An extension in Stevenage is judged against a written design guidance document with numbers in it. Knowing those numbers early keeps a scheme out of trouble later. We build to a structural engineer's calculations, coordinate building control applications and inspections, and work alongside your architect or designer on the drawings.
The design guidance sets the projection and height limits
Principle HD8 of Stevenage's Design Guidance SPD limits a single storey rear extension to 3.5 metres of projection where it would be within 1 metre of a shared boundary. Elsewhere the limit is 4 metres. The same principle sets heights of no more than 3 metres to the eaves and 4 metres to the ridge.
A two storey rear extension should project no more than 2.5 metres where it would be within 1 metre of a shared boundary, and should not exceed the eaves or ridge heights of the original property. Those figures decide roof pitch, beam depth and floor build up, so they belong in the first conversation.
Daylight to the neighbours is tested with numbers too
Stevenage assesses loss of daylight using a 45 degree test in plan and elevation, and a 25 degree test where a proposal sits opposite a neighbouring window. A proposal complies with the 45 degree rule if it passes either the plan test or the elevation test.
Table 1 of the same document sets a minimum back to back separation distance of 25 metres between existing and new two storey dwellings, and 15 metres back to side. Where a scheme sits close to those thresholds, it is worth resolving the design before an application goes in.
Foundations depend on which part of town you are in
Across the Old Town High Street, the Town Square area, Bedwell, Shephall Green, Symonds Green, Poplars, Great Ashby and the Gunnels Wood Road area, the mapped superficial deposit is the Lowestoft Formation, recorded as diamicton. The British Geological Survey describes it as an extensive sheet of chalky till with outwash sands and gravels, silts and clays, of extremely variable thickness, reaching up to 60 metres locally in buried valleys.
At Martins Wood and at Bragbury End the mapped deposit is Anglian glaciofluvial sand and gravel rather than clay till, and the Broadwater area at Marymead sits on mapped Alluvium of clay, silt, sand and gravel. Foundation depth and type follow trial holes on your plot, not a rule of thumb for the town.
Building control route and the levy
Hertfordshire Building Control rules out the Building Notice route where you are building over a public sewer or within 3 metres of one. Where the notice route is open, work can start on site 48 hours after the notice is given.
Stevenage's Community Infrastructure Levy is payable on development creating 100 square metres or more of net additional floorspace, or on development of any size that results in a new house or flat. An extension below that threshold does not pay it, so the floor area is worth checking against the drawings before submission.
- Drainage diversion and build-over agreements with the water authority
- Building control inspections at foundation, damp course and steel stages
- Flat and pitched roofs with rooflights or lanterns
- Insulation, airtightness and thermal detailing to regulations
- Architectural drawings and structural engineer coordination
Why Stevenage Homeowners Choose GS Renovation
Extensions in Stevenage are measured against written figures: 3.5 or 4 metres of rear projection, 3 metres to the eaves, and daylight tested at 45 and 25 degrees. We work to those from the first site visit, alongside whoever is preparing your drawings, so the build and the consent do not pull in different directions. We build to a structural engineer's calculations rather than producing them, and building control applications and inspections are coordinated for you. Fully insured, free no obligation quotations, one point of contact.
- Dust screens and floor protection in occupied homes
- Weathertight shell reached before the fit-out begins
- Drainage diverted or built over with the right approval in place
- Our own trades on site rather than a chain of subcontractors
- Rated 4.9 from 31 reviews on MyBuilder
- One point of contact on the phone, not a call centre