How to Calculate Deck Materials

A deck can be a wonderful addition to your backyard. You can save a lot of time and money by building your own deck. One of the toughest parts of this type of do-it-yourself project is determining the proper amount of decking materials that you need to get started.

Things You Will Need:

• Deck design plan


• Paper


• Pencil

1. Create your deck design. Take the time to examine the location of the new deck and determine its dimensions and the types of materials that you want to use in its construction. Sketch out a rough design including all of the new deck's measurements.


2. Determine how many posts you will need. Deck posts are manufactured from four-by-four inch pieces of treated wood. The general rule of thumb is that you will need to install a post every 4 feet. For every 8-square-feet of deck space, you will need to install nine posts. Write this number down on your list.


3. Add in the related post materials that you will need. For each post that you install, you will need approximately three 3-inch lag bolts with corresponding washers, as well as half of an 80-pound bag of cement to hold the post in place. Calculate all of the related materials that you will need and write them down.


4. Determine how much lumber you need for your frame and floor joists. For every 8 square feet of decking that you install, you will need approximately 72 feet of support in the form of framing and cross-beams. This amounts to 14 joist hangers for every 8 square feet. Based on the size of your deck, write down the number of joists that you will need to purchase. Include a calculation for six 1 1/4-inch wood screws for each support joist that you purchase.


5. Calculate the amount of flooring that you need to purchase. A standard deck board will cover 4 square feet of deck space. Use this estimation to calculate the number of deck boards that you will need to purchase. For a deck with 8 square feet, this amounts to 28 deck boards.


6. Depending on the design of your deck, you will also need to include materials for railings and stairs. For every 8 feet of railing that you install, you will need 22 balusters and 3 rail posts, along with 8 feet of both top and bottom railing. For every step in your staircase, you will need to purchase an additional 4 feet of 1-by-12-inch lumber to create the base of the stairs. Dependent upon the size of your stairs, you will need to purchase additional lumber to create the step.