How to Install a French Drain in Your Garden

What is a French drain and how does it work?

So let’s diffuse two of the biggest fallacies straight away. Firstly, a French drain isn’t French (oddly enough), and secondly, it’s not really a drain in the traditional sense either. Confused? You shouldn’t be. Put simply, a French drain is essentially a gravel-filled trench that contains a perforated pipe, which is designed to redirect surface water and groundwater away from problem areas.

Water should naturally soak into your garden soil – unless that soil is compacted, or another common cause is that the ground or your garden doesn’t slope away from your home, leaving the water nowhere to go. Over time, standing water can damage your plants, cause slippery surfaces, or even seep into your foundations. A French drain gives that water an escape route and helps it drain away.

Why would I need a French drain in my garden?

If after rain your garden stays soggy, pools water near the house, or suffers from water damage around patios, garages or sheds – a French drain could be the fix. It’s ideal for sorting out soggy lawns, damp patches, or water build-up near foundations.

Thinking about installing a French Drain? Call PM247 on 08082 504 203, or book a visit online and let the professionals take care of it for you.

What are the benefits of installing a French drain?

The benefits of a French drain are numerous, however heres some of the reasons that our team likes them in particular.

• They are Low Maintenance: Once it’s in, you don’t have to fuss with it.
• They are a Hidden System: They can be turfed or gravelled over for a clean finish.
• They can be Cost-Effective: They are usually cheaper than more complex drainage systems.
• They’re a Natural Solution: They work with gravity, no pumps needed.
• French Drains are Versatile: Works for lawns, driveways, patios and borders.

What should I think about before installing one?

There are a few things that you need to consider before attempting to put in a French drain. Here’s some of the key considerations:

How do I check if I’ve got the right slope for drainage?

You’ll need a fall of around 1% – that’s 1cm drop per metre of length. Use a line level, string and stakes to plan it out before digging.

Where should the water go once it drains away?

Direct it to a garden soakaway, rain garden, gravel sump or an existing surface drain. Avoid directing it onto neighbouring land or public footpaths.

Do I need to check for pipes and cables before digging?

Yes. Use local ‘dial-before-you-dig’ services or maps to avoid hitting gas, water, or electric lines when you start excavating.

How do I install a French drain: A step-by-step guide

You can install a French drain yourself if you’re comfortable with a bit of graft, digging and DIY. You’ll need plenty of kit, and below is a step-by-step to help you get it right:

Tools You’ll Need:

• Spade or trenching shovel – For digging out the trench
• Pickaxe or mattock – Helpful for breaking up tough soil, roots or clay
• Wheelbarrow – To move soil and gravel around the garden
• Measuring tape – To plan out trench depth and spacing
• Spirit level or string line with a level – To check the slope (1cm drop per metre)
• Gloves and protective gear – For safety and comfort
• Landscaping rake – To level the gravel base and tidy up after
• Handsaw – If you need to trim the drainage pipe to length
• Utility knife or scissors – To cut the geotextile fabric

Materials You’ll Need:

• Perforated drainage pipe (usually 100mm wide)
• Coarse angular gravel – Not pea shingle; you want gravel that locks together
• Geotextile / landscape fabric – To wrap the gravel and pipe, preventing soil ingress
• Topsoil or turf – To finish the surface (or decorative gravel if preferred)
• Marker spray or string and stakes – To plan and mark the route of the trench

Perforated pipe for French drains

Image courtesy of Drainage Central.

Optional but Helpful:

• Laser level – Makes grading easier and more precise if you’ve got one
• Drainage connector fittings – For longer runs or if joining to existing pipes
• Drainage crates or soakaway kit – If you’re discharging into a soakaway system

Step 1: Start by Marking Out the Trench

Use marking paint or string to outline where your French drain will go. Make sure it’s running from the wet area to the planned outlet and that there’s a consistent downward slope (double check the points above).

Step 2: Dig the Trench

The trench should be around 15-20cm wide and at least 45-60cm deep, depending on the water issue. Use a spirit level or line level to maintain the slope. How long it is depends on how far you have to move the water.

Top tip: Keep a wheelbarrow nearby – there is going to be a lot of soil coming out. Alternatively, lay a sheet of plastic alongside the trench (this in particular helps if you are trying to preserve a nice lawn) and stack the soil on top of that (remember that there still will be excess soil to get rid of, once the pipe is laid in the trench). 

Step 3: Add a Base Layer of Gravel

Line the bottom of the trench with coarse gravel (around 5-10cm deep). This gives water a place to flow before it enters the pipe. Use angular gravel, not round pea shingle, so it locks in place.

Step 4: Lay the Geotextile / Landscape Fabric

Line the trench with landscape fabric, letting the edges overlap the sides. This stops soil clogging the drain but still lets water pass through.

Step 5: Add the Perforated Pipe

Place your drainage pipe on top of the gravel. The holes should face downwards – this surprises some people, but it actually helps water enter the pipe more efficiently.

Step 6: Cover the Pipe with More Gravel

Pour more gravel over the pipe until it’s about 5-10cm from the top of the trench.

Step 7: Fold Over the Fabric

Wrap the landscape fabric over the top of the gravel creating a covered top to the trench (see the blue line in the picture). This adds another layer of protection from soil and roots.

Step 8: Finish with Topsoil or Decorative Stone

You can now cover the trench with soil, turf, bark, or decorative pebbles – depending on the look you’re after.

What common mistakes should I avoid when installing one?

Even though it’s a fairly straightforward job, a few common errors can stop your French drain from doing its thing:

• Not including a consistent downward slope.
• Using round gravel instead of angular stone (the water needs to perculate down the gaps).
• Skipping landscape fabric – it prevents soil clogging the pipe.
• Facing pipe holes upward – they should face down.
• Failing to plan a proper exit point for water – it needs to go somewhere where it will not be a problem.

How much does a French drain cost to install?

How much will it cost to install a French Drain myself?

How long will it take me to install one on my own?

For a 5-10m French drain, expect a weekend job. Hard ground, roots, or awkward layouts may take longer.

What will it cost to get a professional to install it?

Professionally installed French drains for domestic gardens usually cost between £750 and £1,500, depending on length, access, and complexity.

Is it worth paying more to get it done professionally?

If you value time, don’t want the hassle of digging, or the issue is widespread – yes. It guarantees proper grading, waste removal, and peace of mind.

When should I call in a drainage expert to help?

DIY is great – but sometimes drainage needs more than just elbow grease and hard labour. Here are a few times when it’s worth getting the experts involved:

• You’re dealing with persistent or widespread waterlogging
• There’s water getting into your house or foundations
• You’re unsure about the drainage route or regulations
• The garden layout is sloped, tiered or complex
• You hit utility pipes or tree roots while digging
• You simply don’t fancy digging a 10-metre trench!

At PM247, we’re on hand to provide a professional assessment and carry out French drain installations safely and efficiently. We know exactly how to tailor drainage solutions to your property, whether it’s a small garden fix or part of a larger landscaping job.

Here’s what our customers say:

Call us now on 08082 504 203, or book online – we’re here to help keep your home and garden in fully functional order. 

What’s the bottom line when it comes to French drains?

A French drain can be a total game-changer for your garden. It’s not the flashiest upgrade, its purely functional and practical, but when it comes to protecting your home from water damage and keeping your lawn usable year-round, it’s a very smart solution.

If you’re confident with a shovel, feeling strong and up for a weekend project, follow the steps above and give it a go. But if you’d rather skip the guesswork and get it done right first time, contact our friendly team and we’ll be around in no time at all.

At PM247, we’re here 247 – not just for blocked drains and plumbing emergencies, but for smart, long-lasting drainage solutions too. Whether you’re just after advice or ready to book an installation, or you can call us now on 08082 504 203.

Frequently Asked Questions about French Drains