One drawback of exposed metal joint members is their poor fire resistance, which, for example, with nailing boards is a maximum of 15 minutes of fire resistance time. If the load-bearing structures are required to exhibit fire resistance, the metal joint members must usually be installed inside the wood structure or protected with, for example, fire-retardant paint or wood cladding.
Glued lattice structures
Glued lattice structures can be based on a lap joint, groove dowel joint or finger joint of the parts connected. A lap joint is the most expensive of these, and due to technical restrictions only used in special cases. A groove dowel joint is easy to manufacture, but the strength of the joint is low. The strength of a finger joint is almost twice as good as that of a groove dowel joint and as great as the strength of ordinary wood. A finger joint is not considered to weaken the wood at all. No metal has been used in glued lattice structures.