How thick should plywood floor be for attic?

by Jerry

I want to setup the space over the Garage to allow us to store itemsI know eventually I will have to install an Attic LadderNeed to know how thick the plywood for the floor should be? (¾", ⅝" or ½")

  9 answers
  • William William on Nov 12, 2018

    3/4" plywood should be enough.

  • Lifestyles Homes Lifestyles Homes on Nov 12, 2018

    This is an important thing to evaluate carefully.

    What are your garage “ceiling joists” sizes?

    Are they really Rafter Ties? Not good, if so. You will pull down your roof framing if they’re rafter ties!

    2x4’s? 20’ is too long of a span to turn them into floor joists.

    How many inches on center are they?

    How do the attach to the garage walls? Toe nailed? Sitting on top of the adjacent walls’ top plate?

    i can guess based on the age of the house, which old?

    What are you storing there? Paper records are extremely heavy.

    3/4” IMO, but if they’re toe-nailed 2x4’s, stop.

    Lmk what your existing conditions are.

  • Mogie Mogie on Nov 12, 2018

    Have you checked to see what building codes are needed? What about permits?

    I would be cautious of how much you put up there without having someone knowledgeable do some loading calculations on it. In all likelihood, you'll be fine for light weight storage, but it would be a shame to find the ceiling down on top of you car some morning.

  • Shore grandmom Shore grandmom on Nov 12, 2018

    Definitely 3/4 plywood.

  • Jerry Jerry on Nov 13, 2018

    I had a Contractor look at my attic and gave his recommendation. He said we are good to put things up there. Just getting started. House built in 2005. Two car Garage with the one wide Door.

    Thank you all for your input.

  • Redcatcec Redcatcec on Jul 10, 2024


  • Johnavallance82 Johnavallance82 on Jul 11, 2024

    Buy Floor grade ( suspect it would be thick poss. 5 ply etc.) OR USE mdf

  • Dee Dee on Jul 13, 2024

    The recommended thickness of plywood for traditional flooring installations is typically 5/8–3/4 in (15–19 mm). This range provides enough support to minimize the risk of squeaking or flexing. The thickness of plywood you choose depends on the project and the intended use of the floor:

    1/2 in: The most common thickness for subflooring

    3/4 in: A good choice for areas that need more support

    5/8 in: Provides extra support for heavy flooring