Structural timber used in construction nowadays should not only be adequately seasoned but also protected against moisture, biological factors and fire.
Wood treatment involves the application of chemical preservatives allowing them to penetrate into the wood cells to protect it against moisture, fungus, insects, etc. while also improving its fire resistance properties.
In the soaking method (wood immersed in preservative) the high moisture levels are conducive to saturating the wood with preservative as its penetration is achieved through diffusion, i.e. by equalising solution concentrations. The longer the wood is submerged in preservative the higher the level of its saturation with preservative.
Timber treated adequately to withstand potential impacts, is a practically indestructible material. Proper preservation is the only sure way to ensure that timber will perform well for decades. And garden furniture, usually exposed to direct weather conditions, is bound to suffer from all such risks.