Roof Support Knee Wall

Purlins as shown in sample photos below are installed for rafter support.

Roof support knee wall. Unlike other kinds of knee walls this kind of wall extends all the way to the rafters but because of the slope of the roof it is shorter than a full height wall. Homeowners cannot take chances with the structural integrity of their roofs. A knee wall is a short wall typically under three feet one metre in height used to support the rafters in timber roof construction. Collar ties rafter ties tension beams structural ridge beams.

The knee wall forms the wall of the attic room and it also creates an enclosed space under the eaves behind the wall. Hold up to the rafter a scrap piece of 2 by 4 lumber a few inches longer than the planned knee wall height with its base on the floor. Add craftsman brackets to your home even it s not craftsman style if it has overhanging exposed eaves. The roof is subject to pressure placed on it by natural forces including snow rain.

Some of these can support the roof and prevent ridge sagging and wall spreading. Ching defines a knee wall as a short wall supporting rafters at some intermediate position along their length the knee wall provides support to rafters which therefore need not be large enough. An important notation is that the purlin bracing should be off of walls or beams as needed. Check that the 2 by 4 is plumb with a spirit level.

In his book a visual dictionary of architecture francis d. The braces struts or kickers should be within every 4 and should not be at a greater than a 45 degree angle towards the roof slope lower side. How to brace rafters in an attic. Knee walls are short usually wooden walls installed around the sides of an attic where the rafters meet the floor.

In most instances they are no taller than 3 feet but some builders may custom fit them according to the roof s shape and size.