ᐅ Roof Terrace on a Flat Roof – Construction – Surface Covering
Created on: 12 Feb 2016 14:28
W
WildThing
Hello everyone,
We have a sloped plot of land, so our garage has a flat roof that will later become a terrace. The terrace is accessible from the living room and is approximately 40 sqm (430 sq ft).
The garage is masonry with concrete ceilings. Bitumen sheets were installed and welded on top, then a slope was created using Styrodur (I think), and the "roof" was finished with welded flat roof membrane.
Now we are wondering what to put on top of this membrane. Unfortunately, we have quite a low build-up height—10 cm (4 inches) below the terrace doors and at one corner even only about 5 cm (2 inches) because of the slope.
Wood/WPC
At first, we considered wood with the appropriate substructure, but I suspect that would be too tall.. :-/ Also, we should not forget the effort required for annual oiling.
We do not like WPC at all; to me, it looks way too "plastic-like" over such a large area. On a smaller terrace, I could imagine it, but not on our large one.
Stone/Ceramic
We were advised to use paving slabs on a gravel bed for the terrace. Specifically, these new "ceramic slabs," which are only 2 cm (¾ inch) thick but suitable for outdoor use. They are simply laid loose on the gravel and held in place by their own weight. However, they are quite expensive—over 50 EUR/sqm (about 5 USD/sq ft). What other affordable stones/slabs/tiles are available?
Questions
What other options are there?
Which of the mentioned options offers the best value for money?
Who already has experience with these ceramic slabs and can share their feedback?
We have a sloped plot of land, so our garage has a flat roof that will later become a terrace. The terrace is accessible from the living room and is approximately 40 sqm (430 sq ft).
The garage is masonry with concrete ceilings. Bitumen sheets were installed and welded on top, then a slope was created using Styrodur (I think), and the "roof" was finished with welded flat roof membrane.
Now we are wondering what to put on top of this membrane. Unfortunately, we have quite a low build-up height—10 cm (4 inches) below the terrace doors and at one corner even only about 5 cm (2 inches) because of the slope.
Wood/WPC
At first, we considered wood with the appropriate substructure, but I suspect that would be too tall.. :-/ Also, we should not forget the effort required for annual oiling.
We do not like WPC at all; to me, it looks way too "plastic-like" over such a large area. On a smaller terrace, I could imagine it, but not on our large one.
Stone/Ceramic
We were advised to use paving slabs on a gravel bed for the terrace. Specifically, these new "ceramic slabs," which are only 2 cm (¾ inch) thick but suitable for outdoor use. They are simply laid loose on the gravel and held in place by their own weight. However, they are quite expensive—over 50 EUR/sqm (about 5 USD/sq ft). What other affordable stones/slabs/tiles are available?
Questions
What other options are there?
Which of the mentioned options offers the best value for money?
Who already has experience with these ceramic slabs and can share their feedback?
My apartment also has a rooftop terrace above the garage. There are 40 x 40 x 3-4 cm (16 x 16 x 1-1.5 inch) colored concrete slabs (sand yellow) installed on height-adjustable pedestal supports.
Google search: height-adjustable pedestal supports
I haven’t checked whether you can use these with a height of only 5 cm (2 inches). In my case, the height ranged between 8 and 14 cm (3 and 6 inches). The advantage is that you can level the terrace very precisely, and water drains very well underneath the slabs towards the roof drain.
I chose a color for the concrete slabs that closely matches the color of the tiles in my living space. When looking out from the terrace door, it always looks like a slightly extended living area without a harsh color contrast.
Google search: height-adjustable pedestal supports
I haven’t checked whether you can use these with a height of only 5 cm (2 inches). In my case, the height ranged between 8 and 14 cm (3 and 6 inches). The advantage is that you can level the terrace very precisely, and water drains very well underneath the slabs towards the roof drain.
I chose a color for the concrete slabs that closely matches the color of the tiles in my living space. When looking out from the terrace door, it always looks like a slightly extended living area without a harsh color contrast.
There are panel supports suitable for this low build-up height, but you should choose a sufficiently large panel with a thickness of 3-4 cm (1-1.5 inches) to ensure stability. In my opinion, at least 40 x 80 cm (16 x 32 inches) panels are recommended, as they have enough own weight. However, for this roof structure, an additional layer to protect the roofing membrane should also be planned.
By the way, is fall protection actually planned for this terrace construction?
By the way, is fall protection actually planned for this terrace construction?
The 40x40 supports work quite well for me. The base plates are relatively large. With 40x80, I could imagine that height adjustment becomes more complex because 80 cm (31.5 inches) already involves overcoming a significant slope. Also, it might be more unstable in that case.
Phew, that’s a relief, Bauexperte!
Thanks for your information, KTB. I’ve heard about that too. However, I’ve also heard that these pedestal supports can shift if, like in our case, the ground is “soft.” Because of the insulation, there is some springiness when walking on it. Have you noticed anything like that?
We have a masonry parapet as a fall protection. I really like it because it also serves as a privacy screen from the street.
What do you think about a “gravel bed”? It currently seems to be the most cost-effective and simplest option. Especially since you can do it yourself.
Thanks for your information, KTB. I’ve heard about that too. However, I’ve also heard that these pedestal supports can shift if, like in our case, the ground is “soft.” Because of the insulation, there is some springiness when walking on it. Have you noticed anything like that?
We have a masonry parapet as a fall protection. I really like it because it also serves as a privacy screen from the street.
What do you think about a “gravel bed”? It currently seems to be the most cost-effective and simplest option. Especially since you can do it yourself.
The build-up height is too low for a gravel bed. Ideally, a gravel bed should be 4-5 cm (1.5-2 inches) thick, at the very least 3 cm (1 inch). However, you shouldn’t even consider laying the 2 cm (0.8 inch) thick ceramic tiles directly on gravel. This setup will be even less stable than adjustable pedestals. The ceramic tiles do not have enough weight, and the gravel base is too thin to absorb the forces applied from above. Additionally, a drainage mat about 2 cm (0.8 inch) thick should be installed under the gravel; otherwise, the tiles may start to float during heavy rain.
For an area of about 40 m² (430 square feet), a wooden solution could be considered. Why not divide the area and build a corner platform?
For an area of about 40 m² (430 square feet), a wooden solution could be considered. Why not divide the area and build a corner platform?
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