Single or double layer partition: which to choose

Whether to use one layer or two is decided by what will hang on the wall and what can be heard through it, not by budget. The frame is the same either way — the difference starts at the boarding.

• One layer: light partitions with no load and no quiet requirement
• Two layers: speech through the wall, hung furniture, a TV, a door
• Thickness and price rise far less than strength and sound performance

What the second layer buys

A second board adds mass, and mass is the main parameter for airborne sound. It also removes the weak point of single boarding: the joints. In the second layer the joints are offset from the first, so a crack along a seam and a sound path through it both become much less likely. The wall also stops sounding hollow when knocked.

When one layer is enough

One layer works fine where the partition simply divides space: a wardrobe, a service box, closing off a niche, splitting a storeroom. If nothing is hung on it, there is no bedroom behind it and no door in it, a second layer is money wasted. Just do not economise on stud spacing: 40 cm instead of 60 buys stiffness more cheaply than a second board does.

When two layers are non-negotiable

Use two layers if people sleep behind the wall, if a TV, shelves or kitchen units will be hung on it, if the partition contains a door (which works the structure loose), and if the wall is long or tall. In a kids room split in half the difference is audible immediately — and redoing it later costs more than building it right the first time.

What it changes in thickness and cost

A second layer adds roughly 12–13 mm per boarded face, which is almost always irrelevant in a flat. In money it is one board, fixings and the labour to fix and fill it. Considerably cheaper than stripping a finished wall because the TV will not hold or the neighbours are louder than expected.