drywall joints can crack in unheated buildings and cottages because of thermal shrinkage, but not always. The problem is actually much less common than most people fear. If I were you, I’d use a modified approach when covering the seams, one that imparts more joint strength. For the first coat of mud, use a setting-type compound like Durabond 90. This comes as a powder that you mix with water. The resulting mixture hardens by chemical reaction in about an hour. This stuff is very strong, but you’ve got to watch for something. It’s not sandable, so all extra Durabond 90 must be removed before it cures. After that, follow up with a couple of coats of regular drywall compound. Even in fully-heated buildings, a base coat of setting type compound makes much stronger outside corners.