How to waterproof a basement?

[JoshyBoy]

I've got an old Queenslander with an under house section (basement) that isn't quite legal height but we want to do something with the space. Problem is when ever we have heavy rain, water seeps through some of the concrete/masonry cracks. I've used Gripset Betta Membrane Bitumen Rubber on the exterior of 3 of the walls which looks like its done the trick however 1 of the walls has a concrete driveway up against the wall so i can't dig down to apply the membrane on the outside. I know i could possibly get a concrete cutter and cut up a section and then get to it but i figured this would be pretty expensive.

I've been looking at the USA product Drylock Extreme Concrete Masonry Waterproofer but it might be too hard to get my hands on it. Does anyone know what the Bunnings equivalent of this product would be? Or has anyone got some advice on waterproofing a concrete/masonry wall from the inside?

[EricL]

Hello @JoshyBoy

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

The two products that I'm aware of that will work in a negative hydrostatic pressure environment are the Dunlop 4L Damp-Proof Waterproofing and the Crommelin CEMPROOF FLEX. Depending on what your local store is stocking the CEMPROOF FLEX will need to be ordered at the special orders desk. 

My only other thought on your current situation is to divert all the possible water sources away from the wall. If rainwater is headed towards that wall put in an Everhard Easydrain, and dig channels to house drain pits to divert water away from your house foundation.

Let me call on our experienced members @TedBear and @Remarka6le for their recommendations.

If you need further assistance, please let us know.

Eric

[MikeTNZ]

Hi @JoshyBoy,

I think by hearing this story, you are going to have to dig down with an excavator to grade level and expose the entire wall to seal it from the outside.

Personally I would let this dry out before you try any treatment to the wall itself, and let the treatment set in place before any back-filling occurs.

Is this on a side of the building that doesn't get a lot of sun?

If so that could make things difficult, to dry this out you could hire a diesel heater.

If you are going to put anything on to the structure, it needs to be dry from the outset, especially where adhesives are used.

I can't help but think that a professional engineer might be required to give their thoughts on this.

Unfortunately, this doesn't sound like a DIY sort of job to actually finish in the way you would like.

[EricL]

Hi @MikeTNZ

Thank you very much for the sound advice. Let me tag @JoshyBoy to make sure they see your recommendation. Having lived in NZ for a while, I know how detrimental to your health a mould infestation is. 

Eric

[Jason]

How did you go with this project @JoshyBoy? I'm assuming by your new bathroom post that work has proceeded? It would be great to get an update.

Thanks,

Jason

[JoshyBoy]

Hi Jason,

I used Eric's advice and used Dunlop 4L Damp-Proof Waterproofing on the inside of the wall. I also used some concrete sealant on the driveway outside the wall and have diverted some of the flow at the top of the driveway. We've had some pretty heavy rain in Brisbane in the past 9 months and not a drop of water has come in to the basement which is good news.

We haven't had the '1 in a 100 year' flood like we did at the start of 2021 to really test it out though. 

Josh.

[EricL]

Hi @JoshyBoy 

Thank you for the update, it's good to hear that the measures you've implemented have stopped the water leaking into your basement. I suggest just keeping an eye on it whenever there is a big downpour to make sure that the seal is keeping the water out.

Eric