GS Renovation builds rear, side and wraparound extensions in Cheshunt, across EN7 and EN8. Foundation design here depends on which part of town you are in, so a structural engineer is appointed before anything is dug. We coordinate the building control application and the inspections, and quotations are free with no obligation.
Why foundation depth changes across Cheshunt
The town sits on a west to east sequence of deposits, and foundation design follows it. BGS records bare London Clay in the west, then Taplow Gravel, then a belt of Enfield Silt, then Kempton Park Gravel through the town centre, then Alluvium on the valley floor. The bedrock under every part of Cheshunt tested on the BGS 1:50,000 map is the London Clay Formation, from Goffs Oak in the west to the Lee Navigation in the east.
The clay is why depth is never a guess. BGS names the London Clay as very susceptible to volume change, the shrink and swell behaviour that causes subsidence and heave. At the Church of St James in Goffs Oak, BGS maps no superficial deposit at all, so London Clay lies directly under the topsoil. On ground like that, the footing is designed for the clay itself.
Gravel and alluvium under town centre footings
Through the town centre the footings start in gravel. BGS maps the Kempton Park Gravel Member as the surface deposit under Cheshunt town centre, covering the whole of Turners Hill and Crossbrook Street and the western part of Windmill Lane. The eastern end of Windmill Lane runs onto Alluvium instead. BGS gives that gravel an average thickness of 6 metres, thicker again where it fills deep hollows, and describes it as sand and gravel, locally with lenses of silt, clay or peat.
East of the town the ground changes again. BGS maps Alluvium on the Lea valley floor at Cheshunt, from the ground around Cheshunt railway station eastwards to the Lee Navigation, and describes it as clay, silt, sand and gravel. A lens of silt, clay or peat under one corner of a footing is what makes a trial hole worth digging before a price is fixed.
Flood zones, Green Belt and protected ground
Flood risk in Cheshunt is an address by address question. Environment Agency Flood Zone 3 covers the Lea valley floor on the eastern edge of Cheshunt, along the Lee Navigation and the Cheshunt marsh land. The Churchgate area sits outside any mapped flood zone. A narrow Flood Zone 2 fluvial corridor runs through the town centre at Turners Hill, so the position there is checked property by property.
Designations bite on the edges of the town. Land at Cheshunt Park and Theobalds Park is Green Belt, which restricts the scale of extension permitted on properties within it. Turnford and Cheshunt Pits is a Site of Special Scientific Interest on the eastern side of the town, reference 2000066. Half Moat Manor House moated site and its associated leat is a scheduled monument, list entry number 1012163.
Permitted development and the Broxbourne planning route
Outside a conservation area, permitted development rights in Cheshunt are not cut back. Broxbourne Borough Council has no Article 4 direction recorded against it on the national planning data register. Churchgate is the only one of the six Broxbourne conservation areas that falls inside the Cheshunt built-up area, and it covers about 15 hectares, under 2 per cent of the roughly 800 hectares of the built-up area.
Where a question needs settling before drawings are paid for, there is a free route. Broxbourne runs a duty planner service for householders, offering ten minute telephone appointments on Wednesdays between 9am and 1pm, bookable up to two weeks ahead. Work to any tree inside a Broxbourne conservation area needs an application to the council, which matters where a new foundation sits close to one.
- Trial holes to set foundation depth near drains and trees
- Party Wall Act notices for excavation near a neighbour's wall
- Planning applications and permitted development assessments
- Bi-fold, sliding and French door openings to the garden
- Brickwork and mortar matched to the existing elevation
Why Choose GS Renovation in Cheshunt
Extensions in Cheshunt are priced on the ground, not on a rate per square metre. We appoint the structural engineer, dig trial holes where the mapped deposits warrant it, and build the foundation the engineer designs for what is actually under your garden. Planning, building regulations and the party wall position are then run as one sequence by one point of contact. Fully insured, registered in England, company number 14611254.
- Brick and mortar matched to the existing elevation
- Free follow-up visit after completion if anything needs attention
- Building control inspected at foundation, damp course and steel stages
- Waste cleared as we go, not left piled in the garden
- Our own trades on site rather than a chain of subcontractors
- Insulation and thermal detailing to current regulations