This is a section from A Beginners Guide to Woodworking: Helping New Woodworkers Make Better Projects, which is available on Amazon. Over the next month, you will be able to read the entire book, and I hope that you like it enough to get tour own copy. Enjoy.
How Wood is Sold
The problem with wood is that it comes in so many different sizes that a system had to be devised to sell it based on buying the same size piece. It could not be done by weight, because wood has such a wide variety of weights, so it had to be by size. So, how do you sell a board by the foot when it comes in so may different sizes?
Board feet. A Board Foot is a unit of measurement that represents a piece of wood that is twelve inches square on the face, and one inch thick. In reality, one inch is really closer to three quarters of an inch, but that’s a topic for another time.
Wood sellers price their wood as an amount of money per board foot, so no matter how thick or wide the piece, you will always pay the same price.
The way to calculate board feet is to measure the length of the board and the width in inches, and then multiply them together. Then, get the thickness of the board and multiply that by the number you already have.
Finally, divide that number by 144 (which is the number of square inches in a single board foot) and you have your answer.
For example, if you have a board that measures 86 inches long and ten inches wide, that is one inch thick, you calculate the following:
(Length X Width X Thickness) / 144 = Board Feet
86 X 10 X 1 = 860, then 860 / 144 = ~6
The board in this example is about six board feet, so if the price is five dollars a board foot, this piece would be a thirty dollar board.
Board feet measurements solves the problem of some boards being thicker than others, and some boards being wider than others. If the ten inch wide board in the example were only five inches wide, and the same length, it would measure three board feet.
The board would have to be twice as long at five inches wide to be the same six board feet as the ten inch wide board.
Once you do the math a few times, you will easily see that the size can change dramatically but still be the same number of board feet.
A really wide and short board can have the same board feet as a really narrow and long board, as long as the math works out. Also, a two inch thick board will be have half the surface area because you are multiplying by two instead of one.
I recommend that you take a tape measure down to the wood store and measure a few boards for practice. If you do the process a few times, you will be all set, and you will understand that you are always measuring the same amount of wood, it’s just a different shape.
The price of the piece is always going to reflect the same amount of wood, so make sure that you buy what you need based on the project that you are making.
Board Thicknesses Explained
There was a time when a 2X4 was actually two inches by four inches. Now, it’s one and a half inches by three and a half inches. By the time I die, I expect it to be much smaller than that.
Well, not really, but you will discover this little trick in labeling a lot when you buy wood. The sizes are based on a 1, 2, 3, 4 system, but the numbers are always missing part of the measurement.
For most wood that you buy in a home improvement store, everything will be missing about half an inch. For example, a 4X4 is really three and a half inches square, not four inches square. Also, a 2X6 is really one and a half inches by five and a half inches. It’s not the end of the world, just make sure you factor that into your measurements for your projects.
If you are making a twelve inch wide piece, you will need more than three 2×4’s, because they are not really four inches on the faces.
For most wood in a hardwood store, the thickness measurements are in quarters. For example, 4/4 thickness refers to “one by” thickness, which is actually closer to 3/4 of an inch. When it comes to hardwood, the typical loss is 1/4 of an inch for each measurement.
That being said, the wood will not be sold by the solid number, it will almost always be sold by the fraction. These look like 4/4, 8/4, 12/4, etc. A 4/4 board is around 3/4” thick and is considered 1 when you multiply for board feet. An 8/4 board measures about 1-3/4” thick, and you multiply by 2 when calculating board feet.
Once you pop into the store and measure some of the wood you will see that it’s not really difficult to understand the different thicknesses. When in doubt, just measure and you will never have to worry about anything when you make your project.
It doesn’t matter that the thicknesses are missing a little when you measure, because you have the actual data from the board.
Some pieces of wood will actually be the same thickness that they say they are, but this is more rare since you don’t get to sell as much when you cut it thicker.
If you are interested, there are minimums that the cutters need to hit in order to call their wood a certain thickness, and that’s meant to prevent them from selling you something that is really too thin and still charging a full size price.
Man made boards are going to have their own sizes too, but again as long as you are measuring the wood that you are buying, it will not make a difference. Purchase the pieces you need based on the actual project you are making, and the minute differences in thickness will not be a factor for you.
One thing to be aware of is that the price of wood that is sold by the board foot goes up very quickly the thicker the board is. A board that is twice as thick will sell for at least twice the price.
This is because that same board could have been milled thinner, and two boards could have been sold from it. This is again why calculating board feet is important. Everyone gets the same volume of wood for the same price.
Selecting the Right Size Board
Now that you understand board feet, you can use this information to select the right boards when you are in the store so that you can keep the wood cost to a minimum for any project you make. Since a certain amount of the wood is going to be waste, selecting the right widths and lengths when buying boards is something to consider.
If you are building up a selection of wood in your shop, you can feel free to over buy your wood a little, because you are going to store it and use it in the future anyway.
Once you have a good amount of stock on hand, then you can start being a little more shrewd in your purchasing. Also, if you are buying wood for a special project and you never plan on using the same species again, this method will help you reduce your waste to the lowest possible amount.
In order to get the best pieces of wood for your project, and minimize waste, you need to know what your project requires in detail. Figure out how many pieces, how big they are, and how they will be cut from the wood.
Draw the pieces out on graph paper so you can keep the sizes in tact, and start laying them out next to each other.
What you are trying to do is come up with a cutting pattern so you can minimize the amount of wood that will fall to the floor as you mill the pieces. For example, if you are making a set of drawers that have six inch tall sides, and they are twelve inches long, you really only need boards that are a bit wider than six inches.
Also, if you find those boards in lengths that are divisible by twelve, you can get an even number of drawer pieces without much waste on the length either.
To show you the opposite, and how it affects waste, consider the same drawers, but now you are buying wood without caring about the measurements. Let’s say you now buy a piece of wood that is 10” wide, and 23” long.
Even though this is a really big board, you will only be able to get one of the six by twelve inch pieces from it. Nearly 70% of the board will be waste, which means you will have to buy much more wood than you need to get all of your pieces.
If you carry that over into your designing and buying processes, you quickly see that buying boards based on how you are going to cut them down makes a really big difference.
When I buy wood for making guitars, I know that I need pieces measuring eight and a half inches wide for my acoustic guitar back plates. Anything more than eight and a half just falls to the floor.
This means I can save money on my material cost by looking for a board that is eight and a half inches wide, maybe nine tops. If I were to buy a twelve inch wide board, I might be able to use the few inches for something else, but it won’t be used for the back plate, and is therefore considered waste.
Take some time and plan out what you are making graph paper so you can see the individual parts. Arrange the parts so that you can see how much wood you need, and take that information into the store when you buy.
A small plan can save you a lot of wasted money on wood that is going to fall on the floor, and it can help you make more projects with less waste.
You are most likely going to end up using manufactured wood for a number of things, especially in cases where you need large flat pieces. You can always laminate several smaller pieces of hardwood, but that can get really expensive really quickly.
Manufactured wood is a nice alternative, and you can use it to save money on hardwood.
There are many different types of manufactured wood, but in the beginning you only really need to know about a few of them. They all work a little differently, and understanding them can help you when you are in the store looking for sheet goods.
The first, and the most common for woodworkers is plywood. This is a series of thin laminations that form a wood sandwich. On the faces of the sandwich is a nicer veneer that makes the board look like a solid hardwood when you can’t see the ends.
The point of this type of material is to give you the look of hardwood without the price. If you use it well, and hide the edges and ends, you can create a solid wood look for a fraction of the price.
Plywood works really well, though you do have to be careful about sanding too much on the surfaces. You can easily go through the nicer looking veneer and into a differently colored layer, which gives away the fact that the board is not solid.
Also, plywood can sometimes split when screwing into the edges, so pre-drill and screw deeply for a nice grip.
Another kind of wood that is popular is particle board, which can come in a number of ways. It can have nicer veneer sheeting on the faces, a melamine coating, or just a particle look.
Either way, this board is made from tiny wood particles and a binder that forms it into a board shape when manufactured. The advantage is the expense, which is very low.
The disadvantage of particle board is that it can be crumbly when you screw into it, and it can break pretty easily when compared to ply or solid. It’s not very easy to screw into the ends and get a long lasting grip, and when it gets wet, it poofs up like a sponge.
Oriented Strand Board is worth mentioning, but it’s not as popular in woodworking, so you may not use it very often. This is a type of particle board where the particles are very large.
Some of them are the size of your palm, and they are pressed together with a binder to make a sheet of wood. This is an effort to take what would be considered wood trash and make it into something usable.
OSB is a good material for benches and for storage shelves in the shop. I have a series of low benches that hold all of my smaller tools, and the OSB made a really simple and inexpensive top.
The edges do not hold screws really well unless you pilot and drill deeply, but going through the faces for bench tops is really easy, and the material holds up well.
Next, Medium Density Fiber Board is taking manufactured boards to a whole new level. For a long time you at least needed to have wood particles to make a board in a manufacturing process.
MDF might as well be called sawdust board, because you can’t see anything you would call a particle at all.
MDF is a sheet good that is made from sawdust and binders, and then shaped into sheets. The material is strong, but screws don’t like to hold in the edges very well. It’s a really flat material, and useful for making jigs and as structural elements in hidden areas.
For most woodworkers, plywood is going to be the manufactured wood of choice, and thankfully it comes in several grades and thicknesses. If you are working on internal structures, you can buy an inexpensive plywood that doesn’t have anything fancy on the faces. It’s going to be hidden anyway, so don’t waste the money.
On applications where you want to see the wood and the species on the faces, buy that particular type of plywood from your supplier. This can be a very economical alternative to using hardwood and laminating pieces together to make larger boards.
If you are making a dresser, using plywood for the carcass and the drawer bottoms, sides, and back will save you a ton but keep the look you are going for just about the same.
Make the face frame and the drawer faces from the actual hardwood, and use more to trim out the carcass, and you will have a project that uses plywood but still has a hardwood look.
Spend a little time looking at the different types of sheet goods that are available in your local wood store and your local home improvement store. In the home improvement stores you will typically find standard construction grade plywood, which is great for hidden areas.
You will also typically find at least two domestic hardwood faced types of plywood, which are great for exposed areas. All of these will come in a couple thicknesses too.
In a hardwood store, you are going to find a lot more variety in species for the faces of the plywood, since furniture and cabinet makers typically shop for their customers in hardwood stores.
If you want to make something from plywood, but with a more interesting species of wood on the faces, then the hardwood store is where to go.
Take a look when you are buying wood, and make a mental note of the types of hardwood veneer faced plywood that you can buy in your local wood store. This way, as you are planning future projects, you will know what kind of plywood options you have.
This wood is going to be the most expensive of the bunch, but it will still be far less expensive than making larger pieces from solid stock. Also, plywood is much better at resisting changes in moisture, so it typically will not change shape over time, like hardwoods can.
Wood is Hydroscopic
Wood is an interesting material in the sense that you have to control for the changes in humidity where the piece will live, because wood is hydroscopic. That means it takes in and releases moisture in response to the amount of moisture in the air.
In places that have a higher humidity, wood will absorb moisture to a point where it is in balance with the surrounding environment. At that point, it will stop absorbing moisture, and remain in stasis.
A piece of wood in a lower humidity area will release moisture until it reaches an equilibrium with the environment, and it will stay there until something changes.
The problem with taking in and letting out moisture is that the wood changes size when it happens. Dry wood gets bigger when it absorbs moisture, and wet wood gets smaller when it lets out moisture.
Depending on the severity, it can pop joints, crack boards, and in some cases cause complete failure to a project. All of that being said, it’s easy enough to control for these changes in size, you just need to understand why it happens so you know what to do.
In most cases, a good finish coats the piece and essentially traps the board in a humidity resistant shell, greatly slowing down these changes in moisture. This is the leading way that you can control how a piece of woodworking will react to humidity.
Another way to control the effects of humidity is to build your project in the same climate that the end user will experience.
If it’s an indoor project, and you both have central air conditioning, you will typically have a much lower humidity, so you can build the project indoors and the end user will store it indoors.
For most of your projects, you do not have to worry about moisture making one of your projects explode in the middle of the night. That’s an extreme example.
If you build with seasoned wood, and apply a nice finish to the entire project, you will reduce any humidity related issues down to nearly nothing for the life of the piece.
Remember though, wood is a natural substance that picks up and lets out moisture to remain in balance with the levels in the environment.
You can slow down the process with a good finish, by building your projects in an environment that is not extremely humid or extremely dry, and by using seasoned wood that is acclimated to the area you are working.
Part 11 – Wrap Up
I hope you liked Part 11 of A Beginners Guide to Woodworking: Helping New Woodworkers Make Better Projects. As you can see, this is a different kind of beginner woodworking book, and I encourage you to get a copy for yourself so you have it all in one place.
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