Piled Structural Raft

Work Type

Installation of Basement and 5 Storey RC frame, including Underpinning, King Post and Hard Landscaping.


Leaders Bespoke


750 Harrow Road, Kensal Green, NW7

Project Overview

Our client Vabel London are carrying out a proposed development comprising of 5 storey reinforced concrete superstructure with 1 level-basement. The redevelopment of a former site which mainly consisted of existing buildings, which comprise a two-storey building in the north of residential and commercial use, a three-storey building in the southwest corner, and single-storey elongated buildings adjacent to the eastern and western boundaries of the site, all of commercial use.

Site Review

The made ground comprised light brown-grey slightly clayey gravelly sand including fragments of concrete, brick and possible tarmac over dark brown slightly sandy slightly gravelly clay including fragments of brick and flint, which extended to a depth of 0.70 m. The London Clay comprised an initial horizon of soft becoming firm brown clay to a depth of around 9.40 m, becoming firm then stiff blue clay to the full depth of investigation at 25.00 m. Claystones were encountered at depths of 9.85 m, and 20.40 m.

Formation level for the proposed basement is expected to be within the London Clay Formation. Piled foundations have been specified as a suitable solution for the proposed development.

Scope of works

It is proposed to support the new structure on piled foundations, while a piled retaining wall is required to support the deep excavation for the proposed single level basement with pile caps located within the basement floor area. The piled retaining wall will also function as a permanent component of the new basement structure. Wall retained height varies from 5.2m in the temporary condition to 4.3m in the permanent condition. In addition to lateral earth/water retention, the pile retaining wall is also subject to service vertical compressive loading of up to 630 KN/pile and overturning moment of up to 160 kNm/m run of wall from the proposed superstructure. The foundation piles are subject to service vertical compressive loading of between 300 KN- 850 KN.

Installation of 98mtrs of 450mm diameter @ 600mmc/c piled retaining wall is required to enable construction of single level basement and reinforced concrete pile caps located within the basement area.

Installation of Underpinning to boundary walls along with King Post system.

Temporary propping to capping beam alongside eastern elevation; installing 4 no 45 degree raking RMD Kwikform 324 tube shores, 1 no Kwikform 324 corner brace, 4 no 1mtr x 1mtr x 1mtr deep mass concrete thrust blocks.

Bulk excavation to basement coordinating with temporary works to ensure that movement monitoring to eastern elevation did need exceed 5mm in movement.

Design and installation of crane base to accommodate Jaso J80PA tower crane which has a height of 23.7mtrs and jib length of 25.5mtrs.

Installation of reinforced liner walls, concrete columns, walls, lift core, and floor slabs which varied between 200mm – 300mm thick, for 1st, 2nd, 3rd,4th floors and roof, each floor was typically 467m2 in size.

Installation of site drainage which covered; 5mtr deep pre-cast manhole chambers, pumping chambers including flow controls, associated rising mains, site attenuation tanks, testing and commissioning all installed works.

Advantages of using SPEEDECK

SPEEDECK contracted works planned for completion Autumn 2018