5 FAQ About Surfaced 4 Sides (S4S)

Sawyers with a successful sawmill operation must be willing and able to fulfill orders from their customers in a timely and cost-effective manner. The ability to do this means milling all kinds of lumber and handling a variety of requests. Lumber that is surfaced on four sides (S4S) is one such request.

In order to help you learn more about S4S, here are the answers to five frequently asked questions about this kind of lumber.

1.  What Exactly Does S4S Mean?

S4S stands for “surfaced four sides.” Some people choose to say “surfaced on four sides” or “sanded four sides.” Another term you might hear for S4S is, “square four sides.” This term for S4S is a little bit different as it relates more to thicker beams and timber. For purposes of this article, S4S refers to “surfaced 4 sides.”

2. How Is S4S Different than Rough Sawn Lumber?

You might also be wondering about the differences between S4S and rough sawn lumber. Any wood or board that comes off the sawmill (either a bandsaw or circle saw) is considered rough. A sawyer cuts rough sawn lumber from either kiln-dried wood or green from a recently felled tree. When cut from green lumber, the wood usually becomes twisted or warped as it dries. There might also be tool marks on rough sawn lumber. Rough sawn lumber takes a lot of work to get it just right.

The only way to give the board a smooth finish is to run it through a sander or planer. The result is S4S, which has two flat and parallel faces, two flat and parallel edges and a smooth finish on all four sides. S4S lumber is also uniformed in thickness. For these reasons, plus the fact it involves much less work for the customer, S4S is one of the more commonly requested kind of lumber.

3. How Is S4S Different Than S2S?

The primary difference between S4S and S2S is the number of sides that are surfaced.  For example, S2S lumber means surfaced two sides. A sawyer runs this kind of lumber through a planer with the result of having two flat faces. The edges, however are left rough. People who work with wood might prefer S2S as they can use their own table saw to rip both sides in order to attain perfectly squared sides. There is also S3S, which mean an S2S board has one edge that has been ripped straight.

4. How Do Sawyers Mill Lumber to S4S?

Some sawmill operations, depending on how they are set up, will allow the option of rough sawn; S2S; S3S; or S4S.  This is mainly dependent on what kind of equipment the sawyer has. In order to produce S2S, S3S, or S4S, sawyers typically need the following kinds of equipment:

• Planer – Shaves down wood surfaces in order to reduce thickness and make them smooth and even.

• Jointer – Type of planer that makes straight edges and flat surfaces along the entire length of the piece of wood.

• Sander – Smooths, polishes, or cleans a wooden surface.

The first step a sawyer takes to mill lumber to S4S is to read the grain of the wood. It’s important to go along with the natural structure of the wood. Doing this simple step saves sawyers time and money, as well as wear and tear on the machines. Knowing the grain is also beneficial for producing a much finer surface.

Next, the sawyer uses a jointer to make one face flat. After making the opposite face straight and flat, they use a planer to produce two parallel sides. For the next step, sawyers choose an edge and straighten it on the jointer. They then use a saw to rip the remaining rough edge to produce two parallel edges. The final step is to square the ends.

5. Is S4S More Expensive than Rough Sawn Lumber?

There are many customers who want to buy lumber for the least amount of money possible. For this reason, customers like rough sawn lumber as it’s usually cheaper than buying a finished product. Buying rough sawn lumber allows the purchaser to finish it to their liking, as long as they have the right tools for the job. Customers who don’t have a way to finish their lumber will most likely end up paying more for S4S. The reason sawyers charge more for S4S is that it takes more time and energy to produce.