How to add drainage to sloped backyard?

Hello Community,

I am seeking some advice on the best option for my backyards drainage. This is a new house in the hills shire, NSW.

The backyard slops towards the house and I believe that slope is around 400-600mm. The backyard size is 10 x 10 meters and presently there is no property on immediate backside of my property.

During rains all the surface overflow water gets collected against the wall. The ground here is mostly clay and hence doesn't absorb much of the water. I am worried this would impact the foundation and as well create the damp for termites to thrive.

The following are the options that came to my mind, however due to the lack of knowledge in the industry I am not too sure. Attached images for reference

1. Cut and level as much possible to reduce the slope, possibly requiring to add more strength to the fencing. The properties on either sides are prity much the same level, except on the back which is higher.

2. Leave the slope as is and put a drain channel next to the wall of the house to take the overflow water out.

3. Leave the slope as is and put a concrete patch next to the wall which has a small slope towards the backyard and put a drain channel at the edge of the concrete to take the overflow water out.

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Comments

JacobZ

Hi @naresh_m,

A warm welcome to the Bunnings Workshop community and thank you for your question.

I don't think option 1 is really worth the expense, as it is a large amount of work will likely cause pooling and drainage issues elsewhere in the yard. It seems better to work with the existing slope, as it is already directing the water towards a collection point against the house.

Either option 2 or 3 will work well, in much the same way as each other; however, option 3 would keep any surface water further away from the foundation of the house, which, for peace of mind, might be worth the added expense.

Whichever option you choose to use, you should have a plumber connect the drainage channel to your stormwater outlet, which can be seen in image 7.

Allow me to tag @Dave-1 for his thoughts.

Let me know what you think.

Jacob

Dave-1

https://www.workshop.bunnings.com.au/discussion/comment/51625#Comment_51625

Good Afternoon @naresh_m

I really like how you have approached the problem with a set of options 🙂 I went straight to option 3 even before I read through all of them 🙂

I like the idea of a path next to the house and a drain away from the house. Even a low gabion wall could be added after the concrete path and drain so you could raise the soil level if you wanted to but really that drain will work well with the path. You have stormwater pipes at either side of your house so getting rid of the water should be easy enough (Maybe ask a plumber just so you are following any rules you need to)

Dave

naresh_m

https://www.workshop.bunnings.com.au/discussion/comment/87964#Comment_87964

Thanks on your pompt reply and inputs @JacobZ and @Dave-1

The reason I was thinking of reducing the slope of the backyard is to ease the other work which I plan to do next

- Brick raised and rendered garden bed near to the left and rear fence, I came across another of our community thread which discusses on that

- Putting a deck with pergola near to the right fence.

With the reduced slope I won't need to put a step on the raised garden bed and for the deck platfrom

Dave-1

https://www.workshop.bunnings.com.au/discussion/comment/109595#Comment_109595

Morning @naresh_m

Nice ideas 🙂 Comes down to how much soil you want to shift and also returf as you have mentioned that its clay underneath I think.

One thing to keep in mind, Clearance of the soil to timber base with a raised deck plus how the height will appear to your fenceline,

I also note that there is a stormwater pipe access grill? Or some kind of piping that would be wise to be able to access if necasary in your right hand photo.

Sketch out how it will appear for the raised garden bed and the deck idea, have the point of reference from your concrete patio and you will get eyelines on what it may look like.

Dave

naresh_m

https://www.workshop.bunnings.com.au/discussion/comment/122134#Comment_122134

Thanks @Dave-1 , exactly on the point... need to understand with the slop how high the deck would stand and how to plan the steps.

The attached rough sketch helps explain my idea

Screenshot 2025-04-29 at 12.12.42 pm.png Screenshot 2025-04-29 at 12.14.39 pm.png Screenshot 2025-04-29 at 12.11.35 pm.png

Dave-1

https://www.workshop.bunnings.com.au/discussion/comment/130158#Comment_130158

Afternoon @naresh_m

Nice plans 🙂 So now the question becomes "How to add height to your fenceline"

Various ways you could do that -

- Dig the ground out..... 🙂 lol I would say a Noooooo Way to much effort and expense.

- Add height to the fence itself, there are a lot of add-ons to fences 300mm-600mm. Adding height will give it an easier ability to want to lean tho.

- Seperate posts supporting a privacy screen. Doable but loose some yard space in the process.

- Posts within or at the rear of those raised beds with a screen at the top to add privacy height (My favorite as its the cheapest and will double as a place for climbing plants or windbreaks fro trees/shrubs)

As a note palm trees do end up with large rootballs So id factor in some growth space for them if you are planting them 🙂

Dave

JacobZ

Hi @naresh_m,

I like the plans, it seems like you've got some fantastic ideas and lots of exciting projects to look forward to in the near future. I'm excited to see things progress.

Looking at what you are planning, I am more certain that I would go with option 3. The side path would tie your fantastic backyard in with the patio and create a transition between the two while still serving the purpose of keeping water away from the foundation. You could even have the path run up to the bottom of the deck so you can move between the patio and deck without getting dirty feet.

I also think you'd find removing soil across the whole backyard is going to be a lot more costly than just working with the slope on your individual projects.

If you were to remove the soil, you would expose underneath the fence, which would mean you'd need additional sleepers to retain the soil from the other side of the fence. You'd also need to install significant drainage to deal with pooling water as it won't naturally drain towards the channel drain that you are planning to install. You would also need to reinstall and reestablish the turf that would be removed along with the dirt.

A deck can be built on posts above the natural slope of the earth, and your garden beds can be dug into the slope as they are installed. Unless the slope was a major annoyance for you, I wouldn't bother touching it.

I'm very excited to see where your plans go and will be keen to help you out along the way.

Jacob

naresh_m

https://www.workshop.bunnings.com.au/discussion/comment/51669#Comment_51669

@Dave-1 Those are really good options and makes me think there is more to look into.

@Dave-1 and @JacobZ I will need your guidance on how I can DIY the concrete path and what I would need to complete and get a proffesional finish.

Dave-1

https://www.workshop.bunnings.com.au/discussion/comment/87982#Comment_87982

Afternoon @naresh_m

I have not laid a concrete path as yet 🙂 Tho have installed a few paving paths.

You could go concrete or paving as both can have a slope away from the house (Only tiny) but with the grill drain at the bottom of the slope to collect and funnel the water elewhere. I prefer paved paths over concrete as ripping up concrete for whatever reason... Been there, done that and nope to wanting more of it 🙂 (personal choice)

As long as you have a hard surface with a drain at the low point to collect the water it will work.

If you go the route of a concrete path, Formwork, reo and expansion joints. I would also do it in sections that you can handle yourself or with some friends. It will provide a hard surface for water collection and as long as it has the grilled drain at the low point it works as well. No maintence is the benifit.

Id choose pavers 🙂 more flexible and easier to install plus there is a warmth about them.

Dave

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