How to Calculate Lumber for a Deck?

Well, deck construction begins with important questions: how much lumber will I need? How to calculate lumber for a deck?  A correct estimation will allow you to set up a proper budget, prevent you from any lack of materials, and decrease the amount of material waste. No matter whether you are going to construct a small backyard deck or a larger one, the calculation of the amount of lumber needed will be much easier if you split your deck into several parts.

So, using a board foot calculator is always helpful to know some basics of the calculation like the volume of the lumber needed.

What Lumber Do You Need for a Deck?

Well, different kinds of lumber can be used to build your deck. This depends on the size of your deck, how high it is, its design, and other factors.

Some components used when building decks are:

• Deck boards
• Joists
• Beams
• Posts
• Rim joists
• Ledger boards
• Stair stringers
• Railings

However, the quantity required for each component is different, and you may want to have a cut list prepared before purchasing lumber.

Start With the Deck Dimensions:

First, find out how long and how wide your deck will be. The product of these dimensions will give you the exact measurement of the surface area of the deck.

For instance, the surface area of a deck that is 12 feet long and 20 feet wide will be:

• 12 × 20 = 240 square feet

Therefore, this will aid you in calculating how much wood you will require based on the number of decks you are going to make.

Keep in mind that you should not make the mistake of assuming that because your decking area is 240 square feet, you will need exactly 240 square feet of wood.

Calculate the Decking Boards

You may wonder: How to calculate the decking boards?

For calculating the decking material, you should calculate the width of the boards used along with the gaps that one intends to keep between the boards.

For instance, the wider the board, the greater the coverage of each board, and smaller boards would need more boards individually. Allow some additional material for cuts, defects, mistakes, and replacements.

In simple cases, 10% to 15% additional material can be considered enough initially.

Estimate Joists and Structural Lumber:

The joists hold up the decking boards and typically are placed at right angles to the decking. The spacing varies based on the type of board being used, its span, the load needs, and building regulations.

After determining the proper spacing, divide the deck length by the joist spacing and add the required end joists to get a rough idea of how many joists there will be.

Moreover, you should figure out the lumber you require for beams, posts, rim joists, and blocking. Since these structural members bear heavy loads, it is advisable to follow the local building codes rather than just using a calculator.

Calculate Lumber in Board Feet:

Let’s discuss: How to calculate the lumber in board feet?

Board feet calculate the volume of lumber taking into consideration the measurements of its thickness, width, and length. This calculation comes in handy when you are buying rough-sawn or hardwood lumber by volume.

However, the use of a board foot calculator is appropriate when calculating the total volume of lumber for individual parts. On the other hand, for dimensional deck lumber that is sold by the piece or linear foot, you might find piece or linear foot calculation to be more helpful. The use of a linear foot calculator is useful for estimating the total length of boards required for dimensional deck lumber.

Additionally, for logs, before milling your own lumber for the deck, a Log Board Foot Calculator can come in handy for estimating the volume of lumber that will come out from the logs.

Account for Waste and Extra Material:

Well, not all decking projects will make use of all their wood completely. However, problems with cutting, trimming, warped planks, knots, deterioration, and mistakes while measuring can cause your needs to increase.

A reasonable waste factor will depend on your design, but adding 10-15% for the deck will usually work well as a start. A separate waste factor might be needed for structural lumber depending on the cut list for the job.

To conclude, getting a little extra material to start with is better than coming up short later on in the project.

Conclusion: How to Calculate Lumber for a Deck?

In conclusion, lumber calculation for a deck is much simpler when breaking down the entire construction process in terms of decking, joists, beams, posts, etc. Therefore, it’s important to measure properly, generate a list of cuts, consider spacing and possible waste, and ensure that there are no structural considerations prior to purchasing the materials.

Frequently Asked Questions (FAQs)

How do I calculate lumber for a 12×20 deck?

For calculating lumber for a 12×20 deck, start with finding the surface area of 240 square feet and estimating the quantity of decking boards based on their width and spacing. Calculate lumber for joists, beams, posts, and other materials, and consider a reasonable waste factor.

How much extra lumber do I need for my deck?

A deck lumber estimate that incorporates waste factors usually assumes an extra 10%-15% of decking. Your specific project may require more or less additional material.

Can I use a board foot calculator for deck lumber?

Yes, you can use a board foot calculator for deck lumber. It will help you calculate the amount of lumber volume in board feet if the dimensions of the boards (thickness, width, length) are known. For dimensional lumber in pieces, calculate the quantity of boards and linear feet.