Snug-tight

Snug-tight is a bolting category under AS 4100 where the bolts are tightened only enough to bring the connected plies into firm contact, as opposed to a fully tensioned (friction-grip) connection used where slip or fatigue matters. The structural drawings specify which category each connection is.

Steel connections are classified by how the bolts are installed and how they carry load:

• Snug-tight (bearing-type, e.g. category 8.8/S): the bolt is run up tight so the plies are in firm contact, the full effort of a person on a standard spanner, or a few impacts of an impact wrench. The connection carries load in bearing (the bolt shank bears against the hole). Most ordinary structural connections are snug-tight.
• Fully tensioned (e.g. 8.8/TB bearing or 8.8/TF friction): the bolt is tensioned to a specified minimum (by part-turn or a tension-indicating method) so the clamped plies resist load by friction. Used where the joint must not slip, or where fatigue or dynamic load applies.

The distinction matters because the two are installed and inspected differently, and they are not interchangeable: a connection the engineer marked TF (friction-grip, fully tensioned) will not perform as intended if it is only run up snug.

For a builder or steel erector the practical point is to read the connection category off the drawings and install to it. Snug-tight is straightforward, but where the drawing calls for fully tensioned bolts you must use the specified procedure (part-turn method or load-indicating washers) and the connection is typically an inspection point. Treating a fully tensioned connection as snug-tight is a real defect, not a shortcut.

Also known as: Snug-tightened, bearing connection (snug).

Category: Steel / Connections.

Related

• AS 4100 steel structures
• M-series bolts

See also

• Load-bearing wall

References

• AS 4100 Steel structures, Standards Australia (verified 2026-06-01)

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Last updated: 2026-06-01. Verified: 2026-06-01. Quarterly review for currency.