How much solid wood should you buy?
We all understand that cutting joinery, assembling a project and applying a finish are skills a good woodworker has. Another skill that might get overlooked is the ability to visualize a project before starting to work on it and purchasing the correct amount and type of material so you can build your woodworking project without delays or added expenses.
Sheet Goods Sketch
Making a simple sketch of all the sheets you’re going to use in a project, and how they will be cut up, makes the process go smoother.
The marked-off area of these two boards show where one board foot is. It’s pretty obvious that deciding on how much wood to purchase according to board footage isn’t overly useful for a woodworker.
This X-base dining table was in our Feb/Mar 2022 issue. The 1-5/8" thick solid top is 84" long × 38" wide.
Long Off-Cuts Can Be Good
If a workpiece can be obtained from a piece of lumber, and you still have an off-cut that’s long enough to be usable, you’re in luck. Still, the best-case scenario involves needing to waste only an inch or two off both ends of a piece of lumber, as in the board on the right. The offcut from the board in the center will likely never get used.
Straight Is Great
When lumber is straight the yield will go up. This is especially true when you’re trying to obtain long pieces.
Knots and Defects
Knots, cracks and other defects have to be accounted for. You can either crosscut these defects out or rip the usable portion of the wood off for use.
Species and Thickness
Not all species will be available in all the thicknesses. Every lumberyard is a bit different. The lumber will be sorted by species and thickness, and the lengths of the boards will generally be written on the ends of the boards.
Change the Plan
There might be times when the available lumber doesn’t suit with the workpieces you need. It’s sometimes possible to change the plans to fit the lumber.
I was recently contacted by a subscriber who wanted to know how much wood to buy for the X-base dining table project in the Feb/Mar 2022 issue. He was also hoping we could start to include a bit of information in each issue regarding how much material to purchase for each project. Sadly, the answer isn’t a simple one. “It depends” was my initial thought, but that clearly doesn’t answer his question. I thought it would be more helpful to share my approach to purchasing lumber with him, but think it’s important enough to share with all our readers.
Sheet goods are easier than solid wood
If a project uses sheet goods, it’s usually fairly simple to calculate how much is needed. If I need multiple sheets for a project, or the way workpieces will need to be cut from a sheet is very complex, I will make a simple sketch of the sheet(s), including lines showing where the cuts will be made, as well as some basic overall dimensions of what size the panels need to be. Once in a while a through cut can’t be made and stopping the cut part way through the sheet is necessary.
In terms of solid wood, even if you’re provided with board footage information, it may not be that straightforward. Solid wood grows naturally and, unlike sheet goods, doesn’t come in uniform dimensions or quality. In short, not all boards are created equal. Having said that, the way a lumberyard sells them is standardized; you’ll purchase all hardwoods, and even some softwoods, by the “board foot.”
What is a board foot?
The term “board foot” speaks strictly to a volume of wood. It has nothing to do directly with any one specific dimension (length, width or thickness) of the wood, but takes into account all three dimensions to come up with the volume of the material. One board foot is equal to 144 cubic inches of wood. For example, one board foot of solid wood can be 1″ thick × 12″ wide × 12″ long. One board foot could also be 3″ thick × 2″ wide × 24″ long. As you can tell, both of those pieces of wood have different dimensions.
Let’s take the X-base dining table in issue #136 as an example. To keep this example simple, I’ll mainly focus on the tabletop. The finished length of the 1-5/8″ thick top is 84″, while the width is 38″. This is equal to 5187 cubic inches, or just over 36 board feet (5187 / 144 = 36.02).
Before we go too much further, we need to talk about waste. As we machine wood, we remove some of it. This means we need to purchase a bit extra in order to have enough to build our project. How much extra wood we need depends on a number of variables.
Thickness is the first variable. Woodworkers almost always dress lumber to final thickness themselves, so lumber has to be purchased thicker than it will be when the workpiece is finished. In the perfect world we would be able to purchase solid wood that’s just a little bit thicker than we need, but that’s not always the case. For the X-base dining table I bought wood that was 2″ thick (labelled “8/4″ and pronounced “eight quarter”) from the lumberyard and dressed it to its final thickness of 1-5/8″. The actual board footage of material for the top just became less important, as when purchasing that wood the focus should now be on the square footage of 8/4 material needed to be able to laminate the top from.
The next variable that affects waste factor is the length of the pieces of wood you need versus the lengths of the pieces the lumberyard has. If you need pieces for the top of this X-base dining table that are 84″ long you’ll almost certainly have to buy pieces that are 96″ long, maybe even longer, as lumber is generally sold in lengths of at least 8′ long. Obviously, purchasing two pieces 42″ long won’t allow you to make the 84″ long top. Having said that, there’s an outside chance the lumberyard may have material that’s just a few inches longer than you need, which is the perfect scenario. If that’s the case you can purchase much less material, otherwise you’ll have to bite the bullet and buy longer material and potentially waste some of the wood.
In some cases, purchasing wood much longer than needed will allow you to make better use of the offcuts after cutting the longer pieces for your project. Since there are no workpieces in the X-base table 12″ long, it would be great if you could purchase a few pieces 11′ long so you could obtain the four X-base cross pieces from the off-cuts and a few pieces 10′ long to obtain the X-base top rails and the angled braces. Either way your overall board footage will be different, and this whole scenario depends largely on what the lumberyard has available. If you show up and they only have 8′ long pieces, it’s a whole different ballgame.
How straight a board is will also affect how much waste will need to be accounted for. A board that’s twisted, cupped or otherwise bent out of shape will need to have more material removed from it to straighten it, and you’ll have to purchase a bit extra to ensure you have enough. You might not even be able to get a full 1-5/8″ finished workpiece from some 8/4 boards if the workpiece is on the long side like the 84″ long boards needed for the X-base dining tabletop.
Knots and other defects also cause challenges. A modern black cherry sideboard doesn’t look appropriate with knots, while a country-style pine corner cabinet is just fine with them. Either way, a large, loose knot should likely be avoided and will have to be accounted for while selecting lumber. Wane, checks, splits and other defects will also have to be worked around to obtain the workpieces you need, meaning you might have to purchase extra wood.
An additional amount of waste to be considered are the kerfs from machining the lumber. If the board you have is 8″ wide and you need to obtain two 4″ wide pieces from it, you’re out of luck, as the kerf of the blade is going to remove at least 1/8″ of material from the center of that board. On top of that, you’ll need a bit of extra width for straightening each workpiece and removing any rough surfaces left by either the initial processing of the lumber or the machining you do in your shop. How much depends on how rough the wood is, how long the boards are, how sharp and tuned your machinery is, and how skilled you are with breaking out material.
As you can see, estimating how much you need for a project is becoming quite the art. There are some basic guidelines, and experience will make it easier in the future. When breaking out workpieces, leaving an extra 1/4″ in width and 1″ in length is usually a good place to start, though it doesn’t always guarantee success.
So how much wood do you need?
Working in a small shop likely means you don’t want to buy a lot more material than is needed for both monetary and space reasons. Another approach is to take a more practical look at the situation when you’re buying solid wood for a project. Even though the lumberyard always charges by the board foot, I almost never go into the lumberyard with that number in my mind. Since wood isn’t cheap, and I’m almost always building a single piece of furniture, I take the time to carefully consider where each workpiece will be cut from as I shop for lumber. I start at home by making a quick sketch of the piece I’m building, complete with overall dimensions as well as a bit of info about some of the details.
For the black cherry X-base dining table, I would have the overall dimensions of the top and the X-base cross pieces and X-base top rails. I’d also be aware of the fact that I need to have a small amount of material left over to obtain the two angled braces that run on a 45° angle and keep the table from racking. The rest of the pieces are all small and if there’s not enough material left, I could easily use some maple or other hardwood left over from a previous project, as it will never be seen.
Once the sketch is complete, I’d make a materials list that included all the parts, the quantities needed and their exact finished dimensions.
To the lumberyard!
Now that I’m armed with some information about what I need, I head to the lumberyard with my list, pencil, erasure, chalk and tape measure in hand. I sometimes bring a block plane so I can remove a small amount of wood to see the colour and grain of the lumber. Most lumberyards don’t mind if you look through the wood storage area at your own pace, but please make sure to neatly re-stack all the wood when you’re done. I almost always head to the local lumberyard that allows me to take my time while selecting the exact pieces of wood I want, even though their prices are higher than another nearby lumberyard. Doing this is often cheaper in the long run, and I end up with wood that will enhance my finished project even more.
Bins of lumber are usually separated by not only their species, but by their thickness. There will likely be different bins for 4/4, 5/4, 6/4, 8/4 and 12/4, though not all species will be available in every thickness. Typically, the length of the board is written on its end, but if it’s not, that’s where I start. I measure the lengths of a few pieces of wood so I can compare them to the others around them. Next, I look at the width, and pull out a few potential boards that might work for the project I’m dealing with.
I always start with the longest pieces I need first, as they’re usually the hardest to find. I take boards out, check how straight they are, measure them and cross reference my list to see if the board will keep waste low. I know wasting a small amount is inevitable, but I try to avoid wasting much off the end of any board. Sadly, there are times when this isn’t possible, though. Once the longer pieces are accounted for, I move on to the shorter pieces.
As I work, I take a look at grain, colour, the straightness of a board, presence of knots, wane, splits or other imperfections and try to obtain the parts from the wood, sort of like a reverse jigsaw puzzle. I mark a rough outline of the parts directly on the wood and label the parts so I will remember what part comes from where when I’m back at the shop. Chalk helps out when dealing with dark woods like walnut. For the record, marking rough lumber is about the only time I use a wood pencil instead of a mechanical pencil while I’m building furniture, as a wood pencil is better at writing on rough lumber.
As I go, I make notes on my list regarding how many workpieces have been accounted for.
Change the game plan entirely
There’s one other important aspect to planning, purchasing and breaking out lumber that’s rarely discussed, and that’s simply changing the drawings and materials list to suit the lumber you have on hand. The width of each X-base cross piece of the dining table is 4″, but there’s nothing to say you can’t change that to 3-3/4″ or even 3-1/2″. If you do end up making changes while at the lumberyard, be sure to note them on your drawing and materials list. There are some limits to this, of course, but as long as you work within a few boundaries you should be fine.
Strength – If a workpiece is structurally important and making it smaller will weaken it too much, I strongly recommend against it. Having said that, a wooden workpiece is usually a lot stronger than it needs to be, and reducing its strength by 10%, 20% or even 30% may not cause problems.
Visuals – Workpieces are sometimes sized to make them look good. Keep this in mind when resizing them. A rail that’s visually too thin is going to look weak even if it’s not.
Critical Dimensions – Whether it’s hardware that needs a workpiece of a certain thickness to work, or some other technical reason, some parts may need to finish at a certain dimension.
Functional Requirements – Chair and table height are usually pretty standard, so changing the length of a leg might be a bad idea. And if you’re building a cabinet to fit a certain opening you might not be able to shrink the size of a workpiece. There are many other examples, too.
So much to think about
All of this info is a lot to take in, especially if you’re new to woodworking. After using this approach on a project or two, some of these techniques will become second nature. Remember, board feet measurements will give you an idea of what volume of wood to buy, but they won’t help when it comes to figuring out what specific boards to purchase, as they are all different. Knowing how to decipher the information provided in an article, or of a design of your own making, is the most critical thing.
Start with a fairly easy project. Make a sketch of the project and a list of all the parts you need, complete with dimensions, then head to the local lumberyard. Start with the larger parts, move on to the smaller parts, making sure you’ve accounted for enough waste. If the lumber selection just isn’t being co-operative, see if you can make a few adjustments to the sketch and materials list to improve your situation. Mark the boards so you know what’s what once you’re back in the shop. And if you have a few extra bucks I’d recommend buying a little more solid wood than you need. A trip all the way back to the lumberyard is a waste of time and gas, and let’s be honest; if you don’t need the extra wood for this project you can add it to your inventory so it’s ready for action later.