Confined site basement

Project Overview

A new build basement built on a very confined site. The outline of the basement is less than a meter from both neighbouring properties.

The basement was built using a ring beam and underpin method, ensuring the excavation never collapsed on the crew and causing damage to the neighbouring properties.

Location: Oadby, Leicestershire
Surface Area: 275 Square Meters
Completed: 2020
Architect: Simplify

Stage 1 - Ring beam & supporting ground beams

The old house was demolished, and the grounds levelled and made ready for the building works to come.

To ensure the neighbouring properties did not collapse into the excavation, a 1.2m ring beam was constructed around the perimeter, holding up the top of the banks.

To give lateral support to the site and the houses next door, three, 4m deep trenches were then dug and cast with reinforced concrete. These were then linked into underpinned sections of the ground beams at either end of the ground beams with a 45o steel beam.

Stage 2 - Underpinning

With the ring beam supported laterally by the three ground beams, the rest of the excavation could begin.

The soils were taken down in small sections due to the confined site, but also to allow the ring beam to be underpinned safely and not leave too much unsupported. Each section of ring beam first had a base cast and then the walls, spreading the footprint of the underpins.

With all underpins cast in reinforced concrete, linked together and packed, all the base sections could be tied together with steel, reinforced drainage for bathrooms and waterproofing alike installed and finally concreted.

Stage 3 - Waterproofing

Type B – Integral protection

The main concrete floor that links all bases for the underpins was cast with waterproof concrete. All joints and protrusions were treated with hydrophilic slurries or expanding water stops

The waterproofing additive was supplied by Triton Systems

Type A – Barrier Protection

The internal face of the basement walls and entire floor was treated with a cementitious slurry stops water coming through. This slurry, linked to the integral protection on the floor provided the first of two waterproofing systems

Waterproofing materials supplied by Koster UK

Type C – Cavity drained protection

All walls and the entire floor had a cavity membrane system installed, linked to two sump chambers with a total of four pumps via perimeter channels

Waterproofing materials supplied by Triton Systems