Overhead Anchors

April 13, 2022

Over the winter I’ve been mostly focused on home remodeling, but I have also been chipping away at getting the ceiling anchor system in place.

I plan to hang a Milos M222 Trio QuickTruss system, which at 10.8 ft x 7.5 ft weighs just over 80 pounds.

The goal is to be able to safely suspend a triangular truss system from the ceiling to attach lights and fly speakers.

The design calls for 12 in. Simpson Medium Twist Straps (MTS-12) straps, made of 16 gauge galvanized steel.

I went with a low profile design that distributes the weight as evenly as possible along all the rafters.

Wrapping around the member is allowed but not required to achieve the allowable load.

I used heavy-duty metal straps, using a metal break to uniformly bend them at the right point.

The straps were attached with the specified #9 x 1-1/2 in. Simpson SD screws.

Improving on the original mocked-up design, I was able to install them so the straps aligned with each other.

This design supports a might higher load rating than the more common approach of driving lags into the bottom of each rafter.

The assembly will be drywalled over, and have the appearance of an exposed beam.

The rafters assembly has a live load capacity of 20 psf and a dead load capacity of 20 psf. The drywall below requires less than 3 psf and the styrofoam above it less than 1 psf. This leaves plenty of remaining capacity for rigging.

I plan to have the boards drywalled over, so I’ll be adding some OSB strips so the drywall sits away from the straps and screws.

I used a template to align the holes of each block and pre-drilled the screw holes to avoid splitting.

I cut and pre-drilled backing blocks that will provide additional strength due to their grain running the opposite direction as the board they’ll be attached to.

The plate under and around the U-bolt increases the surface area, reducing compression of the wood fibers under load.

I used screws to hold the blocks in place, opting for hex-heads as they are easier to drive in tight spaces.

The benefit of the U-bolt design is that I can install and adjust the D-rings after the drywall is on, as there’s no operable parts inside the ceiling bay.

The anchors are evenly spaced 2 feet apart, 5 per side, centered within the room.

I cut the circles using a hole saw on a drill-press, aligned with the same template that was used for placing the U-bolts.

I then added some sheathing to add clearance for the straps and screws. After the drywall goes on, the 6 inch circles will be finished off with some round flanges.

Attic Wiring
Final wiring