How to waterproof external wall?

[tom138]

Hey everyone,

I am hoping to get some advise re waterproofing this external wall before I get a concrete path. 

As you can hopefully see from the picture above I have exposed the footer and was planning to use this waterproofer  but thought I’d check first whether is it the right product for this job. Or is there anything more suitable? 

Few other questions I have:

- how do I prepare the surface before applying the membrane? There is obviously still traces of dirt and stuff and I at first I wanted to use a pressure washer to clean it but not sure whether is it a good idea and whether am I going to loosen up some of the old mortar. Also if I pressure wash it now it might not get dry before the next rain and I wanted to take advantage of the few days with no rain on the forecast. Could I just get away with using a brush or wire brush to get rid of the dirt?

- do I need a primer/sealant?

- where do I apply the membrane? From the footer to the dampcourse?

Any advise is much appreciated!

Thanks,

Tom

[Jason]

Hi @tom138,

I would imagine many community members will recommend getting professional advice, but let me tag some experienced members for you: @Nailbag, @JDE, @Jewelleryrescue, @DIY4Knuckleheds.

One of our resident Bunnings D.I.Y. experts will also be happy to assist as soon as possible.

Jason

[Dave-1]

Morning @tom138 

I was having water enter my garage via the bottommost course of bricks so I used this product gripset betta 4l bitumen rubber waterproofing membrane and it has stood up fine. I am not 100% sure how it will go next to wet concrete Might be worth looking into reactions ect) but it totally stopped my leaks.

Note - It is super sticky and claggy. And stands out in colour I would only waterproof teh bricks up to your new concrete level.

I would also clean the bricks first, loose masonary bits should be removed whichever way beefore whatever you apply as it will cause issues down the track potentially. If it takes an extra week, then you know you have done a proper job and it wont fail down the track. I always get my timelines out of wack  

My project where I sealed the bricks. Its the last step if you want to jump to it. Gabion Wall to stop water ingress to garage 

Dave

[Nailbag]

Hi @tom138 

I think what you're proposing to do is viable. Just make sure the surface is very clean and dry and cover a low as possible and a little higher. 

A few months back I helped a plumber mate of mine with a similar project but the wall was 3' underground with a semi-underground gym on the other side. We lined the wall with blue-board, then sealed it with a similar product to your waterproofer. Then applied a bitumen paint just for the durability against the soil.

Nailbag.

[tom138]

Thanks @Dave-1 and @Nailbag. One thing I realised is that this sort of membrane if only painted on the side of the house and concreted over would only lock in all the moisture coming from underneath the slab. I might just go with a temporary fix for now before I figure out what to do long term.

Also as I am installing ag pipes further up slope from the house to catch water before it gets to the house, I thought it might be a good idea not to lay concrete right away so I can see whether it works and how much water still makes it to the house. I’m thinking builders plastic against the wall and backfill with gravel. 

[JacobZ]

Hi @tom138,

If you can stop the water at the source using agi pipe, this would definitely be ideal. I think your plan to install the drainage and monitor the situation before deciding on the next step is wise.

Builders' plastic is a common method of waterproofing the underside of concrete slabs and if you aren't experiencing significant water entry at present, it is likely your best option.

If you are currently having issues with water entry, I would still use the builder plastic when the concrete is poured, but using a membrane such as the Crommelin 4L Exterior Grade Brushable Waterproofer with Crommelin 100mm x 10m Reinforcing Fabric over the crack between the brick and the slab will add a layer of protection that is worthwhile in the long run.

If you apply this membrane, there's no need for a primer, but you'll need to get rid of as much dirt and debris as possible. Ideally, a pressure cleaner would be used, but as you've mentioned, the surface needs to be completely dry before applying, so using a stiff-bristled brush or wire brush will likely be a better option, but you'll need to be as thorough as possible.

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

Jacob