Here is how you build a jetty at the water: first check whether you need a permit (often from both the council and the water authority), then drive or screw hardwood piles of at least 10×10 cm at least a metre into the bed, lay the bearer beams on top at roughly 40 cm centre to centre, and screw the 28 mm hardwood deck on with stainless A4 screws.
Important to know up front: you must not use treated timber in the water (source: Gadero). So use hardwood such as bangkirai, azobé or cumaru, and only A4 stainless fixings, because A4 is the only grade that stands up well to the salt and to the tannic acid in hardwood (source: rvs-bouten-en-moeren.nl).
For the material, reckon on roughly 60 to 100 euros per m2 for hardwood, excluding piles and labour (source: Hovenier.nl). A complete jetty of a few square metres usually comes in between 500 and 2,000 euros as a self-build, depending on the type of wood, the size and the foundation.
Below you read exactly how to tackle it, from the permit check to the last screw.
Can you just build a jetty at the water?
No, usually not just like that. A jetty, a deck or a mooring structure in or beside the water is almost always a structure, and then you often need a building permit.
Which authority you deal with and which rules apply depend on where you live. Check with your local council or planning office whether your jetty is permit-free or needs a permit, and what the local rules say for that spot.
What to watch out for: there are often two authorities involved at the same time.
- The council deals with the building work and with what the local plan allows at that spot.
- The water authority (or the national waterway authority for major rivers and lakes) deals with the water side: building in or along the waterside.
The water authority checks whether your jetty does not obstruct the flow, the maintenance or the bank. Every water authority has its own rules. Some allow a small jetty under general conditions (sometimes only with a notification), others require a proper permit. On narrow watercourses there are often extra restrictions.
A few more things to sort out before the first pile goes in:
- Owner’s permission. If the water or the bank is not on your land, you need permission from the owner (often the council or the water authority).
- Nature rules. In or near a protected nature area, or where protected plants and animals are present, extra permission may be needed.
In short: start your project at the planning office and call your water authority if in doubt. It costs an afternoon of sorting things out, but it stops you having to tear your jetty down again later.
Fixed or floating: which jetty suits your water?
There are two main types, and the choice mainly depends on how much your water level moves.
A fixed jetty stands on piles driven or screwed into the bed. Solid, tidy and suited to most ditches and ponds with a reasonably stable level. This is the classic jetty.
A floating jetty rests on plastic floats and moves with the water level. Handy on water where the level varies a lot, because you always step in and out of the boat at the same height. You do not need piles in the bed, but you do need good anchoring so the jetty stays in place (source: itfloats.nl).
| Fixed jetty | Floating jetty | |
|---|---|---|
| Foundation | Piles in the bed | Plastic floats + anchoring |
| Water level varies | Less suitable | Ideal |
| Bed hard/soft | Needs firm bed for piles | Works on any bed |
| Feel | Solid and stable | Moves a little |
Not sure? On a ditch or pond with a stable level you usually choose a fixed jetty. On water with a strongly varying level, or on a soft peat or clay bed where piles hold poorly, floating is often the better choice.
Which wood do you use for a jetty in the water?
This is where many DIYers go wrong. You must not use treated softwood in the water (source: Gadero). The protective chemicals wash out and that is bad for aquatic life.
In and above the water, work with hardwood. Good choices:
- Bangkirai (durability class 1): strong, hard and very water resistant.
- Azobé: the classic marine construction timber, extremely durable, widely used for piles and bank reinforcement.
- Cumaru: also durable and hard, a little finer in appearance.
If you want low-maintenance work instead, then composite (plastic decking boards) is an option for the walking deck. The support frame and the piles then stay hardwood or steel.
Pay attention to the fixings, because they matter at least as much as the wood.
Always use A4 stainless steel in the water. A4 stainless (also called 316) contains molybdenum, which makes it the only grade that stands up well to chlorine, salt and the tannic acid in hardwood. The cheaper A2 stainless can still be attacked under those conditions (source: rvs-bouten-en-moeren.nl).
Practical: use A4 stainless torx screws (for example 5×50 mm) or A4 stainless bolts, and always pre-drill hardwood with a bit of around 3.5 mm. Hardwood is so dense that otherwise screws break off or the wood splits (source: Gadero).
Construction: dimensions for piles, bearers and deck
The build-up of a fixed jetty is simple: piles, bearer beams across them (the bearers or “joists”), and the walking deck on top. These guide dimensions come from marine timber merchant Gadero.
| Part | Guide dimension |
|---|---|
| Piles (hardwood, square) | at least 10×10 cm |
| Pile into the bed | at least 1 metre |
| Bearer beams/joists | approx. 5×15 cm hardwood |
| Joists centre to centre | approx. 40 cm |
| Decking boards (deck) | at least 28 mm thick |
| Gap between boards | approx. 5 to 8 mm |
A few things to understand behind those dimensions:
Square piles, not round. In winter, ice can squeeze around a round pile and pull it out of true. Square hardwood piles of at least 10×10 cm hold up better (source: Gadero).
Centre to centre 40 cm for the joists means you lay the middle of one beam 40 cm from the middle of the next. The thinner your decking boards, the smaller that spacing needs to be to prevent sagging. With a 28 mm board, 40 cm is fine.
Gap between the boards. Leave 5 to 8 mm between the decking boards. That lets rainwater drain, lets the wood move (expand and shrink), and lets air through, which counters mould and slipperiness.
Handy rules of thumb for buying
(source: Gadero), per m2 of jetty:
- roughly 7 linear metres of decking board (with 14.5 cm wide boards),
- roughly 3 linear metres of bearer beam,
- roughly 4 piles.
That way you quickly work out how much material you need before you head to the timber merchant.
Building a jetty where children come? Then put a railing on it and keep the bottom rail about 20 cm above the deck, so a child cannot slip underneath (source: Gadero).
Driving or screwing piles: the foundation
The foundation makes or breaks your jetty. Broadly, there are two routes.
Driving piles. The classic method: drive or hammer hardwood piles into the bed until they sit firm at least a metre deep. Works well in firm, sandy beds. On a small scale you can manage this by hand with a heavy hammer or a manual pile driver, but it is hard work.
Screw piles (ground anchors). You turn steel screw piles into the ground, without concrete and without driving. Turning them in by hand is often the safest near the water. They are ideal for smaller jetties, especially when the jetty runs parallel to the bank (source: TerraTechs).
When are you better off calling in a professional? TerraTechs advises this for, among others:
- jetties that stick out at right angles from the bank,
- water depth over 80 cm,
- fast-flowing water,
- large structures with many piles.
Mind the bed. Soft ground like clay and peat often has too little load-bearing capacity. In that case a test pile or ground survey may be needed, or you are better off choosing a floating jetty (source: TerraTechs).
Step-by-step plan: how to build your jetty
- Check the permit. Go to the planning office and call your water authority. Sort this first, always.
- Measure out and draw. Set the length and width, and mark out the pile positions. A common jetty is 1 to 1.5 metres wide, long enough to walk comfortably alongside your boat.
- Set the piles. Drive or screw the corner piles first and work out from there. Measure the centre-to-centre distances accurately.
- Work level from the bank. Stretch a string between two piles at the desired height and use a long spirit level or a water level. Keep the deck well above the highest water level you expect, so it does not flood in rain or high water.
- Cut the piles to height and mount the bearer beams level on top with A4 stainless bolts.
- Lay the walking deck. Screw the decking boards down with a 5 to 8 mm gap between them. Pre-drill, always.
- Finish off. Sand rough edges away to prevent splinters, and fit a step, bollards to moor the boat, or a railing if you like.
Tip: pre-build as many parts as you can on the bank and only lift them into the water once they are ready. Working over the water is awkward and risky.
What does building a jetty cost?
The costs vary a lot with the type of wood, the size and the foundation. These material prices per m2 apply to the walking deck (source: Hovenier.nl):
| Deck material | Price per m2 (material only) |
|---|---|
| Douglas fir or larch | approx. 40 euros |
| Grooved hardwood (2.5 cm) | approx. 60 euros |
| Smooth bangkirai | approx. 100 euros |
| Thick hardwood (2.8 cm) | approx. 100 euros |
On top of that come the piles, bearer beams and fixings, plus any screw piles. If you have it fully installed, reckon on 15 to 25 euros of labour per m2, at hourly rates between 35 and 75 euros (source: Hovenier.nl).
For an average wooden deck or jetty, a realistic total is around 925 to 2,100 euros, with outliers up to 3,500 euros for larger or more luxurious projects (source: Hovenier.nl). Do it yourself and you mainly save on the labour, coming in for a small jetty often between 500 and 2,000 euros of material.
Hardwood costs more to buy, but at 20 to 25 years it lasts far longer than softer types of wood (source: Hovenier.nl). For something that gets wet constantly, that pays for itself.
Safety and maintenance
A jetty at the water needs just a bit more attention than a deck in the garden.
- Keep the deck non-slip. Hardwood gets slippery with algae. Grooved or ribbed boards help, and a yearly clean keeps the growth down.
- Work safely during the build. Wear sturdy shoes with grip and work gloves, and try not to work alone over deep water (source: Ecosteigerhout).
- Clean regularly against algae and moss, especially at the waterside where it is always damp.
- Check yearly. Inspect the piles and fixings. Replace a damaged board straight away, before someone puts a foot through it.
- Treatment is usually not needed. Untreated hardwood greys but stays strong. If you want to keep the warm colour, you can apply hardwood oil periodically.
Common mistakes
- Using treated timber in the water. That is not allowed and it is bad for aquatic life. Only hardwood in and above the water.
- Grabbing galvanised or A2 stainless screws. They rust or get attacked by salt and tannic acid. Use A4 stainless.
- Not setting the piles deep enough. Less than a metre into the bed and your jetty will wobble or sink.
- Skipping the permit. Without permission from the council and water authority, you risk an enforcement notice and forced removal.
- Using round piles. Ice can pull them out of true. Choose square hardwood.
- Not pre-drilling hardwood. It splits or your screws snap off.
- Setting the deck too low. Allow for the highest water level, or your jetty floods when the water rises.
Frequently asked questions
Do I need a permit for a jetty?
Usually yes. A jetty is almost always a structure and falls under building rules. You often need permission from both the council (building work) and the water authority (the water side). Check your situation with your local planning office and call your water authority if in doubt.
Which wood do you use for a jetty in the water?
Hardwood such as bangkirai, azobé or cumaru. That is naturally very water resistant. You must not use treated softwood in the water (source: Gadero). For a low-maintenance walking deck you can also choose composite.
Which screws do you use for a jetty at the water?
A4 stainless (316). It contains molybdenum and is the only grade that stands up well to salt, chlorine and the tannic acid in hardwood. A2 stainless and galvanised material get attacked in the water (source: rvs-bouten-en-moeren.nl). Always pre-drill hardwood with around 3.5 mm.
How deep do the piles need to go?
At least a metre, and into firm ground. Use square hardwood piles of at least 10×10 cm (source: Gadero). In soft clay or peat the load-bearing capacity is often too low, so consider screw piles, a test pile or a floating jetty (source: TerraTechs).
Fixed or floating: which is better?
That depends on your water level. With a stable level, a fixed jetty on piles is the most solid. If the water level varies a lot, or the bed is soft, then a floating jetty that moves with it is often the better choice (source: itfloats.nl).
What does it cost to build a jetty yourself?
Reckon on roughly 60 to 100 euros per m2 for hardwood deck material, plus piles, bearer beams and A4 stainless fixings (source: Hovenier.nl). For a small self-build jetty you often come in between 500 and 2,000 euros. Have it installed and you add 15 to 25 euros of labour per m2.
Ready to get going at the water yourself? A good jetty starts with the right dimensions, the right wood and a plan that adds up.
At www.fredsdiyplans.com you will find clear building drawings and step-by-step plans, so you start straight away with the right dimensions and materials. Measure, set the piles, deck on top and moor up. Good luck with the build!