How To Build Your Own Self Watering Garden

How To Build Your Own Self Watering Garden

With more people living in  urban landscapes now than ever before, and healthy organic food being on the top of everyone’s mind, having your own veggie garden has never been more important. Growing your own food remains one of the best activities your health, the beauty of your outdoor space, and the joy of your family and overall lifestyle. Even financially, there is simply no better investment than growing your own food.

What’s the key to success? Sun, soil, and water, always water!

Between hot summers and busy schedules, keeping your plants watered is everyone’s biggest challenge, especially for people new to the growing game. To overcome that challenge, you need a self-watering garden. Self-watering gardens and planters feature a watering technique called sub-irrigation to remove the guesswork in watering and simplify the growing process. Water from the bottom up, just like a natural water table! The simplicity and water efficiency make them absolutely ideal for the modern backyard garden and for growing on patios, decks, balconies and urban spaces. 

The efficiency and growing environment of self-watering gardens can’t be beat. They emulate nature, and natural is always right. It makes growing and harvesting your own food simple and easy to understand. Fill the reservoir until it’s full, watch the float gauge, and water wicks up into the soil naturally, evenly, creating the perfect growing environment. Ever read the back of a seed pack where it says “Keep your plants evenly and consistently moist?” That's exactly what a self-watering garden does. 

You’re going to save water, save time, and give yourself the best shot at growing an epicly bountiful organic veggie garden…. Even on your first shot.

Whether you are truly DIY, or using one of our prefab GardenWell kits, here’s how to make your own sub-irrigated planter, or self-watering raised bed.

Instructions for building a self watering planter or raised bed

Plans for a self watering sub irrigated planter box, or raised bed garden

Download our woodwork building guides here - (Coming Soon!)


Click here to view our ProjectGarden Box and get everything you need in one convenient bundle!

Project Garden Box - complete kit of a DIY sub-irrigated self watering garden


Before you start Building, you will need...


  1. Tape measure
  2. Level
  3. Chop saw or circle saw (hand saw works too!)
  4. Drill gun
  5. Stapler
  6. Utility knife


  1. Wood for your garden box, screws etc...

  2. Waterproof, ideally foodsafe liner

  3. An Overflow valve

  4. WaterStem, or tube to water your garden

  5. Reservoir materials.


Step 1: Identifying the best place to grow your garden

You thought we would start with wood and tools? Finding the right spot and preparing it properly, is the key to self-watering garden success. Follow these 4 steps and you’ll be growing in no time. Plus garden boxes can be heavy! It’s best to choose the spot before you build.

1. Sunshine

Most Veggies and herbs require full sun: at least 6-8hrs (or more) of direct sunshine. Some cool weather crops like kale, radishes, and spinach can be grown in lower light conditions – so if 4 to 6 hrs of sun is all you’ve got, you can still grow! But having full sun exposure gives you full choice on the veggies. As you’re gauging the location, consider trees, buildings and other objects that may obstruct the sun during the growing season.

2. Convenience

Position your garden in an area that you frequent regularly, or that you can see from your kitchen/living room. This will make your garden more engaging, easier to maintain, and a bigger part of your lifestyle. You’ll be far less likely to miss out on harvests if you’re walking past your garden everyday!

3. Water
Consider the location of your  water source. The obvious benefit of having a self watering sub-irrigation garden, is that your watering frequency is greatly reduced, but you’ve still got to do it! This isn’t a deal breaker, but being aware of where your hose bib or faucet is in relation to your garden can save some annoyance down the road (I once put a garden about 12” out of reach from a fully extended 50’ hose. Oops!).

4. Level

The self-watering function of your sub-irrigation garden relies upon the reservoir at the bottom of your garden. Water naturally self-levels, so make sure your reservoir is level!

  1. Leveling can be done by digging down or building up.

  2. For digging down: consider what your garden will be resting on. Ensure that whatever surface you choose, it’s free from obstructions or anything that could puncture the liner.

  3. For building up: Framing a bottom on your garden allows you to elevate it to any height. Click here for examples.

Step 2: Building your Garden box or Raised bed.

Building the frame of your sub irrigation self-watering garden box

Before getting started, it’s very important to note the size of the sub-irrigation kit you are using. All GardenWell sub-irrigation self-watering kits are ideal for square foot gardening and come in modular 1’x1’ click together tiles, (here are our standard kits) but in actuality, your  garden can be just about any size.

It’s important to build the interior of your garden to full foot interior measurements to create an ideal fit, and to ensure that your garden is free from any framing or other obstructions on the interior of the garden.

This means no 4x4’s stuck on the interior corners - put your structure on the outside, it’s better practice anyway. It’s not essential, and you can cut the GardenWells to fit your raised bed, but if you can build to the full foot interior, it’s going to make things easier for you!

  • Download our easy to follow Raised bed building plans (coming soon!)
  • Using one of our GardenWell kits? Check out our sizes here

  • Want to build a Sub-irrigated garden for trees or shrubs and require soil depth deeper than 12"? Contact us!

Step 3: Cutting & Folding the Liner

Prefold and cut your liner for your self watering sub irrigation garden planter

(Skip to Step 4 if purchasing a prefab GardenWell Kit)

If at all possible, make sure your liner is foodsafe if you plan on eating what you grow. All GardenWell kits and LIfeSpace Gardens use foodsafe UltraLiner. It’s the toughest best product we have found, and safe for all your vegetables and herbs.

1. Cut your liner.

This can be tricky without a prefab kit, but it’s essential for a leak free planter. Cut your liner so that it can be folded seamlessly into your planter box. Ideally the liner should go to the top of the garden walls for full protection of your woodwork.

At the bare minimum, it needs to go 6” up the sides, to ensure a watertight reservoir with no leaking.

To do this, measure the length and width of the bottom of your garden, and then the inside height of the garden walls.

Add these measurements together and you will have the length and width of the Ultra Liner and where your fold lines should be. It’s good to give yourself a bit of wiggle room and then trim off excess liner once you’re done.

For example: 
Our 2’x4’ kit includes a liner cut to 56” wide by 80” Long. This is for a garden with an interior footprint of 24” W x 48” L and walls up to 16” high.

2. Pre-fold your liner.
Once you have your liner cut to size, it’s a great idea to draw out where you’re going to fold. Find center, then trace out the bottom of your garden to create your fold lines. You want to make sure that the flaps that you’re folding are as even as possible ie: 16” all the way around.

We highly encourage you to prefold your liner before you attempt to install it. Your life will be easier. Our prefab GardenWell Kits come with this step done for you.

3. The Liner is now ready for install.

Step 4: Drilling the Hole for the OverFlow Valve

Drilling the overflow hole for your self watering sub irrigated planter box

1. Drill the hole.
Before installing the liner, it’s a good idea to drill the whole for  your overflow valve.

2. The overflow valve is very important, as it’s the overflow which regulates the height of the reservoir.
You want enough water that it will rise right to the top of the reservoir without going over and flooding the soil in your garden. This is key for proper aeration and self-watering. 

If you are using our GardenWell system your overflow hole must be drilled at a center point exactly 3” up from the interior bottom of your garden. 

3. Also, be conscious of where you want your OverFlow to drain.
We also like to have the OverFlows visible while watering so that you know exactly once the water reservoir is full.

Step 5: Installing the Liner

It should go without saying: DO NOT PUNCTURE THE LINER. It’s very tough, but be aware… a leaking liner defeats the entire purpose. The only hole that should be in your liner is the overflow hole.

1. Place your pre-folded liner into your garden. 

Make sure it’s tucked nicely into the corners.  Over time, water pressure will push it into the corners anyway.

2. Begin by folding the flaps UP.
All folds should end up at the top of the garden… think about how water travels and make sure you’re creating a sealed unit.

3. Dry fit your liner so that you’ve got a nice tight fit.
The next step is stapling, so do any adjustments now.

4. Staple the liner into place along the top of your garden.
Try not to go below 1” from the top of your garden. If you’re going for a nice professional finish, consider the aesthetics of the staple pattern, or like we do, plan for a trim piece and cap for a nice clean finish.

5. Trim excess liner.
Once the top of the liner is stapled, take an exacto knife and trim off any excess liner.

6. If you're using a GardenWell kit, your foodsafe Ultra Liner is now installed. The tricky work is over!

Step 6: Installing the OverFlow 

Installing the overflow into your self watering sub irrigated garden box

1. Find the hole you drilled in the wood for your OverFlow. 

Okay, one more tricky step. Use your finger and press around on the inside of your garden to find it.

2. Use your exacto knife to cut a small X in the center. 

You want the X just a bit smaller than the size of the hole. Consider the size of the rubber washer on the inside of your overflow valve…DO NOT cut an X anywhere close to this size.

Installing the overflow into your self watering planter box

3. Insert overflow valve.
Whatever you have used it needs to be leak free! If you are using a GardenWell kit we have a perfect valve that comes with the kit.

4. Your overflow is now installed! 

You can leave it as is, install a drip chain, or connect a hose to direct water outflow wherever you like.

Step 7: Installing the Reservoir

Installing your GardenWell reservoir into your self watering planter

1. Install your reservoir. 

We’re on the home stretch! If you are using one of our GardenWell DIY kits you just click the 1x1 GardenWell grids together, and then place them inside your box. 

2. If you’re not using GardenWells, you can use crushed gravel, river rock, or any material that can suspend soil above to create a water reservoir below. This ads significant weight, if fairly labour intensive, and reduces the size of the reservoir… but will function well if all other steps are followed.

3. The top of your reservoir material should sit midway or above the OverFlow for ideal drainage.

4. An optimal reservoir to soil ratio for growing veggies is 3” water reservoir to 8”-12” of soil depth. 

Step 8: Insert the WaterStem

Inserting your water stem into your sub irrigated self watering garden box DIY

1. You’re now ready for the final step!
Insert your WaterStem ( the watering tube that gets the water below the soil and into the reservoir) into the pre-drilled hole in your reservoir. It should be nice and snug as you insert the tube all the way to the bottom of the reservoir below where the soil will be. 

WARNING: If you haven’t drilled the hole yet, remove your GardenWells from your garden before doing so. IT IS NOT worth risking a cut into your liner – it will ruin your day. All GardenWell kits come with a GardenWell grid with a pre-cut hole already).

2. If you are using a GardenWell kit, you install the float stick into the tube, and your installation is complete!

Self-Watering raised bed with GardenWell sub-irrigation system installedSelf-Watering raised bed with GardenWell sub-irrigation system installed and growing veggies

You did it! It's time to get growing.

You’re now ready to select and install the right soil blend and get your garden watered for the first time! 

(coming soon!)

Click here to read how to fill your garden with soil, seeds, water and get growing! (coming soon!)

To see our specialized seed packs and square foot growing guides for planter boxes click here

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