How to install floor joists for beginners

Updated April 17, 2017

Floor joists are important structural elements of a house. They provide support for the house and their size and spacing during house construction is strictly specified by building codes and regulations that apply to your area. Installing floor joist will take time and should be done with extra care because the strength and sturdiness of the floor rests upon the proper installation of the joists. With enough guidance and the right materials, it is possible to install for yourself the floor joists of the foundation of your home.

Make an architectural diagram of the floor where you want to put joists. Remember to consider any pipes or other services that may run under the floors. If you do not know how to make an architectural diagram, get help from a licensed architect. You will need to submit this diagram to your local planning board or other building authority to get approval for installing the joists.

Treat the wood with weatherproofing. Using a roller, apply a coat of weatherproofing all throughout the wood surface. Apply as many coats as directed by the weatherproofing manufacturer. Once you lay your floor you will not have easy access to the joists so the better prepared they are before laying, the fewer problems you will have later. Let the weatherproofing dry completely.

Lay the joists onto the foundation. Measure the centre of the entire floor and lay the first joist there. Nail the joist into the foundation. Then nail the rest of the joists in 16-inch intervals.


Use I-Joists for better support and easier installation.


The structural integrity of your house depends upon the joists. If you are unsure about what you are doing, get a professional. Sometimes it is less expensive in the long run to get professional help.

Things You'll Need

  • Structurally graded lumber for joists
  • Weatherproofing for lumber
  • Roller
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About the Author

Based in Santa Rosa, Calif., Bill Dale has been writing travel- and lifestyle-related articles since 1988. His articles have appeared in “The Northern California Bohemian” newspaper and “Wine Business Monthly” magazine. Dale received the Fairbanks Public Service Award in 2005. He holds a Bachelor of Arts in liberal arts from Columbia University.