An extension is groundwork, structure, weathering and fit out, in that order, with inspections at each stage that cannot be reopened once they are covered. We build it and coordinate the applications, and we appoint a structural engineer where the design needs one. We are a contractor, not an architect or a surveyor. This page sets out what governs an extension in Brentwood.
Green Belt covers 89 per cent of Brentwood borough
All of Brentwood borough's countryside lies within the Metropolitan Green Belt of London, which equates to 89 per cent of the borough. Brentwood has the sixth highest Green Belt coverage of any area in England measured as a percentage of total area. Where your house sits relative to that boundary changes the policy background for an extension.
Older guidance is a trap here. Policy GB5, Extensions to Dwellings, of the Brentwood Replacement Local Plan 2005 was superseded when the Brentwood Local Plan 2016 to 2033 was adopted in March 2022. Anything written against GB5 is out of date, so work from the adopted plan rather than from an old note or a neighbour's experience.
Which plan judges your application depends on the parish
The Brentwood Local Plan 2016 to 2033 was adopted on 23 March 2022, so householder proposals in the borough are judged against a plan adopted in 2022. In Ingatestone and Fryerning there is a second document. The Ingatestone and Fryerning Neighbourhood Plan was made by the council on 5 August 2022, the day after a referendum in which 86 per cent voted in favour, and it forms part of the development plan for that parish.
There is also a charge to check. Brentwood Borough Council's Community Infrastructure Levy charging schedule was adopted on 27 September 2023 and took effect on 15 January 2024. Whether it bites on your extension turns on the floor area created, so ask the council before the drawings are finalised.
The ground under a new foundation is not the same across the borough
Great Warley sits on low upland formed of an outcrop of Bagshot Sand over London Clay. Holdens Wood Gravel Pits at Great Warley is the type site for the Warley Gravel, now considered part of the Stanmore Gravels, laid down by north flowing tributaries to the ancestral Thames. Sand, gravel and clay each want a different foundation.
The British Geological Survey names the London Clay as very susceptible to volume change. It explains that fine grained clay rich soils absorb large quantities of water after rainfall and become very hard when dry, resulting in shrinking and cracking of the ground. Foundation depth follows the ground and any nearby trees. The engineer sets it from a trial hole, not from a standard detail.
Foundations and drains are inspected before they are covered
Brentwood Borough Council's building control inspection list includes excavations and prepared designed foundations prior to concreting, and drainage prior to backfilling. Neither stage can be revisited once concrete or spoil is in, so both are booked rather than assumed. We make the application and book each stage against our own programme.
Ground history can add a step. Policy NE10 of the Local Plan requires development on or near known or potentially contaminated land to submit a Phase 1 Preliminary Risk Assessment, with a Phase 2 Intrusive Site Investigation where that assessment shows it is needed. Coombe Green Sand Pit at Great Warley is a former sand pit, and Brentwood Brickworks Pit is a former brickworks pit in the London Clay.
- Steel goalpost frames where the rear wall opens up
- Single and double storey extensions
- Insulation, airtightness and thermal detailing to regulations
- Trial holes to set foundation depth near drains and trees
- Levels, drainage and landscaping made good around the new build
Trusted House Extensions in Brentwood
An extension is the job where the expensive mistakes are underground and out of sight by week three. We treat the groundworks as the part to get right: trial hole, engineer's foundation design, excavation inspected before concrete, drainage inspected before backfill. Above ground we carry the structure, the weathering and the fit out on one contract, with one person answering for all of it. We appoint the structural engineer and build to their calculations, and we coordinate the building control application and inspections with Brentwood Borough Council. GS Renovation Ltd is fully insured, registered in England, company number 14611254, and rated 4.9 from 31 reviews on MyBuilder. Quotations are free and without obligation.
- Fully insured, with cover in place on every site
- Brick and mortar matched to the existing elevation
- Foundation depth set after trial holes, drains and trees are checked
- Founder-led team with 30+ years of hands-on experience
- A written scope and programme agreed before work starts
- Building control inspected at foundation, damp course and steel stages