ᐅ Site planning on a gently sloping lot with fill

Hello everyone, this is my first topic here:

We are planning to start building our house this year with a general contractor. The position of the building on the plot is fixed, and we are currently waiting for the building permit / planning permission.

Our plot is approximately 20m by 41m (66 feet by 135 feet) in size, located in a gap between buildings. The shorter side faces the street. The land slopes downward by 3m (10 feet) over the 41m (135 feet) length towards the back, with the steepest slope in the middle of the plot. The neighbors on the left and right have filled their land, which can be seen clearly by the height of the neighbor’s wall on the left side of the photo. The neighbor to the left has built a basement into the slope, the neighbor to the right has not.

According to the soil report, about 50cm (20 inches) of topsoil needs to be removed. Beneath that, the soil is stable. Frost protection material will be used to fill up to the average street level, so that the finished floor level will be about 20cm (8 inches) above the street. Due to the slope in the middle part, the backfill behind the house will be approximately 1.8m (6 feet) above the current ground level. According to the soil report, the fill should be either sloped back at a 45° angle or retained with a retaining wall.

In the rear area of the plot, we want to create vegetable beds and a wildflower meadow. We already established and harvested a small potato patch last year to pass the waiting time.

What do you think would be the most sensible and cost-effective solution in this situation?

• Slope everything back, add stairs and a natural stone wall later
• Build stairs and a wall directly on the right side, slope back the rest
• If building a wall: formwork blocks would be much cheaper than L-shaped blocks; regarding the earth pressure, a structural engineer would probably need to be consulted.

I am looking forward to your suggestions and ideas!

Unfortunately, I have zero talent for landscaping or garden design, but I somehow don’t find the wall running vertically through the property very harmonious. In my opinion, subtle natural stone steps and dry stone walls running across the slope, with climbing plants winding along them, look nicer. Behind those crosswise features, a small pond could be maintained as well – if it ran lengthwise, it would have to be dug extremely deep. Or did I misinterpret the terrain?

Just a quick fun note – I currently have about 850 tons of clay soil left over, in case you need some poor-quality fill material 😀
Have you talked to the professionals mentioned? We had a garden/landscape planner create a layout for the house positioning and elevations, which was very helpful for us.
From a structural perspective, does the slope where the house will stand need to be retained or supported in some way, and how gradual or steep should the embankment be?

So, I have to say, I see an enormous amount of effort involved in the earthworks, especially if you also want a pond with a solid terrace underneath—it looks like a lifetime's work worth its weight in gold. 😱
Regarding the layout, with an elaborate design on the left side and a lawn on the other half, I don't find it harmonious either.
My advice: plan with planting as well, that is, include several structural plants in the design.

Thanks in advance for your input!

@K a t j a
The wall would be behind the terrace area... so about 1.5–2m (5–6.5 ft) behind the house extension there is still a walkway... then a wall could go down about 1.7m (5.5 ft). I would also prefer a natural stone wall, but unfortunately that is not financially feasible at the moment :/
For the area around the pond with the terrace, I would like it to be a bit higher in the long term compared to the lawn shown on the right... but that would require a lot of earthworks again.

@HnghusBY
For around the pond, that wouldn’t be a bad idea at all 😀
Right now, our earthworks contractor is only planning to do the fill and compaction. But since it will be difficult to access behind the house later, the basic landscape foundation will need to be done beforehand. Of course, no clay should be used there 😀

@ypg
We’re aware that it will be expensive until it’s “finished” 😕 Our hope was just to prepare it now in a cost-effective way so that it can be developed further later.
By structural plants, do you mean hedges and flower beds?
I’m also not happy yet with the layout being “nice on the left, nothing on the right.”

I had also considered asking local construction companies about disposal to help fill the garden a bit, but I’m concerned that might result in poor-quality material where nothing will grow.

@HnghusBY
Just noticed, according to the foundation recommendation in the soil survey, the slope should be cut back at a 45° angle behind the embankment.