Lumber strength is generally measured using various factors that influence how well a piece of wood can withstand stress, load, and other forces. The primary properties of lumber strength include:

1. Modules of Rupture (MOR)
Definition: The maximum stress a piece of wood can handle before it breaks when a bending force is applied.
Measurement: It's typically measured in pounds per square inch (psi) or megapascals (MPa).
Significance: This property is crucial when the lumber is being used in structural applications like beams, rafters, or flooring, where bending is a common force.

2. Modules of Elasticity (MOE)
Definition: this measures the wood's stiffness or its resistance to bending under load. A higher MOE indicates that the wood is stiffer and less likely to bend or deform.
Measurement: MOE is also measured in psi or MPa.
Significance: It helps in determining how much a piece of wood will bend under a given load. It's particularily important for applications requiring stability.

3. Compression Strength Parallel to Grain
Definition: The ability of wood to withstand compression (squeezing) forces when the load is applied parallel to the grain.
Measurement: This is usually expressed in psi.
Significance: This property is critical for lumber used in posts, columns, and other applications where the wood is compressed along the grain.

4. Compression Strength Perpendicular to Grain
Definition: This measures how well wood resists compression forces when the load is applied perpendicular to the grain.
Measurement: MOE is also measured in psi or MPa.
Significance: This is important for applications like decking or flooring where the wood is subject to forces from various directions.

5. Shear Strength
Definition: The ability of wood to resist forces that tend to slide its fibers past each other.
Measurement: Shear strength is measured in psi and is crucial when the wood is subjected to forces that cause sliding, such as in joints or fasteners.
Significance: The property determines how well wood can hold screws, nails, and other fasteners.

6. Tensile Strength Parallel to Grain
Definition: The maximum pulling force that a piece of wood can withstand when the load is applied along the grain.
Measurement: Measured in psi or MPa.
Significance: Important in applications where wood is subject to pulling forces, such as roles or cables attached to wooden structures.

7. Tensile Strength Perpendicular to Grain
Definition: The maximum tensile stress the wood can resist when the force is applied perpendicular to the grain.
Measurement: Also measured in psi or MPa.
Significance: This is less important in most wood applications, but it can be relevant in some specialized designs.

8. Durability and Moisture Content
Definition: The strength of lumber is also influenced by its moisture content, which can affect its ability to resist warping, swelling, and shrinking. As moisture increases, strength tends to decrease.
Significance: Wood is often tested at a standard moisture content (around 12%) for strength properties. Higher moisture content can reduce strength, so it's vital to manage wood in various environmental conditions.

Testing Methods
Static Bending Tests: For MOR and MOE, lumber is often tested by applying a gradually increasing load to a piece of wood supported at two ends (like a beam).

Compression and Tension Tests: These tests are performed by applying a load that either compresses or stretches the wood.
Shear Tests: Shear strength is measured by applying a force that causes sliding between the wood fivers, often by forcing a sharp blade or tool into the wood.

Strength Grading Systems:
Visual Grading: Lumber is graded based on visual characteristics such as knots, grain orientation, and other defects that may affect strength.
Machine Grading: Involves using machines to measure stiffness and strength, allowing for a more accurate classification of lumber.

Other Considerations:
Species of Wood: Different wood species have different strength properties. For example, hardwoods like oak tend to have higher strength than softwoods like pine.
Grain Orientation: Wood with straight grain is typically stronger than wood with irregular or cross-grain patterns.
Defects: Knots, splits, and other imperfections can weaken the wood significantly.

This breakdown gives and overview of the primary way lumber strength is measured and the factors that influence these measurements. 

A detailed breakdown of the strongest and weakest wood species commonly found in Ontario for each of the specified mechanical properties:

1. Modulus of Rupture (MOR) - Bending Strength
Strongest: Hickory (Carya spp.) is renowned for its exceptional bending strength, making it highly suitable for applications requiring high resistance to breaking under load.
Weakest: Eastern White Cedar (Thuja Occidentalis) has relatively low bending strength, limiting its use in structural applications where high bending forces are expected.
Most Commonly Used: White Oak (Quercus alba) common for furniture, flooring, and heavy-duty structural beams due to its excellent bending strength and durability. Eastern White Pine (Pinus strobus) widely used for general construction and decorative trim; less strong than oak but easily workable.

2. Modulus of Elasticity (MOE) - Stiffness
Strongest: Sugar Maple (Acer saccharum) exhibits high stiffness, providing excellent resistance to deformation under load, which is advantageous for flooring and furniture.
Weakest: Poplar (Populus spp.) has lower stiffness, making it more prone to bending and less suitable for applications requiring rigidity.
Most Commonly Used: Sugar Maple (Acer saccharum) preferred for flooring and cabinetry where stiffness is key. Black Spruce (Picea mariana) common in constructionn-grade lumber for its balance of stiffness and light weight.

3. Compression Strength Parallel to Grain - Crushing Strength
Strongest: White Oak (Quercus alba) offers high compression strength parallel to the grain, making it ideal for load-bearing structures like posts and beams.
Weakest: Basswood (Tilia americana) has lower compression strength, which make limit its use in structural applications requiring high load-bearing capacity.
Most Commonly Used: Douglas Fir (Pseudotsuga menziesii) imported but popular in Ontario for structural uses like beams and trusses due to its high compression strength. Eastern Hemlock (Tsuga canadensis) locally available and used in timber framing and construction.

4. Compression Strength Perpendicular to Grain - Bearing Strength
Strongest: Black Cherry (Prunus serotina) provides good compression strength perpendicular to the grain, suitable for applications like flooring where resistance to indentation is important.
Weakest: Eastern White Pine (Pinus strobus) has lower bearing strength, making it less suitable for applications where the wood is subjected to perpendicular compressive forces.
Most Commonly Used: Black Cherry (Prunus serotina) often used for flooring, furniture, and applications requiring resistance to indentation. Eastern White Cedar (Thuja Occidentalis) frequently used for outdoor applications like decking and fencing due to its moderate bearing strength and rot resistance.

5. Shear Strength - Resistance to Sliding Forces
Strongest: Black Walnut (Juglans nigra) exhibits high shear strength, making it effective in resisting sliding forces, beneficial for joints and fastenings.
Weakest: Aspen (Populus tremuloides) has lower shear strength, making it effective in resisting sliding forces, beneficial for joints and fastenings.
Most Commonly Used: Black Walnut (Juglans nigra) valued for its aesthetic and mechanical strength, used in furniture and decorative applications. Yellow Birch (Betula alleghaniensis) frequently used in plywood and engineered wood products due to its high sheer strength.

6. Tensile Strength Parallel to Grain - Resistance to Pulling Forces
Strongest: Douglas Fir (Pseudotsuga menziesii) is known for high tensile strength parallel to the grain, making it suitable for applications like beams and trusses.
Weakest: Eastern Hemlock (Tsuga canadensis) has lower tensile strength, which may limit its use in tension-loaded structural components.
Most Commonly Used: Douglas Fir (Pseudotsuga menziesii) a top choice for load-bearing applications like beams and trusses. Black Spruce (Picea mariana) often used in structural lumber due to its good tensile strength and availability.

7. Tensile Strength Perpendicular to Grain - Resistance to Splitting
Strongest: Yellow Birch (Betula alleghaniensis) offers good resistance to splitting, beneficial in applications like plywood and veneer.
Weakest: Red Maple (Acer rubrum) has lower resistance to splitting perpendicular to the grain, which can be a consideration in certain applications.
Most Commonly Used: Yellow Birch (Betula alleghaniensis) preferred for veneers and engineered wood where splitting resistance is critical. Poplar (Populus spp.) used in lightweight furniture and cabinetry despite its moderate resistance to splitting.

8. Dimensional Stability - Resistance to Moisture-Induced Changes
Most Stable: Eastern White Cedar (Thuja occidentalis) exhibits excellent dimensional stability with minimal shrinkage and swelling, making it ideal for outdoor applications.
Least Stable: Red Oak (Quercus rubra) is more prone to moisture-induced changes, leading to potential issues like warping or swelling in varying humidity conditions.
Most Commonly Used: Eastern White Cedar (Thuja occidentalis) popular for outdoor furniture, decking, and shingles due to its excellent stability. Eastern White Pine (Pinus strobus) common for paneling and trim where moderate stability is sufficient.

These assessments are based on general characteristics of the wood species commonly found in Ontario. They are selected not only for their strength characteristics but also for their availability, cost, and ease of processing in Ontario.

It's important to note that individual specimens can vary, and factors such as growth conditions, processing, and treatment can influence the mechanical properties of wood.

For precise applications, consulting detailed technical data and conducting specific tests is recommended.

Weakest to strongest:
1. Pw [softwood]
2. Sw [softwood]
3. Bd [hardwood]
4. PO [hardwood]
5. Pj [softwood]
6. Pr [softwood]
7. Bw [hardwood]
8. La [softwood]
9. Mr [hardwood]
10. By [hardwood]
11. Cb [hardwood]
12. Ash [hardwood]
13. Be [hardwood]
14. Or [hardwood]
15. Mh [hardwood]
15. Hickory [hardwood]

This list is organized roughly by general availability and use cases in Ontario, starting with softwoods that are commonly used for general construction, followed by hardwoods that are progressively stronger and used for specialized purposes. Here's a breakdown of why this order might make sense based on the wood species'characteristics and common applications:

1-6: Softwoods (General Use, Construction)
Softwoods are typically easier to work with, lighter, and more affordable, making them ideal for structural and general-purpose applications:
1. Eastern White Pine: Widely available, lightweight, easy to work with, and commonly used in furniture, paneling, and general carpentry.
2. White Spruce: Stronger than white pine, often used for framing and construction where moderate strength is required.
3. Basswood: Although a hardwood, it's very soft and lightweight, often used for carving and non-structural applications.
4. Poplar: A hardwood that's lightweight and economical, often used in inexpensive furniture and cabinetry.
5. Jack Pine: Stronger than white spruce and used in construction where durability is needed, such as in framing and outdoor structures.
6. Red Pine: Stronger and more durable than jack pine, often used in poles, structural beams, and decking.

7-10: Hardwoods (Mid-Tier Strength, Decorative Uses)
These woods balance strength, durability, and aesthetics, making them versatile for furniture and flooring:
7. White Birch: Affordable and attractive, often used in plywood, veneers, and furniture.
8. Tamarack/Larch: A softwood with strength rivaling hardwoods, used in outdoor applications like poles and pilings.
9. Red Maple: a versatile hardwood used in furniture and cabinetry, with moderate strength and workability.
10. Yellow Birch: Denser and stronger, suitable for high-quality furniture, flooring, and plywood.
11-16: Hardwoods (High Strength, Specialized Uses)
These hardwoods are prized for their strength, durability, and aesthetic value, making them ideal for heavy-duty or high-end applications.
11. Black Cherry: Valued for its beauty and moderate strength, commonly used in fine furniture and cabinetry.
12. Ash: Known for its shock resistance, used in tools, sports equipment (e.g., baseball bats), and furniture.
13. Beech: Dense and strong, often used in flooring, furniture, and veneer.
14. Red Oak: A pupular hardwood for furniture, flooring, and cabinetry due to its strength and attractive grain.
15. Sugar Maple: Extremely hard and strong, often used in flooring, bowling alleys, and high-stress applications.
16. Hickory: The hardest and strongest on the list, used in tools, flooring, and applications requiring exceptional toughness.

Purpose of This Order:
The list prioritizes common usage, strength, and availability in Ontario. It starts with widely used, more accessible softwoods for general construction and progresses toward hardwoods that are stronger, more durable, and often used for specialized or high-end purposes.

Why Tamarack Stands Out
Strength: Tamarack has a higher density and strength compared to most other softwoods, making it useful for outdoor applications like poles, pilings, and railroad ties.
Durability: Its resistance to decay further elevates its value, especially for harsh conditions.

So, while hardwoods like Hickory and Sugar Maple are still the strongest overall, Tamarack is a conifer that can outcompete weaker hardwoods.