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Roof trusses

Knee wall

A knee wall is a short vertical wall or strut under the slope of the roof, forming the low side wall of a room in the roof.

Also known as knee wall, dwarf wall, ashlering, side strut, knee brace

In a room in the roof the ceiling height drops towards the eaves. Knee walls, often around 0.6 to 1.2 metres high, close off the lowest part and support the rafters or top chords part-way down the slope. The space behind them is typically used for storage or services.

In frame (A-) trusses the side struts that form the knee walls are part of the truss itself.

Related terms
Frame truss (A-truss)A frame truss (A-truss) is a roof truss built as an open frame of rafters, tie, collar beam and side struts, leaving the roof space free for a room. Attic trussAn attic truss leaves an open rectangular space in the middle of the roof, so the loft can be used as a room. Storey-and-a-half houseA storey-and-a-half house has a full ground floor and a second floor built into the roof, with sloping ceilings and knee walls.
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