Screw jacks level the scaffold at the bottom and set the beam height at the top. We supply hollow-tube base jacks and U-head jacks, universal jacks and fork heads for cuplock, to buy or on monthly hire.
A base jack sits under every cuplock standard. Its plate spreads the leg load onto the sole board or slab, and its thread takes up uneven ground so the first lift is level. A U-head jack sits on top of the standard and carries the primary formwork beam, with the sides of the U keeping the beam in place during the pour.
Both work the same way, a threaded stem and a nut, which is why extension matters: the further the thread is wound out, the less load the leg can carry. The table below shows how quickly that happens.
Our base jacks and U-head jacks are hollow tube, not solid rod, which keeps them lighter to handle on site. The universal jack is the solid rod type.
Hollow threaded tube with a base plate. Levels the scaffold on uneven ground and transfers the load to sole boards.
Hollow threaded tube with a U plate that seats the primary formwork beams. The correct head for slab support.
A screw jack usable at the base or the head with the matching plate. Not for use as a shoring U-head.
A four-prong head that holds H20 timber or aluminum beams captive on props and standards.
| SKU | Item | Construction | Weight | Used for |
|---|---|---|---|---|
| ACC-BJ | Base jack, adjustable | Hollow threaded tube, 600 to 750 mm | 3.4 kg | Levelling the scaffold and transferring load to sole boards |
| ACC-UH | U-head jack, adjustable | Hollow threaded tube, 600 to 750 mm | 4.2 kg | Seating primary formwork beams on shoring standards |
| ACC-UJ | Universal jack | Solid rod | – | Base or head use with the matching plate; not a shoring U-head |
| ACC-FH | Fork head | Four-prong | – | Holding H20 timber or aluminum beams captive |
Weights are the figures recorded in our stock system; items without a recorded weight show a dash. Every item is listed in the product catalog.
| Jack extension | Allowable axial load | Share of maximum |
|---|---|---|
| 0 mm, fully retracted | 45.0 kN | 100% |
| 100 mm | 42.0 kN | 93% |
| 200 mm | 37.0 kN | 82% |
| 300 mm | 31.0 kN | 69% |
| 400 mm | 25.0 kN | 56% |
| 500 mm | 20.0 kN | 44% |
| 600 mm | 15.5 kN | 34% |
Basis: a single 48.3 mm × 3.2 mm EN10219 standard with an adjustable jack, no eccentricity, a properly tied scaffold and a safety factor of 1.65 on buckling. The same values apply to base jack and U-head extension. When both ends are extended, add the two extensions and use the combined table in our base jack and U-head load tables.
Most jack problems on site come from three things: too much extension, the wrong head, or poor ground.
A leg fails by buckling, so every millimetre of extension costs capacity. The loss is not linear.
Slab support needs a U-head or fork head that holds the beam. A plain universal jack does not.
A jack at full capacity is only as good as the surface under its plate.
Our base jacks and U-head jacks have a threaded tube of 600 to 750 mm, but the usable extension is set by load, not by thread length. As a rule of thumb, keep the total extension, base plus top, under 300 mm. Above 600 mm at either end, have a competent designer check the leg.
For a single 48.3 mm by 3.2 mm standard, the allowable axial load is 45 kN with the jack fully retracted, falling to 31 kN at 300 mm of extension and 15.5 kN at 600 mm, with a safety factor of 1.65. The limit is buckling of the leg, so extension reduces it quickly.
A U-head jack carries the primary formwork beam in its U plate and is the correct head for slab support. A universal jack is a plain screw jack that works at the base or the head with the matching plate. It should not be used as a shoring U-head.
Hollow. Both are made from threaded steel tube with a nut, not solid rod, which makes them lighter to handle on site. A base jack weighs about 3.4 kg and a U-head jack about 4.2 kg. The universal jack is the solid rod type.
A four-prong fork head holds H20 timber or aluminum beams captive on top of props and standards, so the beam stays in place while the deck is loaded.
Tell us the types and quantities, and whether you want to buy or rent. You get a written quote, and a layout if you send the drawings.
sales at scaffworks dot com
Factory & yard: Umm Al Quwain, United Arab Emirates