Roof inside

[Magnus O]

I am renovating the kitchen and have removed parts of the tongue-and-groove boards on the underside of the floor joists to access the wastewater pipes from the second floor.
I'm considering tearing out the rest of these tongue-and-groove boards while I'm at it, thereby removing all the sawdust and replacing it with mineral wool.

What I am wondering is if this layer of tongue-and-groove boards needs to be replaced, for example with some type of board. Have these tongue-and-groove boards had any stabilizing effect on the joists or was their only task to keep the sawdust in place?
I will further sparse and screw drywall. Maybe the drywall could then serve as stabilization?

 

[imported_Byggaren]

They have most likely not had any other function than as the base for the filling. Stabilization between beams in older houses consists of cross bracing, slender sticks placed between the top of one beam and the underside of the adjacent beam and a stick in the opposite direction to form a cross. (Hence the name cross bracing.)

Since you will have plasterboard or another sheet material as the ceiling afterwards, you will likely need to nail up some form of spaced paneling. Choose 28x70 cc 400 and place your mineral wool on top between the beams on the base.

(There technically shouldn't be a need for a vapor barrier (plastic foil) in a floor between levels (as the temperature is the same on both the underside and the topside, with no moisture migration), but it's still good to lay a plastic foil above the spaced paneling to prevent moisture from rising that way from the level below, especially in a kitchen, bathroom, and other places where warm, humid air occurs in large amounts.)
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Byggaren.