Timber frame builder replaces OSB with gypsum fiber boards - equivalent?

Hello everyone!

After months of searching for timber frame house manufacturers who offer credible wall constructions, I have decided on one from Bavaria. I also adopted and believed the mantra of "OSB is a universal weapon" because it is ecological, more or less breathable, super stiff, load-bearing, sound-absorbing, etc.

Now, due to material shortages and price increases, the house manufacturer informs us that they have now planned gypsum fiber boards as an alternative to OSB, which would be price-neutral for us and technically advantageous. Until now, gypsum was planned as ONE layer in addition to the OSB board. Now the ENTIRE wall is to be constructed from gypsum fiber boards.

I doubt that gypsum fiber boards can be an equivalent or even superior replacement for OSB due to their material properties.

What is your opinion?

I also have the mantra of "OSB is a universal weapon" because it is ecological, more or less breathable,

So it certainly is not a weapon – ecological? My architect and home builder consciously do not use it because it is not that ecological. Breathable? How is an inanimate object supposed to breathe? For bracing a timber frame wall, many materials can be used; you are not restricted to OSB. What exactly does the wall structure look like then? What does the structural engineer say?

Hello Daniel!

Certainly, there are much more breathable building materials than OSB, no question.
The structural engineer has not commented yet, but he is likely to agree with the construct since he works for the same company that also commissioned this alternative cladding.

Your assessment is important to me: For bracing, many materials can be used alongside OSB.
I understand you to mean that gypsum fiber boards are one of these materials.

"Breathable" is absolutely nothing on OSB. The material is used the other way around with tongue and groove and glued joints to create an airtight layer. For me, the interesting question here would be, if there is no OSB anymore, what is the airtight layer? Certainly not double-layered drywall.

Gypsum fiber boards should be used instead of drywall. He corrected that in the text. Here, for example, Fermacell Vapor can be used to create a windproof layer.

To my knowledge, gypsum fiber boards are not as load-bearing as OSB boards. That means when mounting tall cabinets and kitchen units, this must be taken into account or is limited.