Plastic Butterfly Wall Anchors

Plastic butterfly anchors are pushed through a hole in a hollow wall and open behind the board into two wings, so the screw tightens against the back face of the plasterboard instead of pulling out of its front face. The wings are the load path: they spread the pull over an area of board that the screw alone could never hold. This tag holds the site's guide to using them in hollow walls.

What the guide here answers

What is a plastic butterfly anchor: guide to hollow wall use covers the sequence that decides whether the fixing holds: drilling the correct diameter, folding the wings so they pass the hole, watching or feeling them open behind the board, and tightening only until the anchor seats. It also covers the two mistakes that cause most failures, which are over-tightening and drilling a hole that is too large.

Why the wings have to open before the screw bites

The anchor carries almost no load until the wings are behind the board. If the screw is driven before the wings open, the anchor spins in the hole and the wings never deploy, and the fixing then relies on friction against the edge of the hole, which is close to nothing on plasterboard. The open span also has to exceed the hole diameter comfortably; an anchor that only just clears the hole concentrates the load on the rim and pulls through.

What a butterfly anchor is not for

It is for hollow substrates: plasterboard, hardboard, thin panel and hollow block. In solid masonry, brick or concrete the wings have nothing to open against and the anchor is a worse fixing than a plain plug. It is also not a substitute for a structural fixing: loads that matter, or anything overhead that a person could pull on, belong in a stud or a properly rated anchor rather than in the board.

Specification reference

Anchor size, drilling diameter, open span and wing depth for each size are listed on the plastic butterfly anchor product page.

What drill size does a butterfly anchor need?

The diameter stated for that anchor size, drilled clean and without wobble. An oversized hole stops the wings from seating and lets the anchor pull through the board.

Why does my butterfly anchor keep spinning?

The wings have not opened, usually because the hole is too large, the wall cavity is too shallow, or the screw was driven before the anchor was pushed fully through.

Can a butterfly anchor hold weight on plasterboard?

It holds far more than a screw alone because the load is spread across the wings, but the limit is the board, not the anchor. Anything overhead or load-bearing should be fixed into a stud.