Solving leaking into the house

[yots]

Hi, with the recent "rainbombs" in Queensland I have had water leaking into the house downstairs. The ground level outside at the greatest variance is about 5 bricks above the height of the inside floor at the corner and height taper off on both ends of the wall.

Outside has a concrete footpath that wraps around the house and I have observed water sheeting off the footpath but nothing major I can see that goes into the house. I believe water is coming in when the ground has soaked too much water and leaking thru the brickwall under the footpath.

What I am thinking of solving the issue is to remove the footpath, have earthworks down to 100mm below the level of the interior floorput with these channels ( https://www.bunnings.com.au/everhard-3m-easydrain-polymer-grate-and-prejoined-channel_p4770175 ) against the house wall to divert water and a retaining wall on the otherside.

The questions I have are:

1. Should the retaining wall be put in first or the concrete footpath with the channels?
2. I read some post that talks about expansion foam between the concrete footpath and retaining wall, what product would suit this?
3. Would I still need to waterproof the exterior wall given it would be just below the interior wall level? If so what product should I use?

I have tried to approach waterproofers, concreters, plumbers and builders, it appears to be a very difficult task and me having one trade refer to another and not getting any quotes for the entire work. So I have exploring options where I could do some of the work.

Thanks heaps in advance!

side of houseback of house

[EricL]

Hello @yots

Welcome to the Bunnings workshop community. It's magnificent to have you join us, and thank you for sharing your question about solving a leak in your house.

I can understand the description of your project, but would it be possible for you to post a picture of the area where you plan to build the retaining wall? Is it a tall or short retaining wall? How long would it need to be? Using the Everhard 3m EasyDRAIN Polymer Grate And Prejoined Channel is an excellent way of diverting the rainwater away from the house into your drain.

Let me ask you the same question. If you built the retaining wall first how would it affect the footpath? What if you reversed the build order and did the retaining wall first? Building the retaining wall first will allow you to put in proper drainage, the footings would be secure and you wouldn't have to worry about the footpath destabilizing due to digging around it. 

Once the wall is built you can then put soil around it and build the footpath. Building the footpath first means there's less room for you to maneuver when building the wall. You'll have to be careful to make sure that you don't compromise the foundation of the footpath.

Waterproofing when you have the chance is always a prudent idea. It's like insurance, you never know when you're going to need it, but it's good to know that it's there. Should you have a channel overflow, it will be good to know that you have a backup system in place to deal with that kind of event. I recommend Gripset Betta 4L Bitumen Rubber Waterproofing Membrane. It's made for interior and exterior use and is easy to apply.

Expansion foam is often used between the gaps of large concrete surfaces and prevents water ingress from forming a channel. 

Let me tag our experienced members @diy_hausdesigns and @Adam_W for their recommendations.

If you need a hand posting the pictures, please let me know.

Eric

[Adam_W]

Hi @yots & welcome on-board.
Okay, sounds likely a somewhat complex issue.
Not quite sure I understand the lay of the land as it is now & how you plan it but just a few points which may help.
- Any wall that is effectively sub-surface which forms or adjoins a habitable part of the house must be waterproofed. There will normally be a damp-course of some sort at least 100mm above the soil level in the brick work to prevent moisture rising up. If the soil is fully against a wall, which is what you describe, then the outside of the wall should have been fully waterproofed with a suitable membrane and there should have been subsurface drainage installed to move water away. Note that attempting to waterproof a wall from inside the house will achieve nothing.

- Any works should have a finished height of at least 100mm below the existing damp-course. So your new path would want to sit at that height.

- Personally I'd be building the retaining wall first, path & drainage second.
- That drain will work however don't rely 100% on a single drain - design for redundancy and try to deal with water at it's origin, not just where it's causing a problem. Is this water flowing from somewhere else? Can you collect it and remove it at a point further away from the house? I'd also be making sure there is excellent drainage added behind the retaining wall.
Hope some of this helps.
Cheers

[yots]

Thanks @EricL  photos added.

The reasoning behind building the retaining wall first then footpath makes sense.

What material would one use at the between the footpath and the retaining wall edge?  Would it be foam flashing like Sika 10 x 75mm 6m Abelflex Expansion Joint Filler - Bunnings Australia or something else?  I have seen something like this on council footpaths as expansion joints before but they dont appear to last long...

Cheers,

Alex.

[yots]

Thanks @Adam_W 

The water is coming from my backyard and as there are no stormwater drain on that side of the house its all coming down towards my house.

If the plan is to have the poly channel against the house wall and a french drain (wrapped agi behind the retaining wall) behind the retaining wall.   connected to the stormwater drain at the front of the place using PVC.  Would this be sufficient or should I have another poly channel on the retaining wall side as well?  My thinking is that the french drain should take most of the water that potentially be raising due to saturated ground and the channel will take away surface water close to my house (which I observed there wasnt alot of even during one of the short but heavy downfall).  

[EricL · Accepted solution]

Hi @yots

Unfortunately, it is the nature of the expansion joint filler to deteriorate after being exposed to the sun for a few years. I suggest using Gripset Betta 1L Concrete Crack Filler as a top cover for the expansion joint filler. However, you'll need to manually check to see if the filler has deteriorated. This means that you'll need to remove the top cover replace the filler and re-apply the concrete crack filler every few years.

In reference to the question, you posed to @Adam_W. It is difficult to predict the amount of rainfall that might occur in your area. But having a second channel that will re-direct excess rainfall is always handy. I suggest testing the area first and seeing if the new system will cope with a large downpour of rain. I'm sure there will always be an opportunity to install a new set of drain channels next to the retaining wall. 

If you need further assistance, please let us know.

Eric