Laminate Posts Vs. Solid Posts

Mechanical Laminates

• Pieces of wood of various lengths are held together by fasteners such as nails, screws, bolts or connecting plates to form a post consisting of three or four vertical layers or plies. Where ply pieces are butted together, they can be spliced or not. The places where wood joins occur can't match up, but are staggered along the length of the post in each layer. Characteristics of nails used are also important in the strength of the laminate. They must be the correct diameter, length and metal type, and properly spaced in distance apart from each other. D. R. Bohnhoff and colleagues, in "Post-Frame Building Design," reported in 1992 that the cost of laminated posts is generally less than that of solid posts, even when cost of connectors and fasteners is considered. There can be slippage between the layers of mechanically laminated wood depending on the applied forces and presence of end joints.

Glued Lamination or GluLam

• Strong adhesives are used to join three or four plies of wood together vertically or horizontally. Wood surfaces need to be planed and then clamped for good adhesion. Wood grains can be alternated, providing additional structural strength. Lengths are customized for specific projects, with lower cost than that for solid wood posts in longer sizes. Pressure-treated preservatives are needed where posts touch soil. It is easier to effectively penetrate the thinner pieces of wood in laminates with the preservative than solid wood posts. D. R. Bohnhoff and colleagues found that glue-laminated posts were stronger than solid-sawn posts. The glued layers equalize out the natural weaknesses that occur in wood, making laminates able to withstand greater stress than solid wood, where weaknesses can be concentrated in certain areas.

Solid Posts

• Posts sawn from a single log are becoming more expensive as long timber becomes more scarce and costly. The demand for taller structures is increasing, and it is more cost-effective to use laminated products for longer lengths. In addition, solid wood posts came in third in a strength test along the vertical post axis compared to glued-laminated and unspliced mechanically laminated products. It is more difficult for wood preservatives to penetrate a solid post, especially of woods that contain heartwood, giving less effective resistance to rot and insect attack.

Uses of Posts

• Wooden posts are used in functional buildings such as horse and dairy barns, garages, machine sheds, airplane hangars, shops and commercial buildings. They are used in spans such as those above windows and doors, and as horizontal elements in decking. Laminated wooden posts have the advantage of being manufactured to consecutive lengths greater than 30 feet for sidewall posts and even longer for endwall posts. Laminates can also be engineered for a custom fit of roof trusses to the ends of the posts to increase strength and reduce shear.