Newly laid terrace with concrete stone slabs -> is that normal?

Hello Gatho

That is (unfortunately) normal... and not a reason for complaint :-(

Concrete is cast in molds at the factory and packaged after hardening; mostly not yet fully dried (not 28 days) and then wrapped in foil. Excess water then accumulates and causes these lime efflorescences. I myself also have this on some concrete slabs on our newly laid terrace. It was almost always the first layer of the pallet. It is supposed to "wash out" over time (rain). If necessary, you can treat it with special stone cleaner. For that, contact the supplier or manufacturer of the concrete stones to see if they offer something like that.

Best regards

What can the patio builder do about it? You chose the stones and their quality, didn't you? The patio builder doesn't have to do anything. He might have told you that something like this can happen, since as the client you are not all-knowing. It can happen. I've seen it several times and read about it here.

It will probably look like that for us too. And we are planning a dark stone for the driveway, like Alex. The terrace will be tiled so that something like this doesn't happen.

So first of all, I don’t blame the patio builder in that sense. He gets the order and is the executing party. He is also in direct contact with the construction management. My concern is only why this batch was even laid at all. In our case, there is still a whole other pallet of concrete slabs. I think they could have sorted that out. If it were just individual slabs, one could probably live with it. But since over 30 slabs are affected and they also form a nice strip across the patio, hopefully the frustration can be understood.

So first of all, I don't blame the terrace builder in that sense. He gets the order and is the executing force. He is also in direct contact with the construction management. My concern is only why this batch was laid at all. In our case, there is actually a whole other pallet with concrete slabs. I do think that one could have sorted that out. If it's just individual slabs, you can probably live with that. But since over 30 slabs are affected and they are also nicely arranged in a strip across the terrace, hopefully the displeasure is understandable.

The displeasure is understandable. But who tells you that after rain and a lot of sunshine, the apparently good slabs won't look like that either?

Pleasant news when I got home.

All "affected" panels were replaced. Who would have thought. It looks great now.

Many thanks to everyone here.

Perfect, you have good craftsmen. Next time, put down a crate of beer.

Completely normal efflorescence of the lime in the concrete, clearly visible that this is mostly in the middle, where the slabs were closely together and stayed damp for a long time. You also have this with paving stones, sometimes more sometimes less, it takes a while until it weathers away.