Douglas Fir and Hem Fir : What to Choose for Your Projects

When comparing Coastal Douglas Fir and Hem-Fir under the latest West Coast Lumber Inspection Bureau (WCLIB) standards, particularly Standard No. 17, several key differences emerge in terms of structural performance, grading, and applications.

Species Overview

Coastal Douglas Fir (Pseudotsuga menziesii)

Renowned for its strength and durability, Coastal Douglas Fir is a preferred choice for structural applications. It is characterized by its high density, straight grain, and resistance to decay.

Hem-Fir

Hem-Fir is a species grouping that includes Western Hemlock, Pacific Silver Fir, Noble Fir, Grand Fir, California Red Fir, and White Fir. This combination is recognized for its uniform texture and light color, making it suitable for both structural and appearance-grade applications. 

Structural Properties Comparison

According to WCLIB Standard No. 17, the following are typical design values for visually graded lumber: 

Property	Coastal Douglas Fir	Hem-Fir
Bending Strength (Fb)	Up to 1,500 psi	Up to 1,400 psi
Tension Parallel to Grain (Ft)	Up to 1,000 psi	Up to 900 psi
Compression Parallel (Fc)	Up to 1,700 psi	Up to 1,500 psi
Modulus of Elasticity (E)	Up to 1.9 million psi	Up to 1.6 million psi

These values indicate that Coastal Douglas Fir generally exhibits higher strength and stiffness compared to Hem-Fir, making it more suitable for demanding structural applications.

Applications

Coastal Douglas Fir: Ideal for heavy structural uses such as beams, joists, and framing where high strength is essential.

Hem-Fir: Suitable for general framing, trusses, and applications where appearance and workability are prioritized over maximum strength.

Grading and Standards

Both species are graded under WCLIB Standard No. 17, which outlines the criteria for visual grading, including permissible defects and moisture content. The standard ensures consistency and reliability in lumber quality for construction purposes.

Conclusion

In summary, Coastal Douglas Fir offers superior structural properties, making it the preferred choice for high-load applications. Hem-Fir, while slightly less strong, provides versatility and aesthetic appeal for a variety of construction needs. The choice between the two should be guided by specific project requirements, considering factors such as load demands, appearance, and cost.

If you need further information on specific grades or applications, feel free to call us.