Scaffold tie anchors: choosing, installing and testing

Before choosing an anchor, decide whether the place you want to tie to can take the tie load at all. A competent person should make that call (TG4:25 §6.3). Work through these questions:

• Is anything already fixed there? Buildings from after 1994 may have anchor points for maintenance. Agree early who answers for them and what they can take, and test them if they may have deteriorated.
• Is it structural? Parapets, balustrades, the panel under a window and other features may not be built to carry load: ask an engineer before fixing to them.
• Is it finished? In new masonry, wait until the mortar has cured and the building stands up by itself. On a house that may mean waiting for the roof, the internal walls and the floors. If you are unsure, ask a structural engineer.
• Is it solid? A load-bearing concrete frame or slab is normally fine once it is strong enough for the load, and so is solid, sound brick or block with sound joints. Cavity walls are on most jobs: check that the leaf you fix into can take the load, and see the depth rules in scaffold anchor types.
• Is it near an edge or corner? Fit packing to protect the edge and spread the load, and fix the packing so it can't drop out.

Only after two checks.

First, check what kind of figure it is. A recommended load or safe working load can be set against the tie duty. A design resistance, which anchors with a European Technical Assessment often quote, already carries the material safety factor but not the factor on loads, so it can't: ask the maker for the recommended load.

Second, check it fits your wall. The figure only holds in a base material at least as strong as the one it was rated in. A concrete figure tells you nothing about brick or block, or about old or cracked concrete: there, run preliminary tests (TG4:25 §6.2). Ratings get revised, so ask for the current data sheet with each delivery. Where you have the choice, an ETA anchor gives you tested, comparable data.

Preliminary tests where the anchor's data doesn't cover the wall, and proof tests on every job.

• Preliminary tests, where there is doubt that the anchor can carry the tie duty in that wall, which usually means brick, stone or timber with no maker's data. Test 5 anchors per base material, away from where the scaffold will be tied, at 2 × the tie duty (3 × for nylon, unless the manufacturer specifies otherwise), then discard them. See preliminary tests on scaffold ties.
• Proof tests, on every job, including jobs re-using anchors already in the wall: at least 5% of the anchors at random, at least 3 per discrete area, at 1.25 × the tie duty. See proof testing scaffold ties.

The scaffold designer or responsible engineer sets the test plan, and a test report records what happened without approving any anchor. See what goes in a site test report. Where a job is specified to BS 8539 instead, our test-load calculator works out its preliminary test load.

Your firm needs settled answers to four questions: who do site teams call when an anchor won't take its load, who tests anchors, who picks them, and how does each job's working load for each anchor reach the people fixing it? The people involved also need training, and method statements to work from. TG4:25 §2 gives the full list.

A tester for scaffold tie anchors should pull on the anchor itself, never through the tie tube, and its gauge should have been calibrated in the last 12 months to an accuracy of 5% (TG4:25 §11.1). On brick or block, keep the rig's feet off the unit the anchor is in; turning the bridge upright usually does it.

The Staht t25 reaches 25 kN and comes with a 12-month calibration certificate, in three-legged and four-legged kits. See scaffold tie testing and pull tester hire.