I'm reinforcing walls in a house with weak standing 45 studs in the interior walls. The walls I've done myself have been soundproofed with stone wool and then fitted with fiber gypsum boards horizontally (studs cc 60 and fiber gypsum is available in widths of up to 90 cm to buy, so it's convenient to lay 90+90+60 = 240 cm). Heavy and somewhat cumbersome to work with, but these walls become much more stable than walls with regular gypsum. You use Fermacell's adhesive joint on the long side, so the boards don't move at all against each other. Possibly horizontal laying contributes to strength as they lock the wall. The idea is to place standard vertical gypsum boards 120 cm on these.
On a couple of other walls, a company has soundproofed with glass wool (incidentally sounds more hollow than stone wool) and then a layer of gypsum. The walls flex significantly under load, and I therefore wish to reinforce these walls.
My question is, will a wall with 45 studs become stable with double gypsum? My other alternative is to place fiber gypsum boards horizontally on top of the gypsum, but then the question is how good it will be with spackling and painting on horizontally set boards, the adhesive joint should prevent them from cracking, but clearly, it would have been better with a stud behind.
