Building near a sewer or stormwater main in Canberra

Can you build near or over a sewer main in Canberra?

Near a main: only with Icon Water's approval and footings designed around the pipe. Over its protection envelope: no. Icon Water's guidance says footings are not permitted within the envelope, and "no permanent heavyweight structure is to be built within an easement or pipe protection envelope".

Icon Water's approval also comes first. Its guidance says you need its building approval before building work starts, even where no ACT planning approval is required. So a carport that is exempt from planning approval can still need Icon Water's approval for its footings.

For a public stormwater main, check whose rules apply: your designer or certifier confirms which utility's permission you need. The design approach below is the same.

What do "zone of influence" and "pipe protection envelope" mean?

They describe the ground around a pipe that your structure must not load. The envelope is the one that decides the design: Icon Water calls it "the controlling requirement in all cases".

Zone of influence

Icon Water: "the space around an Icon Water asset, within which a structure and/or construction activities can have an impact on the asset". Its carport guidance puts it more plainly: "the area below the ground either side of a pipe where the weight of your structure will impact or place pressure on our pipes".

Pipe protection envelope

The space around a pipe that "is the controlling requirement in all cases". Footings are not permitted within it.

Easement

A strip of a block set aside for a service such as a pipe. No permanent heavyweight structure is to be built in one, per Icon Water.

Asset clearance zones

The term the single dwelling development controls use when mid-sized blocks need a utility's endorsement of earthworks and buildings.

Private drain

A drain serving your own block, as opposed to a public main. Building over one has its own ACT rule (below).

Which approvals apply when you build near a main?

Up to five, depending on the work: Icon Water's approval, the planning exemption tests, a utility endorsement on some blocks, building approval and, over a drain, a soundness test. They are separate, and passing one doesn't settle another.

Sources: Icon Water guidance; ACT DA page; NI2025-492; ACT BA page; DI2026-56.

What about building over a private drain?

You need to test it first. ACT Part G10, in the ACT Appendix to the building code (DI2026-56, in force from 1 May 2026), says that before you build over, or restrict access to, an existing operational drain, that part of the drain must be tested for soundness to AS/NZS 3500.2 section 15 and made sound.

It matters whenever an extension or deck will cover part of a drain. Your certifier confirms who tests the drain and what record they need. The structure above still has to be designed so its weight doesn't bear on the pipe.

How do you find where the sewer runs on your block?

Start with the plans you already have. People search for sewer and stormwater "tie searches" to locate pipes on a block; we don't cover how to order one here.

We work from the service and drainage plans you have or can get, and confirm what we can on site. A maintenance hole lid in the yard tells you a main is close, but not its exact line or depth, and the line and depth decide the footing design. Photos of every lid, and of where the house drains leave the building, help us quote.

How do engineers design footings near a sewer main?

By keeping the structure's weight out of the pipe's protection envelope. There are four common ways to do it, and Icon Water's requirements for your pipe decide which one works.

• Deeper footings, taken down so they bear on ground outside the envelope.
• Relocated footings, set back from the pipe, with the floor or slab designed to reach past them.
• Piers and a bridging beam: piers either side of the pipe carry a beam that spans over it.
• A suspended floor on piers, in place of a slab on the ground over the affected strip.

The drawings go to Icon Water and to your certifier. Footing design near a sewer or stormwater main starts at $790 + GST ($869 inc GST), and your fixed quote says if a site visit is needed.

What about stormwater plans and rainwater tanks?

We prepare stormwater plans when your approval needs one, at the same starting price as footing design near a main. Some new homes and extensions also need a rainwater tank.

For DA-exempt single dwellings, the development controls set a minimum tank by block size. They apply to new homes, to extensions over 50% of the existing floor area, and where new plumbing is added. Our sewer and stormwater design page has the tank table and the design service. One more rule: exempt fences and walls must not divert or concentrate surface water onto other land.

When should you call a structural engineer?

As soon as you know a main or drain is near the work, and before the plans are fixed. Moving a footing on paper costs far less than moving it on site.

• Footings near a main, or a stormwater plan: building near sewer and stormwater mains, from $790 + GST ($869 inc GST).
• A second dwelling over a backyard main: granny flat and dual occupancy engineering.
• A pool: pool engineering from $990 + GST ($1,089 inc GST).

We're engineers only. We don't dig, lay pipes or recommend contractors, so the design answers to Icon Water's rules and your plans, nothing else. We cover every Canberra district at the same prices. Queanbeyan, Jerrabomberra and Googong are in NSW, where NSW rules apply; we work with QPRC and your certifier there.