How to determine how much materials are needed to build a deck

Updated April 17, 2017

Home improvement projects can go smoothly if you spend enough time planning. Building a deck onto your home is a big project. But, you can avoid mistakes and save yourself time and money by planning how to build your deck and what you will need.

Determine the outer frame measurements by measuring the width and depth of the area where the deck will stand. If you are attaching the deck to your home, be sure to figure part of the outer frame will be your ledger board (the board attached to your home). Record measurements in your notebook with a large sketch of the frame. On your graph paper, 6 mm equals 30 cm (or 1/4-inch equals one foot). Label each side of the frame with the appropriate measurements.

Divide the sides into 40 cm (16 inch) increments, starting at one end and working your way across to determine how many floor joists you will need at 40 cm (16 inch) on centre. Figure two joist hangers per joist. Draw the joists in your frame.

Draw small squares along one of the middle joists, spacing them at equal distances until you get across the frame -- about one post every 90 cm to 1.2 m (3 to 4 feet). Do this with the second to the last joist, the second joist, and with all four corners. Normally, you can use 10 by 10 cm (4 by 4 inch) posts for deck support, but you may decide on 15 by 15 cm (6 by 6 inch), depending on the size of the deck. Figure approximately half a bag of quick-setting concrete for each support post.

Determine how many 2.5 by 15 cm (1 by 6 inch) deck boards you will need by drawing them perpendicular to the floor joists. Then you can figure approximately how many deck screws you need for the floor by allowing two screws per joist all the way down each deck board. If you have eight floor joists, each deck board will require about 16 screws plus four more screws for the ends.

Draw steps and railings on a separate sheet of graph paper. Use a front- or side-view drawing to determine how much material you will need, based on measurements you have already taken, to build deck rails. Decide the height of your deck based on its function; this will help you determine if you want steps or not. If you require steps, bring the decking to within 5 cm (2 inches) of the bottom of the house's access door.


Always seek expert advice when building your own deck. A designing program can help plan your deck. Always plan hardware as you go so that you don't forget anything.


Before digging holes for your support posts, call to have the area inspected to ensure that there are no water, gas, or electrical lines in the ground.

Things You'll Need

  • Tape measure
  • Graph paper
Cite this Article A tool to create a citation to reference this article Cite this Article

About the Author

Mike Johnson teaches writing at Kalamazoo Valley Community College and Western Michigan University. He wrote Writing Across the Curriculum content for Western Michigan University's Best Practices site. Johnson graduated from Western Michigan University with a Master of Arts in English and a Master of Arts in educational technology.