Lally Column vs Jack Post -What's the Difference?

Lally Column vs Jack Post -What's the Difference?

Lally Column vs Jack Post -What's the Difference?

Often used interchangeably, the terms lally column and Jack Post are used in the context of support for structural beams in residential buildings.

Jack Posts are also referred to as split jack posts in some contexts.

There are important differences between these two vertical members which if ignored can be disastrous for any structure.

What is a Lally Column?

Lally columns are non-adjustable, round-shaped steel pipes, often filled with high-strength concrete to provide support for extended horizontal structural members.

Most importantly, they are permanent and there are clear, well-defined standards for their load-bearing capacities.

What is a Jack Post?

Jack posts are also an assembly of hollow and thin cylindrical steel pipes equipped with an adjusting jack.

They are used to provide supports to beams or joists and their height can be adjusted even after installation.

Differences between lally column and Jack Post

Lally columns and jack posts both are vertical steel members that are used to support horizontal members like ceiling, beams, and others. 

Lally columns can be both temporary and permanent, whereas jack posts are only temporary supports.

Lally columns provide support to horizontal members like basement beams.

Jack posts, in addition to providing support, help in correcting the sagging of horizontal members and require periodic inspection.

When you have a sagging member then jack posts are your solution.

Crucially, lally column heights are fixed and no adjustment is possible after fixing it.

If you want only to provide support to horizontal members then lally columns are what you need. 

A Lally column is a round structural steel column used to support loads from beams, joists, girders, and other components.

Wooden and concrete structures are sometimes used as lally columns, but they offer less resistance to vertical loads.

The durability of wooden lally columns can be a concern if it's exposed to the elements.

Concrete lally columns are durable, but due to their brittle nature, they are prone to failure.

Never use plain concrete (PCC) to build a lally column.

Lally columns are made in different lengths ranging from 3 to 14 feet.

Their diameter typically ranges from 3.5 inches to more than 4 inches.

For permanent use, the diameter of a lally column should be greater than 4 inches.

When you need adjustable support for sagging structural components, a Jack post is used.

Jack posts are made up of hollow cylindrical steel pipes and an adjusting screw.

Generally, the material used to make jack posts is low-carbon steel.

Jack posts range in length from 3.5 feet to 16 feet, with varying diameters.

Standard for lally columns and jack posts

The international residential code includes lally columns (R502, R407 & R802).

R502 of the IRC describes the fastening of lally columns.

R407 and R802, on the other hand, advocate structural requirements and uplift resistance of lally columns.

In the case of jack posts, there is some disagreement about whether they should be accepted as standard by any code in the United States.

The size, strength, and construction of jack posts or metal props, on the other hand, are approved by the British standard code BS 4074:1982.

Metal props are classified into five categories by British standards based on their length. 

What are some situations where a lally column or jack post should not be used?

A solid footing foundation is the first and most important requirement for installing lally columns or jack posts. If you do not have a strong enough concrete foundation, you should avoid installing these two.

Even if your floor appears to be in good condition, supports may sink if the soil beneath it is not properly stabilized. This could lead to a structural failure and a serious accident.

Lally columns and jack posts should also be avoided in flood-prone areas.

As heavy structural load is transferred from vertical members to soft soil. This will result in soil failure.

Also, vertical members should not be installed if you have a sump pump in your basement.

The soil beneath will erode, causing the columns to be forced in.

Can Jack posts be permanent?

No, a jack post's diameter is usually less than 3 inches.

A permanent steel column must be larger than 3 inches in diameter, according to the international residential code (IRC).

Any steel member with a diameter less than 3 inches is considered a temporary member.

Code-enforcing officers/building inspectors consider the permanent use of jack posts to be a structural and safety defect.

Load-bearing capacities of jack posts have not yet been standardized in the USA.

Are Lally columns permanent?

Lally columns can be used on a temporary or permanent basis.

A lally column should have a diameter of at least 4 inches for permanent use.

Also, note that ASTM A53 Grade B or an equivalent grade of material should be used for a lally column steel tubing.

To meet IRC & IBC (international residential code and international building code) standards, the lally column should have a minimum thickness of 11 gauges or 0.120 inches.

When selecting a lally column for long-term use, exercise extreme caution.

How to install a Lally column

If you are preparing to repair your floor or want to remove any wall, you probably need to install some lally columns temporarily or permanently.

Installation of a lally column requires some steps that must be followed correctly,

The installation process can be divided into two phases: the documentation phase followed by the construction or installation phase.  

Here is a step-by-step process guide on how to install a lally column:

Preparation of structural report

A qualified and practicing structural engineer will identify your needs.

The engineer will identify the structural condition, load conditions, and other important factors.

Based on these conditions, he/she will suggest the size, numbers, and locations of lally columns. 

Getting Permits

In most states, you will need building permits to install lally columns permanently.

The approving agency will examine your structural report to validate your application for permanent construction.

Following claim verification, they will physically inspect your structure to determine the validity of your application.

In most cases, your contractor will assist you in filing claims and obtaining the necessary permits from these authorities.

Permissions are typically not required for temporary construction.

However, it is recommended that you check your local building codes to verify this.

After completion of phase one i.e. documentation, you can move to the next phase of construction. The documentation part is not compulsory if you only need a temporary lally column. 

Identification of the location

First, determine the best location for the installation of the lally column.

Mark the spot on the beam and drop a plumb bob from the beam to the floor.

Mark the location of the plumb bob's drop on the floor.

Draw a circle with a diameter of 12 inches, with the marked point in the center.

If your floor is made of concrete, use a hammer or concrete cutter to break the concrete inside the circle.

If you don't have a concrete cutter, you can easily rent one from someone nearby. 

You can simply begin excavating if you have a dirt floor.

Build a strong footing

Footing for Lally Column
Footing for Lally Column

A strong footing is very essential for the erection of lally columns and proper disposal of loads in the ground.

Dig the floor up to two feet underneath the circle.

Mix enough concrete and fill this hole with concrete to the level of the actual floor.

Cure the concrete for the next six weeks for proper strengthening.

Backfill the sides with soil if there is any vacant place and clear the topside. 

Measurements and cutting of lally column

Measure the distance from the bottom of the beam to the top of your concrete footing with care.

To compensate for the thickness of the plates on the top and bottom, reduce the measured length by the thickness of both plates.

These plates typically have 1/4-inch thicknesses.

As a result, you can directly reduce the measured length by 1/2 inches. 

Now mark the resultant length on the lally column.

If necessary, carefully cut the lally column to achieve a smooth surface.

Erection of lally column

Deploy a hydraulic jack right next to the location of your possible lally column. Lift the beam slightly, but not more than 1/4 inches.

Now center your lally column on the footing with plates.

Level your column vertically from two sides to ensure proper straight orientation.

After you've determined the best orientation, mark the location of holes in steel plates, drill them up to 2 inches in the floor, and beam both to insert screw anchors.

Now carefully erect the lally column with plates on top and bottom.

Pay close attention to the orientation of lally columns. It should be perpendicular to the surface and centered on footing. 

Remove the hydraulic jack after proper erection and allow the beam to rest on the lally column.

You have now completed the installation and erection of the lally column.

Do lally columns need to be filled with concrete?

Lally columns are filled with high-grade concrete to avoid buckling.

If you are using a lally column to support light loads then there is no need to fill it with concrete. 

However, almost all lally columns available on the market come with prefilled concrete in them.

How much does it cost to have lally columns installed?

A lally column installation cost typically starts from $2500.

The cost of installing lally columns depends on several factors, including support conditions, member conditions, and the condition of existing horizontal members.

This cost rises as the number of columns and the size/span of existing and prospective beams increase.

How to Install a Jack Post

Jack posts, in addition to providing vertical support, can be used to correct sagging beams or floors in any structure.

They are adjustable and readily available in a variety of sizes on the market.

Jack post-installation is quite simple.

Because it is considered a temporary construction, no special permit is required from any authority.

Jack posts are made up of two hollow cylindrical steel pipes of varying diameters and an adjustable screw bolt.

It's easy to install it by following a step-by-step process.

Identification of location

You need to identify the perfect location where you should install your jack post.

It may be under the sagging portion of horizontal members or under long-span crawl places.

You have to mark your locations properly to avoid any problems during the installation process. 

Preparation of floor

Because jack posts transfer the load from horizontal members to the ground, your floor must be strong enough.

If you have a sufficiently strong concrete floor, you are ready to go.

In case you don't have a concrete floor, you'll need to build a strong foundation ahead of time.

The footing preparation process is the same as for the lally column.

You must dig a 2×2×2 feet hole. Fill this hole with concrete and set it aside for 6 weeks to cure.

After the concrete has been properly strengthened, you can proceed further with the installation process of your jack post.

Measurements and selection of Jack Posts

Measure the distance from the bottom of your beam or horizontal structure to the top of your footing surface.

According to this measured length you have to select the length and adjustment range of your jack post. 

Assembling the parts 

There will be two hollow steel cylindrical pipes, one with a larger diameter and the other with a smaller diameter.

Both of these pipes have carriage holes on one end. This is known as the carriage end.

Insert the smaller diameter pipe's carriage end through the larger diameter pipe's carriage end.

Grease your adjusting screw and insert it into the smaller diameter pipe's non-carriage end.

Keep your adjusting bolt at the bottom of the adjusting screw before fitting the screw in the pipe. 

Erection of jack post

At the desired location, place the flat side of the plate against the bottom of the beam.

Drop a plumb bob from the center of the plate to the ground and mark the location of the plumb bob's fall.

If you don't have a plumb bob, you can make one with a string and a key.

Maintain your bottom plate on the ground, perfectly centered on the dropping point and oriented with the top plate.

Place the column assembly vertically and keep the adjustable jack in the center of the bottom plate.

Move the outer pipe upward until it tightly touches the bottom of the beam.

Finish your installation

To make your post perfectly aligned in a straight position, insert the driving screws through the carriage holes of both pipes in two directions.

Maintain the column's straight position by vertically leveling it.

After that, using a suitable tool, move the adjustable jack bolt until it encounters its first resistance.

Your installation process is now complete.

When properly installed, jack posts can take loads from the beam and dismantle loads in the ground.

Once in a while, tighten the adjustable jack again.

How much does it cost to have a Jack Post Installed?

A jack post installation typically costs between $10,000 and $15,000.

This price includes labor, jack post costs, and mobilization fees.

The cost of jack post-installation is affected by several factors, including the span, length, and load-bearing capacity of the jack posts, among others.

How much weight can a lally column support?

A lally column's weight-bearing capacity is quite sensitive to its dimensions.

A short lally column can support more load than a long column.

The length of a lally column can be anywhere from 3 to 14 feet.

A 6 foot long, 4-inch diameter lally column can withstand a maximum load of 21,300 pounds.

A lally column with a span of 4 feet and an 8-inch diameter can withstand a maximum load of 27,200 pounds.

A decrease in length and an increase in diameter will result in a higher load resistance capacity.

Aside from dimensions, the weight-bearing capacity is also related to the strength of the top and bottom plates, as well as the strength of the screws.

How much weight can a jack post hold?

A jack post can hold a load of 20,000 pounds to 32,000 pounds. Jack posts can hold the loads coming from sagging beams, porches, or roofs. 

Can lally columns be used outdoors?

Yes, lally columns can be used outside, but with caution. To prevent rusting at the base of the lally column, use exterior grade paint.

Lally columns are designed to withstand vertical loads only, not horizontal or lateral loads.

Lally columns should therefore be avoided in situations where there is lateral load.

Frequently Asked Questions (FAQ)

Are lally columns necessary?

No, lally columns are generally used to encounter the heavy structural load while performing maintenance tasks or to support a weak member. There is no compulsion of the use of lally columns in any structure. It is among one the practical solutions to counter the heavy loads of a structure. 

What Are the Types of Lally Columns?

It is very difficult to classify the lally column based on its size. Plenty of dimensions are available in the market and you can choose the best-suited option for you. 

Majorly lally columns can be classified into 3 categories:

Lally column- it is a temporary or permanent vertical support to capture the loads from top members and transfer these loads to the ground. It is associated with two plates at the top and bottom. It is a non-adjustable support column filled with high-strength concrete. 

Mono posts- mono posts -it is an adjustable support system designed for permanent use but with caution. Normally they have an adjustable range of 12 feet. They are permanently locked by concrete or by spot welding. It is equipped with an adjustable mechanism at the bottom to alter its height as per your requirements. 

Floor jacks- it is also known as jack post. It is temporary support that requires proper assembling. It is the weakest one among all types of support systems. It is also equipped with a height adjustment mechanism. 

How much does it cost to install a lally column?

The installation cost of a lally column starts from 2500$ and can go above based on your requirements. Roughly the cost is dependent on load-bearing capacity, dimension, and the number of lally columns. 


About V Susan

Hi! I'm Susan. I am passionate about woodworking, general DIY and home improvement. If you'd like to connect with me or talk about something you like at mellowpine, drop me a mail at susan@mellowpine.com

DIY Profile
V Susan

Hi! I'm Susan. I am passionate about woodworking, general DIY and home improvement. If you'd like to connect with me or talk about something you like at mellowpine, drop me a mail at susan@mellowpine.com

Connect With Me


The comments are closed.