ᐅ Is drainage necessary under the entrance platform?

Hello everyone,

We want to install a natural stone-covered entrance platform for our single-family house. It is basically just one step, approximately 2.40 x 1.20 m (7 ft 10 in x 3 ft 11 in) in size. For the material, I chose 60 x 60 cm (24 x 24 inches) flamed basalt slabs.

The platform was poured from screed several months ago. It slopes downward away from the house, so rainwater can drain off.

The question now is, do I still need a drainage system for this? The tiler says no, but a civil engineer friend says yes. If the slabs are properly glued, how could they freeze and be damaged? What benefit would a drainage system actually provide? Water would never penetrate that deep anyway.

Best regards

If there is a risk that water can penetrate through the joints between the panels and the screed, this can already cause damage during freezing conditions. In the worst case, the panels could come loose.

Masipulami schrieb:
If there is a risk that water can penetrate through the joints between the boards and the screed, this can cause damage during freezing temperatures. In the worst case, the boards could come loose.

However, if water is getting through the joints, then there is something wrong with the joint itself.

Why? Joints are not necessarily waterproof – and how would you even notice? If it's too late, it's too late – so make sure to seal properly beforehand or provide adequate drainage.

Could this backfire if you try to drain water deliberately into the drainage system but are unable to do so because the ground is frozen, and then frost occurs again? Wouldn't everything freeze completely in that case?

Yep, there are heated drainage channels for that.

I personally prefer covered solutions, so you have (almost) no problems.