Formwork ties, clamps and accessories: what a wall set needs
Panels are the visible part of a wall form, but the accessories decide whether it can be set up, poured and struck safely. Ties carry the concrete pressure, clamps join individual panels into one face, walers and props keep it straight and plumb, and corners and fillers make a panel grid fit a real drawing. A used lot without the right accessories is not a working set, however good the panels look.
Tie rods, wing nuts, cones and sleeves
The tie system connects the two faces of a wall form through the concrete. It is usually made up of these parts:
- Tie rod: a high-strength steel bar with a coarse, continuous thread, so a nut can be run on at any point. Diameters of 15 mm and 20 mm are common, and the rod must suit both the nuts and the tie capacity of the system.
- Wing nut or plate nut: a cast or forged nut with a broad bearing plate that spreads the load onto the frame or the waler. Swivel versions allow for walls with a slight batter.
- Spacer sleeve: a plastic tube that keeps the faces at wall thickness and allows the rod to be withdrawn after striking.
- Cones: seal the sleeve ends against the facing and leave a clean recess.
- Plugs: fill the remaining hole in the finished wall.
Watertight structures such as basements and tanks call for lost ties with a water bar or for sealed sleeve systems instead of a plain tube. Tie rods are recovered and reused, whereas sleeves, cones and plugs are consumables bought again for each pour.
Never weld, heat or bend a tie rod. The high-strength steel loses capacity, and the damage cannot be seen from outside.
Clamps, walers and push-pull props
Panel clamps and aligning clamps
Panel clamps draw the edge profiles of neighbouring panels together so the joint is tight and the face flush. Aligning clamps also span the joint with a stiff section that keeps the panels in line, and some types can hold a narrow filler between two panels. Clamp jaws are shaped for the edge profile of one particular system, which is the main reason clamps do not cross over between systems.
Walers
Walers are steel sections fixed across the back of the panels. They stiffen long runs, bridge filler zones, connect stacked panels and carry load around infills. Multi-purpose walers in several lengths also form the backbone of stop ends and pilaster details.
Push-pull props and kicker braces
Push-pull props link the form to the slab or the ground and adjust it to plumb. They hold it against wind and against knocks during the pour. Short kicker braces fix the foot of the panel. Both need secure anchorage at the base and must be sized for the wind expected on site. Concrete pressure is taken by the ties, never by these props.
Corners, fillers, lifting hooks and brackets
- Inside corners form the internal angle where walls meet; outside corners or corner clamps close the external angle. Hinged corners cover angles other than 90 degrees.
- Filler pieces close the gap between the panel grid and the true wall length, either as metal fillers from the system or as timber fillers held by aligning clamps or walers.
- Stop ends close the wall at its end or at a construction joint, using dedicated brackets or ties with walers.
- Lifting hooks connect the crane to single panels or ganged units. They have a rated working load and may only be attached at the lifting points the manufacturer designates. Never lift a form by its ties, clamps or props.
- Concreting brackets with decking and guard rails provide the working platform along the top edge.
Why accessories must match the panel system
Every panel system is designed and tested as a whole. The permissible concrete pressure, the tie spacing and the clamp capacity in the manufacturer's tables apply only to the original combination of parts. Typical problems with mismatched accessories:
- Clamp jaws that do not close fully on a foreign edge profile, so the joint opens under load.
- Tie points at a different spacing, so ties cannot be placed where the design needs them.
- Waler connections that sit loosely and therefore carry no load.
- Lifting hooks rated for a lighter panel or intended for a different lifting point.
The safe rule: keep tie rods and nuts to one thread type, and keep every other accessory within the panel system it was made for. Where the instructions for that system are missing, ask for them before buying.
Estimating quantities without a fixed ratio
Accessory quantities cannot be expressed as a flat number per square metre of wall. They follow the geometry of the walls and the panel layout:
| Accessory | Quantity follows | Note |
|---|---|---|
| Tie rods and nuts | formed area, pour height and the tie spacing in the system tables | taller walls and higher pressure need more tie rows; one nut on each face |
| Sleeves, cones and plugs | number of ties in each pour | consumables, reordered per cycle |
| Panel clamps | number and length of panel joints | many narrow panels need more clamps than a few large ones |
| Aligning clamps and walers | filler zones, stacked panels and long straight runs | driven by the layout, not by area |
| Corners | wall junctions and wall ends | counted from the drawing |
| Push-pull props | wall length and panel height | spacing per manufacturer, often on one face only |
| Lifting hooks | number of gangs moved at one time | a small number per crane |
In practice, lay out one pour cycle on the drawing using the panel sizes of the system, count joints, ties, corners and fillers from that layout, and add a reserve for loss and damage, since sleeves and cones go missing on every site. If a seller's list shows far fewer clamps or ties than the panel count suggests, the set is incomplete and the gaps will have to be filled separately, for example with new formwork parts.
Checking used accessories
- Tie rods: run a nut along the full length by hand; it should turn freely. Reject rods with flattened or worn thread, bends, weld spatter, heat marks or heavy corrosion.
- Wing nuts and plate nuts: look for cracks in the casting, especially at the wings and around the bearing plate, and for worn internal threads that let the nut wobble on the rod.
- Clamps: jaws not spread, wedges or spindles moving freely, no cracks in cast parts, no welding.
- Walers: straight, connection holes not elongated, flanges not bent.
- Push-pull props: threads clean and turning, tubes straight, pins and connection plates present, foot plates free of cracks.
- Lifting hooks: no deformation, safety catch working, rated load legible. Many manufacturers call for periodic inspection by a competent person; follow their instructions and the lifting rules in your country, and withdraw hooks with an unknown history.
- Corners and fillers: the same checks as for panels, covering straightness, welds and a facing fit for the intended finish.
Our quality check covers accessories as well as panels. Lots are listed under used formwork parts and matching panel sets under wall formwork, while the guide to buying used formwork explains how to plan a complete set.