Garden Drainage Solutions for New Homes

Weather patterns are becoming increasingly more extreme, causing excessively damp conditions in our gardens and posing a particular problem for new-build homes. 

Discover why and some effective solutions:

First, Identify the Cause

A number of factors can cause water-logging of your garden. In a new home garden, there are two common causes, soil compaction and shallow topsoil over clay subsoil, sometimes both together. Here are some solutions.

Assessment

Dig a test pit. A hole 45cm x45cmx45cm is usually plenty to see what’s underground. Leave a clean vertical side to the pit and you should be able to see the soil ’profile’. In this context the first two profiles are of most interest. These are the topsoil and the subsoil.

Topsoil

This supports the growth of your shrubs or lawn. It may be soil that has been removed prior to the build and then re-spread, or an imported ‘blended loam’- a mixture of crumbs of clay, coarse sand and organic matter.

The topsoil should be at least 15cm thick for satisfactory lawn growth, 30cm for shrubs and ideally deeper still for trees. If less, plant growth may be adversely affected.

Subsoil

This will typically have very little organic matter and depending on your locality could be formed mostly of clay, chalk or sand. Poor drainage is usually associated with clay subsoils. To identify the subsoil, you should see a clear change in colour, texture or composition where the topsoil meets the subsoil layer.

Soil Condition

Now assess the soil. Commonly the topsoil will be saturated because the subsoil is not absorbing any water. This may be due to the physical nature of the subsoil (heavy clay is simply not free draining), compaction due to heavy site traffic during the build, or both.

A test pit will reveal the soil profile and condition

Other Factors

There are a few other possibilities to be aware of: It may be that the garden is low laying and acting as a sump for the surrounding higher ground, there may be a high-water table in the locality, broken water or drainage pipes or large areas of paving next door causing rainwater to run-off into your garden. These are not issues specific to new build drainage problems and not addressed in detail here.

SOLUTIONS

Compaction

Compaction can be relieved by cultivating the soil. If the compaction is within the subsoil, then the topsoil needs to be removed first and then replaced.

Heavy Clay Impeding Drainage

The clay must either be removed or improved. This means either replacement with good topsoil or mixing-in coarse sand, grit and organic matter.

Shallow Topsoil

To support plant growth more soil should be added. This may mean removing subsoil first to retain current ground levels or building up the soil level over the subsoil. In doing this, a greater depth of permeable soil is also created with the effect that rainwater can be dispersed even if the subsoil is not free draining.

Talk to the Builder

Sadly, gardens are rarely a high priority for house builders, but it is likely they will be well aware of any drainage problems. To tackle them across the whole site would significantly add to their costs but if pushed they may take action to help resolve your particular problem.

A waterlogged garden in need of a drainage solution

Land Drainage

If the causes of the bad drainage can’t be fully remedied, it may be possible to remove the water from the soil. This could involve gravel filled trenches at strategic positions (known as ‘french drains’), or even a full piped land drain system. To be effective, the water must be able to reach the chosen drain so attention must be given to siting, spacing and depth of the drains, as well as improving the soil condition. Then the water must have somewhere to go. For land drainage an adjacent ditch is ideal or if you have a large garden, a lower lying area which you don’t mind becoming a seasonal pond or ‘swale’, may suffice.

Draining Hard Surfaces

Non-porous hard surfaces are always laid to a fall, so water runs-off. This can add to an existing drainage problem. In this case, pot gully drains can be set within the area or slot (‘acco’) drains along the low edge. Subject to site specific planning rules it may be possible to then pipe it to your storm drains (but not the main or foul drains), otherwise it must discharge to a soak-way. This is a hole in the ground filled with hardcore or better, plastic drainage crates. To be most effective it must be sited in ground that drains reasonably well otherwise it will quickly fill and be of less benefit. Addition of an overflow pipe may help, as long as there is somewhere to discharge the excess water to.

Raised Beds allow plants that are intolerant of wet soil to thrive

Creative Solutions

It is sometimes better to go with, rather than to fight nature. Stepping stone slabs laid through a lawn that is wet in winter will provide a firm dry pathway.

For happy plants, adopt the ‘right plant, right place’ principle. Some plants hate wet feet, others will tolerate some winter waterlogging.

If your favourite plants don’t like wet soil, plant them in raised beds or just gently mounded borders to lift roots out of wet ground.

Wet Garden Ideas

With an understanding of the causes and appropriate solutions your problem garden can be transformed into something beautiful. The image below shows a garden design solution for the waterlogged garden pictured above. Because the garden is situated in an area with no means to effectively drain it, we took a ‘go with the flow’ approach and got creative. It now features an elevated boardwalk over a ‘dry’ steam bed which becomes real in winter and has an added pump system backup. You can read the full case study here. 

Creative garden design solution for the waterlogged garden shown above

If you are struggling with your muddy garden being walked into your new home or it’s simply a no-go area from Autumn to Spring, our landscape gardeners have the wellies, solutions and expertise to help. 

At Haywood Landscapes our garden landscapers have been designing and installing gardens for over thirty years across Kent and the South East.

Contact us here or call 01227 733447 for more information.