The difference between sawn timber and planed timber is the finish or the look and feel of the wood's surfaces. Sawn timber has rough faces whilst planed timber is smooth.
Sawn timber is cut to size with a saw (a cutting tool that has a blade or series of blades with 'teeth' as a jagged edge) leaving rough surfaces. Planed timber is further processed by planing these sawn, rough, faces and edges to smooth finish, this is carried out using planing tools, from hand planers to a multi-head planing machines that can smooth all faces with one 'run' of the wood
All wood can be sawn to size and then planed.
Here is a very simplistic overview of wood from tree to home. Wood comes from trees, as you know, and there are thousands of wood species on earth. As humans, we use many for lots of applications.
Firstly a tree is cut down, it then logged. The journey of the timber then depends on it's final use. For the purpose of this article, of how we get to sawn and, ultimately, planed wood (and beyond), let's assume this is hardwood, say, oak, for a dining room table.
The wood is the cut to into boards, please see the illustration below for the 'cuts of wood'. Each method of cutting or sawing into boards, as shown, affect the appearance of the timber. This is because the growth rings and grain will show differently based on the angle of the cuts through the log.
The wood is the dried. The method and level of drying, again, is dependent on usage, species, transportation and other considerations. For our example - this wood will kiln dried. These ensures that the lowest level of moisture is present after the drying process. For more about moisture in wood please click here.
Once the boards are cut and dried - we then have the 'sawn' finish. The timber can then be sold or distributed to the end user in this sawn state, as our sawn board options. Or it can be further processed by planing all round (PAR) and PSE (planed square edged). For more about the types of planing please click here.
Here is an illustration of sawn vs planed wood and the some cutting methods.
So we have determined that planed wood is just sawn timber further processed. The question is - what option is best for you? Buying wood in its sawn state has more flexibility and will cost less that buying it already planed. But, depending on your desired use, you may need to plane it smooth anyway, in which case you will need the tools and the skills. Planed wood will be supplied with all surfaces square and smooth you can then use as this or machine to mouldings, profiles, carving, sections or components of timber products - whatever you wish. The choice is yours.