Structural calculations in Croydon

Clay in the north, chalk in the south

Croydon's flood risk assessment describes the ground in plain terms: London Clay north / chalk south, with river terrace deposits along the river corridors. That split affects foundations and any lowered floor.

Croydon decided 786 householder applications in its latest year, and 60.2 per cent of its households live in a house or bungalow, so rear extensions and lofts are the common case. Their foundations depend on the soil, so we ask what is known about the garden before a depth is assumed.

A basement is a separate matter. Where there is groundwater flood risk, Croydon's Local Plan asks for a basement impact assessment inside the flood risk assessment, informed by ground investigation: BIA informed by ground investigation; pumped device. We design the structure above the ground, and we say so when a basement needs a specialist.

Heritage, demolition and construction paperwork

Croydon has 19 conservation areas and 180 listed entries, and it publishes the Conservation Areas General Guidance SPD. Where an application touches a heritage asset, the validation list asks for a heritage statement that includes a structural survey where demolition proposed.

Demolition has its own list. A prior approval for demolition should come with demolition method statement + dust risk assessment, covering hours, noise, air quality and restoration.

For larger schemes a construction management or logistics scoping note is also requested, and the validation list records: CMP/CLP scoping note; smaller minors on request. Basements are not named as a trigger, so ask the council whether it will want one for your job.

How our Croydon survey works

We visit before we calculate. We measure the opening, record the thickness and type of the wall, note what sits above and below, and photograph anything unusual such as a chimney stack or an earlier alteration. In an older semi-detached house the wall you hope to open may carry a first-floor partition and part of the roof.

Those facts go straight into the calculation. We write down every load we have assumed, so anyone checking it later can see where each figure came from.

Gardens matter here too. The Greater London land-use survey put domestic gardens at 32.8 per cent of the land in the borough. When a wide opening is formed at the back of the house for an extension into the garden, we check how it affects the stability of the wall that remains.

Where a loft is involved, the existing joists are rarely adequate for a habitable floor, so new joists or steel are sized and shown on the layout.

Croydon fee and turnaround

Structural calculations start at £295 including VAT, fixed after the constraints check. You receive the calculations, a beam and padstone schedule and a layout drawing, normally about a week after the survey. A second technologist checks the set, and if the examiner asks for changes we revise at no charge.

The figures carry straight into our building regulations drawings in Croydon, and into the planning drawings in Croydon when an application is needed.

Nearby and related

Start from architectural drawings in Croydon for the whole borough, or read how the structural calculations service works. Next door, the paperwork differs in Bromley.