What does the term 'nominal size' refer to in lumber?

The term 'nominal size' in lumber refers to the dimensions originally assigned to the lumber before it undergoes any drying or surfacing processes. When lumber is first cut, it is assigned a nominal size based on its rough-cut measurements. For example, a piece of lumber referred to as a 2x4 actually measures about 1.5x3.5 inches after it has been dried and planed smooth.

This distinction is important because once the lumber dries and is processed, its dimensions change slightly due to shrinkage, which is why the measurements usually differ from the nominal size. Understanding nominal size is crucial for construction, as it impacts how lumber will fit into a project, making it an essential concept for anyone working in the electrical contracting field or any construction trade.