Teak resists water and fungal damage very well and makes one of the best choices for construction in damp environments. Teak's natural oils and high silicon content repel water naturally. Builders choose teak for its beautiful grain and rich brown color, as well as for its practical advantages. Popular applications include interior floors and fixtures as well as marine construction. Except in well-ventilated outdoor showers, using teak for the walls of shower stalls can create expensive problems.
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Teak's water-resistant nature and exceptional stability make this wood the best choice for ship-building and other marine construction. Tectona grandis grows wild in the jungles of southern Asia and Malaysia, but teak plantations in tropical areas throughout the world provide much of the teak sold today. Plantation teak can't match the quality of the scarce old growth teak. Since termites can't digest the silicon-laden heartwood, beams of teak can last for 1,000 years even in tropical climates. Teak could withstand the heat and dampness of a shower, but solid teak shower paneling would soon develop faults.
Even very stable hardwood such as teak expands and contracts when exposed to heat and moisture. Uneven exposure, as in an indoor shower stall where one face of the wood lacks ventilation, causes one side of a plank to move more than the other. Even though movement may be slight in comparison to other types of wood, teak planks shift and change shape. Adhesives bond poorly to teak because of the wood's oil and silicon, putting glue joints at risk of failure. Tongue-and-groove joints made to allow movement also admit moisture to the sealed side of the teak panel.
Sealing all surfaces of the teak prevents some of the problems caused by moisture. Thermal movement continues and panels thoroughly protected by waterproof finishes can still develop faults. In outdoor applications, regular upkeep with oil finishes restores the natural moisture repellent in teak wood and sunlight prevents mold from growing. Completely sealing the pores of teak requires at least three coats of penetrating resin, according to the Utah State University Cooperative Extension. Indoors, fungi can take root even on top of wood sealant, permanently marring the finish and staining the wood beneath it. Behind the panel, mold can grow unchecked.
In the walls of an airy outdoor shower stall, teak should last for decades. Exposed to sunlight, teak's color deepens. If cleaned and oiled regularly, teak's appearance improves with the years. Even with intensive upkeep, indoor shower stalls built of solid teak won't keep their original beauty. Special waterproof composites can give the appearance of teak without all the problems. Teak veneers laid over layers of paper form the core of the panels. After saturation with phenolic resins, presses mold the material into a solid sheet. A clear outer layer protects the teak veneer from abrasion and moisture, according to Carmenta Bathroom Innovation Technologies.