| Cross-pieces may not be needed to prevent the wall from racking, but they might be a good idea to put in as firebreaks. They may be required by building code in your area, for precisely this reason, especially if you've got any electricals in the wall that may be a point for fires to start.
The idea is to prevent any flames from racing up the entire interior of the wall. Smaller cavities means smaller, slower fires if any do start in the wall. It can make the difference between the firemen saving your house and saving your basement. |