ᐅ Is drainage necessary under the entrance platform?

Created on: 13 Apr 2016 07:42
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hg6806
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
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hg6806
13 Apr 2016 14:47
Well, whether there is just a thin layer of moisture on it due to a roof cover or several centimeters of standing water, it probably doesn’t make a difference for small cracks where water could penetrate.

As a construction layperson who understands some physics, I would say that the mortar and joint compound need to be applied in a way that no cracks form. Anyway. Maybe thinner? At least not "damp from the ground"!
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Payday
19 Apr 2016 14:43
You could also make the base slab from a single piece. That way, there are no joints and the structure is solid. Our entrance platform is made from one piece.

PS: The link above is not allowed here in the forum.
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Sebastian79
19 Apr 2016 14:44
You still have expansion joints.
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hg6806
19 Apr 2016 14:59
Sorry about the link, I can’t delete it anymore either.

Speaking of joints. For the 60x60cm (24x24 inches) large tiles with a thickness of 3cm (1.2 inches), how "narrow" can the joints be to prevent cracks or gaps? Is under 5mm (0.2 inches) possible?
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Payday
19 Apr 2016 15:35
Sebastian79 schrieb:
You still have connection joints

Where else except right at the front door? That one is covered
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Sebastian79
19 Apr 2016 15:37
But not in the case of the original poster, and a roof covering only offers limited protection against driving rain or snow – even if it represents extreme conditions.

And yes, I meant exactly that joint.