Seal the joint in the masonry

Hello,

how is a masonry joint properly closed? Does it depend on the width? Are there any options besides mortar? I am unsure how to fill a deep but very narrow joint with mortar. Specifically, it is about the joints between the RH partition walls and the exterior walls. The joints extend over the entire room height.

Best regards, HerrNolte

This type of joint is generally not sealed - at least not with mortar, as this would weaken the sound isolation between the two buildings. Mortar, being a fairly hard material, would transmit structure-borne sound from one partition wall to the other.

A partition wall joint can be professionally sealed with a silicone compound designed for this purpose over a backing (not for amateurs), or a panel material can be used that is attached to one facade over the entire height and uniformly covers the joint (do not attach it to both facades, otherwise we have the problem of sound transmission again). A sheet about 10 cm wide, fiber cement board, or plaster carrier board (which can be plastered over) would be suitable.