St Albans Permitted Development Dining Extension
A crisp 15m² single-storey rear extension in St Albans, designed and permitted under Permitted Development rights. Roof lantern, timber screen panels and bi-fold doors transform a narrow rear into a full-width dining space.
The Brief
Our clients — a professional couple in a three-bedroom semi-detached property in St Albans — wanted to reclaim their rear ground floor. The existing kitchen was compact and the dining area non-existent; meals were eaten at a small table pushed against the back wall. They wanted a dedicated dining space that felt generous, light-filled and connected to the garden, without the disruption of a large-scale project.
The constraint was the plot. A relatively modest rear garden meant the extension needed to be efficient in footprint while feeling as open as possible. The brief was clear: maximum light, minimum bulk, and a room that works equally well for a quiet weekday supper and a Saturday dinner party.
Design Approach
We designed a 15m² single-storey rear extension running the full width of the rear elevation. At this scale, the design challenge is making a relatively modest room feel generous — and the answer lies in light. A full-width roof lantern runs the length of the space, flooding the interior with natural light throughout the day. In the evening, the lantern becomes a dramatic frame for the night sky.
Bi-fold doors span the garden-facing elevation, opening the full width of the room onto a level terrace. When fully open in summer, the indoor and outdoor spaces merge into a single entertaining zone. Timber screen panels line the side wall — a considered detail that provides filtered privacy from the neighbouring property while adding warmth and material interest to what could have been a flat, plain wall. The polished concrete-effect floor reflects light into the room from every angle, amplifying the sense of space.
Planning and Approvals
At 15m² and within the height and depth limits for a semi-detached property, this extension fell comfortably within Permitted Development rights. No planning application was required. We obtained a Lawful Development Certificate — providing our clients with formal written confirmation from the local authority — which protects them at any future point of sale and removes any ambiguity about the extension's planning status.
Building Regulations approval covered the structural steel beam spanning the new opening in the original rear wall, foundation design for the extension slab, insulation to Part L standards, and drainage connections. Full building regulations drawings and structural engineer's calculations were included within the Hampshire Build Pre-Build Package.
Key Design Features
- Roof lantern: Full-length lantern with thermally broken aluminium frame and anti-glare glazing — the primary source of natural light in the room
- Bi-fold doors: Full-width bi-fold doors in a slim aluminium frame, with a flush threshold for level indoor-outdoor access to the terrace
- Timber screen panels: Vertical hardwood slats on the party-wall elevation — providing privacy and acoustic separation while adding natural warmth to the interior
- Polished floor finish: Light-reflective floor surface throughout, maximising the effect of the lantern light and unifying the space
- Permitted Development: Full design within PD limits, backed by a Lawful Development Certificate for complete planning certainty
The Result
The finished extension is exactly what the clients wanted — a room that is both calm and generous, working effortlessly for everyday use and evening entertaining. The lantern and bi-fold combination means the space is flooded with natural light from mid-morning to late afternoon, while the timber screens add the kind of considered detail that distinguishes a well-designed extension from a standard rear addition.
At a build cost of £40,000, this project demonstrates what a tightly planned 15m² extension can deliver when the design brief is disciplined and the detailing is right. The Lawful Development Certificate provides complete planning certainty and adds measurable value to the property in the St Albans market.
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