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House & Home Physics

Floor Joist Deflection

y(x) = w·x²(3L − x)/6EI
Floor Joist Deflection

A loaded floor joist sags in a smooth curve set by the load and its stiffness EI — building codes cap the mid-span deflection to L/360.

Computed & rendered in pure C# on the frozen OnlyCSharp 1.8 library — animation baked to GIF with the library's own Gif encoder (no GPU, no ffmpeg, no external packages).