Services

Loft Conversion Architects and Structural Engineers in London

Victory Design designs loft conversions across London, from single dormers on Victorian terraces in the East End to full mansard conversions. Our architects, planners and structural engineers work in one team, so the drawings, the calculations and the council submissions come from the same place.

We start with what your roof can actually take: the head height at the ridge, where the staircase can land, and whether the structure below can carry a new floor. That assessment decides which conversion type is worth pursuing, and it happens before you spend anything on a planning application.

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Completed loft conversion with roof windows and a plastered ceiling by Victory Design in London

Loft conversion types we design

The right type depends on your roof shape, the planning constraints on your street and how much space you need back. These are the four we work with most often.

  • Single dormer — a box projection on the rear roof slope. The most straightforward way to gain usable head height, and often within permitted development.
  • Hip-to-gable — converts a sloping side hip into a vertical gable wall, which creates full-height space on the side of the roof. Common on semi-detached and end-of-terrace houses.
  • L-shaped — combines a rear dormer with a smaller side dormer over the rear addition, useful where the house already has a back extension.
  • Mansard — a near-vertical rear roof slope that maximises floor area, but the most structurally involved and the most likely to need full planning permission.

What the design work covers

A loft conversion is a structural change to your house, not an interior alteration. The package we prepare covers the parts that builders, building control and the council each ask for.

  • Measured survey of the existing roof, first floor and staircase arrangement.
  • Feasibility advice on head height, stair position and structural viability before you commit.
  • Existing and proposed plans, sections and elevations.
  • Structural calculations for the new floor, the beams carrying it and the roof alterations.
  • Building regulations drawings covering structure, fire safety, thermal performance and ventilation.
  • Planning application, permitted development assessment or lawful development certificate, with submission and liaison handled for you.

Not sure what your property needs?

Send us the address and what you are trying to achieve. We will tell you what is likely to be possible, what approvals it involves, and what the design work would cost.

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Planning permission for loft conversions

Many loft conversions in London fall under permitted development, which means no planning application is needed. The allowance is limited by volume — broadly 40 cubic metres for a terraced house and 50 cubic metres for a semi-detached or detached house — and rear dormers have their own conditions on size, materials and position.

Those allowances can be removed. Conservation areas, Article 4 directions and flats or maisonettes routinely mean a full application is required, and some boroughs take a stricter view of dormers that front a street. We check the position for your specific address and, where permitted development applies, can apply for a lawful development certificate so the position is documented if you later sell.

Building regulations and fire safety

A loft conversion is assessed under the building regulations regardless of whether it needs planning permission. Structural design, fire resistance, means of escape, thermal insulation and ventilation all have to be shown to comply.

Fire safety is usually the item that shapes the layout. A new storey at the top of the house normally means a protected escape route down the stairs, fire-resisting doors on the rooms opening onto it, and interlinked smoke and heat alarms. We design the stair and landing arrangement so those requirements are met without eating the space you are converting.

Working with your builder

Our drawings and calculations are issued at a level a builder can price and build from, and we are available to answer technical queries during the works. If you would like the project overseen as well, project management is one of the services we provide — site visits, checking work against the drawings, and coordinating with building control.

Where we work

We cover all of London and the surrounding areas, including Tower Hamlets, Newham, Hackney, Islington, Redbridge, Waltham Forest, Barking and Dagenham, Greenwich, Lewisham, Southwark, Camden, Haringey, Enfield, Barnet, Ealing, Brent, Harrow, Hillingdon, Richmond, Kingston, Merton, Wandsworth, Lambeth, Croydon, Bromley, Bexley, Havering, Westminster, Kensington and Chelsea, and Hammersmith and Fulham.

Frequently asked questions

Do I need planning permission for a loft conversion in London?

Often not. Many loft conversions fall within permitted development, which is limited by volume — broadly 40 cubic metres for a terraced house and 50 cubic metres for a semi-detached or detached house. Conservation areas, Article 4 directions and flats usually need a full application. We check the position for your address before any work starts.

How much head height do I need for a loft conversion?

You need enough clear height at the highest point for a habitable room and, more critically, enough room for a staircase to arrive safely. Where the existing roof is tight, a dormer or hip-to-gable conversion creates the additional height. We measure this at the survey and tell you honestly whether the roof works before you commit to a design.

Do I need a party wall agreement for a loft conversion?

If your works affect a wall or structure shared with a neighbour — which is common on terraced and semi-detached houses — the Party Wall etc. Act 1996 normally applies. We flag where it is likely to be triggered and can recommend surveyors who handle the notices, though the agreement itself sits outside the design work.

Can you provide the structural calculations my builder needs?

Yes. Structural calculations are part of what we do in-house: the new floor structure, the beams supporting it, roof alterations and any steel required. They are issued with the building regulations drawings so your builder and building control are working from the same documents.

How much does a loft conversion cost?

Cost depends on the conversion type, the span of the roof, the stair arrangement and what the structure below needs. Rather than quote a figure that would not survive contact with your house, we price the design and submission work for your specific project once we have seen the property.

How long does the process take?

The design and approval stage depends on the council and on whether planning permission is needed, since applications run to the local authority's own timetable. We set out the sequence and the likely programme for your project at the outset, so you know what is in our hands and what is in the council's.

Planning and building regulations guidance on this page is general and applies to England. The position depends on your property, its history and your council's policies, so it is not a substitute for advice on your address. We check the specifics before any work begins.