How to repair large chip in sandstone?

[nila]

Hi I have a brick fence which sits on some sandstone supports. The inside of one block has a large chip and crack. I am going to build a garden in that section, but I wanted to fill in the chip. I was wondering what substance you would recommend using. I originally thought about using a lime mortar to allow the stone to breath, but it seems to be a specialist product - would another product work without destroying the sandstone further? 

[JacobZ]

Hi @nila,

Welcome to the Bunnings Workshop community, it is great to have you with us.

Do you know what caused the crack? Was it a sudden impact? Was it the weight bearing down on top of it? 

It looks to me like there might be a void underneath the sandstone block. My suspicions are this could play a part in what has caused the crack.

Before I looked to conduct a cosmetic repair, I would be looking to fix the underlying issue. As this is of a structural nature, it would be worth having a professional, such as an engineer assess the wall.

Let me know if you have any other questions.

Jacob

[nila]

Thanks JacobZ for coming back. I believe the crack was caused some time ago by a thick layer of tree roots which I've removed. The prior repair seems to be old - I'd guess at least 20 years old. I've been cleaning out the area in front on the wall to create a garden and a concrete slab which exposed the chipped sandstone. I washed down the wall today which removed a little more dirt which has given the illusion of a void but there are brick foundations under the sandstone block which aren't as wide as the sandstone creating the void. I believe the wall was made in the 50s so I think it's fairly stable. Does that make a difference? 

[JacobZ]

Hi @nila,

Thank you for the added information.

If you are confident that the issue is not a structural one, and the problem causing it has been removed, I think it should be fine to proceed with a cosmetic repair. It's worth noting that whatever you do is only going to mask the fracture beneath and should be treated as a temporary fix that may need to be repeated in the future.

You should start by thoroughly cleaning the stone of all loose material, then applying Bondcrete to the affected area. This is a multi-use concrete additive that can be used, following their instructions, as a bond coat to increase adhesion.

Then mix Dulux Avista Oxide 1kg Sandstone Cement Colouring with Dingo Mortar Mix following the instructions on the packaging. It is worth mixing a small test batch, to best colour match before committing to mixing up the whole product.

You would then need to apply the mortar and shape it to match the existing stone. This could be done using a brick trowel or a timber form.

Please remember to wear all necessary personal protective equipment when working with cement products. This includes a mask, gloves and eye protection.

Allow me to tag some of our knowledgeable members to get their opinions on how they'd go about this repair @Dave-1, @Nailbag, @Jewelleryrescue.

Let me know if you've got any further questions.

Jacob

[Dave-1]

Afternoon @nila 

I like the idea of a cosmetic repair before you put in your new garden bed  @JacobZ suggests a way to do it and I think it may be the easiest solution overall. I thought the colour was a black oxide lol until I went back and fourth and realised he has matched it well with yoyur sandstone. 

Dave

[nila]

Thanks again @JacobZ and @Dave-1 you both are stars!

[JacobZ]

Hi @nila,

Not a problem.

Let us know if you need any assistance when it comes time to carry out the job.

I look forward to seeing the result.

Jacob

[Nailbag]

Hey @nila again I am with @JacobZ recommendations on how to fix your issue. Just ensure the area is clean (wire brush) and dry before commencing the repair.

Regards Nailbag