How to fix water pooling in clay soil next to foundations?

Question

I’m hoping for some advice on how to fix a drainage issue that’s developed next to my house in New Zealand so it rains a lor. Over the past few months, the soil beside my foundation has turned into compacted clay, and it’s now holding water instead of draining.

* When it rains, the water pools on the surface, can’t run off anywhere, and ends up flowing under my house through the vent. 
* The area is boxed in by my concrete driveway on all sides, so the water has nowhere to escape.

My photos show

* The clay turning into a hard, slick surface that doesn’t absorb water
* Pooled water sitting for hours/days after rain
* The vent where water is entering under the house
* The concrete edges trapping the water

I’m looking for ideas on how to:

* Improve drainage in a space with no natural runoff
* Break up or amend the compacted clay
* Create a safe path for water to escape
* Prevent water from entering under the house
* I've dug out about 20cm of soil and added gypsum but it's holding water

Any suggestions or examples from similar projects would be hugely appreciated.

R4addZ · Answer

Hi @LostTramper

There are a couple of issues here the first being the height of the soil in your garden beds next to the airbricks, you may need to enlist the aid of a builder to resolve that issue as you can't block them off without causing future problems and it may be necessary to install more smaller ones higher up.

The way Dave is suggesting drilling under the path with the pipe I have used myself in the past and it works well in sandy soil but I am wonering how well the hose will wash away the clay. I will keep my fingers crossed for you.

The old fashioned way of dealing with clay is to add lime to the soil as it breaks down the clay and makes it clump allowing water through the gaps but lime is difficult to work with as it is corrosive and can cause burns to the skin especially if it gets wet so if you decide to add lime, use long gloves, goggles  and a mask is a good idea. The other problem with lime is it is a longer term solution and you need a short term one at the moment.

TedBear · Answer

Hi @LostTramper, I agree with the advice given by @Dave-1. The water needs to be removed from the area since it isn't going to drain into the soil fast enough. I would (and have at my place) place some slotted drainage pipe under the existing garden strip and place stones or gravel all around it. Then connect that to a pipe to take the water away, as Dave-1 has outlined. It would mean replacing the in-soil plants with plants in pots, but getting water to stop invading your home, I would think, is a number one priority.

Dave-1 · Answer

Good Evening @LostTramper

Woooo I know that clay feeling so well :) Yeah I have water issues with it before.

So a question. Does your yard slope at all after the path? The reason I am asking is if you can install a pipe under the path then it could potentially drain away.

You can do this by digging two holes either side of the path, down about a shovels blade depth and square (Use a Flat blade shovel)

Then the hole on the outside of the path, you double the width. With a 50mm piece of conduit, remove your hose nozzle and insert the hose into the pipe. Turn on the hose hard as you can. (Its going to get muddy and messy for a bit) push the conduit against the soil under the path, then push the hose as far as it can go, keep the pressure up gently as the water eats away the soil/clay from under the path. Keep pushing the 50mm pipe in as well. Eventually you should come out the other side of the path. I wish I had done it this way under my path (I used a crowbar, a drill with a two foot 12mm drill bit and lots of effort)

Now you have a passage way for water to exit. You can have it drain away via pipe to a lower point. or you could install a sump pump somewhere else in your garden that will kick in once the pit fills with water. Always be cautious digging trenches in your yard as water pipe and internet/phones may be about.

I would install a low pit with a grill top (to stop debris entering your new drainage) in the garden area, I would install the other pit maybe along your front garden so you can use the water that drains there.

Here are my excavations of "the hard way" to dig under a path…. (shaking my head at myself)

Oh and yeah thats an old ozito battery powered drill (the model before the red ones) (Borrowed from work potentially) from 2016

Dave