L Shaped Dormer Loft Conversions in Chelmsford, Essex
L shaped dormer conversions join two dormers at right angles, one on the main rear roof and one over the back addition, forming an L in plan. The configuration depends entirely on the property having a rear outrigger, which in Chelmsford means the Victorian and Edwardian stock rather than the inter-war suburbs that make up most of the city. Where that outrigger exists it produces substantially more floor area than a single dormer, routinely delivering two bedrooms and a bathroom.
Finding an Outrigger Property in Chelmsford
The back addition, or outrigger, is the narrower two-storey projection running off the rear of a house, usually containing a kitchen or scullery below and a small bedroom or bathroom above. It gives the building an L-shaped footprint rather than a plain rectangle.
In Chelmsford these are the older properties, built before the great inter-war expansion. Look around Moulsham Street, the roads behind the city centre, and the Victorian terraces put up for workers at the Crompton and Hoffmann works in the later nineteenth century. Walk those streets and the profile repeats along the whole length.
The suburbs that followed are a different proposition. As Chelmsford spread through Springfield, Broomfield and out toward Writtle between the wars, the semi-detached house with a plain rectangular footprint became the standard. Those properties have no outrigger at all, and the right answer there is a rear dormer, usually combined with a hip to gable.
Where the outrigger does exist it is almost always dead space. Its roof void typically sits empty above a bathroom, and folding it into a conversion is the cheapest floor area on the property — the walls already carry it and the structure is already there.
One thing to check before assuming: outriggers on Chelmsford’s Victorian stock were often extended or rebuilt during the twentieth century, sometimes with a shallower pitch or a flat roof. A flat-roofed rear addition cannot form part of an L shaped dormer without being rebuilt first, which changes both the design and the cost.
Our L Shaped Dormer Process
- Outrigger survey. We check the back addition roof structure and its junction with the main roof. The two frequently differ in age and construction, and that junction is where the design work concentrates.
- Structural design. Steel is usually needed where the two dormers meet, since that point carries load from both roof planes.
- Forming the L. Both dormers framed, then the critical detailing at the junction, where lead soakers and flashings weather the meeting of the two roofs.
- Fit-out. Floor, insulation, staircase, electrics, plastering and finishes across both sections.
L Shaped Dormer Costs in Chelmsford
An L shaped dormer conversion typically runs from £66,000 to £90,000 in the Chelmsford area, producing two bedrooms and a bathroom. Where the outrigger roof needs rebuilding rather than adapting, add roughly £8,000 to £12,000.
Measured per square metre of usable space gained, this is often the best value of any conversion type, because much of the structural and staircase cost is fixed regardless of how much roof you end up converting.
Frequently Asked Questions
Do I need planning permission?
An L shaped dormer usually stays within permitted development on a house, but the combined volume of two dormers runs close to the 40 cubic metre terrace limit. We calculate it rather than assume, and conservation area status restricts it further.
Will it be visible from the street?
Rarely. Both dormers face the rear, so the front elevation is unchanged. That is also why permitted development generally applies and why these succeed on streets where a front dormer never would.
Is the junction between the dormers a weak point?
It is the detail that matters most. Properly executed with lead soakers it is entirely sound. Done badly it is the first place water appears, which is why we do not use sealant as a substitute for lead.
How long does the work take?
Ten to fourteen weeks. Two dormers and the junction between them take longer than a single rear dormer, and terraced properties may need party wall notice periods beforehand.
Areas We Serve
We carry out L shaped dormer loft conversions across Chelmsford and the surrounding area, including Braintree, Witham, Billericay, Maldon and South Woodham Ferrers.
Where there is no outrigger to build on, we also carry out dormer conversions, Velux conversions, hip to gable conversions and mansard conversions.
Volume allowances for loft conversions under permitted development are set out by the Planning Portal.