Supporting Roof Rafters Without Kneewall

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.

Supporting roof rafters without kneewall.

This article describes and illustrates the different types of support that prevents roof sagging and wall bulging at buildings including definitions of collar ties rafter ties and structural ridge beams. Collar ties rafter ties tension beams structural ridge beams. Use a hammer and nails to fasten the new rafter to the old and drive nails through the rafter and into the ridge beam at its top end. 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.

A knee wall is a short wall typically under three feet one metre in height used to support the rafters in timber roof construction. You can see the image below for an example of a knee wall. Some of these can support the roof and prevent ridge sagging and wall spreading. Install the second rafter leg in the same manner.

In his book a visual dictionary of architecture francis d. Check that the 2 by 4 is plumb with a spirit level. Knee walls are short usually wooden walls installed around the sides of an attic where the rafters meet the floor. Repeat the process on the other side of the old rafter so that the old is sandwiched between two new pieces.