You install a bank revetment along your pond or ditch by driving a post every 50 cm, with 2/3 of it in the ground, then screwing horizontal boards against them with geotextile behind. Up to a retaining height of 1 metre, this is a fine weekend job. Reckon on 85 to 200 euros per running metre for hardwood materials, and 90 to 175 euros for plastic. A simple notification to your water authority is usually enough, and you often don’t need a permit.
Below you get the whole story. Material choice, costs, the rules, and a step-by-step guide you can actually use.
What is a bank revetment and why do you need one?
A bank revetment is a retaining wall along the waterside. It holds the soil in place so your bank doesn’t cave in.
Without a revetment, the soil slowly washes into the water. Your bank crumbles, your lawn sinks away and your pond or ditch silts up.
You see them along ditches, ponds, gullies and on sloping ground. In a garden they also give a clean, tidy edge at the water.
In short: a bank revetment keeps the line between dry and wet. And that saves you a lot of hassle and subsidence down the road.
Which material do you choose for a bank revetment?
The material choice sets your price, your lifespan and how much maintenance you get. These are the five options that really matter.
Hardwood (azobé, angelim, bilinga)
The classic. Heavy, strong and naturally water-resistant. Durability class 1. Easily lasts 25 to 40 years, thicker boards even longer.
Plastic (for example Prolock, PVC sheet piling)
Lighter, easier to work with and completely maintenance-free. Doesn’t rot, doesn’t splinter. Lifespan of 50 years or more.
Composite
A mix of wood and plastic. Looks wood-like but has the maintenance-free properties of plastic. A bit more expensive to buy.
Steel sheet piling
For heavy work and high retaining heights. Strong, but you often need machines to install it. Not really a DIY material.
Recycled plastic or concrete
Durable and very long-lasting. Concrete is dead heavy and usually a job for the contractor.
For most garden jobs you’ll choose hardwood or plastic. Here they are side by side:
| Material | Lifespan | Maintenance | DIY-friendly? |
|---|---|---|---|
| Hardwood 40 mm | 25-40 years | Little | Yes |
| Hardwood 50 mm | 30-50 years | Little | Yes |
| Plastic | 50+ years | None | Yes, light work |
| Composite | 30-50 years | None | Yes |
| Steel sheet piling | 40+ years | Little | No, machines |
| Concrete | 50+ years | None | No, heavy |
Watch out with wood: always use stainless steel or galvanised screws and bolts. Ordinary steel rusts and leaves ugly black streaks on your hardwood.
What does installing a bank revetment cost per metre?
Doing it yourself saves you plenty. The labour of a specialist is often half the bill.
This is what you pay for materials alone, per running metre:
| Material | Cost per running metre |
|---|---|
| Light hardwood revetment (up to 40 cm) | from 85 euros |
| Hardwood sheet piling 40 mm | 80-130 euros |
| Hardwood sheet piling 50 mm | 120-200 euros |
| Plastic (Prolock and similar) | 90-175 euros |
| Plastic sheet piling, high | 180 euros and up |
Posts come on top of that: reckon on 25 to 60 euros per post, depending on length and thickness.
Having it installed by a landscaper? Then add 50 to 150 euros per metre for labour. All together, an installed revetment sits between 150 and 400 euros per running metre.
Do it yourself and you save that labour cost entirely. For a 10-metre bank in plastic, you’re quickly talking hundreds of euros of difference.
The price also depends on the retaining height (higher is more expensive), the soil type and how well you can reach the spot.
Do I need a permit for a bank revetment?
Usually not. For a revetment up to 1 metre high, a notification is often enough, not a permit. That notification is free. Applying for a permit does cost money, even if it’s rejected.
Important: the water is almost always managed by a water authority. So always check first before you start. The rules vary by authority.
Here’s what it looks like at a typical water authority if you can get away with a notification:
- You install the revetment on the water line.
- Posts are at least 1.60 metres long and at least 8 cm thick.
- The spacing between posts is at most 50 cm (centre to centre).
- Posts sit at least 2/3 in the ground.
- The revetment does not rise above ground level and closes off well at the bottom, so no soil washes into the water.
- You don’t obstruct the flow of the water.
Where is it usually not allowed? In waterways, Natura 2000 areas, Water Framework Directive waters and along nature-friendly banks. Check your water authority’s water register map to see which status your water has.
Does the water border a neighbour? Give them a heads-up. That prevents trouble afterwards.
What tools do you need?
Nothing exotic. You probably already have most of it lying around.
- Earth auger or hand auger (for the post holes)
- Heavy hammer or drive cap (to knock the posts fast)
- Cordless drill/driver with Torx bit
- Ring spanner size 13 (for coach bolts)
- Long spirit level
- Spade
- Staple gun (for the geotextile)
- Possibly an auger for tie-back anchors in soft soil
How do you install a bank revetment yourself? Step-by-step
Below is the guide from start to finish. Work calmly and measure twice.
Step 1: Determine the height and calculate your materials
Measure the retaining height: the height difference between your ground and the water. Everything else follows from that.
The rule of thumb for posts: 1/3 above the ground, 2/3 below. At a retaining height of 100 cm you use posts of 300 cm.
For the number of posts, count two posts per metre, plus one extra. For 10 metres of revetment you therefore need 21 posts.
Choose boards or ready-made panels of at most 100 cm high per piece. Hardwood posts of 7×7 or 8×8 cm are standard.
Step 2: Prepare the bank
Cut the bank line straight. Remove loose soil, roots and growth.
This is much easier with a low water level. So preferably wait for a dry spell, or work in winter when ditches are lower.
You want a clean, straight line where the boards will later sit tight against the soil.
Step 3: Set the posts
Drill the holes every 50 cm along your marked-out line. Set the posts in and drive the last 20 cm home with the hammer or drive cap.
Tilt each post about 5 degrees towards the ground, so leaning slightly inward. The soil will push against the wall later, and that slight lean absorbs it.
Check with the spirit level that all posts stand straight and at equal height. This is the foundation of your whole revetment, so take your time here.
Step 4: Fit the boards
Screw or bolt the boards horizontally against the posts. Start at the bottom and work up layer by layer.
Use three fixing points per post and make sure the boards join well against each other. No gaps, because that’s where the soil washes through.
If you work with M8 coach bolts of 120 mm, tighten them with the size 13 ring spanner. Loose boards you can fit with galvanised 50 mm Torx screws.
Step 5: Apply the geotextile
This is the step many people skip, and that’s a mistake. Fix geotextile against the back of the boards with the staple gun.
The fabric lets water through but holds back soil and sand. Without geotextile, your bank still empties out through the seams between the boards.
Let the fabric stick out a bit above the top edge; you’ll trim it neatly later.
Step 6: Place tie-back anchors in soft soil
Is your revetment standing in soft or wet ground, or is it higher than about 60 cm? Then place tie-back anchors.
Set them every 2 metres, or closer with a lot of soil pressure. A tie-back anchor anchors the wall backwards into the ground, so it doesn’t tip forward.
Step 7: Backfill and finish
Backfill the soil gradually against the back. In layers, and not all at once.
Too much pressure at once pushes your fresh wall crooked or forward. So take it easy.
Finish with a capping strip or a hardwood ledger on top. That gives a clean finish and protects the top of your boards from rain getting in.
Do you work dry or underwater?
Both are possible, but dry is always more pleasant and tidier.
Working dry, you see exactly what you’re doing and set the posts straight easily. Lower the water level if needed or wait for a dry spell.
If you do have to work underwater, count on a muddy, less stable base. The posts then have to go extra deep, and tie-back anchors are almost always needed.
For a garden pond you can usually pump it partly empty. That makes the job a lot more manageable.
Common mistakes when installing a bank revetment
These mistakes cost you the most work later. Avoid them straight away.
Posts too shallow. If you don’t stick to 2/3 in the ground, the wall sinks or tips. This is mistake number one.
No geotextile. Without the fabric, your soil washes away through the seams and within a few years you still have a sunken bank.
Too little anchoring. With high walls or soft soil and no tie-back anchors, the whole thing starts to move and warp.
Backfilling too fast. Pushing it all in at once shoves your new wall forward. Backfill layer by layer.
Wrong screws. Ordinary steel rusts and marks your hardwood black. Always stainless steel or galvanised.
Forgetting the notification. Quickly sending a notification to the water authority is done in no time and prevents problems afterwards.
Frequently asked questions
How deep does a revetment post need to go into the ground?
At least 2/3 of its length. At a retaining height of 1 metre you use a 3-metre post, of which 2 metres sit in the ground and 1 metre above it.
How high can I install a revetment myself?
Up to about 1 metre retaining height it’s fine to do yourself, with some DIY experience. Above that, the soil pressure gets so big that you really need heavier constructions and usually machines. Then you’re better off calling in a specialist.
Do I need a permit?
For a revetment up to 1 metre, a free notification to the water authority is usually enough, not a permit. Rules vary by authority, so always check first before you start.
How long does a bank revetment last?
Hardwood 25 to 50 years depending on the thickness. Plastic and composite 50 years or more and virtually maintenance-free. Stainless steel fixings are a must with these.
What does a revetment cost if I install it myself?
Materials only: for hardwood 85 to 200 euros per running metre, for plastic 90 to 175 euros. Posts come on top, 25 to 60 euros each. If you have it installed, add 50 to 150 euros of labour per metre.
What’s the best material for a garden pond?
For a garden you usually choose hardwood (a nice natural look) or plastic (maintenance-free and light to work with). Both last for decades. Steel sheet piling and concrete are for heavier jobs.
When is the best time to install a bank revetment?
In a dry spell or in winter, when the water level is low. Working dry is easier, tidier and more stable than mucking about underwater.
Get started
Installing a bank revetment isn’t rocket science, but good preparation saves you a lot of repair work. Measure your retaining height, choose your material and sketch out your bank first before you start digging.
Want to lay out your garden project neatly before you begin, or looking for a complete guide with dimensions? Have a browse through the building plans and garden projects at fredsdiyplans.com. Then you know exactly what you need and get it right the first time.