A spoon drain is a shallow, dish-shaped drain formed at ground level to collect surface water and carry it away before it can soak into the ground. Around houses it is usually concrete, though a spoon drain can also be shaped into the natural ground. Spoon drains are one of the simplest and most reliable ways to keep stormwater away from footings.
In the video below, Matt Cornell explains what a spoon drain looks like, how we detail them, and why we often prefer them to grated drains and ag drains.
What Is a Spoon Drain?
A spoon drain is a wide, shallow channel with a gently curved, spoon-like cross-section. The ground on either side falls towards it, so rain running across the surface is caught in the drain. The base of the drain falls along its length, carrying the water to a safe outlet.
Its job is to deal with water on the surface, before it has a chance to soak into the ground beside a building.
Concrete Spoon Drain Detail
When we specify a concrete spoon drain for a house site, it is typically:
- about 1 m wide, which is wide enough to catch water reliably and easy to walk across or mow beside;
- 80 to 120 mm thick at the centre, thickened to about 120 to 150 mm at the edges to hold the shape and resist edge damage;
- reinforced with light mesh, typically SL72 (7 mm bars at 200 mm centres each way), to control shrinkage cracking; and
- jointed at about 2 m centres with tooled or cut joints, so shrinkage cracks form neatly at the joints rather than randomly.
The size and fall needed for a particular site depend on how much water the drain has to carry and where it can discharge.
Spoon Drains Formed in the Ground
A spoon drain does not have to be concrete. Where flows are light, we sometimes specify a spoon drain shaped into the natural ground and grassed or turfed: a broad, shallow depression that collects surface water and carries it clear of the building.
Earth spoon drains are cheaper but need a stable surface and a consistent fall. Concrete is better close to buildings, on steeper falls, or where water flows regularly.
Where Spoon Drains Are Used Around a House
- On the uphill side of a house, to intercept water running down the slope before it reaches the building.
- Between a house and a retaining wall on cut sites, where water otherwise collects in the narrow strip with nowhere to go.
- At the base of basement and retaining walls, to take away surface water before it soaks down behind or against the wall.
- Along property boundaries, to manage water arriving from a neighbour’s land.
Where a concrete spoon drain or path runs against a house, the joint between the concrete and the building should be properly formed and sealed, for example with Abelflex and a flexible sealant, so water does not run down the gap to the footings.
Spoon Drain Outlets
A spoon drain is only as good as its outlet. The water needs to go somewhere safe, typically a stormwater pit connected to the property’s stormwater system, or a legal point of discharge downhill of the house.
Make sure the drain falls consistently all the way to the outlet. A low spot along the drain holds water against the building, which defeats the purpose. Stormwater connections are plumbing work, so have a licensed plumber confirm the discharge arrangement.
Why We Prefer Spoon Drains to Grated Drains
The main reason is maintenance. A spoon drain is open and shallow, so leaves and dirt are easy to see and sweep out, and much of the debris is washed through by the next rain. In practice, a spoon drain needs very little maintenance.
Grated and box drains fill with leaf litter, dirt and rubbish out of sight. Once blocked, they overflow, often right where the water is least wanted: beside the house.
Spoon Drains vs Ag Drains
These are different drains with different jobs:
- A spoon drain collects water that is on the surface.
- An ag drain (a slotted pipe in a gravel trench, also called a French drain) collects water that is already in the ground, such as groundwater moving from uphill or from a neighbouring property.
It does not make sense to let surface water soak into a gravel trench just to carry it downhill. Surface water should be drained at the surface. Ag drains that are fed surface water are also a common cause of moisture problems around houses.
Spoon Drain vs Dish Drain, Swale and Table Drain
- Dish drain: essentially another name for a spoon drain. The term is more common in civil and roadworks.
- Swale: a broad, shallow, usually grassed channel for carrying or slowing surface runoff. It is similar to an earth spoon drain, but often larger and used at a landscape or subdivision scale.
- Table drain: an open drain running beside a road, typically to collect water from the road surface.
Precast, Plastic and DIY Spoon Drains
Precast concrete and plastic spoon drain sections are available and can work for light flows, such as along a path or garden edge. Whatever the product, the same rules apply: catch the water, fall consistently, and discharge somewhere safe.
A spoon drain is within reach of a capable DIYer or landscaper. The shape is usually formed with a shaped screed board, and joints are formed with a concrete groover. Getting the fall right is the part that matters most.
Some product links on this page are Amazon affiliate links. If you buy through them, Cornell Engineers may earn a small commission at no extra cost to you.
Drainage Problems Around Your House?
Poor surface drainage is one of the most common contributors to slab heave, cracking and water entry through basement and retaining walls. Cornell Engineers investigates these problems and provides practical drainage and stormwater advice for existing houses, including on sloping sites.
If you have a drainage problem that is affecting your house, send us the property address, photographs, a short description of where the water goes when it rains, and any reports you have. We will review the information and let you know whether the matter is a good fit for Cornell Engineers before preparing a fee proposal.