Ties are the component argued about most and questioned least. A façade scaffold appears to stand on its own feet; in reality it takes its safety against overturning from the points where it is tied to the structure. There is no single answer to how many ties a scaffold needs, but what determines the answer is clear.
What does a tie do?
Three separate jobs:
- It prevents overturning. A scaffold is a slender, tall structure, very long compared with its width. Without ties, a horizontal force pulls it away from the building.
- It transfers wind load into the structure. Wind load rises sharply on a scaffold covered with sheeting or netting.
- It shortens the buckling length of the standards. A tie divides the free length of the vertical member, and load capacity depends on that.
What sets the number and position?
The tie pattern is not judged by eye; it comes out of the scaffold design. What goes into it:
- Façade height and scaffold width
- Whether sheeting or netting will be fitted (if so, wind load multiplies)
- The location of the building and its wind zone
- Which lifts will carry loaded platforms
- The strength of the structural element the tie fixes into
This pattern is part of the design rules in TS EN 12811; the product standard for the system, TS EN 12810, also describes tie arrangements for type-tested scaffolds.
Where does a tie fix?
A tie goes into a structural element that can carry the load: a concrete wall, column or slab edge. What should not be done shows up on site often enough:
- Anchoring through insulation board
- Fixing to a handrail, a rainwater downpipe or an air-conditioning bracket
- Relying only on rods jammed into a window opening
On insulated façades the tie must reach the load-bearing element behind the insulation; the external insulation is completed afterwards.
"It was in the way, so we took it off"
Ties disappear most often during cladding or external insulation: the tie sits in front of the work, the crew removes it and does not put it back. Losing one point shows nothing immediately; the system spreads the load to neighbouring ties. The problem appears when the second and third point in the same row go too, usually with the first strong wind.
The rule is simple: if a tie has to come out, its replacement goes in first. That decision belongs to the crew that erected the scaffold, not to the cladding crew.
When you take delivery
Keep ties on your check list: are they in the pattern the design shows, are they all fitted, has any been anchored through insulation? We listed the other items to check in a separate article.
Send us your façade dimensions and whether you will use sheeting, and we will work out the tie pattern along with the take-off.