Hang a Heavy Mirror and Keep It Centered on the Wall
It might seem like hanging something really heavy, like a mirror, is more difficult than hanging a small painting. However, with the right anchors, things are pretty straightforward. Here’s a tip to keep your recently hung mirror from warping.
Before you hang anything, you need to decide what kind of wall you have. From plaster and lathe to brick or drywall, each type of wall requires a different set of anchors. This handy drawing serves as a guide to the selection of anchors for walls and wall surfaces.
Use two anchors to keep the heavy mirror flat on the wall. Place a piece of wood (8-12 inches, depending on the size of your mirror) under the taut hanging cable. Then measure the distance from the wire to the top of the mirror frame. This measurement will help you place the mirror on the wall. Mark the ends of the pieces of wood on the wall, and this is where the bottom of the hook should be placed.
Watch the video above to see this DIY tip in action.
How to hang a heavy mirror “wiki useful This old house (YouTube)