How to build a PVC dome for raised garden bed?

TTN

Hi everyone,

I’m looking to build a simple dome structure over my raised garden bed using PVC pipes, similar to this video:
https://www.facebook.com/BlackwoodHomeHardware/videos/1553482165927491/

The goal is to protect young fruit trees from frost in winter and heatwaves in summer.

I currently have two types of garden beds:

• Type 1: Round bed (diameter ~97 cm)
• Type 2: Rectangular bed (W31 × L183 × H74 cm)

I’d really appreciate your advice on a few things:

1. Pipe size: 20mm vs 25mm
   

Would either of these be suitable for bending into a dome shape?

Holman 25mm x 3m Class 12 PVC Pressure Pipes https://www.bunnings.com.au/holman-25mm-x-3m-class-12-pvc-pressure-pipes_p4770099
Holman 20mm x 3m Class 12 PVC Pressure Pipes https://www.bunnings.com.au/holman-20mm-x-3m-class-12-pvc-pressure-pipes_p4750039

I’m aiming for something that bends easily but is still stable.

2. Connecting the top of the dome:
In the video, they mentioned using a cross connector to hold the two pipes together at the top.
I’m not quite sure what this piece looks like. Could someone point me in the right direction?

3. Securing the pipes into the soil:
I’m thinking of using reinforcing bars like these:

Jack 12 x 300mm Reinforcing Bar https://www.bunnings.com.au/jack-12-x-300mm-reinforcing-bar-5-pack_p0231508
Jack 12 x 600mm Reinforcing Bar https://www.bunnings.com.au/jack-12-x-600mm-reinforcing-bar-5-pack_p0231504

Would 300mm be sufficient, or is 600mm a better option for stability?

4. Transporting the pipes:
For 3m (or even 6m) pipes - How do people usually transport these home?
Is it possible to bend them into a small SUV?

5. Alternative approach (modular frame)
I’m also considering building a square/rectangular frame using shorter pipes and connectors (based on Holman’s garden cover guide):
https://www.holmanindustries.com.au/garden-cover-guide/

With the modular frame, I will use coupling, 3 way and 4 way corner connectors to connect a bunch of 1m pipes together. My concern is how stable the structure will be. My raised bed is already 70cm above the ground.

Any suggestions, improvements, or alternative ideas would be greatly appreciated.

Thanks in advance for your help! 🌱

JacobZ

Hi @TTN,

That sounds like a great project that I'd love to help out with.

1. Pipe size (20mm vs 25mm)

Both will bend, but they will behave a bit differently as their flexibility won't be the same. 20mm is going to be a bit easier to bend and better for smaller domes like your round bed. The downside is it’s a bit more flexible so it can wobble in wind. 25mm is stiffer and stronger, better for your longer rectangular bed, but it's going to be harder to bend into a tight dome.

If you’re only buying one size, I’d lean toward 20mm for ease of use, then just add more hoops if you find that you need extra strength.

2. Top connector

What they’re referring to is a 4-way cross fitting that looks like this.

From what I can see, they seem to be in limited supply in our network and are not currently being shown on our website. What I'd suggest, if you are hoping to use them, is to give your local store a call and have the team check if they have any in stock. The item number for the 20mm variant is 0139319.

That said, a lot of people skip this for domes and just cable tie or clamp the pipes together at the top. It’s simpler and actually gives you a little bit more flexibility as the pipes do not need to connect at perfect 90-degree angles.

3. Securing into the soil

Use the 600mm lengths, especially since your beds are raised and more exposed. The extra depth makes a big difference in stability.

4. Transporting pipes

3m lengths might fit through your car depending on what it is, so it is certainly worth a try. If this does not work, then you can speak to the team about use of our courtesy trailers or hiring a vehicle such as a van or ute. Alternatively, we can arrange delivery to your home through the Trade Desk at your local store.

5. Modular frame option
That style works, but it’s more rigid and can catch wind more than a dome. Domes are popular because they flex and shed wind better. For a raised bed, that’s a big advantage.

If you go modular, just make sure it’s well anchored, otherwise it can wobble or lift.

Let me know if you have any further questions or require some help along the way and please remember to post some pictures when it is done. It'd be fantastic to see it once it is done.

Jacob