Hi, I had a tiled area in the garden that I wanted to slightly expand. The tilers poured some concrete where the new tiles will go. They poured it directly over the soil and it is not reinforced (no rebars or mesh). The soil had fair bit of rocks/pebbles in it. The concrete is in the thickest sections 5cm thick, in the thinnest about 2.5cm, and generally around 3.5-4cm. The top is flat but the bottom side is not (don't think they compacted the earth well before the pour). They will put about 1cm tile adhesive and install 2cm thick tiles which are 80x80 in size. There will only be foot traffic and chairs perhaps in this area - no cars or very heavy objects.
My concern is that the slab is not thick enough. Is there a risk that when / if ground freezes or the ground settles for any reason the concrete will move enough to disturb the tiles above? We are in London, so it does occasionally get below freezing in the winter, though not sure if cold enough for the ground to freeze properly under the tiled/concreted area.
Breaking the concrete and redo-ing will be painful. Is 3.5-4cm sufficient to hold the tiles straight?
My concern is that the slab is not thick enough. Is there a risk that when / if ground freezes or the ground settles for any reason the concrete will move enough to disturb the tiles above? We are in London, so it does occasionally get below freezing in the winter, though not sure if cold enough for the ground to freeze properly under the tiled/concreted area.
Breaking the concrete and redo-ing will be painful. Is 3.5-4cm sufficient to hold the tiles straight?
