How to stop water from flowing underneath concrete stairs?

[sirblew]

We have water flowing under concrete stairs that run down the side of our house. The water enters under the stairs from the neighbour's garden bed adjoins our stairs on the boundary, so we don't have space to excavate along the side of the stairs. The water has eroded under the stairs and flows under the concrete path at the bottom of the stairs, which I think is the cause of some subsidence we've seen as cracking in our brick wall of our house that adjoins the path.

[MitchellMc]

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

You might like to start by sharing some images of the stairs and indicating on them where the water is coming from and travelling to. This would allow our knowledgeable members to understand better what exactly is occurring and offer helpful solutions. Let me know if you need a hand uploading images.

There are likely several options that you could pursue to resolve this situation, but they all heavily depend on the exact layout of the area. Those images will really assist.

Mitchell

[sirblew]

Hi Mitchell. Thanks for the suggestion.

I've attached photos showing the gap between the stairs and the garden (which I've excavated a bit to inspect), a gap under the stairs where water flows underneath, and of the stairs and path in context with our house and the neighbour's garden. There are more places in the staircase which have the have gaps too.

Gap under stairs.Gap under stairsBetween stairs and neighbour's garden. The gap is just below.The staircase between our house and neighbour's garden with fence along the border.

[Dave-1]

@sirblew 

Ohhh Yeah Makes a lot more sense with the photos.

If tou looked at the steps front on down the concrete steps touch the top tread of the one bellow?

I am asking that as the steps at least from top down look like they are preformed and placed insitu. So maybe one could be levered out to have a good look undeneath for subsidance or runoff. Another option would to be to drill down at the back of a step gently (so not to crack it) to see if theer is soil undeath the step? Not sure how well that would work. I know you can buy little usb cameras to put down walls and cavitys but have not seen them myself.

You could also use a hammer to "tap" the steps and see if they sound hollow. Around my pool I have this issue I think and yeah the concrete does sound hoow at points.

Slurry could be poured down holes that you create to fill teh voids but you also need to know where it could come out otherwise it would be a big mess.

Will think about it some more.

Dave

[sirblew]

Hi Dave, thanks for the suggestions. I've already put a drain camera in various places underneath the stairs and can see that it's quite spacious underneath. Lots of rocks and other debris but not much soil, if any. I also *think* I can see where it dips below the foundation, but am not certain.

It's hard to discern exactly what I'm seeing there, but there's definitely a lot of space and the concrete looks like a relatively flat ramp from below the stairs.

[EricL]

Hello @sirblew 

Since you 've had a chance to look underneath your steps, you then make a determination if it should be repaired. This would include removal of the existing steps fixing the foundation and relaying your concrete steps. While you are doing this repair, this would be the best opportunity to set up a drain system under your steps to divert the water coming from your neighbour's side of the fence.

Another possible solution is to dig a drain channel next to your steps but on your neighbour's side of the fence. I recommend speaking to them first and explaining what is happening and what your proposed solution is. 

I recommend building a French drain using Vinidex 100mm x 20m Socked Slotted Draincoil. I suggest using two coils side by side to make sure that even in a large downpour the channel will not be overwhelmed, and water will still be diverted away.

I've placed a sample image below to give you an idea of where to place the French drain. 

Let me call on our experienced members @Adam_W, @TedBear and @JoeAzza for their recommendations.

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

Eric