ᐅ Transition from terrace to lawn

Hello,
I installed new terrace slabs on pedestals over an old concrete foundation.
I’m now a bit unsure about how to finish the transition neatly.
The terrace slabs are porcelain stoneware, 60x60cm (24x24 inches) and 3cm (1.2 inches) thick.

• The bitumen membrane on the concrete foundation is very uneven at the edge. How can I create a clean transition here? Metal sheets? Edging stones? I see it as a problem that I would actually need to push the terrace slabs further out to get a neat vertical edge, but then the pedestals would be half hanging in the air.
• Unfortunately, there are no supports to stand cut slabs upright underneath the edge (these only exist for 2cm (0.8 inch) thick slabs).
• When standing at the edge of the outer slab, it wobbles or even lifts and tilts forward because the pedestals don’t fully support the slab at the outer edge.

How would you design this transition? How is this typically done?

Thank you very much and best regards, Robert.

You should have installed curbstones, palisades, or deep edge restraints before building the actual terrace, and of course, you should have leveled the unevenly bounded concrete foundation beforehand.

I would suggest using natural stones, such as solid blocks, as a retaining wall. Stack two or three rows. If needed, place a membrane from bottom to top in between and fill the gap with gravel, in case the distance between the existing structure and the wall becomes too large.

MachsSelbst schrieb:

Before constructing the actual terrace, you should have installed edging stones, palisades, or deep curbs, and naturally leveled the unevenly bounded concrete foundation beforehand.

That’s probably correct. I even think the concrete itself is okay. But there is an old bitumen membrane underneath, which extends roughly around the edge. Then a new bitumen membrane was placed on top, also roughly wrapped around the edge. I’m not exactly sure if or how this can still be properly corrected. Maybe I could cut both bitumen membranes flush with the concrete and then install a new membrane (which type) along the edge instead? Would that work?

ypg schrieb:

I would suggest using natural stone blocks as a retaining wall. Stack two or three rows. If necessary, insert a membrane from bottom to top between the existing structure and the wall, then fill the gap with gravel if the distance becomes too large.

That sounds like a very good idea!
There will be a 2–3 cm (about 1 inch) gap between the natural stone and the terrace slabs, which will be difficult to fill since there is a large cavity underneath the slabs.
Are the natural stones placed on a gravel bed or mortar?

I just had an idea: maybe line the cavity with some kind of WPC (wood-plastic composite) paneling, and possibly place one row of natural stone in front of the foundation. I would then need to check how the space between the natural stone and the foundation looks. It could be filled with gravel or small stones.

Any other ideas?

Thanks and best regards.

Make sure to choose the natural stones yourself. Their sizes can vary significantly, which makes the process more difficult and requires some experience to achieve a good result. Otherwise, it’s better to use concrete blocks, as they are usually consistent in size within certain limits.

The wall doesn’t need to be load-bearing, but I would still recommend laying a 20 to 30 cm (8 to 12 inch) deep gravel base and setting the first row in 5 to 10 cm (2 to 4 inch) of cement mortar or concrete.

To reduce the gap between the wall and your terrace, you can set the stones slightly further back with each row. You need to see if it looks good and how far back you want to go. If you’re doing that, I would also consider adding one or two steps. These can be made from masonry stones as well; they don’t have to be precast concrete steps.