How to build Wicking Garden Beds – Part 2

In my previous post, we constructed the base of some self watering wicking garden beds (you can read all about it here).  We made our wicking beds out of old railway sleepers, recycled corrugated iron and other timber we had lying around.  You can make wicking beds out of anything suitable for holding the weight of the gravel and water you plan on putting in them.

The next step is to line the beds with some cardboard or old carpet underlay to protect the water proofing plastic liner.

How to build a wicking garden bed

Cardboard can be used to line wicking beds

If you have some old carpet underlay, you can use it to line the beds.  Most underlay provides a good base that is resistant to rotting quickly.  It doesn’t have to be pretty – just cover the base.

How to build a wicking garden bed

Old carpet underlay is ideal for lining wicking beds

The next step is to line the base with a waterproof membrane.  We initially priced pond plastic, but it is incredibly expensive.  A suitable alternative is builder’s plastic.  We bought a large roll, which we doubled over to give two layers.  The tape holds the plastic in place while we fill it.

How to build a wicking bed

Builders plastic is held in place temporarily with masking tape

Now comes the fun part.  Time to fill the beds with gravel.  We constructed a ramp to make it easier to run the wheelbarrow up and tip gravel into the beds.  This is done in stages.  Firstly a 100mm layer of gravel is put into the base of the beds.  We used 20mm recycled concrete for our gravel bed, mainly because it was extremely cheap.

A temporary ramp for the wheelbarrow helps when filling the beds

After you have a 100mm gravel base, it is time to put in the irrigation pipe.  We used standard 50mm PVC pipe and brackets for the filler tube  or riser.  To distribute the water quickly and evenly through the bed, some 50mm Agricultural Pipe (ag pipe or drainage pipe) was curled around the bed.  The PVC fittings were glued, using PVC glue, however the ag pipe was simply taped to the PVC pipe using cloth tape.

How to build a wicking bed

The Ag Pipe is laid on a 100mm bed of gravel.

Once the filler pipe and ag pipe is in position, the hard work begins.  If you’re able to hire a strapping young lad for this part of the process, then that makes life a lot easier.  We enlisted the help of a friend’s 15 year old and in a few hours of intense labour, managed to fill three of the new beds with gravel to the required depth.

How to build a wicking garden bed

Filling wicking beds with gravel is easy if you have a helper

With the gravel filled to the required depth, it is a good idea to check for level.  You can do this with a fancy sirit level, or by filling the beds with water.

The next step is to put a drain in the beds.  We used a 12mm irrigation pipe, protected by a 19mm pipe.  Some old pantyhose over the end stops mosquitoes from breeding in the beds.

The half inch irrigation pipe is protected by the 1 inch pressure pipe offcut

The drain is hard to spot, and the pantyhose mesh stops mosquitos from entering the beds

Once you have the drain installed it is time to put some weed mat or shade cloth over the gravel.  This helps keep the soil on the top from disappearing into the gravel.  It also allows the moisture to wick into the soil.

Finally it is now time to fill the top third of the beds with soil.  Again it is handy to hire a strapping young assistant for this process, but if you don’t have one to hand, I’d suggest gently asking the person who desired the beds to be built to lend a hand..

How to build a wicking bed

Do not offer advice during this phase of the construction – or you might find yourself wearing some of the wonderful compost!

We were fortunate to source some of the most expensive compost in the world for our garden beds. You buy good quality horse food, and process it through the said horse. Then you mix it with fine quality straw, that is used for a short period as a soft bed, before the horse wees and tramples it into the mud. This product is then turned and mushed for a few days before you rake it and apply it to your garden beds.

How to build a wicking garden bed

Alternating layers of soil and compost helps build organic matter in the wicking beds

And you’re done.  If you’re like us, it will be just in time for winter – a particularly difficult time to grow anything on the Rock Farm.  I guess it doesn’t matter when you finish your project… it is just important that one day you do finish… even if it is 18 months after you started!!!

Good luck and happy vegetable growing ūüôā

How to build Wicking Garden Beds – Part 1

If you think lush green vegetables require too much water to produce  successful crop, or if water is a precious resource, then think again.  Wicking or self watering garden beds may provide the solution you require.  Even of the Rock Farm, we have been able to enjoy some fresh vegetables during a long hot summer by this simple principle.

How to build a wicking garden bed.

Lush green vegetables even in severe drought.

Wicking beds essentially provide water from below, meaning that they are particularly frugal with water consumption, especially during a long hot summer. ¬†They also don’t cost a fortune to make – especially¬†if your wife is a hoarder and you have plenty of old railway sleepers and corrugated iron lying about the place.

The basic concept is simple.  Water is held in a reservoir at the base.  Moisture is drawn up into the soil via capillary action or wicking.  The moisture is distributed more evenly through the soil, creating better growing conditions for plants.

How to build a wicking garden bed.

Basic design principles – wicking bed

The best part is that you can make these beds out of almost any material.  It is simple to modify the style and shape of these beds to suit your garden or materials at hand.

We chose to make our wicking beds in a wedge shape around a central fire pit.  This allowed us to recycle some original railway sleepers.  In this way, each wicking bed only used three sleepers.  The 2400mm sleepers were cut at the 16000/800mm mark to make the wedge shape.  The corrugated iron sheets were 2400mm long.

The first step was to clear the ground where the new beds will go and get everything nice and level.
How to build a wicking garden bed.

Once I was happy that the base was in the right spot, I placed the next sleeper on top, and secured it using a backing plate and bugle head screws.  This is extremely hard work on the electric drill.  Indeed it destroyed my first drill Рso be careful with your drill.  Pre-drilling the holes only helps marginally.


Our wicking beds were designed to be the height of three sleepers.  We anchored the sleepers to each other using the backing plate.  This will be hidden once the beds are constructed.

How to build a wicking garden bed.

After I had built both ends, I fitted a hardwood brace or frame for the corrugated iron.  This brace was cut to the same length as the corrugated iron and will anchor the iron and provide an edge for the beds.  I had to take out a small corner in each end to allow the boards to sit level between the two end sections.

How to build a wicking garden bed.

I then cut the corrugated iron to fit.  You can use tin snips for this, but an angle grinder makes short work of it.  The cut edge is placed on the ground and is buried slightly, and the original edge is placed along the timber frame.  I used regular roofing screws to hold the iron against the frame.

How to build a wicking garden bed.

After I had fitted the corrugated iron, I placed a bracing piece in the centre of each sheet.  This provides an anchor for the sheets and helps prevent the beds from swelling or bulging once the beds are full of gravel and water.

How to build a wicking garden bed.

After I was happy that all was in its place, It was time to scrape back the dirt and smooth out the base of the beds.

How to build a wicking garden bed.

How to build a wicking garden bed.

The bulk of the construction is complete. Now to line and fill the beds

At this time the main construction of the beds is complete.  There is still a whole heap of work to go.

  • The beds need to be lined with old carpet underlay / cardboard to protect the builders plastic.
  • Then the beds need to be lined with builders plastic to make them watertight.
  • A filling tube needs to be inserted to allow the beds to be watered from ‘underneath’
  • Once the pipe-work is installed,the beds need to be filled with gravel to about 2/3rd depth
  • A drain or overflow pipe needs to be fitted at this mark
  • Shade cloth or weed mat is to be laid over the top of the gravel
  • Then soil and compost fills the remainder of the beds.

These steps will be covered in Part 2 of this series.

The beautiful thing with these garden beds is that you can build these with just about any material.  It takes a little imagination and work to bring your ideas to life.  If you have wicking beds, please feel free to share photos of them with me at and I will post them for others to see here.