Lordship Lane

client: Heritage of London Trust Operations (HOLTOP)
engineer: Abbas Contractor
status: On site
value: £ 800,000
role: Structural Engineers
procurement: Traditional competative Tender procedure
duration: 1 year construction period

Lordship Lane  was constructed in 1873, and is one of the earliest remaining portland cement concrete structures in Britain. The mass concrete construction was designed by Charles Drake an early innovator in the use of concrete. Drake developed a patented shuttering system involving iron shutters which could be re-used and adapted for multiple constructions. To this day the lines of the shutter lifts remain visible on the front elevations to the property.

The building was on the Buildings at Risk Register for several years, having been left derelict and in a perilous condition, until 2010 when the house was acquired by compulsory purchase by Southwark Council. The building preservation trust HOLTOP undertook the conservation project starting on site in 2012.

The condition of the building was very poor at the start of the works, with numerous areas of diagonal cracking, in particular at corners and over openings. In a few locations the mass concrete walls had failed and the broken segments lay adjacent to the building. The timber floor joists, largely missing,  were damaged and the roof members had been left exposed to decay. The deterioration and cracking of the walls was probably caused by the lack of maintenance- the missing roof left the walls exposed to water ingress, as well as causing possible subsidence of internal walls which would have been particularly harmful to the already vulnerable building.

Before the repairs works began, material testing of the mass concrete was conducted in order to investigate a compatible repair material. The early mass concrete structure is constructed of a unique formulation of burnt ballast as aggregate, small brick fragments for the concrete which gives a honeycombed texture.

A compatible low strength similar lightweight cast in situ concrete product was selected for the concrete repairs and partial rebuilding. In this respect Lytag product provided low strength and honeycombed effect to mimic a close match to the original construction. The Building required underpinning to prevent future subsidence. However, given the state of the building, it was decided to carry out the required extensive structural repairs initially and then to proceed with the underpinning.  Partial rebuilding of the bay window to the front elevation was carried out, as well as crack stitching, and reinstatement of the retained failed segments of concrete. Finally a new reinforced concrete slab was cast at ground level, timber suspended first and second floor installed and roof reinstated.