How to Construct a Basic Concrete Jetty

A basic concrete jetty extends your shoreline access, supports light boats, and withstands seasonal water-level changes better than timber alone. Building one is a weekend-to-weekon project for two handy adults who can mix and move concrete steadily.

The finished structure rests on driven posts, a simple reinforced slab, and rubble footing that lock it in place against waves and ice push. Expect muddy work, sore muscles, and a permanent asset that outlasts any prefabricated dock kit.

Choose the Site Before You Touch a Tool

Stand on the shore at lowest water and picture the line where your pier will end. If the lakebed drops quickly, start the jetty closer to shore so you need fewer posts and less concrete.

Walk the footprint at both high and low water to confirm you will not block neighbours’ access or boat lanes. Mark four corner stakes on land and run a string line out to the desired tip; any bend in the string signals a snag or shallow rock that will complicate post driving.

Count how many posts you can place in a straight run without hitting submerged logs; each extra angle adds labour and bracing. If you hit soft muck, plan wider footings; if you hit hardpan, budget for a rented auger or water jet to seat posts deeper.

Design the Jetty on Paper First

Sketch a rectangle 0.6 m wide by 3 m long for a basic fishing pier; scale up only if you own a boat that needs side-tie space. Add a 0.4 m knee-high curb on the edges to keep rods and tackle from rolling off.

Draw every post at 1.5 m centres; closer spacing wastes concrete, wider spans risk slab cracks. Note the top elevation 0.3 m above normal high water so waves splash under, not over, the deck.

Calculate Materials from the Sketch

Count posts: length of jetty divided by 1.5 m plus one extra for the outer corner. Allow one 20 kg bag of ready-mix concrete per post for the footing and two more bags per square metre of deck.

Buy 10 mm rebar rods equal to the total jetty perimeter plus 20 % for overlaps. Add one roll of 150 mm mesh for the slab; offcuts become post ties.

Gather Tools and Supplies in One Trip

Rent a manual post driver, a wheelbarrow, and a concrete mixer for one day; buying them is overkill for a single jetty. Bring a sledge, water barrels, shovels, float, and a 2 m straight board for levelling.

Pack safety gear: gloves, rubber boots, and a life jacket for anyone who works past knee depth. Keep a spare length of rope to tether tools to the jetty frame; dropping a shovel in murky water kills momentum.

Set and Brace the Posts

Drive the first post at the shore end until the top sits 0.2 m above planned deck height. Check vertical with a short level every few blows; a leaning post is easier to fix now than after concrete sets.

Work outward, aligning each new post with the string line and the previous top. When the driver rings instead of thuds, the post has hit refusal; stop and cut the top square.

Lash horizontal braces between pairs of posts at mid-depth to keep them from drifting while you place footings. Leave the braces loose enough to slide up later when you pour the slab; you will cut them off after the concrete cures.

Pour Post Footings Underwater

Slip a 200 mm cardboard tube down each post to 0.3 m below the lakebed; the tube keeps concrete from washing away. Mix the first batch stiff, like oatmeal, and shovel it through a funnel made from a cut jug.

Poke the mix with a thin rebar rod to release trapped air; underwater concrete sets colder, so eliminate voids now. Stop filling 100 mm below the future slab bottom; this lock joint bonds post to deck later.

Build a Simple Reinforced Slab

Nail 150 mm wide boards across the posts to form the slab edge; the top of the board becomes your finished deck level. Drop the 150 mm mesh into the box and chair it 50 mm above the footing tops with broken bricks or stones.

Lay two 10 mm bars around the perimeter, overlapping corners 300 mm and wiring them to every post. These bars absorb edge impact from boats and ice sheets.

Mix concrete in small batches so you can place and screed before bleed water appears. Work a wooden float in wide arcs to push aggregate down and bring fat cream up for a smooth, slip-resistant finish.

Add Curb and Rub Rail

Strip the forms after 24 hours and screw a 100 mm by 50 mm timber along each edge; this curb stops wheels and feet from sliding off wet planks. Pre-drill the timber and use 150 mm hot-dipped screws so you can replace it years later without chipping concrete.

Run a 50 mm PVC pipe through the curb every 2 m as a rod holder; cap the ends with rubber plugs to keep spiders out. A coat of raw linseed oil on the timber slows rot and gives a non-glare surface.

Cure and Protect Fresh Concrete

Flood the slab with lake water twice a day for a week; gentle curing prevents surface cracks that salt or ice could widen. Drape wet burlap over the deck if sun is harsh; concrete that dries too fast powders underfoot.

Avoid placing anchors, chains, or fuel cans on the slab for the first month; early loading can hairline the underside where you cannot see. After 28 days, a single coat of clear concrete sealer brushed on edges slows freeze-thaw spalling.

Install Basic Access Hardware

Lag a 200 mm galvanized ring to the outer corner as a bow line point; locate it 100 mm below deck so cleats sit flush. Add two recessed pad eyes on the inner face for spring lines; keep them back from the edge to prevent tripping.

Slip a short ladder made from 20 mm galvanized pipe down the side; hang it with removable pins so you can lift it before winter ice. One ladder rung every 250 mm matches most dock steps and saves knees.

Maintain the Jetty Year-Round

Each spring, wiggle every post; if one shifts more than 5 mm, pack fresh grout around its base before waves worsen the gap. Tap the slab edges with a hammer; a hollow sound signals delamination that you can patch with vinyl cement.

Swap the timber curb for a new board when cracks open enough to snag rope; untreated, it lasts about seven seasons. Grease the ladder pins and ring shackle each fall so they open next year without a fight.

Remove the ladder and any loose gear before ice-in; flowing ice will shear off anything proud of the deck. A jetty left clean stands ready when you return, no matter how high the spring runoff rises.