Components
What is a tie?
A tie connects a scaffold to the building it is built against. Ties stop the scaffold moving away from or into the structure, and without enough of them a scaffold is free-standing whether or not it was designed to be.
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<img src="https://scaffoldoptix.co.uk/glossary/tie/diagram.svg" alt="tie — scaffold diagram from ScaffoldOptix" width="880" height="620" loading="lazy">
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<a href="https://scaffoldoptix.co.uk/glossary/tie">What is a tie?</a> — diagram by
<a href="https://scaffoldoptix.co.uk">ScaffoldOptix</a>
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</figure>A scaffold leans on the building far more than it looks. Wind load on a sheeted or netted scaffold is substantial, and the ties are what transfer it into the structure. The taller the scaffold and the more it is sheeted, the more the ties matter — sheeting a scaffold that was tied for an open one changes the loading significantly.
There are several common types. A through tie passes through an opening such as a window. A box tie encloses a column or a pier. A reveal tie is wedged across an opening using a reveal screw pin. An anchor tie fixes into the fabric of the building with a drilled anchor.
Tie patterns and tie duty are design decisions, and anchor ties are proof-tested to confirm the fixing can take the load the design assumes. Neither the pattern nor the testing regime is something to work out on site.
What goes wrong on site
- Ties removed by other trades — a window fitter taking out a through tie is the classic — and not reported or replaced.
- Sheeting or netting added to a scaffold that was tied as an open structure, which increases wind loading without the ties to match.
- Reveal ties used where the opening is not sound enough to take the load, or left without the pin tightened.