What adhesive for loose stone cladding to block wall?

[Hemmas]

I’m looking to apply dry stack loose stone (20-40mm thick) cladding to a new core filled block work wall. The rear of the wall has been water proofed before backfill.

if I’m stone cladding the front face of the wall:

*Do I need to water proof

the wall before stone cladding?

*Do I need to render the wall before applying the Adhesive? If so I assume it would only be a single scratch coat?

*Can I avoid rendering by using a primer instead?

*Is the Davco SMP EVO the best adhesive for loose stone cladding?

*Is there a recommended sealer for once the stone cladding is complete?

 

[EricL]

Hello @Hemmas 

Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about what adhesive loose for loose stone.

Please allow us to double check with our supplier in regards to your intent to use the adhesive to anchor stone to your masonry wall. Although the website does mention stone, I think it refers more to stone tiles. As soon as we have more information, we'll get back to you.

In regards to your other questions, I don't believe there is a need to render the surface of the masonry wall. I propose looking at the Crommelin 1L Natural Finish Penetrating Sealer And Water Repellent to seal the stone surface.

Thank you for your patience.

Eric

[JacobZ]

Hi @Hemmas,

I'm just confirming that our suppliers have confirmed Davco SMP Evo Tile Adhesive is a suitable adhesive for this purpose.

Jacob

[Hemmas]

Thanks Jacob,

Would you recommend a water proofing application, primer or scratch coat render for this job?

[JacobZ]

Hi @Hemmas,

I'm just in communication with the Sika team, who are sending me a specification for stacked stone cladding.

So, I can give you the most relevant information possible, can you advise what kind of stone you were using? The moisture sensitivity of the stone can sometimes be a factor.

They have recommended using Sikalastic 1-K as a negative side waterproofing membrane, which should be standard regardless of the type of stone used.

I just need to confirm whether a specific primer would be needed, and that the SMP Evo is the best choice for your specific stone.

Jacob

[Hemmas]

Hi Jacob,

thanks once again for your help.

I'm looking to use the below stacked stone

https://nuway.com.au/free-form-clouds-random-cladding-20-40mm

could you confirm the negative side waterproofing is applied before the adhesive (including primer if required) and that no scratch coat render or similar is needed?

[JacobZ]

Hi @Hemmas,

The specification I received from the Sika technical team says that the wall should be rendered according to the following recommendation.

"A splash coat must initially be applied to the face, which consists of:

1 Part Lankolatex 751, 1 part water and 2 parts neat cement.

The splash coat should be applied with a brush or broom and must not exceed 2mm in thickness. Whilst the splash coat is still moist and tacky, the render must be laid. 

It is required that 1 part Lanko 751, 3 parts water be used as an added mixture in the render mix in place of water. This enhances adhesion, flexibility, tensile strength, impact/water resistance in the rendered wall. The use of plasticisers in the render mix is not permitted.
 

The render mixture should be:

1 part cement, 3 - 4 parts clean, washed sand

Renders shall be allowed to dry for 5-7 days prior to applications of waterproofing membrane or stone adhesives."

Once the render has dried for 5-7 days, apply a minimum of 2 coats of Sikalastic Sikalastic 1K, allowing it to fully dry between coats.

You should then apply your Davco SMP Evo over the waterproofing membrane and install your stacked stones.

I have forwarded a copy of this specification to your email address for your perusal.

If you had further questions, please don't hesitate to reach out. You could also contact Sika's technical team on 1300 223 348 for further guidance.

Jacob

[JacobZ]

Hi @Hemmas,

Just to add a point that I missed, Sika's technical team recommended using Davelastic Additive mixed 50/50 with clean water to mix your SMP Evo.

This adds flexibility, strength and water resistance to cement-based products such as SMP Evo.

Jacob

[seanl]

 

 

Im about to do the same with a double brick feature wall 3m high. Im going to use davco waterproofing on the whole wall with membran sheet from footing upwards a couple of feet and keep the weep holes (double brick in WA) via plastic weep hole inserts. Then use smp evo as adhesive and develastic, but i get conflicting information online about if there is a requirement for a drainage mat on top of the waterproofing membrane and also what should be used as mechanical support along the way, as the total weight of all cladding is 900kg. Any advice?

[MitchellMc]

Welcome to the Bunnings Workshop community @seanl. It's wonderful to have you join us, and many thanks for your question about cladding.

This is one of those projects where it is very easy to head down a complicated path without realising just how many variables are involved, so it is good you are asking the questions now.

To be honest, this is starting to move well beyond typical DIY territory and into specialist stone and masonry work. Waterproofing membranes are generally used to prevent water ingress into habitable spaces or to protect substrates that are sensitive to moisture. In a standard external brick wall, moisture management is already handled through the cavity, flashing and weep holes. Introducing a membrane behind adhered stone can sometimes create more problems than it solves if it traps moisture rather than allowing the wall to breathe.

The mention of a drainage mat behind the cladding is something you would normally see in ventilated facade systems or engineered rainscreen systems rather than adhered stone finishes. Those systems are designed from the ground up to deal with moisture, drainage and mechanical fixing loads. Adhered stone cladding systems typically rely on the substrate, the adhesive system and the stone size and weight being within the limits specified by the manufacturer. Mixing systems and advice found online can quickly lead to a setup that is not compliant with Australian standards or manufacturer requirements.

The biggest concern here is the total weight you are talking about. Nine hundred kilograms of cladding on a three-metre-high double brick feature wall is significant. Brick walls are not generally designed to carry large additional dead loads applied to one face. The ties, footing design and overall wall construction would not have been engineered with that load in mind. This is very different from standard lightweight stone veneers or tiles. In many cases, heavier stone systems require mechanical fixing systems that transfer load back to the footing or structure rather than relying purely on adhesive.

Adhesive alone is normally considered the primary support for adhered cladding, but only within strict limits on stone size, thickness and weight. Temporary bracing during installation is common, but that is not a substitute for proper long-term mechanical support where required. Once you get into larger or heavier stone, most manufacturers and codes start requiring engineered fixing systems.

Given the height, the weight involved and the fact this is an external wall, I would strongly recommend speaking directly with a stonemason experienced in adhered stone systems, or a structural engineer who can confirm whether the wall can safely take that load and what fixing system would be required. It may also be worth contacting the cladding manufacturer for confirmation that your proposed system is suitable for the application and weight involved.

You are clearly putting a lot of thought into doing this properly, which is good, but this is one of those cases where getting professional advice up front could save you from serious structural, moisture or compliance issues down the track.

Please let me know if you have any questions.

Mitchell