How to stop water seeping through concrete walls under house?

auszi

Hi ! we have water seeping through concrete in our under house garage after heavy rains.

I can’t see any visible cracks in the wall and it looks like the water is seeping / permeating / weeping through the solid concrete.

We are on a sloping block with the garage under our living room on the low side (north side) of the block (see blue highlights on the picture for location). The leak is on the south garage wall, which is under ground and covered by the rest of our house. There are French drains installed on the surface at the edge of the house on the high side ( south side)

Any thoughts on
1) whether this will cause structural damage the concrete wall?
2) how to remedy this?

MitchellMc

Welcome to the Bunnings Workshop community @auszi. It's sensational to have you join us, and many thanks for your question about water leaks.

Water seeping through concrete walls, especially in an under-house garage, can be concerning, but there are ways to manage and mitigate the issue. Ideally, waterproofing is best applied to the side of the wall where the water is penetrating. Since this isn’t feasible in your situation due to the location of the leak under your house, the focus will need to shift to preventing water ingress into the garage itself.

It's worth noting that your bricks should have a dampcourse to stop water from being wicked up into your dwelling, and the moisture in the concrete walls and base is unlikely to cause structural damage. However, for peace of mind and to rule out potential long-term impacts, you may want to have the wall inspected by a professional.

To address the issue internally, start by sealing any gaps or cracks between the floor and walls with a product like Sikaflex 11FC, which is durable and flexible for areas experiencing water ingress. Once sealed, apply Bondall 20L Silasec Waterproofing Cement Additive to the corners and up the walls. This product can help create a barrier to minimise water seepage and protect the affected surfaces. While these steps can reduce water intrusion, monitoring the area during future rains and considering further drainage improvements outside the house may also help manage the problem more effectively.

Please let me know if you have any questions.

Mitchell