How to dig a garden pond

Digging is the part of a pond that is hard to undo. A pump can be returned, but a hole cut through a drain or a cable cannot. Most of the work happens before the first spadeful: the outline, what is under the lawn, and where the soil will go.

Before you dig

Settle the site first. Where to site a garden pond covers sun, shade, trees and sightlines from the house. How big should a garden pond be covers depth and surface area. Decide both before you mark anything out, because the shape you dig is the shape you will be lining.

If young children live in the house or visit, read pond safety for children now, not after the hole is open. An unfenced hole that fills with rain is already a pond as far as a toddler is concerned.

Cables, pipes and drains

Garden soil hides more than roots. Water supply pipes, drains, soakaway runs, gas pipes, and cables to sheds, outside lights or an old pump can all run across a lawn, often not where you would guess. The bigger and deeper the hole, the more that check matters.

Ways people narrow it down:

• Look at where the services enter and leave the house: the stopcock, the gas meter, manhole covers, gullies and rainwater downpipes. Drains usually run between those points.
• Ask the previous owner, or look through the house paperwork for a drainage plan or a survey.
• LinesearchbeforeUdig describes itself as a free online search service for anyone planning works that disturb the ground, including small garden jobs. You enter the site and the asset owners who have pipes or cables nearby send plans back.
• If anything electrical might be in the way, such as a cable to a garden building or an old pond pump, ask a qualified electrician to identify and deal with it before you dig. Tracing and making safe a buried cable is electrical work. We do not give wiring instructions, and this page does not suggest locating or moving a cable yourself.

Dig carefully near anything you are unsure of. If you hit a pipe, a duct, a marker tape or anything that looks like a cable, stop and get the owner of that service or an electrician to look at it.

The RHS step-by-step guide for a rain-fed wildlife pond also says to keep the pond away from buildings, and to take advice from a geotechnical adviser or registered ground engineering professional if it is closer than 5 m to a house. That figure is the RHS's, on that page. It is a reason to talk to someone qualified, not a clearance this site has calculated.

Mark out the outline

Lay a hosepipe or a rope on the lawn and live with it for a day or two. Change it now, while it costs nothing, then mark the line with sand or spray paint.

Then mark the inside features on the same plan: the long shallow beach the RHS wants for wildlife, any planting shelf, and the deeper pocket. A wildlife beach is easier to dig as a gentle slope from the start than to carve into a steep bank later.

Digging the hole

Strip the turf first and stack it somewhere away from the hole. Do not use turf as a pond edge or a liner bed. The wildlife pond guide explains why grass right up to the water draws it out of the pond.

Work from the outside in, taking the whole area down to the depth of the first shelf, then cut the deeper section inside that. Keep the sides sloping rather than vertical. The size guide gives the gentle side slope the RHS suggests so ice has room to expand, and a slope is kinder to a liner than a cliff. Check the rim is level as you go with a long straight board and a spirit level. A pond that is out of level shows liner on one side and overflows on the other.

Take out any stones, roots and rubble you meet in the base and the sides. The liner goes on top of that surface, so anything sharp left in it is a future puncture. Underlay and fitting are covered in fitting a pond liner. Measure the finished hole before you order, using the method on the liner size page.

The spoil heap

A pond produces much more soil than people expect, and it bulks up once it is out of the ground. Decide where it is going before you start. People use it for a raised bank or rockery, and send the rest away in a skip or with a waste carrier. Keep topsoil and subsoil apart if you plan to reuse either. Do not pile spoil where it will wash back into the hole, sit against a house wall or block a drain. If you build a wildlife pond, the Freshwater Habitats Trust warns that turf and soil left in a pond add a large dose of nutrients, so the spoil should go downhill of the pond, not above it.

Spade, mini digger or contractor

A small pond is a spade job. A larger one is many days of heavy work, and a mini digger can do it in a fraction of the time. Hire firms often supply an operator, which is the sensible choice if you have not used one before. A digger needs safe access and ground that can take its weight.

Bring in a contractor or a landscaper when the pond is large, the soil is heavy clay or full of stone, access is tight, or the site is close to the house. The RHS rain-fed pond guide itself notes that the project could be done with the help of a good landscaper. A contractor should still check for services before they dig. Ask them how they will do it.

Once the hole is dug, the next stages are the liner and, if you want frogs and newts rather than fish, how to build a wildlife pond. If the pond will have a pump, plan the supply now with a qualified electrician. See pond pump electrics.

When is the best time of year to dig a pond?

The RHS wildlife pond guide says autumn and winter are ideal times to make a new pond. That is after the main breeding season, and rain is more likely to be available for filling.

Do I need to check for buried services in a small garden?

Yes. Small gardens still have drains, supply pipes and cables, and they are often closer to the surface than people think. Look at the visible clues, ask about plans, and use a search service before you dig.

Can I dig the pond by hand?

For a small or medium pond, yes. A larger pond, heavy clay or a stony site is where a hired digger with an operator, or a contractor, starts to make sense.