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What is the holding pull-out strength difference,relatively speaking, between using wood screws or lag screws when attaching a steel angle plate three-hole to a red cedar 2 x 4 joist ? Access to only one side of the joist, and the fastener cannot penetrate completely through.

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  • (a) is this a modern 2x4 - i.e., actually 1.5" x 3.5"? (b) are you going into the short side (2/1.5) so you have the long distance (4/3.5) to put in the screw? Or into the long side (4/3.5) so you have a much shorter distance (2/1.5)? Sep 3, 2023 at 3:26
  • Can you describe what you're doing a little more? If an angle plate is attaching to the side of a joist, where is pullout force coming from?
    – jay613
    Sep 3, 2023 at 4:43
  • a) going into long side 3.5
    – Roger
    Sep 4, 2023 at 1:16
  • The 2x4 is 60” long span, connecting to large beam (8x6 wood) at each end with the 3” steel angle having 3 holes each side for screws, nails, … the down vertical load is midpoint of span. ps I was able to find some charts on various screw designs with holding capacity and pull out strengths. Thank you.
    – Roger
    Sep 4, 2023 at 1:20

2 Answers 2

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Wood screws or lags.... really it depends on which wood screws or lags you have, the main figure of merit is obviously pull strength but if you don't have access to that measuring the volume of between the screw thread peaks and troughs will give some indication of how well it will hold.

So screws or lags, if you want hexagon heads use lags, if you want round heads use screws,

If you want it to hold stronger, longer teeth, larger major diameter of the threaded parts, and more threaded length is better. also don't ignore the possibility of the screw itself snapping

If the lags you can get are better suited than the screws you can get use the lags etc.

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To compare like for like is difficult, The strength mostly depends on the thickness of the screws and the thread size and material.

All things being equal, one could argue that since lag screws do not have threads all the way, a similar wood screw would win.

Perhaps, follow the instructions for the steel plate.

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