Seismic Ceiling Grid in Colorado

It is on the first sheet of the structural drawings — seismic design category A through F. Most of the Front Range comes out C. Mountain counties vary, and the site's geotechnical report decides. Anything C or above changes the ceiling.

• Heavy-duty main tees instead of intermediate-duty.
• 2" wall angle around the perimeter, so the grid can float on two sides and is attached on the other two.
• Compression posts and splayed wires — a post and four wires at 45 degrees, every 12 feet in each direction, tying the grid to the structure above.
• Seismic separation joints in ceilings over 2,500 square feet.
• Perimeter clips where the grid is not attached.

The seismic component on our shelves is the ACM7 clip, which goes over the bulb of the grid and sits behind the wall angle. On the jobs we supply, that is what gets used, and our counter's read is that our design categories do not call for more.

So if your drawings specify a full kit — posts, splayed wire, heavy mains, 2" angle — call before you order. Two things come out of that call. Sometimes the jurisdiction genuinely wants it, and we bring it in with a real lead time. More often the spec came off a template written for a coastal project and was carried onto a Colorado job unchanged, and the architect will approve a substitution once somebody puts the question to them. Either way it is a phone call before the grid ships rather than a change order after.

Your engineer and your building department decide what the assembly needs — we are not the ones to tell you. We are just the ones who have made this call a hundred times and know which way it usually goes.

Compression posts and wire go in above the tile without tearing the grid out. If a ceiling was hung without bracing and the inspector caught it, it is fixable.