Is a terrace with natural stone slabs on a concrete foundation possible?
We would like to have a terrace with natural stone slabs, and we currently have the following construction (13 years old):
Compacted recycling. Concrete slab 18 cm. Sloped screed (only 1% slope!) with reinforcement and sealing film under the screed. Laminated porcelain stoneware. Aluminum extrusions on the edges. The aluminum profiles are now loose, and some of the edge tiles are also loose and/or broken.
We now want to build a patio with natural stone tiles, and we have the following idea:
Remove the stoneware tiles. Grind the sloped screed down to a 2-3% slope. Laying sheets with dimples (dimples up, overlapping, like shingles) >= 3 cm of basalt rubble on top and sand to 2% slope. Place unbound slabs on crushed stone. Install curbs.
Now our questions:
Is it possible to lay natural stone slabs on crushed stone on a concrete slab in this manner? If not, how else is it possible? Is it necessary/necessary to use a drainage fleece? If so, is it directly on the bubble wrap or directly under the slabs? As for laying on gravel: can it stay constantly wet under the slabs (even with a slope) due to drips remaining and would that be a problem?
P.S.: Overall construction height is not an issue for us.
Answer
Possibly without a drainage fleece. It is important to have at least a 6 cm layer of sand. And very important: use a grit of 5-8.
Otherwise you will get the famous wet spots on the natural stone. If you don't know what that is, just google it.
Most people use 2/5 or 0/5 grit, but they don't destroy capillaries. No problem with concrete slabs, but with natural stone you will get wet spots.
