In our neighborhood, there has also been a shell construction covered with a tarp for months. I am really glad that we chose a flat roof. Bitumen prices have indeed gone up, but for > 100 m2 of flat roof, even that does not really matter. Overall about €4,300 for all sheets including installation. The price for this position would probably have been 20-30% cheaper last year, but it would have been lost in the general noise of the offer differences. However, the offer includes a price adjustment clause.
According to our contractor, he sees no problems with material availability for our shell construction, which is supposed to be erected in September. However, we had to switch from Poroton to aerated concrete because it was uncertain whether we would get bricks in time during the last inquiry… Allegedly, they are currently accepting orders again at least.
At the moment, I am worried about the windows. We will probably only order them according to plan around September/October, hoping to receive them by January at the latest. Bad timing if there is no gas anymore then, maybe one could order some in Poland…