How to Build a Wicking Bed in Australia: The Complete Guide

If you’ve ever watched your raised garden beds turn into a dusty wasteland during an Aussie summer, wicking beds might just change your life. They’re not new — people have been building them for years — but they’re having a proper moment right now, and for good reason. When water restrictions tighten up and your council starts sending passive-aggressive letters about hose usage, a garden that waters itself from the bottom up starts looking pretty bloody clever.

I’ve built more wicking beds than I can count, from dodgy first attempts with recycled IBCs to properly engineered timber setups. This guide covers everything you need to know about how to build a wicking bed in Australia — materials, costs, step-by-step build process, and which plants absolutely thrive in them.

What Actually Is a Wicking Bed?

A wicking bed is a self-watering raised garden bed with a built-in water reservoir underneath the soil. Water is stored in a gravel or scoria layer at the bottom, separated from the soil by geotextile fabric. The soil “wicks” moisture upward through capillary action — the same way a paper towel soaks up a spill.

Think of it like this: instead of watering from the top and losing half of it to evaporation (which is exactly what happens in a standard garden bed during a 42°C Adelaide day), you fill a reservoir at the bottom and let physics do the work. The water moves upward through the soil to where the roots need it.

The Basic Anatomy

Every wicking bed has five key components:

1. A waterproof container — the outer shell that holds everything
2. A water reservoir — the bottom section filled with gravel or scoria (typically 200-300mm deep)
3. An overflow outlet — a pipe or hole that prevents waterlogging (critical!)
4. Geotextile fabric — separates the gravel from the soil so they don’t mix
5. Growing medium — quality soil mix on top where your plants actually grow

The overflow is the bit most people forget. Without it, heavy rain turns your wicking bed into a swamp, and root rot follows fast.

Why Wicking Beds Work So Well in Australia

Let’s be honest — Australia isn’t exactly kind to gardens. We cop long dry spells, water restrictions, and the kind of heat that makes you question why anyone gardens at all. Wicking beds address every single one of these problems.

Water Savings That Actually Matter

Here’s where it gets interesting. A standard raised garden bed in an Australian summer loses 50-70% of applied water to evaporation and drainage. That’s not a guess — that’s what research from various agricultural studies shows.

A properly built wicking bed? Water usage drops by 50-80% compared to conventional garden beds. The reservoir holds water below the surface where evaporation can’t touch it. The only moisture loss is through plant transpiration (which you want) and a small amount of surface evaporation.

In practical terms: where you might water a standard raised bed daily in summer, a wicking bed might only need topping up every 5-10 days depending on size, plant density, and how brutal the weather is.

Perfect for Water Restrictions

Most Australian water restriction schemes allow watering with a hand-held hose or watering can. Filling a wicking bed reservoir through an inlet pipe takes about 2 minutes and uses a fraction of the water. You’re not standing there with a sprinkler watching half of it evaporate before it hits the ground.

Holiday-Proof

Going away for a week or two? A large wicking bed with a full reservoir can keep plants alive for 1-3 weeks without any attention at all. Try that with a standard garden bed in January.

IBC Wicking Beds vs Timber Builds: Which Should You Choose?

This is the big decision, and it comes down to budget, aesthetics, and how handy you are.

IBC (Intermediate Bulk Container) Builds

IBCs are those 1000-litre plastic tanks in a metal cage that you see on farms and industrial sites. Cut one in half and you’ve got two instant wicking bed shells.

Pros:

• Cheap — $50-100 for a used IBC gives you two beds
• Already waterproof — no liner needed
• Quick to set up — you can have a working bed in an afternoon
• Sturdy metal cage provides structure

Cons:

• They look industrial (some people love this, others hate it)
• Fixed size — about 1200mm x 1000mm per half
• Height is fixed at roughly 500mm per half
• Can get hot in direct sun (the black plastic absorbs heat)

Cost for an IBC wicking bed: $150-250 each, all up (IBC, scoria, soil, fittings, geotextile)

Timber Builds

Timber wicking beds give you full control over size and look a lot more polished in a backyard setting.

Pros:

• Build to any size or shape
• Look great — especially with hardwood or treated pine
• Can be built to ergonomic height (great for older gardeners or anyone with back issues)
• Better insulation than plastic

Cons:

• More expensive
• Need a pond liner (adds cost and another failure point)
• More complex build
• Timber eventually rots (even treated pine has a lifespan)

Cost for a timber wicking bed (2400mm x 1200mm): $350-600 each, depending on timber choice and liner quality

The Honest Cost Comparison

The IBC is clearly cheaper, but the timber bed gives you roughly twice the growing area. Per square metre of growing space, they’re actually pretty comparable.

Step-by-Step: How to Build a Timber Wicking Bed

Right, let’s build one. This is for a 2400mm x 1200mm timber wicking bed — a good all-purpose size.

Materials List

• 6x treated pine sleepers (200mm x 50mm x 2400mm) or equivalent hardwood
• 1x EPDM pond liner (3m x 2m minimum — you need overlap)
• Approximately 0.3 cubic metres of 20mm scoria or blue metal
• 1x roll of geotextile fabric (non-woven, not weedmat)
• 1x 25mm PVC pipe (for inlet — about 1m length)
• 1x 25mm PVC elbow fitting
• 1x 25mm overflow fitting or bulkhead connector
• Quality potting mix / raised bed soil (approximately 0.5 cubic metres)
• Compost and aged manure
• Coach screws or heavy-duty timber screws
• Drill, saw, spirit level

Step 1: Build the Frame

Construct a rectangular frame from your sleepers. For a 600mm tall bed, you’ll stack three sleepers high on each side. Screw them together solidly at the corners — these beds get heavy once filled.

Make sure the frame is level. This matters more than you think — if it’s not level, one end of the reservoir will be deeper than the other, and water distribution gets uneven.

Step 2: Line It

Lay your EPDM pond liner inside the frame, pressing it into all corners and up the sides. Leave at least 100mm of overlap at the top — you’ll trim this later. EPDM is the go-to here. Don’t use cheap plastic sheeting; it’ll degrade in UV and develop pinholes within a year or two.

Pro tip: Do this on a warm day. EPDM is much more flexible when it’s warm and moulds into corners more easily.

Step 3: Install the Overflow

This is the most important fitting in the entire bed. Drill a hole through the liner and frame at exactly 200mm from the bottom (or whatever depth you’ve chosen for your reservoir). Install a bulkhead fitting or overflow pipe.

The overflow ensures water can never rise above the reservoir level into the soil layer. Without it, you get waterlogged soil, anaerobic conditions, and dead plants.

Step 4: Install the Inlet Pipe

Take your 25mm PVC pipe and attach an elbow to one end. The vertical section sits inside the bed, reaching from above the soil line down to the bottom of the reservoir. The elbow at the bottom sits on the base of the liner.

Some people drill small holes in the bottom section of the inlet pipe to help distribute water. I reckon it helps, but the scoria does most of the distribution work anyway.

Step 5: Add the Reservoir Layer

Pour in your scoria or blue metal to a depth of 200mm. Scoria is lighter and arguably better (it’s volcanic rock — very porous), but blue metal works fine and is often cheaper. Level it out.

Step 6: Lay the Geotextile

Cut your geotextile fabric to size with about 100mm of overlap on all sides and lay it over the scoria. This layer is critical — it stops soil washing down into the reservoir and clogging everything up. Use proper non-woven geotextile, not cheap weedmat.

Step 7: Fill with Soil

Add your growing medium. A good mix for wicking beds is:

• 60% quality potting mix or raised bed soil
• 20% compost
• 20% aged manure or worm castings

Fill to about 50mm below the top of the frame. The soil depth above the reservoir should be at least 300mm for most vegetables.

Step 8: Fill the Reservoir and Test

Pour water into the inlet pipe until it starts trickling out the overflow. That’s your reservoir full. Now water the soil surface once to settle everything in. From here on, you’ll primarily water through the inlet pipe.

Best Plants for Wicking Beds

Wicking beds suit almost everything, but some plants absolutely love them:

Stars of the Wicking Bed

• Tomatoes — consistent moisture means fewer split fruit and less blossom end rot
• Lettuce and leafy greens — the steady moisture keeps them sweet instead of bitter
• Strawberries — fruit stays clean and the even watering produces excellent berries
• Herbs (basil, parsley, coriander, chives) — thrive with consistent moisture
• Silverbeet and kale — almost unkillable in a wicking bed
• Capsicums and chillies — love the warmth and steady water supply
• Zucchini — one plant will feed the whole street (wicking bed or not, let’s be honest)

Plants That Need a Bit of Thought

• Root vegetables (carrots, parsnips) — work well but need deeper soil (400mm+)
• Potatoes — can work but need careful management of soil moisture levels

Skip These

• Mediterranean herbs (rosemary, lavender, thyme) — they prefer drier conditions and can get root rot in wicking beds
• Native plants adapted to dry conditions — they’ve evolved to handle drought, and constant moisture can actually harm them

Maintaining Your Wicking Bed

Wicking beds are low maintenance, but they’re not no maintenance.

Weekly: Check the reservoir level by pouring water into the inlet pipe. If it overflows quickly, it’s still full. If it takes a while, top it up.

Monthly: Check the overflow is clear and not blocked by soil or roots.

Seasonally: Top up soil as it settles and compacts. Add compost and organic matter. Check the inlet pipe is flowing freely.

Annually: Refresh the top 50-100mm of soil with compost. Consider a liquid seaweed feed through the inlet pipe — it does wonders.

The Flushing Trick

Every few months, deliberately overfill the reservoir and let water flush through the overflow for a minute or two. This washes out any salt buildup in the reservoir layer. In areas with hard water, this is especially important.

Scaling Up: Multiple Wicking Beds

Once you build one, you’ll want more. Trust me. Here’s how to think about scaling:

• Three beds (each 2.4m x 1.2m) gives you enough space to feed a family of four with fresh vegetables year-round in most Australian climates
• Connect inlet pipes to a single hose point for easy filling
• Add a timer and float valve to automate reservoir filling entirely — this is where it starts getting into set-and-forget territory

If you’re keen on taking your wicking beds to the next level with automation — float valves, soil moisture sensors, and smart irrigation — Set and Forget: The Aussie Guide to Automated Gardening covers exactly how to turn a wicking bed setup into a fully automated food production system. It’s the logical next step once you’ve got the basics down.

Common Mistakes to Avoid

Using the wrong liner. Cheap poly sheeting will fail. Use EPDM or food-grade pond liner. It’s more expensive but lasts 20+ years.

Forgetting the overflow. I’ve said it three times now. That’s how important it is.

Soil too shallow. If the soil layer is less than 250mm, you’ll struggle with most vegetables. Aim for 300-400mm.

Using garden soil instead of potting mix. Garden soil compacts in raised beds and wicks poorly. Use a quality potting mix as your base.

Not enough organic matter. Wicking beds love rich soil. Be generous with compost and aged manure.

Building in full shade. The wicking bed handles the water — you still need to give your plants adequate sunlight. Most vegetables want 6+ hours of direct sun.

Final Thoughts

Wicking beds are genuinely one of the best things you can build for an Australian garden. They save water, reduce maintenance, produce better yields, and survive the kind of heat that kills conventional gardens.

Whether you go the cheap-and-cheerful IBC route or invest in a proper timber build, you’ll wonder why you didn’t do it sooner. Start with one, learn the system, then scale up. Your water bill — and your plants — will thank you.