An extension involves two approvals that run separately: planning, decided by Welwyn Hatfield Borough Council, and building regulations. GS Renovation builds the extension, appoints the structural engineer for the foundations and beams, and coordinates the building control application and inspections. We are fully insured, and quotations are free and carry no obligation.
The authority and the plan your application is decided under
Welwyn Hatfield Borough Council is the local planning authority for Hatfield and decides householder planning applications in the town. The Welwyn Hatfield Local Plan 2016 to 2036 was adopted at a meeting of the council on 12 October 2023, and it is the plan a householder application is assessed against.
The council is also preparing a new local plan running to 2043. Its Draft Local Plan consultation ran from 12 February to 26 March 2026 under Regulation 18, and a Regulation 19 stage will follow before examination. The council names no neighbourhood plan covering Hatfield, so there is no further tier of local policy over the top.
Where permitted development is restricted
Welwyn Hatfield Borough Council lists Estate Management Scheme areas and high density housing estates among the places where permitted development rights are more restricted. In a conservation area the council states that permission is needed for raising the ridge of the roof, installing dormer windows, installing cladding and constructing extensions.
Trees and heritage settings add their own steps. Owners must notify the council six weeks before carrying out certain works to trees in a conservation area. The park and garden at Hatfield House is on the Register of Parks and Gardens at Grade I under entry 1000343, and registered parks and gardens are heritage assets, so setting can be a consideration for work close by.
The ground your foundations will sit in
The British Geological Survey maps the bedrock beneath central Hatfield as Lewes Nodular Chalk Formation and Seaford Chalk Formation, undifferentiated. Over central Hatfield and parts of the Old Hatfield area, the superficial deposit is mapped as Kesgrave Catchment Subgroup sand and gravel, which the survey describes as cross-bedded and massive, moderately sorted sand and gravel.
South Hatfield is different again. Lambeth Group, a sedimentary bedrock of clay, silt and sand, is mapped beneath much of it rather than chalk, chalk returns a short distance to the east, and much of that ground carries no superficial deposit. Hertfordshire Building Control names foundations as one of the items its inspectors examine on site, and the depth and design come from the engineer.
Getting an early read from the council
Welwyn Hatfield Borough Council runs duty planning appointments. Face to face appointments are held at its Campus East office in Welwyn Garden City from 10am to 12pm on a Wednesday, and telephone appointments run from 10am to 12pm on Monday, Wednesday and Friday. Slots are capped at one 15 minute slot, so take one specific question rather than an open one.
It helps to know what you are extending. At the 2021 census, 11,254 households in Welwyn Hatfield, or 24.4 per cent, were semi-detached, and 9,217, or 19.9 per cent, were detached. The form of the house sets whether a rear, side or wrap around extension is available at all.
- Drainage diversion and build-over agreements with the water authority
- Trial holes to set foundation depth near drains and trees
- Full fit-out, finishing and making good
- Architectural drawings and structural engineer coordination
- Roof works and structural alterations at roof level
The GS Renovation Difference in Hatfield
The variable that catches extensions here is the ground. Chalk, sand and gravel, glacial till and Lambeth Group clay are all mapped within the town, so a foundation design that suited one street is not evidence for the next. We appoint the structural engineer, build the foundations to the calculations, and have them inspected before they are covered, because that is one of the items Hertfordshire Building Control examines. Applications and inspections are coordinated, and we are fully insured.
- Building control inspected at foundation, damp course and steel stages
- Straight advice on what is and is not worth spending money on
- Aftercare and snagging support once the job is finished
- Permitted development checked before you pay for a planning application
- Insulation and thermal detailing to current regulations
- Itemised pricing, so you can see what every stage costs