How to waterproof exterior brick wall? (in-ground)

[ChrisG1]

Good evening all,

We had a garden bed  in the rectangular space on he photo, and overtime, water must have seeped into the exposed bricks. The bottom row on the photo was completely covered in soil (high clay content) and the second row was half-covered. Our pest inspector has reported high moisture readings on the room behind this wall, which I suspect must have been caused by the water slowly seeping from the soil into the bricks. Also, this water / moisture ingress must have caused efflorescence which can be seen here on the bricks and also through the render.

In order to prevent this from happening in the future, I would like to a) waterproof the exposed brick surface, and b) fill the former garden bed with concrete. Especially during the winter months this are gets hardly any sun, and any rain will sit in the soil for an extended period of time, especially since the clay does not allow for the water to drain away naturally.

I am looking for advice please on the following questions:

1) What is the most suitable waterproofing method for exterior, exposed bricks such as these (bearing in mind that there will be concrete slab instead of soil in the future). I had thought of the black, rubberlike paint that I have seen on construction sites, but open to advice.

2) I am letting the bricks dry out and have already given them a thorough scrub with a dry, hard brittle brush (to clean out soil and moss that had accumulated on the bricks and mortar. Prior to applying any waterproofing paint, how thorough do I need to clean the bricks? Is a dry brush sufficient or should I consider a pressure cleaner instead or would this cause even more trouble by pressing water into the brick and possibly washing out the mortar between the bricks?

3) When filling the former garden bed with concrete, is there anything further that I need to consider to protect the bricks, e.g. placing a foam barrier between the concrete and the bricks?

Many thanks in advance for your input!

__PRESENT__PRESENT

[EricL]

Hello @ChrisG1 

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

Allow me to make some inquiries with our supplier. I'll need to double check if our bitumen products can be covered with concrete. As soon as I have more information, I'll get back to you.

Thank you for your patience.

Eric  

[MitchellMc]

Hi @ChrisG1,

Crommelin 4L Exterior Grade Brushable Waterproofer would be suitable for your project. Apply with a brush to the exposed bricks. 

It would be best to pressure wash the bricks. Keep the nozzle at a downward angle so it doesn't blow any mortar out. If the mortar is so degraded that a pressure washer might damage it, then you'd need to consider whether it needs repointing. Wetting the bricks whilst pressure washing is likely not going to cause further water ingress as it will dry up quickly. It was the long-standing damp soil that constantly allowed water to weep into the wall.

You can place an expansion joint between the new slab and the wall and the two slabs on either side. However, the most important thing is to ensure the slab slopes away from the wall and not towards it. This allows the rain to run off away from your bricks.

Please let me know if you have any questions.

Mitchell