It is reasonable for a lot of novice DlYers and woodworkers to get confused by the sizes of lumber products. The confusion may be as a result of the anticipation that the nominal dimensions of a piece of timber or any other lumber product for example a 2 x 4 piece of timber represent its actual dimensions. This is not the case since the lumber measurement displayed at the store is not equal to the actual dimensions that you will get after measuring the lumber.
As we have just seen the actual lumber sizes is different from the nominal dimensions displayed at the lumber store. Lumber manufacturers have a reason why they don’t match actual and nominal measurements of lumber as they process the products.
Since dimensional lumber is cut from a tree immediately after the tree has fallen and still wet; it is difficult to maintain the standard measurements after the lumber has been dried during processing. The wet lumber whose nominal dimensions are equal to the actual dimensions is dried during processing to attain the required level of moisture; this loss of moisture causes the reduction in sizes as wood cells reduce in size when they lose water.
After the wood has been dried, the resulting boards are then polished to standardized their sizes which reduces the dimensions further; for example, a piece of timber which initially measured 204 inches is reduced to about 1.5 x 3.5 inches. Though these measurements may differ, it is rare because lumber producers employ modern techniques during processing to achieve consistency in dimensional lumber sizes. Consequently, a construction project built using dimensional softwood lumber from a local store is actually thinner than its supposed thickness. To achieve the desired thickness apiece made using dry wood must be attached it.
Also it is important to note that this method of measuring wood is applied to dimensional softwood lumber which is intended for construction purposes but not for advanced woodworking projects. A different method that uses board foot is applied to measure the dimensions of hardwoods intended to be used in advanced woodworking projects.
In addition, it is import to remember that some lumber products such as plywood and hardwoods have a different measurement method which you will need to master well for you to work with them correctly.