interlinked smoke alarms on the mains
• insulation and ventilation to the roof
• windows sized and placed to suit the new room, since in most two-storey houses an escape window from the loft is not accepted in place of a protected stair

With council building control you apply through full plans or a building notice. A registered building control approver can be used instead, working from an initial notice. A completion certificate follows the final inspection.

How much will the stairs take up?

The staircase usually takes the most thought. A new flight needs floor space on the storey below, so a bedroom or landing can lose a little room to gain a whole new one. Good drawings show that trade-off early, so you can judge it before committing to anything.

Will a loft conversion need a party wall notice?

Often yes in a semi-detached or terraced house. Putting steel beams into a shared wall, or cutting into a chimney breast that is shared, is work to a party structure, and the Party Wall etc. Act 1996 requires you to serve notice at least two months before it starts. Your neighbour may consent, or surveyors may be appointed to agree the terms. The gov.uk party wall guidance explains the steps.

What about bats?

Bats and their roosts are protected by law, and older roof spaces can be used by them. If you find signs of bats, or the council asks for a survey, stop and take advice before any work begins. Mention it early, because it can change the timing of a project.

What should I include in my enquiry?

• your postcode and the style of your house
• whether it is semi-detached, terraced, detached or a bungalow
• what you want the room for, such as a bedroom with an en suite
• whether the roof space is already boarded or has a fixed stair
• whether the house is listed or in a conservation area

How does the enquiry travel?

We pass it, with your consent, to one architectural designer who covers your postcode, and to nobody else. If nobody covers your area, we say so and keep your details to ourselves.