Lumber futures slid below $520 per thousand board feet, the lowest since September 2024, because the expected autumn demand lull collided with an unexpectedly large physical overhang.  New single-family starts and builder takeaway have softened as higher financing costs and an existing housing inventory overhang have trimmed prompt buying, while sawmills and distributors that front-loaded purchases into tariff headlines are now offloading material into thin physical offtake, swelling dealer stocks and triggering discounts.  At the same time anti-dumping and tariff talk earlier in the quarter encouraged speculative stocking that magnified the excess once ...