Structural calculations in Haringey

London Clay and what it means for foundations

Haringey's basement guidance note, which is a draft from some years ago, describes the ground in direct terms: London Clay almost entire borough. Clay shrinks in dry summers and swells when wet, and trees draw moisture from it, so new foundations in Haringey may need to go deeper than a standard trench.

We do not design foundations from a desk. We ask the builder or your neighbours what they know about the soil, check for mature trees near the extension and flag any case where a trial pit is worth paying for before the depth is fixed.

Haringey's basement test

Haringey's Development Management policy on basements sets a structural stability test. The validation list requires All basement applications to carry a Basement Impact Assessment, and it asks you to prove that a basement will not harm the structural stability of your house, the neighbours or the highway. The structural limb of the policy is recorded as: Structural stability test.

The policy has a quirk worth knowing. It sets No numeric limit in DM18, so there is no fixed depth or garden percentage to design to. The case rests on the evidence, and the assessors must be independent and qualified, with their fees paid by the applicant.

Our calculation covers the structure of the house and the opening or beam involved. It does not replace the assessment, and we will tell you plainly where a specialist is needed.

Houses, Article 4 and the Tottenham SPD

Haringey's households are split between flats and houses: 38.9 per cent live in a house or bungalow, and 37.2 per cent own their home. The borough has 33 conservation areas, 25 Article 4 directions and 289 listed entries.

In the south of the borough the council publishes the House extensions in South Tottenham SPD (revised), which shapes what can be added to a house there. Our structural layout has to agree with any extension drawn to that guidance, and we check the two against each other before they leave the office.

That mix of houses and flats produces two kinds of request. A ground-floor flat wants to open a wall between living room and kitchen and needs the freeholder's consent. A house owner wants a rear extension with wide glazed doors, which means a beam over the opening and a foundation for the new walls. Both need the same discipline: find what is load-bearing, size the member, and show the bearing.

In its latest year Haringey decided 689 householder applications and granted 90.3 per cent. That is general context, not a forecast for your street.

Our Haringey fee and deliverables

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 technologist who did not draft the set checks it, and we revise at no charge if the examiner asks for changes.

The same figures go into our building regulations drawings in Haringey and, where you need an application, into the planning drawings in Haringey.

Where to read next

For the borough, see architectural drawings in Haringey. The structural calculations page explains the service, and structural calculations in Hackney shows a neighbouring council's rules.