L-shaped dormer drawings in Croydon

Big gardens, big roofs

Domestic gardens cover 32.8 per cent of the borough's land, and about 60.2 per cent of households live in a house. That means many semi-detached and terraced homes with deep roofs at the back.

An L-shaped dormer over a rear outrigger is a natural fit for those homes, because it gives a second room and a bathroom on one landing. We model the volume on a survey so you know early whether the L stays within the limit.

Permitted development or planning

Outside protected areas, the national allowance applies: volume 40 m³ (terrace house) / 50 m³ (any other house) additional roof volume, with this height limit: No part higher than the highest part of the existing roof. Where the new roof joins a rear extension, the rule is: Eaves-retention and 0.2 m set-back do not apply where the enlargement joins the original roof to the roof of a rear or side extension.

Croydon received 494 lawful development certificate applications in the latest national return, so the certificate route is well used locally. Where the L fits permitted development, a certificate on our drawings gives you written proof when you sell.

How quickly Croydon decides

The council decided 94.4 per cent of householder applications within eight weeks or an agreed extension, against a grant rate of 86.6 per cent. These are borough-wide numbers, not a forecast for your roof.

Value also plays a part. The average Croydon home costs 390,041 pounds, with prices moving -3.4 per cent over twelve months, so many owners add a bedroom instead of moving.

Structure, stairs and notices

Steel across the junction carries most of the load, so we coordinate the beam positions with your engineer. The stair needs this headroom: Loft conversions where 2.0 m cannot be achieved: 1.9 m at the centre of the stair, 1.8 m at the side (half width). A loft this large also triggers the fire rule: New storey above 4.5 m by loft conversion: protect the full escape route with fire-resisting doors (min E 20) and partitions (min REI 30).

Terraced and semi-detached pairs share structure, so the notice rule applies: Party structure notice at least 2 months before work. We prepare the notice drawings with the planning set.

Interwar semis and the hipped-roof question

Much of Croydon's suburban stock is interwar, and a good share of it has a hipped roof. An L-shaped dormer needs a pitched or gabled return to turn along, so a plain hipped semi often needs a hip-to-gable change first. We tell you at the survey whether the L is possible as it stands or needs that extra step.

Where a hip-to-gable change is needed, it is a separate operation with its own limit, and we price the two together so the volume allowance is not spent twice.

Houses in multiple occupation and your loft

If you plan to let the new loft rooms to unrelated tenants, the use of the house matters as much as the dormer, and an Article 4 direction on small shared houses would change the route. We note it on the first call, because a loft designed as two bedrooms with a shared bathroom can change how the house is classified.

Seeing the survey before you decide

Our measured survey records the ridge height, the eaves line, the pitch of the outrigger and whether the rafters are old cut timber or later trusses. Those facts tell you whether an L is a sensible proposal, and what steel the engineer is likely to want.

We then model the house in Revit and show you the design options in 3D and plan, so you choose the shape of the L in writing before it is frozen.

Next steps in Croydon

Our sets include existing and proposed plans, a roof plan, junction sections and elevations, each checked by a second MCIAT chartered technologist, and we redraw at no charge until approval.

Compare options in loft conversion drawings in Croydon or house extension drawings in Croydon, see the Croydon architectural drawings hub, or read the national L-shaped dormer guide.