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Hi guys! We recently had a retaining wall done with sandstone blocks. We went with B grade cuts not thinking about how the soil would fall out of the cracks. Can anyone suggest a way we could plug up these holes to stop the soil from flowing out that wouldn’t be overly obvious?
Hello @Liv95
Thanks for sharing your question about your sandstone retaining wall. Due to the large gaps in your sandstone, I suggest using Easy Mix 20kg White M4 Mortar in combination with Brunnings 20kg Landscape Paver Sand to add a rough finish in combination with Dulux Avista Oxide 1kg Sandstone Cement Colouring. Your goal is to try and mix the mortar in to a colour that is very close to your existing sandstone.
I recommend using a shop vac to remove the sand that has been trapped in between the sandstone. Do not overfill the gap as you want the filler to look as natural as possible. Do not add too much water to the mortar so that it will hold its shape and not turn into slurry.
Let me call on our experienced members @Dave-1 and @Nailbag for their recommendations.
If you have any other questions we can help with, please let us know.
Eric
Good Evening @Liv95
Now that is an interesting one! 
How much time do you have comes straight to my mind 
So first off I would also have chosen B grade cuts, why not Id say. Save me a bundle of money that I can spend elsewhere
The reason why I ask how much time is my answer will take a little bit of time to do but really should hold up long term.
Since you soil hasnt had a chance to trully settle I would suggest to do this for every join, dig out so you dig down to the base of each join, well maybe 5cm bellow it. Tamp the area with a timber offcut. Say 35 * 70mm and just ram down on that spot.
Purchase some Tuscan Path 30-50mm 15kg White Pebbles or similar sized pebbles. These are fill.
Purchase some 3mm Felt Light Grey 90 cm From Spotlight. Dosnt have to be from spotlight or the same material. Something close weaved that will last awhile in the ground. I used old upholstery material that was going to the skip bin fro my retaining walls.
You could use a strip of the cloth material maybe 30cm wide over the rear of the sandstone blocks on the joins as I fine filter to stop the soil fines from flowing through.
Now its pretty much a slow tetris game.
Slowly use those white pebbles and place one in the middle of the join, then two either side. Then back fill the bit behind, keep working your way up and tamp evey so many rows. Not hard just to compact a little. I would do 1 larger rock then the join and then two smaller stones behind it, you could do more if you wanted. Its just a layering exercise from then on. The rocks will naturally wedge into the join.
Here is an example of my retaining walls that I used old upholstery cloth on, Step 4 is the one that shows you how I used mine. For you as your wall is solid except for the join I would just go with a 30cm cut over the join. You could put the cloth against the stone or after the pebbles. Probarly be easier against the stone tho. Gabion wall for front pathway
If you work your way along the wall you will close out the joins. You should be able to see the cloth or bebbles as they will be at the back of the stones.
Dave
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