Air gap under the collar beam

Since I already received help here with my question about "editing the screed block" ... here is my next one: My house was built in 1948. Wooden beam construction and the walls are "bundled together" with a mixture of clay-gravel-marl. My question concerns the structure, in that a 1 - 3 cm air gap was left under the collar beam. In other words, this house is a "castle in the air." Question: DOES THIS AIR GAP HAVE TO REMAIN???? In 2016 I insulated the gable roof. At that time, after consulting with the roofing membrane manufacturer about whether the roofing membrane is vapor-permeable or not, I installed a 3 cm ventilation gap. Now I am working on the ceilings of the basement, and so far it has been such that wind can sweep through the house under the floorboards, or more precisely the ceiling to the upper floor, through this huge gap under the collar beam in a north-south or opposite direction. A proper clay coating existed only over the living rooms. Otherwise, just a bucket of construction debris was dumped onto the so-called "clay sticks." My consideration regarding this question of whether the air gap must remain is this: WOOD MOVES. And it does so its entire life. I see it every year on our shed door outside. In summer I have to close it twice; in winter it sticks. So I am aware that wood "moves." And the collar beams are exposed to outside air. So the question: Leave this gap if I insulate the intermediate floor? Then the wind will simply whistle against the insulation if necessary. But I also don’t want to renovate this house in a way that damages it. LESS IS OFTEN MORE I also do not want to turn this hut into a "low-energy house." Ulrike

My consideration regarding this question of whether the air gap must remain is this: WOOD MOVES.

I see it the same way. However, the gap should also be able to close - just elastically, I would advise against rigid.

Yes, I have to see. Last winter I stuffed in a bit of URSA insulation as an "emergency measure." It does compress, but as a final solution, I'm not quite sure. Maybe my son has an idea....

Good day dear community,
I have a question about the issue with the collar beams...
We chose a collar beam ceiling from the upper floor to the attic and now we have noticed a few things...
As can be seen from the pictures, there is an air gap under the collar beams.
I know that this is OK with "non" load-bearing walls. But what about load-bearing walls..?
On the upper floor, we have some load-bearing walls, but none of the beams rest on the walls! According to the structural calculation, this should be the case.
Instead, our site manager gave the following instruction to the shell builder... "Put the collar beams under plaster."
As a layman, I have no idea whether this is good or bad. Now an outsider told me that this is pure sh***. He also called it botched work.
The plastered stuff can be removed with the hand... simply not load-bearing.

Can you quickly give me your opinion?