How to Build Barn Roof Trusses – A Step-by-Step Guide

Barn roof trusses keep the roof strong and stable. They spread the weight evenly so the roof doesn’t sag and can handle tough weather. Trusses are usually made of wood or metal and come in different types, like king post, queen post, and Howe trusses, each designed for different weight loads.

If you’re in Upstate New York and planning to build or upgrade a barn, knowing how to build barn roof trusses is important. Whether it’s for storing farm equipment, housing animals, or setting up a workshop, the right truss system makes your barn stronger and last longer.

Step 1: Understanding Barn Roof Trusses

Before jumping into the building process, first you must have a clear idea on barn roof trusses.

What Are Barn Roof Trusses?

Barn roof trusses are strong, triangular frames that support the roof and spread its weight evenly across the walls. Among different types of roof trusses, barn-style roof trusses are pretty similar to the gambrel truss.

Barn trusses help keep the structure stable, prevent sagging, and create open spaces without needing extra support beams.

Unlike traditional rafters, trusses provide better weight distribution and last longer. This makes them ideal for barns used for storage, livestock, or workshops—especially in areas with heavy snow or strong winds, like Upstate New York and surrounding areas.

Most trusses are made from wood or metal and come in different designs to match various roofing styles and weight needs. Choosing the right truss keeps your barn sturdy, efficient, and ready to handle the elements. 

If you’re looking for high-quality trusses, Structural Wood Corporation offers reliable solutions to meet your construction needs.

Types of Barn Roof Trusses

Different truss designs serve specific structural needs. Here are the most common types:

Standard Trusses

Standard trusses, like king post and queen post trusses, are simple and work well for small to medium barns. They have a central post and diagonal beams for support. These trusses handle moderate roof loads and are a budget-friendly option for homeowners looking for a basic, strong design.

Gambrel Roof Trusses

Gambrel trusses have a double-sloped design that creates the classic barn-style roof. This design adds extra attic or loft space, making it perfect for hay storage, workshops, or even living areas. It also helps with water runoff and snow shedding, which is great for barns in snowy areas like New York.

Pole Barn Roof Trusses

Pole barn trusses use large vertical poles for support. They span long distances without needing interior walls, making them ideal for storing equipment or housing livestock. These trusses are often pre-engineered, making installation faster and cutting down on labor costs.

Choosing the Right Truss Design for Your Barn

Picking the right truss design depends on a few important factors:

Barn Size: Bigger barns need stronger trusses. Gambrel or pole barn trusses work best because they can handle more weight and span wider distances.

Roof Load: Think about the weight of your roofing, insulation, and possible snow buildup. Standard trusses are fine for light loads, but if you expect heavy snow or extra weight, gambrel or pole barn trusses are a better choice.

Weather Conditions: If you live in a place like New York, where winters bring heavy snow, go with a gambrel truss. It helps shed snow easily and reduces stress on the structure. If your area gets strong winds, reinforced trusses will keep your barn standing strong.

By considering these factors, you’ll build a barn that lasts. Next, gather the right materials and tools to start constructing your trusses. 

If you need expert guidance or have specific requirements, feel free to Contact Us for professional support.

Step 2: Materials and Tools Needed

What Wood to Use for Barn Roof Trusses?

Choosing the right wood for barn roof trusses is crucial for durability and structural integrity. The two most common options are 2×4 and 2×6 lumber, each offering unique benefits depending on the barn size, roof load, and local weather conditions.

Lumber Type	Strength & Durability	Weight	Best For	Cost
2×4 Lumber	Suitable for light to moderate loads	Lightweight	Small barns, moderate snowfall areas	Lower
2×6 Lumber	Stronger, handles heavier loads	Heavier	Large barns, heavy snowfall areas	Higher

For barns in New York, where winters can bring significant snowfall, 2×6 lumber is the better choice. It provides additional strength, ensuring the trusses can support heavy snow accumulation without sagging or failure. 

However, for smaller barns with lighter roof materials, 2×4 lumber may be sufficient and more cost-effective.

Pressure-treated wood is also recommended for added resistance to moisture, rot, and insects, particularly in barns with high humidity levels or exposed conditions.

Must-Have Tools for Building Trusses

Building barn roof trusses takes careful cutting, strong joints, and precise measurements. To get the job done right, you’ll need these essential tools:

• Circular Saw or Miter Saw: A circular saw works for cutting, but a miter saw makes precise, repeatable cuts easier. It’s the best choice for trusses.
• Drill with Screws or Nails: A power drill helps secure everything tightly. Use galvanized screws or nails to keep the structure strong and long-lasting.
• Metal or Plywood Gussets: These reinforce the joints and add strength. Metal gussets are tougher, but plywood gussets work well for smaller barns.
• Measuring Tape and Carpenter’s Square: Accuracy is key. A measuring tape ensures the right length, and a carpenter’s square keeps angles perfect.
• Clamps: These hold the wood steady while you assemble and fasten the trusses.
• Hammer or Nail Gun: A nail gun makes the job quicker and secures nails firmly. If you prefer, a hammer works too, just with more effort.
• Ladder or Scaffolding: These keep you safe while assembling and installing trusses up high.

Using the right tools and materials will make sure your barn roof trusses are solid, secure, and built to last. The next step is cutting and assembling each piece with care to create a sturdy framework.

Step 3: Calculating and Designing Your Trusses

How to Measure and Calculate Truss Dimensions

Before building barn roof trusses, you need precise measurements to ensure structural integrity. The three key factors to consider are roof pitch, span, and load capacity.

1. Determining Roof Pitch

Roof pitch is the slope of the roof and is expressed as a ratio of rise (vertical height) to run (horizontal length). The standard pitch for barns varies based on usage and climate conditions.

Pitch Ratio	Angle (Degrees)	Best For
4:12	18.43°	Standard barn roofs, moderate snow loads
6:12	26.57°	Steeper barns, improved water runoff
8:12	33.69°	High snow load areas like New York

For New York homeowners, a 6:12 or 8:12 pitch is recommended to allow snow to slide off rather than accumulate, reducing excess weight on the structure.

2. Calculating Truss Span

The truss span is the total width the truss must cover. Typically, the truss span equals the barn width. For example, if your barn is 30 feet wide, your trusses must span 30 feet from wall to wall.

3. Load Capacity Considerations

Trusses must support dead loads (roofing material weight) and live loads (snow and wind). In New York, the live load for barn roofs typically ranges from 20-30 pounds per square foot (psf) due to snowfall.

Roof Truss Load Calculation – Simplified Formula

To calculate the total load on a roof truss, you need to add the dead load and the live load:

Total Load = Dead Load + Live Load

🔸 Dead Load

This is the weight of the roof and any permanent parts of the structure (like beams, concrete slabs, tiles, etc.).
Formula:
Dead Load = Volume × Unit Weight of Material

Example:
If a concrete slab is 0.15 m³ and the unit weight is 24 kN/m³,
Dead Load = 0.15 × 24 = 3.6 kN

🔸 Live Load

This includes temporary or movable weight – like people, furniture, or snow on the roof.
Live loads are measured as Uniformly Distributed Load (UDL) or point loads, depending on the usage.

🔸 Load Factors (for safety)

Engineers use load factors to account for unexpected changes:

• Dead Load Factor: 1.2
  
• Live Load Factor: 1.6
  

Example Calculation:
If Dead Load = 10 kN/m² and Live Load = 5 kN/m²:

• Factored Dead Load = 10 × 1.2 = 12 kN/m²
  
• Factored Live Load = 5 × 1.6 = 8 kN/m²
  
• Total Factored Load = 12 + 8 = 20 kN/m²

Using a Gambrel Roof Truss Calculator

If you’re building a gambrel-style barn, calculating angles and cuts manually can be complex. Online gambrel roof truss calculators simplify the process by generating measurements based on your barn’s dimensions.

How It Works:

1. Enter the barn width, roof pitch, and desired loft height.
2. The calculator provides rafter lengths, gusset angles, and truss spacing.
3. Use the results to cut and assemble the truss pieces accurately.

Recommended Truss Calculators:

• Blocklayer – Provides free gambrel roof calculators with customizable settings.
• MyCarpentry – Offers a simple interface for calculating angles and cuts.

Using a truss calculator minimizes errors and ensures the barn roof has proper weight distribution and stability.

Barn Roof Truss Spacing Guidelines

Proper truss spacing is essential for load distribution and roof strength. The spacing depends on barn size, truss type, and local weather conditions.

Barn Type	Recommended Spacing	Best For
Pole Barn	8-12 feet	Large spans, minimal interior walls
Gambrel Barn	4-8 feet	Loft storage, heavy snow loads
Small Shed	2-4 feet	Lightweight roofing materials

For barns in upstate New York, a truss spacing of 4-8 feet is recommended, especially for areas with heavy snowfall. Wider spacing requires stronger lumber (e.g., 2×6 instead of 2×4) to handle increased weight loads.

Final Considerations

• Trusses closer together increase strength but also raise material costs.
• Wider truss spacing can work if reinforced with purlins and bracing.
• Always check local building codes to ensure compliance with your area’s structural safety standards.

With precise measurements, the right calculations, and proper truss spacing, your barn will have a strong and durable roofing system.

Step 4: Installing the Roof Trusses

Lifting and Positioning the Trusses

Installing roof trusses the right way is key to making your barn strong and stable. If the trusses are heavy, use a crane or pulley system to lift them safely. If you’re working with a small team, set up scaffolding and use ladders to guide each truss into place. Start by positioning the first truss at one end of the barn, making sure it lines up with the wall plates. Once it’s in the right spot, secure it with temporary bracing before moving on to the next one.

In upstate New York, trusses must be installed with precision to handle heavy snow and strong winds. If they aren’t placed correctly, they can lose up to 30% of their strength, which increases the risk of structural damage.

Attaching the Trusses to the Barn Frame

After positioning the trusses, they need to be securely attached to the barn frame. Use galvanized metal brackets and hurricane ties to keep them stable against wind and other forces. Fasten each truss to the top wall plate using 16d nails or structural screws to create a tight, secure connection.

Building codes in New York require trusses to be fastened with approved metal connectors to ensure safety. Proper fastening prevents roof sagging, misalignment, and failure in extreme weather.

Bracing and Securing the Trusses

Before finishing the installation, trusses need temporary bracing to keep them from shifting or collapsing. Use 2×4 lumber to create diagonal and lateral braces, securing them at multiple points across the truss system.

Permanent bracing should also be installed based on the manufacturer’s guidelines. This is especially important in upstate New York, where snowfall can reach over 50 inches a year. A well-braced truss system keeps the roof strong and protects the barn from weather damage.

Common Questions About Building Barn Roof Trusses

Is It Cheaper to Build Your Own Roof Trusses?

The cost of building your own roof trusses depends on factors such as material prices, labor, and expertise. DIY trusses can save money, especially if you already have woodworking experience and access to tools. However, pre-built trusses offer precision, structural integrity, and time savings.

Factor	DIY Trusses	Pre-Built Trusses
Material Cost	Lower, but requires sourcing	Included in price
Labor Cost	Free if self-built	Included in purchase
Time Required	Several days	Delivered ready to install
Structural Accuracy	Requires careful planning	Precision-engineered
Permit Approval	May need an engineer’s approval	Typically pre-certified

If budget is the primary concern, DIY trusses can be a viable option. However, pre-built trusses are often more reliable and compliant with local building codes.

Can You Legally Build Your Own Trusses?

Yes, you can, but the rules depend on your local building codes in New York. Most counties require a permit for any structural changes, including roof trusses. Your trusses also need to meet load-bearing standards, and you might need an engineer’s approval.

Before you start, check with your local building department to see what’s required. Some areas may require a professional inspection to ensure your trusses can handle wind and snow loads. If you ever plan to sell your property, poorly built trusses could cause legal and safety issues.

How to Build Barn Roof Trusses for a Shed

Shed trusses work the same way as barn trusses but are usually smaller and easier to build. Follow these steps:

1. Measure the Roof Pitch: Pick a slope that allows proper drainage and strong support.
2. Cut the Rafters: Use good-quality lumber and cut accurate angles for strong joints.
3. Make Gussets: Reinforce the joints with plywood or metal plates.
4. Assemble the Truss: Fasten the rafters together with screws or nails, making sure they are uniform.
5. Install and Brace: Place the trusses on the shed frame and secure them with bracing.

For small sheds, you won’t need heavy machinery, but precision is key. If your measurements are off, your trusses could sag or fail over time.

Build Strong, Safe, and Long-Lasting Roof Trusses

Building barn roof trusses takes careful planning and attention to detail. Choosing the right materials and following New York building codes will help ensure safety and durability.

Whether you build them yourself or buy pre-made trusses, you need to understand weight distribution, bracing, and fastening techniques. Always measure carefully, use high-quality materials, and get professional advice if needed.

Safety should come first—wear protective gear, follow load limits, and secure any required permits. A well-built truss system not only makes your barn stronger but also increases its lifespan and value.

With the right preparation, you can build reliable trusses that stand up to tough weather and serve you well for years. Take your time, do your research, and build with confidence!