Guide · 6 min read
Utility Ducting on a Construction Site
Utility ducting is the buried network of pipes that power, telecoms, water and gas services are later pulled or laid through. Each provider specifies duct type, depth, bedding and separation, and the ducting has to be installed before roads and slabs are closed up.
The short answer
The site contractor digs the trenches and installs the ducts, chambers, draw pits and bases; the utility provider then pulls in its cable or lays its main and makes the live connection.
Getting the ducting in early — and installing spares on road crossings — is one of the cheapest decisions on a site, because retrofitting a duct means cutting up a finished surface.
What each utility needs
Requirements differ by provider, and each publishes its own specification for duct type, colour, minimum cover, bedding material, warning tape and separation from other services.
- —ESB Networks — duct routes, draw pits, and mini-pillar or meter cabinet bases
- —Eir and Virgin Media — telecoms ducting with chambers at pull points
- —Gas Networks Ireland — duct or service routes to the meter position
- —Water and rising mains — trenching, bedding and marker tape
Depth, bedding and separation
Ducts laid too shallow, bedded in unsuitable backfill or run too close to another service will be refused at inspection, and the trench then has to be reopened. Cover depth also differs depending on whether the route runs under a road, a footpath or open ground.
Sand or fine bedding protects the duct, warning tape above it protects it from future excavation, and draw ropes left in the duct make the later cable pull possible.
Sequencing with drainage and roads
Deep drainage goes in first, then shallower utility ducting, then the road or slab build-up. Duct routes and draw pit positions are agreed with the engineer and the providers before the sub-base is placed.
As-built duct routes are recorded as they are installed, both for the connection applications and for anyone digging on the site in future.
Frequently Asked Questions
Who installs the ducting — the contractor or the utility company?+
The site contractor normally installs the ducting, chambers and bases to the provider's specification. The provider carries out the cable pull or main laying and the live connection.
When should ducting be installed?+
After deep drainage and before road build-up or floor slabs. Once a surface is closed, adding a duct means cutting and reinstating it, which is far more expensive.
Are spare ducts worth installing?+
On road and driveway crossings, almost always. The additional cost while the trench is open is small compared with breaking out a finished surface later.
What records should be kept?+
As-built duct routes, depths and chamber positions, recorded as the work is installed, so connections are not delayed and future excavation avoids the services.