How to water-proof single skin brick?

[Greg_W]

I need to lay a single skin row of bricks up against sandstone that appears damp. The bricks will be rendered but I want to ensure the moisture from the sandstone doesn't end up through the bricks / render over time. Will this product Crommelin 2L Dampstop work if I apply it over the sandstone prior to laying the brick? We are probably looking at an area of a couple of square metres. I was thinking to lay the brick and fill in the small gap with cement. There wont be a lot of room to apply the Crommelin 2L Dampstop to the brick once laid so was hoping apply it to the sandstone before bricking and filling would do the job. Can you assist?The landscaper had arranged to have the brick wall above the sandstone rendered but didn't know the sandstone would remain exposed. A single skin of brick will cover the sandstone and blend in with the other block work but the sandstone is always wet and I don't want this coming through the brick / render over time

[Jason]

Hi @Greg_W,

Welcome to the Bunnings Workshop community. 

Sorry for the delay in responding to your post. I've asked one of our resident Bunnings D.I.Y. experts to make it a priority in the morning. 

Thanks for your patience.

Jason

[Jewelleryrescue]

Hi @Greg_W 

I use a  cementuous  paint. 

Regular general purpose Cement powder that is  combined with  bond crete  basically a polymyer resin liquid that creates a cement tough thin water proof barrier that will hold  100% water from flowing out of the wall and into the wall. It looks exactly like you rendered wall now I would  paint that area from top to bottom including the cement ground. As it is cement it will also aid in smoothing/filling the rough concrete at the base.

Notice the green webbing at the base of the wall that can also be filled to give a better look if you wish.

I have it in a pond over a meter deep holding water perfectly. So if you coat that   area just be mind full it will trap water  there if water runs down to it or make a drain hole some where.

After  you fill that area  cement movement may occur simply patch the cracks with the same cementuous paint.

Look  for Bond crete at  bunnings and follow  directions as to mixing it with General  purpose  cement powder. Use  dust mask and  gloved hands

The best   part is you  simply paint it on with a straw renders brush (you can  use other old  brushes but they will get trashed)  is best two  coats and any one can do it.

You can also add a bit of  cement powder oxide to it if you want a  different color. (usually earthy colors on offer .)

Ps   Crommlins is not UV safe  for outdoors   Bondcrete is 100% weather proof rain hail shine and UV prove as it is concrete.

Hope this helps.

[JacobZ · Accepted solution]

Hi @Greg_W,

A warm welcome to the Bunnings Workshop and thank you for your question.

I've spoken with the technical team at Crommelin who have advised against using a sealer as you would essentially be locking the moisture inside the sandstone which will cause issues with the integrity of the wall sitting above over time.

Are you aware of the source of the moisture in the sandstone? Sandstone is naturally porous and will wick groundwater up through the soil, but it should not be wet all the time unless there is a source of water nearby. It is a long shot, but if you can stop the moisture at its source, this would be a much better option.

If you can't find a source of the moisture, I would be more inclined to suggest putting Sika 10 x 150mm 6m Abelflex Expansion Joint Filler Foam against the sandstone, followed by a plastic membrane such as this GRUNT 2 x 10m Black 140um Multi Use Plastic Film before laying the brick up to the plastic.

Having the Abelflex sit directly against the wet surface with the plastic between the Abelflex and the brick will give the moisture a location it can escape through while still preventing water from transferring into the brick. While it is not a perfect solution, it would give the sandstone that little bit of breathing room that a sealer applied directly to it would not.

Let me know what you think and if you have further questions, please don't hesitate to ask.

Jacob