ᐅ Constructing a concrete floor for a terrace.

Hello

I will be constructing the terrace floor on top of the ceiling slab of my double garage. The area measures 770cm by 600cm, so about 46m² (495 sq ft). The floor (or ceiling slab) is made of waterproof concrete. Unfortunately, it was not finished smoothly. There are many uneven spots and no slope.

I have never done anything like this before. My plan:

I will prime the concrete surface with ASO-Unigrund-S (my building materials supplier carries the brand and it sounds reliable; I think a 25-liter (6.6 gallons) container should be enough). Then I will apply about 15 to 20 bags of leveling compound Soloplan-30-Plus. (According to Schomburg’s customer service, it is also suitable for outdoor use if it is not constantly exposed to moisture.)

After that, a roofer specialized in flat roofs will install a vapor barrier. On top of that, Styrofoam insulation (custom-made for me with the correct slope) will be laid, followed by two layers of roofing felt (which I know as "Elefantenhaut").

Once that is complete, a protective mat for construction will be installed, then about 5cm (2 inches) of gravel, and finally, the floor will be covered with granite tiles measuring 600 x 300 x 30mm (24 x 12 x 1.2 inches).

What do the experts think? Is this plan sound or could it be improved? This is my first time doing this and it needs to last a loooong time.

Best regards

Steven

Replace leveling and slope insulation with a sloped screed. It is likely to be more cost-effective. However, this is only possible if the structural design allows it and the garage is unheated.

Hello guckuck2

I just disposed of the screed. I had it installed but was never happy with it.
Well, I didn’t seal it properly.
I quite like the polystyrene. I need to build up 30cm (12 inches). With screed, gravel, and granite slabs, I could already run into weight issues.

Steven