What is the maximum adjustable height of the base jack as specified by OSHA?

OSHA does not specify a particular value in millimeters, but rather requires adherence to the manufacturer's specifications. If the manufacturer specifies a travel of 18 inches (approximately 450mm), extending it 19 inches in the field is considered a serious violation.

What is Base Jack?

Scaffolding screw jack base is made of screw tube and sheet metal plate, and assembled with casted nut. The application is support scaffolding system, ringlock scaffolding system, cuplock scaffolding system, kwikstage scaffolding system, haki scaffolding system, tube&clamp scaffolding system and also formwork system, adjusting the construction system height flexibly.

Construction is usually carried out at a height above the ground. Scaffolding is used to provide a stable and secure working platform for construction workers on the ground or where ladders or lifting devices cannot reach.

Scaffolding is usually considered a temporary structure entered by internal or external workers. Many workplaces are uneven, and scaffolding adjustable base jacks help to provide a safe and level working surface at a variety of working heights on the ground.
A scaffolding leveling jacks is a scaffolding jack used to hold scaffolding in place horizontally. The scaffolding screw jack is mounted on a stable base and contains a large adjustable screw for moving scaffolding up and down. After scaffolding is built, use base jack scaffolding to level the working platform before use. Adjustable U-Head Jacks are designed to be used in conjunction with adjustable system scaffolding. The main function of adjustable U-Head jack is to hold timber beams securely in place.

Production Flow

We have a full set of production equipment, including model machine, punching machine, roll machine, sand blasting machine and so on. These production equipment will show how the products are produced, and we can also use these equipment to produce according to your requirements.

Inspection

The professional quality inspection team will carry out strict quality inspection in the production process and before delivery to ensure that the scaffolding jack quality meets customer requirements and improve the positioning of EK scaffolding leveling jacks in the market with high quality.

Packing&Loading

Experienced packing & loading team can effectively monitor the loading schedule of base jack scaffolding, make adjustable base jack arrive at the port of shipment within the scheduled time, and promote customers to receive the scaffolding leveling jacks on time.

Quality Test

According to customers' different requirements, we test the products through the professional third-party quality inspection center according to the data and standards provided by customers, so as to prove to meet customers' requirements.

How To Check If A Base Jack Is Qualified?

1. Weld inspection: The weld between the base plate and the screw must be fully penetrated, without porosity or cracks.
2. Thread inspection: The nut should be able to rotate and tighten smoothly on the screw without jamming.
3. Material certification: A material certificate (Mill Certificate) conforming to standards and a load-bearing capacity test report (SGS) are required.

Base Jack Report

Name	Thumbnail	Download
28-02-900 NJIN2309002411ML04_EN.pdf		Download
24-03-001 NJIN2309002411ML05_EN.pdf		Download
01-04-002 NJIN2309002411ML03_EN.pdf		Download
01-04-001 NJIN2309002411ML06_EN.pdf		Download
01-03-002 NJIN2309002411ML02_EN.pdf		Download
01-03-001 NJIN2309002411ML01_EN.pdf		Download

Base Jack International Standard

BS 1139 / EN 12811 VS OSHA / ANSI A10.8

Characteristic Dimensions	British Standard (BS 1139 / EN 12811)	American Standard (OSHA / ANSI A10.8)
Terminology	Adjustable Base Jack	Leveling Jack / Screw Jack
Base Jack Thickness	5 mm	Designed according to load
Adjustment Method	Mandatory Handle Nut	Handle Nut or Grooved Adjustable Nut
Calculation Logic	Limit State Design Method	Allowable Stress Design Method (ASD)
Typical Applications	Ringlock / Cuplock System	Frame / Tube & Clamp System

What is the maximum adjustable height of the base jack as specified by OSHA?

OSHA does not specify a particular value in millimeters, but rather requires adherence to the manufacturer's specifications. If the manufacturer specifies a travel of 18 inches (approximately 450mm), extending it 19 inches in the field is considered a serious violation.

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What Are The Common Specifications And Adjustment Ranges Of Base Jacks?

scaffolding leveling jacks Classification:
♦ The scaffolding jack is used at the bottom of the vertical steel rod and the bottom plate is at the bottom. The bottom plate can be folded or not folded.
♦ According to the lead screw material, can be divided into hollow base jack and solid base jack.
♦ The screw of hollow base jack is made of thick wall steel pipe, which is light in weight.
♦ The base of solid base jack adopts round steel bar, which is heavy in weight.

Standard base jack specifications typically include:

Screw diameter	30mm, 32mm, 34mm, 38mm (compatible with different standard pipe diameters)
Base plate size	120x120mm, 150x150mm (thickness 5-8mm)
Total length	450mm, 600mm, 750mm, 1500mm (customizable upon request)
Surface treatment	Electro-galvanized, Hot-dip galvanized (HDG), Painted
Adjustment range	It is recommended that the adjustment length should not exceed 2/3 of the total length

Scaffolding Solid Adjustable Base Jack

Adjustable solid scaffolding screw jack with base plate in 150*150*5mm or customized, screw rod made from high strength steel rod structure with casting or forging scaffolding jack nut for scaffolding system as ringlock scaffolding system, cuplock scaffolding system, kwikstage scaffolding system, haki scaffolding system, tube&fitting scaffolding system and others.

High Load Carrying Capacity Scaffolding Solid Adjustable Base Jack
Name	Base Jack Type	Solid Adjustable Base Jack Size		Solid Adjustable Base Jack Weight (KG)
Name	Base Jack Type	Screw Rod (MM)	Base Plate (MM)	Solid Adjustable Base Jack Weight (KG)
Solid Adjustable Base Jack	Solid	30*400	1201205	3.10
Solid Adjustable Base Jack	Solid	30*600	1201205	4.07
Solid Adjustable Base Jack	Solid	32*400	1201205	3.39
Solid Adjustable Base Jack	Solid	32*600	1201205	4.50
Solid Adjustable Base Jack	Solid	34*400	1201205	3.70
Solid Adjustable Base Jack	Solid	34*600	1201205	4.95
Solid Adjustable Base Jack	Solid	35*400	1501505	4.17
Solid Adjustable Base Jack	Solid	35*500	1501505	4.84
Solid Adjustable Base Jack	Solid	35*600	1501505	5.51
Solid Adjustable Base Jack	Solid	38*500	1501505	5.48
Solid Adjustable Base Jack	Solid	38*750	1501505	7.48
Solid Adjustable Base Jack	Solid	45*400	1501505	6.04
Solid Adjustable Base Jack	Solid	45*500	1501505	7.18
Solid Adjustable Base Jack	Solid	45*600	1501505	8.32
Specifications can be customized according to requirements

Scaffolding Hollow Adjustable Base Jack

Scaffolding hollow adjustable base jack made by high strength steel structure in hollow tube diameter 35/38/48mm with screw thread. Usually used at the bottom of scaffolding system verticals, it makes the whole scaffold system more stable.

High Load Carrying Capacity Scaffolding Hollow Adjustable Base Jack
Name	Base Jack Type	Hollow Adjustable Base Jack Size		Hollow Adjustable Base Jack Weight (KG)
Name	Base Jack Type	Screw Rod (MM)	Base Plate (MM)	Hollow Adjustable Base Jack Weight (KG)
Hollow Adjustable Base Jack	Hollow	354600	1501505	3.32
Hollow Adjustable Base Jack	Hollow	384600	1501505	3.50
Hollow Adjustable Base Jack	Hollow	484600	1601606	4.41
Hollow Adjustable Base Jack	Hollow	355400	1501505	2.96
Hollow Adjustable Base Jack	Hollow	355500	1501505	3.33
Hollow Adjustable Base Jack	Hollow	355600	1501505	3.70
Hollow Adjustable Base Jack	Hollow	385500	1501505	3.52
Hollow Adjustable Base Jack	Hollow	385750	1501505	4.55
Hollow Adjustable Base Jack	Hollow	455400	1501505	3.46
Hollow Adjustable Base Jack	Hollow	455500	1501505	3.95
Hollow Adjustable Base Jack	Hollow	455600	1501505	4.44
Specifications can be customized according to requirements

How To Choose Between Solid Base Jacks And Hollow Base Jacks?

The choice of base jack primarily depends on project load requirements and cost control. It is recommended to match the base jack to the design value of the axial force of a single upright based on engineering calculations, ensuring a safety factor of no less than 2:1.

Solid Base Jacks: Offer extremely high load-bearing capacity and are typically used in heavy-duty support systems (such as for cast-in-place bridge beam construction). They are heavy and highly stable.
Hollow Base Jacks: Made from seamless steel tubing, they are lighter and easier for workers to handle. They are suitable for standard building formwork system and offer good cost-effectiveness.

Base Jack FAQ

What are the strict prohibitions during base jack installation?

Prohibit excessive elongation: Do not exceed the manufacturer's specified maximum adjustment height (generally, the length of the screw remaining inside the tube should not be less than 25% of the total length).
Prohibit eccentric pressure: Ensure the upright is vertically pressed into the center of the base to avoid horizontal forces that could cause overturning.
Prohibit unstable support blocks: Wooden blocks or channel steel must be used on soft ground; never place it directly on loose soil.
Safety precautions for installing a base jack?

1. Level ground: The base plate must be in full contact with a solid surface or a wooden mat must be laid. It must not be suspended in mid-air.
2. No excessive length: Do not overtighten the nut to increase height, as this can cause the bolt to bend and become unstable.
3. Verticality: The bolt must be aligned with the axis of the upright. The tilt angle deviation should be controlled within 0.5%.
4. Lubrication and maintenance: Apply grease to the threaded parts regularly to prevent rust and subsequent inability to adjust.
Why do Base Jack screws typically use a "cold rolling" process?

1. Higher strength: Cold rolling causes work hardening in the metal, increasing the tensile strength of the thread.
2. Smoother surface: Compared to machining, rolled threads have a smoother surface, resulting in less resistance when adjusting the nut.
3. Higher material utilization: Chip-free machining better meets modern green manufacturing standards.
How to calculate the load-bearing capacity of a base jack?

The load-bearing capacity depends on the diameter and material of the screw (e.g., Q235 or Q345 steel). The slenderness ratio must be considered in the calculation.
Note: The higher the adjustment height, the weaker its stress stability.
How does the surface treatment of an adjustable base jack (galvanized vs. painted) affect its lifespan?

Surface treatment directly determines the lifespan and corrosion resistance of the base jack:
Hot-dip galvanized: Offers the strongest corrosion resistance, with a zinc layer thickness of 60-80μm. Suitable for outdoor projects in high salt spray and high humidity environments, with a lifespan of over 10 years.
Electro-galvanized: Provides a smooth and aesthetically pleasing surface at a lower cost, suitable for general environments.
Painted: Lowest cost, but the coating is prone to peeling during construction and handling. Short-term use in dry environments is recommended.

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Scaffolding Adjustable U-head Jack

Scaffolding adjustable U-head jack is designed for use in combination with adjustable system supports. The main function of the Scaffolding adjustable U-head jack is to hold the wooden beam in place. The Scaffolding adjustable U-head jacks we offer are of high quality standard, and these have a pure zinc plated finished, thus adding to its gloss. These are all adjustable and therefore the greatest advantage of these products. This was done under the scrutiny of experts, thus ensuring superior performance.

What Is The Difference Between U-Head Jack And Base Jack?

Although both use screws to adjust height, their functional logic is completely different:

Base Jack: Typically used for bottom support, with a flat steel base, focusing on pressure resistance and preventing settlement.
U-Head Jack: Typically used for top support, equipped with a U-shaped open steel plate, focusing on creating crossbeams and preventing tipping.

What are the standard dimensions of U-Head Jack (U-Plate Jack)?

The dimensions of a U-Head Jack must match the width of mainstream beams (such as wooden or aluminum beams):
Standard Width: Commonly 150mm or 170mm.
Side Wing Height: Typically 100mm or 150mm, used to prevent the beam from slipping under load.
Steel Plate Thickness: Core standards require between 6mm and 8mm to prevent deformation under heavy loads.

Features	Standard U-Head Jack	Heavy Duty U-Head
Screw Diameter	30mm / 34mm	38mm / 48mm
Typical Load Capacity	30 - 50 kN	60 - 100 kN
Packet Shape	Fixed U-Head	Swivel U-Head
Material Grade	Q235	Q345 / S355

High Load Carrying Capacity Scaffolding Adjustable U-head Jack
Name	U-head Jack Type	Adjustable U-head Jack Size		Adjustable U-head Jack Weight (KG)
Name	U-head Jack Type	Screw Rod (MM)	Base Plate (MM)	Adjustable U-head Jack Weight (KG)
Solid Adjustable U-head Jack	Solid	30*400	15012050*5	3.11
Solid Adjustable U-head Jack	Solid	30*600	15012050*5	4.08
Solid Adjustable U-head Jack	Solid	32*400	15012050*5	3.40
Solid Adjustable U-head Jack	Solid	32*600	15012050*5	4.51
Solid Adjustable U-head Jack	Solid	34*400	15012050*5	3.71
Solid Adjustable U-head Jack	Solid	34*600	15012050*5	4.97
Solid Adjustable U-head Jack	Solid	38*500	15012050*5	5.18
Solid Adjustable U-head Jack	Solid	38*750	15012050*5	7.17
Hollow Adjustable U-head Jack	Hollow	303.0400	15012050*5	1.98
Hollow Adjustable U-head Jack	Hollow	303.0600	15012050*5	2.38
Hollow Adjustable U-head Jack	Hollow	323.0400	15012050*5	2.04
Hollow Adjustable U-head Jack	Hollow	323.0600	15012050*5	2.47
Hollow Adjustable U-head Jack	Hollow	343.0400	15012050*5	2.04
Hollow Adjustable U-head Jack	Hollow	343.0600	15012050*5	2.47
Hollow Adjustable U-head Jack	Hollow	384.0500	15012050*5	2.86
Hollow Adjustable U-head Jack	Hollow	384.0750	15012050*5	3.70
Specifications can be customized according to requirements

U-Head Jack FAQ

Installation requirements for the U-Head Jack?

According to 1926.451(a), all load-bearing components must be able to support four times the maximum expected load.

Lateral support: OSHA emphasizes that the higher the U-Head top extends beyond the upright, the worse its horizontal stability. It is generally recommended that the screw extension length should not exceed 2/3 of its total length, and a horizontal tie rod must be installed at the top to counteract lateral forces.
How to handle "eccentric loads" on a U-Head Jack?

Severe eccentric compression is strictly prohibited. The centerline of the beam must be aligned with the centerline of the screw. If the beam does not completely fill the U-groove, wooden wedges must be used to tighten it and prevent the beam from twisting.
How to determine if a U-Head Jack needs to be scrapped?

U-shaped plate deformation: The flatness error of the bottom of the pallet exceeds 2mm or the side wings flare outward by more than 5 degrees.
Welding cracks: Visible cracks or severe corrosion appear at the connection between the screw and the pallet (usually a circumferential weld).
Screw bending: The overall straightness deviation of the screw exceeds 1/500 of its length.
What factors primarily affect buckling in a U-Head Jack?

Extension Length: The longer the screw extends beyond the upright, the greater the risk of buckling.
Constraints: Is there horizontal bracing at the top of the upright?
Thread Wear: Frequently used top supports will cause the threads to thin, leading to a reduction in effective cross-sectional area and decreased load-bearing capacity.

Scaffolding Base Plate

Scaffolding base plate is a type of footplated for scaffold system and tube&clamp scaffolding. The spigot for scaffolding base plate can be made from round rod or scaffolding hollow tube. The size of scaffolding base plate can be divided into 50mm, 110mm, 120mm, 140mm, 150mm and so on according to EN74 / BS1139 standard and can customize according to your requirements. Depending on the usage and size of spigot, scaffolding base plate can be in insert type and socket type.

High Load Carrying Capacity Scaffolding Base Plate
Name	Base Plate Type	Scaffolding Base Plate Size		Scaffolding Base Plate Weight (KG)
Name	Base Plate Type	Rod / Tube (MM)	Base Plate (MM)	Scaffolding Base Plate Weight (KG)
Scaffolding Base Plate	Rod	12*80	1201205	0.62
Scaffolding Base Plate	Rod	12*100	1201205	0.63
Scaffolding Base Plate	Rod	12*80	1201206	0.73
Scaffolding Base Plate	Rod	12*100	1201206	0.74
Scaffolding Base Plate	Rod	12*80	1501505	0.94
Scaffolding Base Plate	Rod	12*100	1501505	0.95
Scaffolding Base Plate	Rod	12*80	1501506	1.11
Scaffolding Base Plate	Rod	12*100	1501506	1.13
Scaffolding Base Plate	Tube	353.050	1201205	0.67
Scaffolding Base Plate	Tube	363.050	1201205	0.69
Scaffolding Base Plate	Tube	384.050	1201206	0.85
Scaffolding Base Plate	Tube	384.0100	1201206	1.02
Scaffolding Base Plate	Tube	353.050	1501505	1.01
Scaffolding Base Plate	Tube	363.050	1501505	1.02
Scaffolding Base Plate	Tube	384.050	1501506	1.23
Scaffolding Base Plate	Tube	384.0100	1501506	1.40
Specifications can be customized according to requirements

Base Plate FAQ

How to determine if a base plate is compliant?

Centered Holes. A qualified base plate typically has 2-4 pre-drilled holes for securing it to concrete or wooden mats if necessary.
Verticality. The uprights must be fully inserted into the inserts and flush against the base plate surface, with a gap not exceeding 2mm.
What are the most common violations when installing the base plate?

1. Missing locating pins: Using a flat steel plate instead of a base plate with insert rods may cause the bottom of the frame to shift laterally.
2. Suspension: Due to slight ground undulations, the base plate may be partially suspended, and the shims may not be properly secured.
3. Insufficient weld strength: The weld between the insert rod and the base plate is only a tack weld instead of a full weld.
Does the thickness of the base plate affect safety?

Standard thickness: Typically 5mm, 6mm, or 8mm. Risk point: If the base plate is too thin (e.g., < 4mm), "dishing" will occur under concentrated loads, causing the load to concentrate in the center rather than be evenly distributed, thus crushing the wooden pad underneath.
What are OSHA's guidelines regarding the use of Base Jacks (Base Plates)?

OSHA mandates that scaffolding must be vertical. If the ground slope exceeds 1:60 (approximately 1 degree), OSHA recommends using Base Jacks (adjustable bases) instead of fixed Base Plates to avoid unsafe methods such as leveling with bricks.
What are the requirements for corrosion protection of the base plate according to BS 1139 standard?

Because the base plate is in constant contact with ground moisture, BS 1139 recommends hot-dip galvanizing (HDG).

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Base Jack Scaffolding "Screw Thread " Production

Components

The Advantages Of A Base Jack.

♦ Material: Q235 round bar or ERW pipe.

♦ Diameter: 30mm/32mm/34mm/38mm/48mm or as your request.

♦ Adjustable Length: From 100mm to 1000mm as your request.

♦ Type: Solid / Hollow for your choose.

♦ Surface Treatment: Black, Paint, Electro Galvanized, Hot Dip Galvanized.

♦ Main Components: Threaded bar, Cast Nut and Base Plate.

♦ Certificate: SGS, CE.

♦ Packing: In Bulk or Steel Pallet suitable for sea transportation or as your request.

♦ OEM service available.

♦ Sample is available if with needs.

♦ BS1139 scaffolding jack with or without stiffeners.

♦ Good joint, high efficiency with strong loading capacity.

♦ Leveling jacks with many types of plates.

♦ Simple structures, simple erection.

♦ Widely application for many types of scaffolding system, such as ringlock system, cuplock system, kwikstage system, haki system, frame system and pipe&fitting system.

The Application Of Base Jack Scaffolding.

The base jack scaffolding is widely used in combination with scaffolding systems for building, hall, bridge, high-rise building inside and outside the row of scaffolding, used for electromechanical installation, hull construction, decoration engineering activity platform, building a simple roof, temporary site dormitory, warehouse, temporary observation platform, etc.

How To Install Base Jack To Level The Floor.

If the building is built on expansive soil, therefore, with regular movement, a scaffolding screw jack can replace concrete piers between solid wood columns and girders that support the floor joists.

A scaffolding leveling jacks is a metal support column that can be adjusted to make the floor level. It consists of two heavy steel tubes, one inside the other. The inner tube is threaded and adjusted up and down by turning a large wing nut. scaffolding screw jack are fixed with nails to the underside of the girder and to wooden blocks on top of the concrete wharf.