Vertical diagonal brace

The inclined brace that turns a rectangular bay into two triangles and stops the scaffold from racking along the facade.

Also called: diagonal brace, face brace, diagonal, ledger brace, bay brace

Picture a scaffold without diagonals: nothing but rectangles of standards and ledgers. Rectangles skew easily, and that is what happens once someone pushes hard at the top or wind acts from the side. The vertical diagonal prevents it. It runs at a slope through a bay, from the bottom of one upright to the top of the next, turning the soft rectangle into two stiff triangles.

It provides stiffness along the facade. Across the scaffold the frames themselves do that job on a frame scaffold; on a modular scaffold the transoms and decks do it together with the ties.

Design and variants

A vertical diagonal is a steel tube, usually 48.3 mm, with a connector at each end. Its length follows from bay length and lift height, so a brace for a 2.57 m by 2.00 m bay is a different part from one for 3.07 m.

• Frame scaffold: the ends are mostly flattened and drilled or fitted with claws, then placed over bolts or drop-lock pins on the frame uprights and secured.
• Modular scaffold: swivelling brace heads with wedges are driven into the large holes of the rosette.
• Material: almost always galvanised steel; aluminium braces exist for lightweight systems.
• Related: the horizontal diagonal does a similar job in plan; where no system brace fits, tube and swivel couplers are used.

Fitting it correctly

1. Install it in the very first bay before the decks go in.
2. Place the lower end as low as possible: on frames at the base just above the jack, on modular systems at the lowest disc on the base collar.
3. Fix the upper end to the neighbouring upright one lift higher and lock it: let the pin engage or drive the wedge.
4. Fit diagonals on the outside face so the working space stays clear.
5. Choose the pattern from the instructions: continuous zigzag over several lifts or stacked tower-fashion in the same bay. A common rule allows at most five bays per diagonal, in every lift.
6. Carry the bracing up lift by lift. A level without a diagonal weakens the whole scaffold.

Faults on site and on used parts

• Braces are taken out "just for a moment" to pass material through, then forgotten. Any proper inspection picks this up – in the UK the scaffold is inspected before first use and at intervals of no more than 7 days.
• An unsecured pin or loose wedge at the brace head is as good as no brace.
• Braces must be straight; a kinked one no longer takes compression.
• Check end plates and heads for cracks and elongated holes.
• Use the right length. A brace that only fits with force belongs to another bay size.

Continuous bracing spreads evenly across the facade; tower bracing keeps other bays free for hoists, rubbish chutes or windows that must stay reachable. Used braces in system lengths are listed under diagonal braces; see also scaffolding inspection.