The Short Answer
On our estimates, fixing a waterlogged lawn with a drainage system (land drains laid in gravel, running to a soakaway) costs about £1,500 to £4,000 for a typical back garden. A soakaway on its own is £900 to £1,600 with rubble, or £1,200 to £2,500 with plastic crates. French drains are £120 to £250 per metre.
Find the cause first. The RHS says waterlogging is usually down to heavy or compacted soil: compacted lawns often just need aerating, which costs far less. On heavy clay, drains only help if the water has somewhere to go, such as a ditch, a drain or a soakaway.
Garden drainage prices
| Job | Typical cost |
|---|---|
| Lawn drainage system, typical garden | £1,500 to £4,000 |
| French drain, per metre | £120 to £250 |
| French drain, 10m | £1,200 to £2,500 |
| Soakaway, rubble filled | £900 to £1,600 |
| Soakaway, plastic crates | £1,200 to £2,500 |
Causes and fixes
The RHS lists the usual causes of a waterlogged lawn: soil compacted by machinery (especially after building work) or by feet, heavy clay that drains poorly, and poor preparation when the lawn was laid. Its advice:
- Compacted soil: spike or aerate it once standing water has drained, so rain can soak in.
- Heavy clay across the garden: consider a drainage system, but only if there's an outlet for the water.
- No outlet: it's sometimes better to replace the lawn on improved soil.
- Timing: late autumn and winter are the best times to act.
For a patio or drive that puddles, the surface needs relaying to a proper fall (Marshalls recommends at least 1 in 80) or a channel drain.
Soakaways
Approved Document H says soakaways shouldn't be built within 5m of a building or road, in unstable ground, or where the water table reaches the bottom of the soakaway at any time of year. A percolation test shows whether the ground can take the water; where it's marginal, an overflow to a drain can be acceptable.
Having a soakaway put in
We estimate a soakaway at one to three days' work. The percolation test and taking the spoil away aren't always included, so I'd check both are in the price you're given, in writing.
Once it's in, a soakaway should drain from full to half empty in 24 hours or less. If it takes longer, it may be silted up, blocked or too small for the area draining into it.
Related
For a single drain run, see French drains. For water against walls inside the house, see damp proofing.
Get garden drainage quotes
Drainage is priced by what's causing the water and how far it has to go.
Free, no obligation. We're paid by MyJobQuote when a tradesperson buys your job, never by you.
Frequently asked questions
How much does garden drainage cost?
On our estimates, about £1,500 to £4,000 for a lawn drainage system in a typical garden, or £900 to £1,600 for a soakaway on its own.
How do I fix a waterlogged garden?
Find the cause. The RHS says compacted lawns often just need aerating; heavy clay may need a drainage system, but only if the water has a ditch, drain or soakaway to go to.
How much does a soakaway cost?
About £900 to £1,600 rubble-filled or £1,200 to £2,500 with crates, installed, on our estimates. It must be at least 5m from a building or road.
How long should a soakaway take to drain?
We'd expect it to go from full to half empty in 24 hours or less. Slower than that suggests it's silted up, blocked or too small.
Does a soakaway work on clay?
Often poorly, because clay doesn't let water soak away. A percolation test shows whether it can work; if not, the water needs another outlet.
How we priced thisView sources (3, 1 official)
Rules come from the legislation and official guidance, read at source. Prices are our estimates: we check them against trade price data, retailer shelf prices and specialists' price lists, then build them up from their parts so the totals add up. Below are the sources behind the page; the trade price guides we only compare against aren’t listed. Where sources disagreed, we've said so. More on our method.
- OfficialApproved Document H: Drainage and waste disposal (2015 edition), GOV.UK. Checked 15 Oct 2026.
- IndustryWaterlogged lawns: solutions, Royal Horticultural Society. Checked 16 Oct 2026.
- IndustryInstallation guidelines for concrete paving (Issue 8, January 2023), Marshalls. Checked 15 Oct 2026.
