STI-8171 Mounting Backplate for 8100/8200 Series

The STI-8171 backplate is made for use with the STI-8100, STI-8100-BK, STI-8100-W, STI-8200-SS, STI-8200-W, STI-9601, STI-9601-SS, STI-9602, STI-9609, STI-9609-SS and STI-9610 smoke detector covers. If your cover is one of those, the backplate mounts behind it.

It is a situational part, not a required one. STI recommends the 8171 backplate where the mounting surface is unstable or uneven, and for weather applications. On a flat, solid interior ceiling or wall the cover mounts without it; on corrugated, textured, or exterior surfaces the backplate gives the cover a flat, continuous surface to seal and fasten against.

Yes, weather applications are one of the uses STI calls out for it. The plate is polycarbonate, so it will not rust or corrode behind an exterior-mounted detector cover the way a metal plate would.

For the uneven substrates, yes. Rough block, metal deck, and ribbed panel surfaces are exactly the unstable or uneven condition the 8171 is recommended for, and adding one per opening keeps the install consistent across the facility. Smooth drywall or plaster locations do not need it. Order the backplate to match whichever of the 8100, 8200, 9601, 9602, 9609 or 9610 covers you are standardizing on.

Polycarbonate. That is the same impact-resistant plastic family used for the detector covers themselves, so the backplate behaves consistently with the cover in gymnasiums, corridors, detention areas and other high-abuse spots where these covers get installed.

One part. The STI-8171 is a single model that serves the whole listed group of 8100 and 8200 Series covers plus the 9601, 9602, 9609 and 9610, so there is no size or color variant to pick when you order.