Structural calculations in Hackney

Terraces, flats and the Article 4 streets

Only 18.8 per cent of Hackney's 106,081 households live in a house or bungalow, and 24.6 per cent own their home. Structural work here is often inside a flat or a converted terrace, where a lease sets conditions on the wall you want to open.

The borough has 37 conservation areas and 77 Article 4 directions, mapped as 197 separate areas. Article 4 limits permitted development on some elevations and roofs, so structure and appearance should be decided together.

Hackney's householder decisions give a sense of scale: the council decided 415 in its latest year and granted 84.6 per cent. Those figures cover every kind of householder project, so they say little about a beam, but they show how much householder work the council handles.

In a Victorian terrace, a rear opening between kitchen and dining room may also mean taking out the chimney breast. Each of those means support for the stack and a beam sized for the span.

What the December SPD says about structure

Hackney's Residential extensions and alterations SPD, adopted in December and in effect from January, says in its paragraphs on structure that alterations such as loft conversions need Building Regulations approval, and that you must show the proposal can be built to comply. We use that as the working rule: Building Regulations for structural alterations.

The planning checklist says little about structure. It asks for a structural survey in one case, recorded as Listed/heritage only, and for air quality and waste information where demolition and construction are significant: Significant demolition/construction.

The council also publishes a Retrofit SPD. Insulation can change wall thicknesses and loads at the edges of a floor, so a retrofit alongside a structural alteration is worth coordinating on one survey. Our survey records wall build-up, floor depth and what sits above each opening, and the same notes serve the structural calculation and the retrofit design.

Before the calculation is issued, a second technologist checks each figure against the layout. A beam that is correct in the working but drawn one size smaller on the plan is exactly the error an examiner or a builder will find, and we would prefer to find it first.

Basements in Hackney

Hackney asks for a flood risk assessment for Basement development in CDAs / elevated groundwater risk. The SPD then sets design limits for a basement: Single storey; <1.5x footprint; 1 m soil cover; 2.15 m headroom.

The beam calculation for the house above is only part of the structural case for a basement. Underpinning and excavation need an engineer and a ground investigation, and we say so when the brief includes one. If you are only altering the ground floor, none of this applies.

Hackney price and the set you get

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.

The calculations feed our building regulations drawings in Hackney, and the planning drawings in Hackney when an application is needed.

Nearby pages

See architectural drawings in Hackney for the borough, or the structural calculations service page. Across the border, structural calculations in Haringey shows how that council words its requirements.