Raised garden bed - Timber sleeper or Limestone bricks?

[Abhi_2691]

Hi,

I’m planning to build a garden bed in my backyard, which measures approximately 12.5 metres in length. I’d appreciate your advice on whether timber sleepers or limestone bricks with mortar would be the better choice.

Is the decision primarily based on aesthetics, or are there practical or long-term durability considerations that make one option more suitable than the other?

Also, I’ll be installing reticulation in the area, if that makes any difference to your recommendation.

Thanks in advance for your guidance.

[MitchellMc]

Hi @Abhi_2691,

What height are you planning for the garden bed? The answer can make a big difference in whether timber or limestone will be the more practical choice.

If you’re going for something fairly low — say, one or two sleeper courses high — treated pine or hardwood sleepers are generally quicker and cheaper to install. They’re also easier to cut to length, and you can usually anchor them with simple steel posts. The downside is that even treated timber will eventually break down from constant moisture and soil contact, especially if your reticulation regularly wets the inside face. You can slow that process down with a liner and by keeping irrigation aimed at the plants rather than the walls, but you’re still looking at a lifespan of perhaps 10–15 years for softwood, or longer for hardwood.

Limestone blocks with mortar, on the other hand, are a bigger upfront investment in both time and cost, but they’ll last for decades with minimal maintenance. They won’t rot, they won’t attract termites, and they can handle constant soil contact without issue. They also offer a more permanent, structural look and can help with retaining if your garden bed doubles as a small wall. The trade-off is that you’ll need a solid footing, and the build is more labour-intensive, especially if you’re mixing and laying mortar.

Reticulation itself won’t be a problem for either option if it’s designed well, but limestone’s durability makes it the more “install and forget” choice, while timber will require some eventual replacement. 

Please let me know if you have any questions.

Mitchell

[Abhi_2691]

Hi Mitchell,

Thank you for explaining this so clearly.

The height I’m looking for is 350 mm, matching the existing 350 mm retaining wall at the back. I’ve attached a photo of the backyard for reference.

I also think limestone would be a good option; however, I’m considering the amount of labor involved, as I plan to do it myself.

Given the grass at the front, there will likely be water splashing onto the timber sleepers, which could shorten their lifespan.

[MitchellMc]

Thanks for the extra info and photo @Abhi_2691. 350 mm height is a good, manageable size for either material.

Given that height, limestone bricks would offer superior durability and longevity, especially since water splash from the grass could accelerate timber decay over time. The downside, as you mentioned, is the extra labour involved with laying mortar and ensuring a solid, level base.

Timber sleepers would be quicker and easier to install yourself and still look great, but you’d need to accept that with regular moisture exposure, their lifespan may be shorter. Using a good quality timber, adding a moisture barrier or liner on the inside, and directing irrigation away from the sleepers can help extend their life.

If labour is a big concern and you want a balance, you might consider using concrete sleepers—they’re easier to install than limestone with mortar and more durable than timber but come at a higher cost.

Mitchell