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How to fix garage leaking from concrete slab under walls?

Hi team would be great if I can get advise on how to fix this once and for all.

This part of the garage is used as a study and unfortunately it appears water has been getting in via the rear and right side of the garage for quite some time (without us knowing it). The excess rain over last week got in so bad that our carpet and some of our stuff got completely ruined.

What I will point out is Agi line was installed on both sides and rear a couple of years ago, however I am aware that it is problematic that the height of the outside concreate and dirt are at the same level as the garage slab.

My question is should/can I do one of the following options

1 - cut out part or all of the outside concreate and just decrease this part below the garage slab (say 100-200mm depth and width) and attach hardiplank to go a below the slab outside to stop incoming water?

2 - Run a channel drain instead of agi line or over the concreate area to help with water flow plus cut below for the above hardiplank solution

3 - something entirely different?

Appreciate the help! let me know if more info is required?

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EricL

Hello @Brycem

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

This is a bit of a difficult situation. Part of your solution is applicable, but I'm afraid Hardi Plank will not be enough to stop the water from entering the garage.

I propose digging about 300mm down at the edge of the slab and cleaning it as best as possible. The surface must be free of dirt and debris. I then suggest sealing this section with Gripset Betta 1L Waterproofing Membrane Bitumen Rubber and at least 100mm past the slab top.

I then suggest pouring a new concrete walkway outside that is sloped away from the house and at the end of the slope install an Everhard 3m EasyDRAIN Polymer Grate And Prejoined Channel installed with a proper fall. This will catch any rain that is coming from the fence side and any rain fall coming into your area.

I've placed a sample image below to give you an idea of what it can look like.

If you have any other questions we can help with, please let us know.

Eric

MitchellMc

Hi @Brycem,

Just a note for yourself and our other readers: It's best to check with your local council or building regulator in your area before completing any work that could be considered plumbing. Although installing the drainage channel would be a project you could partially do, connecting it to stormwater water would certainly be a job for a licensed plumber.

Mitchell

Brycem

Thanks Eric and Mitchel sorry for the belated reply. I have started what you have suggested and so far have dug the ground outside to a lower point than the internal slab as a safe guard for water pulling. However it is a good thing that I am taking my time as it appears water is possibly coming up through the slab (see below image). What would you recommend I do here? In case it matters the plan is to use leveler on this floor and to install floating boards(once the outside work is completed)

MitchellMc

Moisture could quite possibly be coming up through the slab, @Brycem, but given that this wet patch is in the corner against the wall, I think it points towards the issue of water on the slab penetrating under the wall.

You might be at the point now where you need to start inspecting the damage to the wall frame. I suspect that it has suffered a significant level of decay.

Mitchell

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