House Extensions Grays

An extension is a foundation job, a structural job and a fit out inside one programme. We coordinate the structural engineer, the building control application and the trades, and build to the design issued. This page covers what an extension in Grays involves, from the ground underneath it to the plan it is judged against.

For Grays, on London-derived ranges a single-storey rear extension typically starts from £40,000, or £2,000 to £2,800 per m²; Essex work generally runs below that. GS Renovation Ltd, a building contractor based in Potters Bar, does the work in Grays: the structural engineer we appoint designs the structure, we build it, and building control signs it off.

Thurrock Council publishes what building control will charge for an extension

Thurrock Council runs its own building control service for Grays, contactable on 01375 652 655 or building.control@thurrock.gov.uk. Its charges from 1 April 2026 give a single storey extension with a floor area of no more than 30 square metres a building notice charge of £726.99 plus VAT, which is £872.39 including VAT.

A first floor or second floor loft conversion of no more than 30 square metres carries the same charge, £726.99 plus VAT, or £872.39 including VAT. The charges are set on the basis that the work takes no more than 24 months from start to finish, and that the cost estimate excludes professional fees and VAT. We put the charge in the quotation rather than leaving it to arrive later.

Housing in Grays

Around 17,360 homes make up Grays on the valuation list; 30% are flats and 70% houses, and 14% date from before 1919, 25% from between the wars and 61% from after 1945. 29% of homes here are terraced; a rear extension on a terrace in Grays digs foundations close to both neighbours, so notices to both are normal.

The ground under Grays is mapped as chalk and sand, not the London Clay of much of Essex

British Geological Survey 1:50,000 mapping records the bedrock beneath Grays town centre and Grays Riverside as the Seaford Chalk Formation. Across the RM16, RM17 and RM20 postcode areas the same mapping gives chalk, Thanet Formation or Lambeth Group rather than the London Clay that underlies much of Essex. London Clay is mapped at the northern fringe of RM16, including points in Stifford Clays and around North Stifford, so it is a boundary rather than an absence.

The mapping records the bedrock beneath Little Thurrock, and beneath parts of Stifford Clays, as the Thanet Formation, described as sand, silt and clay. It records the Boyn Hill Gravel Member, a sand and gravel, as the superficial deposit beneath Stifford Clays, Little Thurrock Blackshots and Chadwell St Mary. A foundation detail carried over from a clay site is the wrong starting point here, which is why the engineer designs from trial holes on your plot.

Parts of Grays sit on ground that was dug out or filled in

Around two thirds of the Chafford Hundred site was previously used as a chalk quarry. British Geological Survey mapping records Made Ground along the West Thurrock riverside in the RM20 postcode area, and at points on the Grays riverside near the station in RM17. It records Infilled Ground at points in South Chafford, West Thurrock and Chadwell St Mary.

Older workings are part of the same picture. The dene holes in Hangman's Wood, Little Thurrock, are a scheduled monument, National Heritage List for England entry 1002156, and there appears to have been more than 70 of them at one time, dug to extract chalk and flint. None of that decides your foundation on its own. It decides how seriously the ground investigation is taken before a depth is priced.

Planning here is decided against a plan adopted in 2011 and updated in 2015

Thurrock Council's adopted development plan is the Core Strategy and Policies for Management of Development, originally adopted on 21 December 2011 and updated on 28 January 2015. The council is a unitary authority, so planning and building control for Grays sit with the same body. It states that the Core Strategy will remain its adopted statutory planning document for the borough until the new Local Plan is adopted.

A new plan is in progress. The council consulted on its Local Plan Initial Proposals from 18 December 2023 to 19 February 2024. Its Cabinet approved a new Local Development Scheme on 9 October 2024, with an administrative update in March 2025 that left the Local Plan timetable unchanged. We are contractors rather than planning consultants, so where a design needs an application we say so and build to the decision.

Kitchen extensions in Grays

46% of the houses in Grays are semi-detached or detached, which usually leaves room for a kitchen extension across the full rear width, with a steel beam over the opening into the house. The fit-out is priced on its own page, kitchen renovation in Grays; the build figures are in the table above.

Side return extensions in Grays

Side returns belong to Victorian and Edwardian terraces, and only 14% of homes in Grays predate 1919, so they are the exception here; most extensions run across the full rear width instead. Our side return extension page covers the build in detail, with build rates of £2,400 to £3,200 per m².

Double storey extensions in Grays

Under permitted development a two-storey rear extension can go no more than 3 metres beyond the original rear wall and must stay at least 7 metres from the rear boundary, and in a conservation area it is not permitted development at all. Many gardens are too short for the 7 metre rule, so a double storey extension in Grays often needs planning permission from Thurrock Council. With 32% of homes here semi-detached or detached, the side of the house is often an option too. Our double storey extension page explains the build, at £1,800 to £2,600 per m² across both floors.

• Levels, drainage and landscaping made good around the new build
• Single and double storey extensions
• Steel goalpost frames where the rear wall opens up

VOA Council Tax stock of properties, March 2025, for all 5 statistical areas in Grays. Counts rounded by the VOA.

Next steps that tend to follow house extensions in Grays: RSJ and steel beam installation in Grays, house extensions in Dartford, double storey extensions, the Party Wall Act process for extensions, house extensions anywhere in London and Getting Planning Permission.

Why Grays Homeowners Choose GS Renovation

An extension in Grays is settled under the ground as much as above it. We appoint the structural engineer, build the foundations to the design they issue after the trial holes, and make the building control application to Thurrock Council, which runs its own service and publishes its charge. Because planning and building control sit with the same body, there is one authority to deal with rather than two. We coordinate the applications and the inspections, and you keep one point of contact for the engineer, the groundworks, the shell and the finishes. GS Renovation Ltd is fully insured, registered in England, company number 14611254, with free no-obligation quotations.

• Permitted development checked before you pay for a planning application
• Building control inspected at foundation, damp course and steel stages
• One point of contact on the phone, not a call centre

Checked by Abdelaaziz Saaid, founder and director of GS Renovation Ltd (Companies House no. 14611254). Structural design is by the consulting engineer appointed to your project.