Frequently Asked Questions About Heavy Timber Construction

What Is Heavy Timber Construction?

Heavy timber construction is the process of using natural timber beams or glulaminated beams that have a cross section larger than 6″x6″ to form the structural frame work of a building. It is classified as Type IV Construction for fire protection purposes. The beams can be joined with traditional wooden joinery, like mortise and tenons with hardwood pegs, or with steel gusset plates or knife plates connected with bolts. It is a building system that has been used for thousands of years. The term “Heavy Timber Construction” is similar to timber frame construction and post and beam construction, but tends to refer to larger buildings with longer spans and higher loads.

What is Glue Laminated Timber (Also Called Glulam)?

Glue laminated timber refers to large timber beams that have been glued together from strips of common 2x construction wood like 2×4’s, 2×6’s, 2×8’s and 2×10’s. Relatively short  2x’s are finger jointed together at the ends to make long strips of wood. The strips are flooded with glue, then laminated into larger beams in a specially designed press that clamps the strips together under high pressure. The resulting beam is planed down on the sides by three eights of an inch, or so, to even up the laminations. A typical size for a glulam beam is 6 3/4″ x 13 1/2″. Any depth can be achieved by simply adding more laminations; 10 3/4″ x 46 1/2″ is possible as is 3 1/8″ x 7 1/2″.

The advantage of using glulam beams is strength and length. The beams can be 60 feet or longer and can be made very strong by increasing the number of laminations and the depth of the beam. Because the beam is made up of many laminations, it is also more uniform in its strength characteristics.  A natural timber might have large knots or checks in the middle that reduces its overall strength, where as a glulam timber has limited defects relative to its overall size. Therefore a high modulus of elasticity can be used for glulams when the engineers calculate their bending capacity.

The disadvantages of glulam timber is the higher cost compared to natural timber and the aesthetics. The laminations are visible and don’t look like a natural wooden beam.

When Is Heavy Timber Construction Used?

Heavy Timber is used in all types of public and private buildings – Churches, Welcome Centers, Pavilions, Schools, Museums, Houses and Barns . Just about any building can use heavy timber. The term heavy timber is mostly associated with larger commercial or public projects, where houses and barns might be more likely to be called timber framed buildings.