ᐅ Order of Screed and Plaster Work

@: "xray107"
I’m not sure whom you directed your additional request to, unfortunately without greeting.
"What advantages do you see in the order screed/plaster versus plaster/screed?"
No one mentioned any pros or cons here.
It is common practice (and also the simplest way) to apply the screed against existing wall plaster.
But then Christian also asked:
"Lately you often read that the plaster must be applied down to the floor slab for airtightness reasons... is that really the case?"
This question has not been answered yet.
The answer is: NO.
Wall plaster never has anything to do with airtightness.
The reason to apply a screed over edge strips against wall plaster (and not the other way around) is simply because it makes handling the sound insulation or the edge strip easier.
And it is wrong to say that wall plaster is applied down to the floor slab!
The edge strip (which you, Christian 123, probably confused with plaster) must, according to DIN 18560, be installed down to the floor slab or, in cases of thicker layers, down to the lower insulation layer, which usually forms thermal insulation on ground floors.
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Hoping that this clears up any remaining questions: KlaRa

@KlaRa
I have asked the thread starter my question without a greeting.

"Nowadays, you often read that plaster must be applied all the way down to the concrete slab for airtightness reasons... is that really necessary?"
This question has not been answered so far.
Answer: NO.
Wall plaster has absolutely nothing to do with airtightness.

Maybe I completely misunderstood your post, but everywhere you read that the interior plaster must be carried down to the concrete slab.
Wall-to-floor connection:
Especially exterior walls must be plastered right up to the concrete slab, otherwise unpleasant cold air pockets may form near the floor later on. There must be no gap anywhere between the screed and the plaster.


By the way: I also miss a "Hello" and a "Best regards" in your post to me. *surprised*

Hello,

...and thanks for the previous replies.

@xray107
On one hand, I thought it was quite pointless to build the walls with highly insulated bricks, insulate the roof and the slab heavily, and then apply plaster all around right up to or just above the slab... In my opinion, this creates a continuous thermal bridge because the plaster is nowhere near the thermal conductivity of the PUR insulation with a lambda value of 0.023 W/(m·K). On the other hand, I would prefer to have a continuous insulation layer directly on the slab, on top of which the pipes can be installed and therefore stay "warm." Of course, this is not possible if I plaster first.

@KlaRa: Thanks!

Best regards,
Christian

KlaRa schrieb:
In any case, wall plaster has nothing to do with airtightness.

I find this answer surprising coming from an expert... of course, the interior plaster serves as the airtightness layer – where else would it come from? That’s why plaster is always applied down to the floor.

And what about a thermal bridge? Sometimes you can exaggerate – after all, the slab or ceiling is also insulated on the sides, so how should there be a thermal bridge caused by the plaster or insulation that is not perfectly flush?

Hi Sebastian79,

side insulation: yes, but there is no insulation under the floor slab... The idea of extending it up onto the slab is relative, as the plasterer will at most go up to the upturned vapor barrier, if I understand correctly. Because the plaster would not adhere to that.

Regards
Christian

I wasn’t talking about under the slab, but rather on the side, because there definitely needs to be perimeter insulation there.

The plaster will stick to it – it’s not a membrane (or do you actually have one there?). Are you perhaps confusing this with the roof area?