I make these chairs for sale and I refer to it as “hurricane proof” it’s made from
1×6 decking , 1×4 and 2×6 I use ceramic Sq drive deck screws and heavy duty structural screws. I’m no small fry I weigh about 280
And when I made my first one I could jump on it twist it around and it didn’t loosen up.
Also it weighs so much , when we get high winds right near the ocean it doesn’t budge.
With 2 coats of solid deck stain and
Pt lumber these can last at least 8 -10 years although I’d be wrong if I said they don’t need a coat of stain every few years if left outdoors but covered or brought in for the winter you just might never have to do a thing. For 40$ in wood and screws well worth building than buying already built.