How to build shed on elevated area with battered landscaping?

[Johnnyl]

Hey everyone,

I’m in the process of preparing an area for shed and landscaping, the shed will be on an elevated area of compacted clay/fill and then have battered landscaping / garden bed with brick edging delineating from turf. Dimensions of elevated area is 4.3m x 3.9m and there is roughly 20m2 of batters / garden bed. Height of elevated area will be no more than 400-500mm from finished level of shed to turf. Due to existing easements there will be paths around shed required.

I’m choosing to do battered landscaping instead of extending existing concrete sleeper walls as the existing wall is within 900mm of existing boundary and to connect into existing wall will require a DA, I’d rather it look like an aesthetically pleasing landscaped corner and I don’t want to wait 6-8 weeks and spend thousands on DA. On the boundaries there is concrete sleeper wall on one boundary and timber sleeper on the other. I’m on the lower side of both boundary walls. 

I spoke to my plumber yesterday who said the front end of concrete sleeper wall is connected to our house service so the end that we’re planning on building does not require connection. His main concern is making sure I set the site up so that I reduce ability of run off to pond at the base of retaining walls, he also suggested to not use river gravel at all for any paths as this only encourages water to sink and water won’t effectively drain from site.

This is the scope of works I’m looking to do

*compact and shape subgrade so that there is a swale in the centre of paths that promotes fall away from shed slab and away from boundaries to encourage run off to gardens and batters, this removes the need to concrete spoon drains to faces of existing boundary fencing/walls. 

*lay geotextile over entire elevated area once subgrade is compacted and shaped

*place 100mm roadbase ontop of geotextile and 30mm crusher dust on top of roadbase for paths surrounding shed

*for shed slab, lay waterproof membrane on top of compacted roadbase, shed slab to 100mm thick concrete, shed slab proposed to be 500mm from edge of batters, thicken edges of slab that are parallel to batters with 300mm wide x 200mm deep footing. Reo mesh to slab. 

*top elevated area to be bordered by brick edging to top of batters and along fence/walls facing

*paths surrounding shed on elevated area to be 30mm crusher dust on 100mm roadbase 

*batters and garden beds to be landscaped  with mulch, landscaper recommended to use Lilly pillys at base of batters as these are excellent at absorbing water and consider ground covers to assist with mitigating scouring. No planting will take place until late August /September due to us now being in winter however I was going to do prep work with gypsum, compost and then fill all areas with native mix and mulch for the time being.

*the way the batters will slope is that part of the garden bed will be in front of my wall however the turf level at front of my wall is 20-30mm below footpath and there is a house drainage collection point 400mm inside footpath. For this area I was planning on laying roadbase and crusher dust and slope it so that it falls away from my wall towards turf area and also towards footpath to allow run off into drainage collection point. For this little section I was going to use pot plants with established Lilly pills or similar planting.

I feel I’ve given a pretty good description of works without the need to share photos. Do you guys think this is a good plan if I’m looking to achieve an aesthetic finish and does the scope for the elevated area and drainage sound acceptable?

[MitchellMc]

Welcome to the Bunnings Workshop community @Johnnyl. It's sensational to have you join us, and many thanks for your question about installing a shed and landscaping.

You've done a great job outlining your plan — it's a very detailed description of the works, and clearly you've given it plenty of thought. That said, without being able to see technical details or site photos, it's hard to provide a definitive answer on whether it’s the best approach, though everything you've described certainly sounds like a workable method. Let me know if you need a hand uploading images.

It seems like you've considered key issues such as drainage, runoff management, and visual appeal. Your plan to shape the subgrade with a swale to direct water away from the shed and boundaries is smart, especially given the complications with the retaining walls and easements. The use of geotextile, roadbase, and crusher dust is a solid combination for stable paths, and your proposal for a thickened shed slab footing near the batter edges is sensible from a structural point of view.

One thing to keep in mind is that clay soils typically don’t absorb water well and tend to promote surface runoff. That means your drainage planning becomes even more important, ensuring that runoff has somewhere to go without pooling around your walls or paths. Since you’re not concreting spoon drains, your proposed swales need to be well-graded and maintained to be effective. And your plumber’s advice to avoid river gravel makes sense in this case — while it normally assists with infiltration, it can create soggy conditions in clay-heavy sites where water doesn’t move away fast enough.

Your approach to landscaping the batters also sounds thoughtful. Using mulch now, with compost and soil prep ahead of planting in spring, is a practical strategy. Lilly pillies and ground covers are great choices for stabilising the soil and managing runoff over time.

Overall, it sounds like your plan could definitely work — the only missing piece is whether your elevations, slopes, and drainage features will function as expected. If you’re able to add a few site photos or a sketch, it could help others give more targeted advice. But from what you've shared, it sounds like you’re on the right path to a solid, aesthetic, and functional outcome.

Since you're in the planning stage, you might like to read through this helpful article on How to give your garden a makeover and check out our Top 10 most popular garden makeovers for inspiration.

Please let me know if you have any questions.

Mitchell