How to fill gaps in Sandstone retaining wall?

[Liv95]

 

 

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? 

[EricL]

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

[Nailbag]

Hi @Liv95 

What @EricL is recommending is exactly what I would be to. It will provide a stable fill, that cosmetically will blend seamlessly with the stone work.

Nailbag

[Dave-1]

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

[Vortech]

Thankyou for your advise as I had a similar situation here.

I was also looking for something like this for the purpose of deterring snakes away which I believe could possibly be hiding within.

The only comment I had in relation to your recommendation is how would water run off be affected? By putting this solution together would it create structural problems for the wall by not allowing water to run through it the event of a storm etc.  

[Dave-1]

Morning @Vortech 

With the stones wedged into the joins they will still allow water to flow so drainage shouldnt be any more of an issue then normal. Snakes will be able to climb the blocks themselves, they probarlly wont be able to dig through the stones in the joins tho You could always put some stainless fine grill mesh behind the joins if concerned.

Dave

[almunderr]

Hi @EricL , I have the same issue and am wondering:

1. Should I mix the Mortar, Paver Sand and Colouring all together? Any idea on ratios?
2. Will this solution hold-up in the rain as water and soil currently goes through these gaps?

Thanks

[MitchellMc]

Welcome to the Bunnings Workshop community @Vortech. It's brilliant to have you join us, and many thanks for your question about filling gaps.

That depends on how much water is transferring through the gaps in the wall at the moment. If you are to seal them all with cement, then the water will need to go somewhere else, or it will be retained behind the wall. If this is an issue, you might consider installing drainage behind the wall to carry the water elsewhere.

Please let me know if you have any questions.

Mitchell
 

[MitchellMc]

Welcome to you, too, @almunderr.

Do you also have sandstone blocks, or is your wall made from a different material? 1 part mortar to 4 parts sand would be a reasonable mix. The colouring is added in small increments until the desired colour is reached.

As mentioned above, if you block the holes with cement, then the water that is currently transferring through them will be blocked. It might then seep through somewhere else or get stuck behind the wall. If this is a significant quantity of water, then you should invest in drainage behind the wall to carry it away to an appropriate location, such as your stormwater pipes.

Please let me know if you have any questions.

Mitchell