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Top Hat Span Test™

Bigger Spans Require Stronger Steel
Test Before You Buy

Enter Your Bay Size
or use the
Quick Bay Size Presets

What is Deflection?
Deflection is the amount of bend or sag over the span.
The Australian Standards® limits deflection.

What is Allowed?
Span/300 as per AS/NZS 1170.0 or
10 mm over 3 meters.

Why is it important?
Bigger spans require stronger steel.
It is Illegal to Sell or Certify a Shed
in Australia that is not deflection compliant.

Why are centers important?
Centers means the distance between Top Hats.
Bigger centers require stronger steel.
A Top Hat's strength dictates its maximum centers.

For The Mathematically Curious
These formulas are not closely guarded trade secrets.
They are basic engineering calculations.
Maximum Legal Deflection
Span / 300
Actual Deflection
(5/384) x P x Span4 / (E x Ix x 106)
Maximum Legal Centers
(Maximum Legal Deflection x (E x Ix x 106)) / ((5/384) x Governing Roof Pressure x Span4)

About the Top Hat Span Test
This Test and its results are limited to Bluescope® Hi-Tensile Australian Steel.
Deflection & centers cannot be calculated without the certified structural properties and span tables for the steel. Bluescope® publishes this information.
This calculator is a guide only and does not apply to roof only structures.
Engineering is site specific, so take your quote, design specifications and site address to an Independent Registered Structural Engineer.