What have I been writing here for weeks. Exactly that!
What do the construction companies want to do? The price doesn't even matter. It is impossible to get any material.
And as I said, I wouldn't calculate in percentages, but rather by how much the house construction doubles.
Still, first try to have a conversation. Try to find a solution together. Without a lawyer and all that crap.
The best solution in my eyes is simply to let the contract rest on both sides as it is. Wait and watch the market. And if the situation doesn't ease, then terminate it by mutual agreement.
Just imagine the following situation. The general contractor builds the shell, the carpenter the roof truss, and the roofer can't get any roof tiles anymore. What happens then? The whole shell building will get flooded. Who is helped then? You the least of all. Possibly irreversible damage occurs to the building. Then you sue, which certainly costs money, but also a lot of nerves. Not to mention the move-in date.
Now it doesn't have to be roof tiles, but underlay membrane, screws, nails, gutter hooks, or gutters. If one part is missing, it's game over.
The construction companies are now all pulling the emergency brake one after the other. What else are they supposed to do?
Welcome home!