What is the standard roof truss spacing?

24 inches on center is the most common residential truss spacing because it reduces the number of trusses needed and lowers material costs. 16-inch spacing is used for heavier roof loads (such as tile roofing or high snow zones) or when the roof sheathing requires closer support.

Can I reuse old trusses?

Generally no. Engineered trusses are designed for specific spans, loads, and code requirements. Reusing trusses from a different structure without a licensed engineer's review and approval is not safe or code-compliant, as the original design may not match your new loading conditions.

How much do roof trusses cost?

Truss prices depend on span, profile, and regional lumber costs. Simple 24-foot Fink trusses typically cost $75 to $150 each, while 36 to 40-foot trusses run $150 to $300 each. Specialty trusses (scissors, attic, or cathedral) cost $200 to $500 each. Add $500 to $1,500 for crane rental on delivery day.

How many trusses do I need for my roof?

Divide the roof ridge length in inches by the truss spacing (24 or 16 inches) and add one for the starter truss. A 40-foot ridge at 24-inch spacing needs 21 common trusses, plus 2 gable-end trusses (one at each end), for a total of 23. Always order 1 to 2 extras for damage during delivery or installation.

What is the difference between trusses and rafters?

Trusses are pre-engineered, factory-built assemblies that span the full building width and are faster to install. Rafters are individual boards cut and assembled on site, allowing for open attic or cathedral ceiling space. Trusses are less expensive and stronger for the same span but do not allow usable attic space unless attic-style trusses are specified.

How long does it take to get trusses delivered?

Lead times for custom trusses are typically 4 to 8 weeks from the time engineering drawings are approved. During peak building season (spring and summer), lead times can stretch to 10 to 12 weeks. Plan your truss order early in the project timeline to avoid costly delays.

Roof Truss Calculator

How many roof trusses do I need? Free calculator for 600 mm standard spacing — enter roof length for instant truss count and layout.

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Enter Your Measurements

How to Use This Calculator

1Measure the roof length (ridge length) in feet.
2Select your truss spacing (24" OC is standard for residential).
3Click Calculate.

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About This Material

Roof trusses are pre-engineered triangular wood assemblies designed to span the full width of the building without requiring interior load-bearing walls. Each truss is factory-built to a specific engineering design using 2x4 or 2x6 lumber connected with metal gusset plates. Common truss profiles include Fink (W-pattern, the most common), Howe, and scissors (for vaulted ceilings). Trusses must be ordered from a licensed truss manufacturer based on your building plans, and they typically have a 4 to 8 week lead time. Standard residential trusses are spaced 24 inches on center and can span 24 to 40 feet depending on design. Truss pricing depends on span and complexity — simple 24-foot span Fink trusses cost $75 to $150 each, while 40-foot spans or specialty profiles can cost $200 to $400 each. Delivery usually requires a flatbed truck, and installation requires a crane or boom truck for lifting trusses into position.

Next Steps:

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Installation Tips

•Order trusses 4–6 weeks in advance — lead times can be long.
•Have a crane or boom truck on site for lifting.
•Brace trusses laterally during installation — they are unstable until sheathed.
•Follow the truss placement diagram from the manufacturer.

Common Mistakes to Avoid

Not ordering gable-end trusses (different from standard trusses).
Insufficient temporary bracing during installation — trusses can collapse.
Placing trusses on bearing walls only — do not load non-bearing partitions.

Roof Truss Calculator

How to Use This Calculator

About This Material

Installation Tips

Common Mistakes to Avoid

Frequently Asked Questions

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