Project Type
Single-Storey Rear Extension with Roof Terrace
Duration
16 weeks
Project Value
£115,000
The Challenge
Westminster's conservation area policies in St John's Wood are exacting about the design quality of extensions. The clients wanted Crittall-profile steel-framed glazing — a premium product — which required careful specification to satisfy thermal performance requirements under Building Regulations. The roof terrace above required a structural design that could carry the loading of a sedum planted roof with drainage, paving, and occasional occupation.
Our Solution
Our architect specified the Crittall Homelight W20 steel system, which achieves the slim sightlines the clients wanted while meeting Part L thermal performance with thermally broken sections. Westminster approved the application in 10 weeks. The roof structure used a composite steel and concrete deck sized by our structural engineer to carry the planted roof, paving, and a 1kPa imposed load for the terrace.
Results
- ✓Westminster planning approval in 10 weeks — conservation officer complimentary
- ✓32m² open-plan living space created
- ✓Crittall Homelight W20 full-width glazed end wall and roof lights
- ✓Sedum planted roof terrace above — accessible from first floor bedroom
- ✓New bespoke kitchen with Miele integrated appliances
- ✓Structural rooflight flooding dining area with daylight
- ✓Estimated property value uplift: £195,000
Key Features
- ✓Westminster conservation area planning consent
- ✓Crittall Homelight W20 steel glazing system
- ✓Sedum planted roof terrace — accessible from first floor
- ✓Structural composite steel and concrete roof deck
- ✓Bespoke kitchen with marble worktops and Miele appliances
- ✓Wet underfloor heating throughout extension footprint
Specification
| Item | Specification |
|---|---|
| Glazing system | Crittall Homelight W20 thermally broken steel, RAL 9005, double-glazed low-E glass |
| Roof terrace deck | Composite steel and concrete, 200mm slab, 1kPa imposed load capacity |
| Planted roof system | Alumasc Hydrotech waterproofing, filter fleece, 100mm sedum blanket with drainage layer |
| Kitchen | Bespoke painted in-frame, Calacatta Viola marble, Miele Generation 7000 appliances |
| UFH | Polypipe wet underfloor system, 75mm screed, individual zone thermostat |
| Flooring | Large-format Lapicida natural stone, 900×900mm, running through to garden terrace |
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