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I plan to put sandstone blocks around this area as garden edge. The paver side is 600 higher than the concrete side. The sandstone I bought is 600(length) x 300(height) x 120(thickness) mm size. I only plan to lay one course. I have a few questions:W
1. Do I need any base layer below the sandstone block? What kind of base layer should I put down first?
2. Given I need to ensure each block is level, and the next block will drop a bit of height, I need to do it one block at a time right? i.e. I cannot put down all the base layer sand and then put all blocks.
3. I want to add grout between each block (for better looking), how much gap should I leave between each block for grouting?
Hello @renshao
Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about laying your sandstone blocks.
You have a very good plan for this garden edging project, and the sandstone blocks you have chosen will create a strong and attractive boundary between the concrete and paved areas. Because of the 600 mm height difference and the size of your sandstone blocks, preparing the right base and setting method will be important to ensure both stability and a professional finish.
A proper base layer is essential beneath the sandstone blocks. The type of base depends on the level of load and soil movement expected in the area. For garden edging that holds soil but does not carry heavy traffic, a compacted road base or crushed rock foundation works best. Lay around 75–100 mm of road base, compact it thoroughly using a hand tamper or plate compactor, and then spread a 20–30 mm layer of coarse bedding sand or mortar mix to help with levelling and minor adjustments. This combination creates a solid and stable footing while still allowing some flexibility when positioning the blocks.
Because your garden edge steps down gradually, it is best to install the sandstone blocks one at a time. Avoid preparing the entire base at once. Instead, level and set the base for one or two blocks at a time. Begin at the highest point, ensuring the first block is perfectly level both side to side and front to back. Each following block can then be adjusted to follow the slope consistently. A string line or long level will help you maintain a smooth, even top line while stepping down gradually as required.
For a refined and cohesive look, leave a 10–15 mm gap between each sandstone block. This joint width allows for neat grouting and accommodates small variations in block size. Use a flexible landscape adhesive or stone bonding product suitable for outdoor use, such as Sika Landscape Adhesive or If you prefer a full mortar joint, a traditional mix of four parts brickies sand to one part cement, with a bonding agent like BondCrete, will achieve a strong and durable finish. Apply the mortar cleanly between the joints and smooth it once it begins to set.
Please remember to wear personal protection such as gloves and goggles when working on your project.
If you have any other questions we can help with, please let us know.
Eric
You are correct, @renshao. If you use only coarse bedding sand, it won’t harden when exposed to moisture. Sand alone acts as a levelling layer but remains loose, which is fine for minor adjustments and small blocks, but for taller sandstone blocks like yours, it’s better to use a mixture that will harden and lock the blocks in place.
A common approach is to use a sand-cement mix. This will allow you to adjust the block as you place it, but it will harden over time to provide a stable base. For extra bonding and durability, you can also add a bonding agent, such as BondCrete, to the mix. Spread about 20–30 mm of this mixture under each block, level it, and place your sandstone block on top, pressing gently to ensure good contact.
This method gives you the flexibility to fine-tune each block while ensuring your garden edging is solid, stable, and long-lasting once the mix cures.
Please let me know if you have any questions.
Mitchell
Thanks @MitchellMc and @EricL for your advise. I've started laying the sandstone blocks and they look really good. I have another question. For the corner block I need to cut the sandstone in a diagonal line. I used a 230mm grinder to cut from both side but the blade is not big enough to cut through. Can I use a chisel to cut the middle bit out? Should I use a normal chisel or a chisel bit on a hammer drill ? Could you recommend something that I can use to cut the remaining bit out ? (hopefully affordable too). Thanks!
Ren
Hello @renshao
I propose looking at using either a Trojan 115m Brick Bolster or a Trojan 600g Steel Brick Hammer. Both tools are designed to chip and break brick or stone.
Please remember to wear personal protection such as gloves, goggles and a mask when working on your project.
If you need further assistance, please let us know.
Eric
