Post Frame Trusses Explained: Load Ratings, Spacing, and Snow Load
When it comes to building a strong, long-lasting pole building, the truss system does most of the heavy lifting. Whether you're planning a garage, shop, or storage building in the Twin Ports area, understanding how trusses work can help you make better decisions and avoid costly mistakes.
At Boon Buildings, we design buildings specifically for the demands of northern climates like Duluth and Superior, where snow load, wind, and temperature swings all play a major role in structural performance.
Let’s break down the three key factors: load ratings, spacing, and snow load.
What Post Frame Trusses Actually Do
In post-frame construction, trusses span from post to post and carry the entire roof load. Unlike traditional stick-frame buildings, where loads are distributed across many closely spaced walls, post-frame systems transfer loads more efficiently:
Roof - Trusses - Posts - Ground
This allows for:
Wider spans
Fewer interior load-bearing walls
Faster construction
Strong, open interior spaces
1. Load Ratings: What Your Trusses Are Designed to Handle
Every truss is engineered with a specific load rating, which determines how much weight it can safely carry.
Types of loads include:
Dead load – the weight of the building materials (roof steel, purlins, insulation)
Live load – temporary loads like snow
Wind load – lateral pressure from storms
In areas like Twin Ports, snow load is often the controlling factor in truss design.
Why load ratings matter
If trusses are under-designed:
Roofs can sag over time
Structural members can fail under heavy snow
The entire building can be compromised
Proper engineering ensures your building is designed for real conditions, not best-case scenarios.
2. Truss Spacing: Wider Doesn’t Mean Weaker
One of the biggest differences in post-frame construction is truss spacing.
Common spacing:
8 feet on center
10 feet on center
12 feet on center
Compared to stick-frame construction (typically 2 feet on center), this wider spacing might seem less stable, but when engineered correctly, it’s extremely strong.
Why wider spacing works
Trusses are designed to carry larger loads
Purlins distribute weight evenly between trusses
Posts transfer loads directly into the ground
This system reduces material while maintaining structural integrity.
3. Snow Load: The Biggest Factor in Northern Builds
In the Twin Ports region, snow load is one of the most critical design considerations.
Heavy, wet snow can add significant weight to a roof system. If that load isn’t properly accounted for, it can lead to long-term structural issues or even failure.
How trusses handle snow load
Engineered to meet or exceed local code requirements
Designed with proper pitch to encourage snow shedding
Supported by purlins and bracing to distribute weight
Why it matters locally
Buildings in Duluth, Superior, and surrounding areas like Hermantown and Proctor must be built to handle consistent winter stress.
Ignoring snow load is one of the fastest ways to create problems down the road.
How Spacing and Load Work Together
Truss spacing and load ratings aren’t separate decisions, they work together as a system.
For example:
Wider spacing requires properly sized purlins
Higher snow loads may require stronger trusses or tighter spacing
Roof pitch can reduce or increase snow accumulation
A properly designed building balances all of these factors.
Common Mistakes to Avoid
We often see issues caused by:
Using “standard” designs not suited for local snow loads
Improper truss spacing without adjusting other components
Skipping or underestimating bracing requirements
Trying to cut costs on structural components
These shortcuts can lead to sagging roofs, structural stress, and expensive repairs.
Built for the Twin Ports Climate
Post-frame buildings perform exceptionally well in northern climates, but only when they’re designed correctly.
At Boon Buildings, every building is planned with local conditions in mind, from snow load requirements to spacing and structural layout. That attention to detail ensures buildings stay strong, straight, and reliable for years to come.
Planning a Pole Building in the Twin Ports Area?
If you're planning a post-frame building in Duluth, Superior, or the surrounding Twin Ports area, make sure your structure is designed for real-world conditions.
Contact Boon Buildings today to discuss your project, get expert input on truss design, and start building with confidence.