There's a general set of guidelines for that on page 577, or here on AoN. Contrary to what others have said, there are indeed rules for their statistics.

Bit of a tangent, but oddly, despite listing AC for objects, there's not really a way (other than spells, of course) for characters to, as-written, attack and damage objects; the Strike action only lets you target a creature. They've stated an aversion to sundering rules in this edition, which factors in to why it's rare for spells to be able to target objects, but if that's the case they could've just distinguished between attended and unattended objects. As-written, your only real mundane option for breaking through doors and windows with brute force is the Force Open action.