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The reason for the concern is the much higher volume of water (and hence water pressure on the sides) of the swim spa exerting forces on the wood framing. The swim spa will be indoors and, of course sump pumps and drains will be present, but a failure of the frame due to the water pressure would be a bad thing! If steel can rust and wood can rot in a wet environment, what is the solution? The manufacturers of steel framed swim spas typically powder coat the frame to prevent rust issues. It would just seem that a steel frame will resist bowing of the sides from the pressure of the water more than wood framing.Does anyone know of any other companies that offer a steel framed swim spa?Kathleen