Heavy Timber Trusses

Heavy Timber Trusses

Strong, Timeless, and Engineered for Beauty and Performance

Heavy timber trusses are among the most striking and structurally reliable roof framing systems used in residential, commercial, and institutional construction. Whether you’re building a lodge, a custom home with exposed timber architecture, a barn, or a church, heavy timber trusses deliver both functional strength and unparalleled aesthetic appeal.

In this guide, we’ll cover everything you need to know: what heavy timber trusses are, how they differ from steel and light wood trusses, common wood species, typical spans, joinery types, how glulam compares to solid sawn timbers, the engineering and fabrication process, and a robust FAQs section below to answer your most pressing questions.

What Is a Heavy Timber Truss?

A heavy timber truss is a load-bearing structural framework made from large wood members (typically 4” nominal thickness and above) arranged in triangulated patterns. The truss transfers roof and floor loads to supporting walls or columns, efficiently spanning broad areas without interior supports.

Unlike stick framing or lightweight trusses, heavy timber trusses use substantial lumber—often visible from the interior—making them both functional and architectural features.

Key characteristics of heavy timber trusses:

• Large cross-sectional lumber — generally over 4×6 inches, often 8×8, 10×10, 12×12 and larger.
• Triangulated geometry — triangles distribute loads efficiently and resist deformation.
• Exposed visual appeal — selected for both engineering and aesthetics.
• Durable performance over time — heavy timber resists fire differently than steel, and ages gracefully when detailed correctly.

Heavy Timber vs. Steel Trusses vs. Light Wood Trusses

Understanding the differences between these structural systems helps in selecting the right solution for your project.

Heavy Timber Trusses

• Material: Solid wood or engineered wood (glulam)
• Appearance: Natural, warm wood tones; ideal for exposed interiors
• Weight: Heavier than light wood trusses, lighter than steel
• Fire Performance: Char layer can protect inner wood in certain fires
• Cost: Moderate to high depending on complexity

Steel Trusses

• Material: Structural steel sections
• Appearance: Industrial, often concealed or paired with wood cladding
• Strength: High tensile strength; excellent for ultra-long spans
• Fire Protection: Requires specific coatings or encapsulation for fire ratings
• Cost: High fabrication and erection costs in many markets

Key differences: Steel can achieve longer spans for the same depth, but lacks the natural look of timber. Heavy timber trusses often integrate better in architectural spaces where wood is a defining aesthetic.

Light Wood Trusses

• Material: Dimensional lumber (2×4, 2×6)
• Appearance: Typically covered with drywall; not architectural
• Cost: Lower cost and faster to install
• Span Limits: Effective for many residential roofs but limited compared to heavy timber

Key differences: Light wood trusses are common in tract housing, less costly but not designed for exposed architectural features or very long spans under heavy loads.

Common Wood Species for Heavy Timber Trusses

Choosing the right wood species affects strength, availability, cost, and appearance.

Douglas Fir (DF)

• Strength: Excellent structural properties
• Use: Heavy timber, glulam, exposed trusses
• Appearance: Rich grain and color; attractive finish

Spruce-Pine-Fir (SPF)

• Strength: Good structural performance, easy to work with
• Use: Economical heavy timber applications
• Appearance: Lighter color; often finished with stain or clear coats

Southern Yellow Pine (SYP)

• Strength: High density and stiffness
• Use: Heavy framing, beams, and trusses
• Appearance: Strong grain and color contrast

Cedar

• Strength: Moderate strength, excellent decay resistance
• Use: Specialty projects with high aesthetic or exterior exposure
• Appearance: Aromatic, stable wood with rich tones