What is the reason behind keeping the cement surface uneven before placing tiles?

Thank you Bryan for clearing my doubts. Your answer is really helpful.

So that, when you are tapping it, will level bed to set and air pocket will get out giving a level bed for bonding.

Hi Raul,

Basically, there is no need to install an underlayment between concrete and the tile.

We just have to need to prepare the surface before placing the tile.

No doubt that various uneven areas in the concrete can cause damage to the tile above and uneven, uncontrolled moisture in the concrete can destroy the mortar and loosen the tiles.

I strongly recommend you to please prepare your floor properly for a long-lasting tile installation. The tile must be placed on a rigid and structurally sound surface.

Thank you.