ᐅ Handling natural stone slabs for a terrace?

Nida35a schrieb:

Our landscaper said that fine gravel locks into the joints, reduces wobbling, and only then gives the surface stability.
And make sure to sweep it in nicely, about 3-5 times, with intervals of 4 weeks.

The same sand or always new?

I have to admit, since the slabs are closely butted together, nothing really gets through there.

If there are no joints at all, then from my layman’s perspective, that’s already a mistake. The gravel provides stability for the slabs. Due to rain and slight movements, the gravel shifts in the joints, so it needs to be regularly refilled during the first few weeks.

My neighbor told me that in his company, they only install patio slabs on gravel with a written disclaimer excluding any remediation work for settlement. According to him, such issues almost always occur, sometimes earlier, sometimes later.

Steve_D schrieb:

The same sand or always new?

The landscaping contractor left two buckets full of fine gravel, and I have been occasionally sweeping it back in. There were always some joints where the gravel had shifted again.

At our place, about 10 slabs, if not more, have sunken. A friend who frequently does this kind of work said that because so many slabs have sunken and they are laid directly next to each other without any joint or gap, the terrace builder would need to remove, level, and reinstall almost 75% of the slabs completely. He also mentioned that quartz sand is not suitable; instead, a minimal joint should be left and resin brushed in, which then hardens over the years.

What should I do if the terrace builder says this is normal for natural stone and nothing can be done?
Or what if he doesn’t want to remove all the slabs but only the ones that have sunken, which cannot be removed because of the tight installation and must therefore be broken to insert new slabs?

Steve_D schrieb:

What do I do if the patio installer says that this is normal for natural stone and nothing can be done?

He wouldn't be entirely wrong, but the issue is not with the natural stone itself, rather with the installation method. Even after repairs, you will experience further settling. Alternatives would be pedestal supports, but of course, that costs more. Even better would be a unigranular (single-sized aggregate) or drainage concrete base. However, at this stage, that would require a full teardown. The main problem, in my opinion, is the lack of joints, as the slabs cannot support each other without them.

We were aware of that, and he had also mentioned it, always adding that we could fix it later. But I didn’t expect there to be so many panels. Additionally, I was told that using lime putty was also the wrong choice for him, as it eventually breaks down. Overall, very disappointing for nearly 14,000 euros.