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How to Design and Detail Gussets

Gussets are galvanized steel plates with formed attachment flanges. Gussets are used in lieu of conventional framing to attach and support a cornice installation.

Gussets are installed to the building at either 24″ or 32″ centers, depending on your structure’s framing requirements. The shape of a gusset is defined by the shape of its mating cornice members.

Gussets offer many benefits over conventional framing:

  • Eliminate expensive wood or steel framing & sheathing.
  • Provide a more precise sub structure to attach your cornice.
  • Reduce the need for field verified dimensions.
  • Improve installation time.
  • Offer greater assurance for wind resistance.
  • Will not burn or contribute to combustion.

Unique expansion reliefs, slotted fastening holes, and the flexibility designed into our gussets allow your cornice to move freely as temperatures change.  Gussets allow you to design your cornice to simulate a cast stone “stacking joint” or the more sleek design that wood offers with their tightly fitted joints.


A custom cornice must be complete before designing gussets.  Basic steps to designing gussets are:

  1. Place your custom cornice into position on a typical wall section where the cornice will be applied.
  2. Sketch an outline of the gusset with all lines perpendicular to one another, and aligned with the cornice moulding’s fastening flanges.
  3. Place angular edges (lines) where there are large voids in the gusset’s outline.
  4. Apply relief cuts at flanged fastening edges where the gusset design constrains flex.  Flanged fastening edges are any edge that accommodates a cornice moulding’s fastener.
  5. Send your custom design to Perimeter Systems for final review.


Our recommended spacing for gussets is 24″ O.C.

A gusset must always be located at a cornice joint to back up and support moulding splices. Splices are small sections of a moulding’s profile used to join cornice mouldings.  Since cornice mouldings are not fastened to this “splice”  gusset, additional gussets must be located at 12″ on either side of the “splice” gusset.

All other gussets are spaced 24″ apart.

Gusset spacing may be increased to 32″ centers for small or interior cornices, however, gusset spacing at splices must remain 12″.

Review gusset application illustrations below:

gusset framing guidelines
wall with gussets
gussets osm
gussets ism
gusset end cap