ᐅ Patio without slope – According to which standard or regulation?

Hello!

Our outdoor area, including the terrace, was recently installed by a landscaper. Since our house is a timber frame construction, a base channel was installed between the house and the ground-level terrace. It is an Aco Profi Line with a width of 25cm (10 inches) and a height of 30cm (12 inches), which drains through the side slots into the gravel bed. The terrace consists of concrete slabs laid on a layer of gravel. The joints were filled with joint mortar, so no significant drainage through the terrace joints is expected.

Now we have noticed that the terrace has no slope...

What could be the worst-case scenario, and are there any measures that could be taken without completely relaying the terrace?
I see the risk that during heavy rain, a large portion of the water will flow toward the house, and the base channel might not drain the water fast enough through the drainage slots.
Also, I have read about algae growth. Does this actually occur in practice?

Which DIN standard or other regulation specifically states that a slope away from the house is part of the recognized rules of technology?

Apart from heavy rain, you will initially notice very practical effects in daily life. Your joints are sealed, it’s drizzling, and the water just stays on the terrace. Then you either have to use a foam rubber strip or let it evaporate, otherwise, you’ll end up with wet feet.
With heavy rain, of course, this can also lead to overloading the gutter, although so much water comes down during that, it’s questionable whether a slope really helps.

Which direction does the terrace face?

But in the end, a slope is mandatory, especially for fully sealed stone terraces; it is extremely important. They will have to redo the whole thing... I wouldn’t pay anything.

Thank you very much, the terrace is located on the north side of the house.

HausbauFrage schrieb:

Now we noticed that the terrace has no slope...

Did you see that, measure it, or test it?

If your wooden house does not withstand water occasionally, it is built incorrectly. Temporary overloading of a gutter is not an issue as long as water does not remain in direct contact with the wood of the house for days or weeks.

HausbauFrage schrieb:

Thank you, the terrace is located on the north side of the house.

Please upload a photo, including of the area around the terrace.

Just placing a spirit level on it is probably enough.

However, trying to convince him that the terrace is fine without any slope... no idea. Terraces, especially those with mortar joints, need a slope; otherwise, in Germany, they are unusable for much of the year because water constantly collects on them. They become algae-covered, mossy, or in the case of wood, simply deteriorate quickly unless subjected to intense maintenance.

If you didn’t explicitly order the terrace without a slope, then the contractor was sloppy and must correct it.
Period, there is no room for interpretation.