Timber heading sewer connection

Project Overview

Premier Drainage Solutions was appointed to deliver a 150mm lateral connection into a 300mm public sewer at a depth of 4.5m, in one of central London’s busiest areas. With the site located on a TfL-designated Red Route, traditional open-cut trenching would have incurred significant costs due to lane closures and daily rental scheme charges.

To overcome this, we proposed a timber heading approach — a traditional yet highly effective trenchless method still widely used in complex urban environments. This enabled us to tunnel safely beneath the highway, making the required connection while eliminating disruption to traffic and drastically reducing project costs for the client.

Scope of Works

• Shaft Excavation from Site Boundary

  Working within the client’s property boundary, we excavated a vertical shaft to reach the required invert level of 4.5m, determined from level measurements taken at adjacent manholes in the carriageway.

• Timber Heading Tunnel Construction

  From the base of the shaft, we manually excavated a 7m timber heading tunnel, using traditional timber sets to provide structural support. This precise technique allowed us to reach the main sewer without impacting the carriageway above.

• Connection to Existing 300mm Sewer

  Once we reached the main, a pre-formed clay saddle was installed to create a secure and permanent 150mm lateral connection, following Thames Water standards and industry best practices.

• Manhole Construction and Backfill

  The new sewer pipe was carefully laid within the heading, and the void backfilled by hand with dry-packed concrete to fully stabilise the tunnel. A pre-cast concrete manhole was then constructed at the shaft location, complete with a stub pipe for the client’s final internal connection.

Key Challenges

• Traffic Management Constraints

  Located on a Red Route, any open-cut method would have triggered daily lane rental charges and required significant traffic management. The timber heading method allowed us to complete the project without road disruption or costly permits.

• Urban Site Restrictions

  Limited space and tight access conditions meant that manual tunnelling was the only viable option. Our team’s experience in timber heading ensured both safety and precision throughout the works.

• Cost Control

  Our approach delivered major cost savings for the client by removing the need for prolonged road closures, while still delivering a high-quality, permanent sewer connection in line with Thames Water specifications.

Why Timber Heading?

While traditional, timber heading remains a highly relevant solution in today’s urban infrastructure projects. In cities like London, where streets are congested, access is limited, and utility conflicts are common, this method remains a go-to for cost-effective and non-disruptive sewer connections.