ᐅ Foundation/Base for WPC Decking

Sebastian79 schrieb:
It’s interesting that water drains just as well or poorly on a slope as without one – physics gets explained to you all over again here

How much water actually drains with a 1% slope? In the end, there is always a water film left on the terrace, whether there is a slope or not. With grooves, the water even stays in place at 1% and doesn’t drain at all. Proper drainage only happens with a steep slope (terrace roofs around +/- 10%) and not on terraces.

Of course, decking suppliers recommend a slope, and I would too, to avoid liability issues and complaints about defects.

P.S. Although my job title is bank clerk, I have been involved in real estate for 20 years and can therefore draw on considerable experience with properties – from small condominiums to large commercial buildings with tens of thousands of square meters of space.

Neige schrieb:
In my experience, decking that holds a water film deteriorates much faster.

That may be the case with ordinary wood, but when it comes to the more resilient tropical hardwoods, the problem only occurs if the wood remains waterlogged for a long time. In my experience, problems tend to arise more with the substructure because the structural wood protection is often neglected (for example, placing joists directly on well-prepared gravel and letting them get soaked, or screwing the decking boards directly onto the substructure).
The water film usually dries within a very short time after rain, just like any damp surface – whether wood or concrete. The last few drops simply won’t drain off at such a mild slope.

The original poster’s situation is even less problematic, since they were directed towards WPC by their boss. Those are even more resistant – though they are not wood.

Warping in WPC is not only recommended...

And with all due respect to your real estate experience, why should you be particularly competent in something like this?

WPC would not even be an option for me. The problem, as I have often seen, is that the surface tends to crumble over the years if it is exposed to the sun for too long and intensely (when it actually shines here ).
But this is a topic that can be discussed endlessly.
It is true that the substructure or framework is a significant and not to be underestimated part that requires special attention. Most mistakes are probably made here.


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andimann schrieb:
you still need enough support points because the wooden beams tend to bend quite quickly.

The wooden beams rest on appropriate rubber pads. The spacing to the support points depends on the thickness of the beams (I have a support point every 50 cm (20 inches)).

andimann schrieb:
And the wooden beams also rest in water

No, they do not, that's what the rubber pads are for.

andimann schrieb:
Which wood do you use there

I used Bongossi, which is also commonly used for boat docks or fence posts because it withstands prolonged contact with water very well.

andimann schrieb:
I was already considering designing the load-bearing substructure using IPE 80 steel profiles.

Won't that be expensive? But of course, it can also be done.

Sebastian79 schrieb:
And respecting your real estate experience, why should you be especially knowledgeable about something like this?

When you work for many years with project developers, planners, architects, and regularly coordinate construction projects together with project controllers, appraisers, and other experts (not just from an office, but actually on site—in boots and helmet ), you learn an enormous amount about real estate.
There are plenty of properties that include wooden terraces—whether in landscaping, terraces for restaurants, rooftop terraces on office buildings, and so on.

So I base my experience on that, in addition to having built four terraces myself and helping friends with theirs.

andimann schrieb:
Just how to fix the Garapa decking boards onto the steel profiles

Addendum: Not directly, use a wooden substructure on top of the steel profiles.