Originally Posted By: jpeck
This post was automatically imported from our archived forum.
Take a cardboard box, lay it on its side and leave both the bottom and top closed. Push on on top edge, pushing toward the other top edge. The entire box moves sideways. If you glued the box down, it would be strong.
Now, open the top and bottom of the box (so you can see through it). Now push on that top edge, the box leans to the other side, in the direction you are pushing it. The box is racking.
The top and bottom acted as the sheathing and wall covering, adding strength to the wall. Without them, or with weak coverings, the wall can be pushed over, just like the box,until it collapses onto itself.
There are many forces which can rack in inadequately braced wall, one of which is wind.