4 Storey Underground Car Park

Work Type

Design & Build basement and 4 storey reinforced concrete frame, appointed engineer for both sub-structure and super structure works.


Leaders Bespoke


Station Road, Gerrads Cross, SL9

Project Overview

Our client Leaders Bespoke were appointed on behalf on Titan Properties to construction underground car park and 18no apartments including hard landscaped area, for release in Autumn 2017.

The site itself is square in shape, generally flat and measures 1066sqm. Access to the site was gained off Station Road along the Southern Boundary of the site.

The site is bounded to the North by residential dwellings, to the East by Marsham Lane residential dwellings, to the South by commercial buildings and a railway and to the West by commercial buildings and car parking.

Site Review

The site investigation carried out indicates that the bedrock is of Lambeth group formation (clay, silt and sand) overlain by superficial deposits of Gerrads Cross gravel (sand and gravel).

Groundwater was encountered at between 2.00 to 2.90m BGL (80.21mOD to 80.76mOD), which would have meant constructing the basement slab underwater. To gain a greater understanding of the potential risk of water SPEEDECK commissioned their own site investigation works, from this we identified that the water was perched at a general level of 79.300mOD, enabling the basement to be constructed without the risk of the water table.

Scope of works

SPEEDECK were contracted by Leaders Bespoke to install the following work packages;

Appointed structural engineers for sub and super structure.

Design and installation piled contig wall close to site boundary walls. SPEEDECK specified 300mm piles to be installed to an average depth of 8.1mtrs except along the west elevation where 450mm piles were required due the surcharge imposed due to existing buildings foundation, these piles were installed to an average depth of 6mtrs tied into our capping slab.

Design and installation of piled reinforced crane base; 6.5m x 6.5m 500mm deep, cast with RC Kryton (waterproof) concrete.

Installation of RC capping slab 3.25mtrs wide by 0.3mtrs deep alongside the west elevation at ground floor level tied into 450mm piles. By installing the capping slab at ground floor before the excavation of the basement SPEEDECK were able to remove the requirement for any temporary propping works.

Bulk excavation to basement managing localized soil remediation strategy due to contamination within the sub-soils.

Installation of reinforced liner walls, concrete columns, walls, lift core, and floor slabs typically 225mm thick, installation thermal breaks to balconies for 1st, 2nd, 3rd floors, each floor was typically 465m2 in size.

Installation of site drainage and storm water design to include; Pipework, rodding eyes, inspection chambers, connection of new services to existing, Hydro-brake, pumping station including chamber, soakaways.

Advantages of using SPEEDECK

By appointing SPEEDECK for the Basement, and RC frame element of works on a particularly tight site due to building close to the proximity of existing building boundaries, we engaged early with party wall surveyor SPEEDECK resolved all queries to ensure that the piling works commenced on-time without delaying the project commencement.

SPEEDECK carried out further site testing to understand risks associated with the water table. Once the true level was ascertained, we carried out cone penetration testing to the footprint of the building to understand the soil profile, once we analyzed this information we were able to remove the requirement for bearing piles by utilizing a thicker reinforced concrete slab, saving our client time and money.