Structural engineer in Harrow

Structural engineering in Harrow

Harrow is a borough of family houses, from the hilltop village of Harrow on the Hill (HA1) to Rayners Lane and South Harrow (HA2), Kenton and Wealdstone (HA3), Pinner (HA5) and Stanmore (HA7). We have completed 62 projects here since 2019. Most involve owners adding space to interwar semis, along with conversions, small new-build plots and investigations of cracking near trees.

Harrow's housing is more uniform than inner London's, but that does not make every job the same. Ground conditions change between the hills and the valleys, earlier additions vary in quality, and many owners want a loft, a rear extension and a side extension in one go. Getting the structural strategy right at the start makes each part simpler to build.

Metroland semis, Pinner cottages and Stanmore detached houses

Most of Harrow was built in the 1920s and 1930s alongside the Metropolitan and Bakerloo lines. Rayners Lane, North Harrow, Kenton and Queensbury have streets of semis and short terraces with hipped roofs and front bays. Many already have rear extensions or garage conversions, and a large share have had lofts.

Older centres survive at Pinner, Harrow on the Hill and Stanmore, with Victorian and earlier cottages. Wealdstone has Victorian and Edwardian terraces, and Stanmore and Harrow Weald have large detached houses on spacious plots, where basements and full-width two-storey additions become possible.

Ground conditions across Harrow's hills and valleys

London Clay underlies most of the borough. The higher ground at Harrow on the Hill, Harrow Weald and Stanmore has more variable sandy and gravelly layers on top, which can hold water and create springs and soft spots where they meet the clay. Lower ground along the borough's brooks can have softer alluvium.

Clay shrinkage is the main foundation issue. Most gardens have trees or hedges, and many bays and garages sit on shallow footings. On sloping plots, such as those around Harrow on the Hill, a retaining wall design is often needed for terraced gardens or a lower ground floor.

Typical structural projects for Harrow homes

Harrow owners usually extend outwards and upwards rather than down, so lofts and single and two-storey extensions dominate. Converting larger houses into flats and HMOs is common near Harrow and Wealdstone town centres, and crack investigations near trees are frequent.

• Hip-to-gable and full-width rear dormer lofts
• Single-storey wraparound extensions
• Two-storey side extensions on semis
• Garage conversions
• Converting houses into flats or HMOs
• Subsidence and crack investigations

Harrow Council, Article 4 areas and party walls

Harrow has conservation areas in Pinner, Harrow on the Hill, Stanmore and some of its best-preserved interwar estates, with Article 4 directions restricting permitted development in places. Harrow Council's planning department will confirm whether your house is affected before you design a loft or extension.

Semis share a party wall, so hip-to-gable lofts, beams bearing on the party wall and foundations near the boundary usually need notices under the Party Wall etc. Act 1996. Building Control is a separate approval from planning, and our package of calculations and drawings goes to whichever inspector you appoint.