Lally Column vs Jack Post: What’s the Difference?

When building or renovating a basement it’s important to note that there are often posts strategically placed supporting one or more beams that help carry the upper floors. The posts may be wooden posts, lally columns, or jack posts. If you’re wondering about a lally column vs jack post and what’s the difference, we’re here to help.

A lally column is a 3” or greater diameter concrete-filled non-adjustable steel column typically used for permanent structural support. A jack post is a two-section adjustable steel pipe post often used as temporary support but can be used as permanent support provided it meets code requirements.

In this article, we’ll explain what a lally column and a jack post are, their pros and cons, and compare them based on key points. We’ll discuss whether they need footings, their spacing and if they can be permanent or temporary. Our aim is to provide you with the information to make the best choice for your project.

Lally Column vs Jack Post

Lally Column vs Jack Post: Key Points

Lally columns and jack posts can both be used as permanent or temporary supports. However, even though the terms are often used interchangeably, they are not the same. This is very clear when comparing the two using key points as illustrated in the Table below.

 Lally ColumnJack Post
Material3” to 4” diameter columns of 16 to 11-gauge tubular carbon steel with rust-resistant coating and filled with high-strength concrete.11- and 12-gauge rust-resistant coated 3” to 4” tubular carbon steel with 3-gauge top and bottom plates.
Temporary/PermanentUsually permanent due to fixed size, but can be used as a temporary post.Temporary or permanent adjustable posts. Must be at least 3” in diameter to be used for permanent support.
Weight CapacityVaries with height, diameter, and type of steel: 72” tall 3” dia. can support 18,000lbs, 72” x 4” dia. 29,100lbs, and a 72” x 4” Schedule 40 steel lally can support 41,500lbs.Varies with height, diameter, manufacturer, and type and gauge of steel. Adjustable between 60” and 96” by 2-3/4” 11- & 12-gauge steel two pipe jack post will support 8,090lbs at 60” and 3,720lbs at 96”.
Code ComplianceLally columns are code compliant.Must meet set code requirements to be used as a permanent post.
Installation ComplexityTypically installed during the construction phase, so easier.Temporary jack posts are usually installed after construction to lift or support existing structural components, so often more difficult.
LifespanBarring corrosion can last as long as the building they support.Temporary usually means 1 to 3 months, permanent is the life of the building barring corrosion.
UsesPermanent structural support for beams or joists.Temporary support for beams, joists, headers, lintels, ceilings, floors, stairs, etc., or permanent for beams and joists.
Installation Cost$200 to $500 for DIY and $2,500 by a contractor during the build. Retrofitting a new lally post can easily exceed $10,000.Temporary $50 to $200 for DIY and up to $1,500 by a pro. Permanent similar to lally column installation.

What Is a Lally Column?

What Is Lally Column

A lally column is named after patent holder John Lally and is often called a lolly or lollie column or post. It is a hollow round thin-walled (16 to 11-gauge or 1/4” or less) carbon steel column used to permanently support long-spanning structural beams or timbers to prevent sagging. It is filled with high-strength concrete to improve compressive resistance, strength, and structural stability, and to help prevent buckling. The columns must be installed true to vertical as engineered structural components, so there are building code requirements for their use.

Lally columns today typically are 3” or 4” in diameter or square so they will better fit within a stud-framed wall. Historically though, the columns could be up to 6” or 8” in diameter.

A true lally column isn’t adjustable, so is often cut to length on site. The steel casing can be cut using a lally column cutter, or power saw with an abrasive carbide blade, and the concrete core usually breaks off with a hammer blow or two.

Modern lally columns are much the same as the original columns, just smaller diameters. Today the columns may have a welded plate at the top and/or base to allow for easier placement between a 2’x2’ concrete footing pad and beam.

In the past, a cup-shaped indent at the top of the footing pad was used to help secure the column in place. In both past and present practice, the base is secured in concrete when the basement floor is poured and finished.

Today, the top and bottom of the lally column commonly have a flat 1/2″ or thicker (9-gauge) steel plate with holes for securing it in place, however, it may have a ‘U’ flange or saddle plate at the top. The plate or flange may be welded to the column or rely on compressing fitting. It may also be a plate with a welded cup or dimples for extra security.

Lally columns range from 1’ to 24’ in length or longer, but are usually 4’ to 10’. Load maximums depend on diameter, the gauge of steel, and length, with shorter lengths typically able to support greater loads.


  • Permanent
  • Resistant to buckling
  • High compressive strength
  • Improves structural stability
  • Fits within a 2×4 or 2×6 wall


  • Must meet code requirements
  • Susceptible to rust
  • Non-adjustable
  • Permanent

What Is a Jack Post?

What Is Jack Post

A jack post, also known as a screw jack, floor jack, or split post, is an adjustable telescoping steel post or column. They are commonly used as temporary vertical support for beams, joists, walls, and ceilings, and even as horizontal support for shoring up trenches. However, they can be used for permanent support too. Usually designed to extend almost double their length, they have a fine and gross mechanical adjustment for easier placement.

The lower hollow 12-gauge steel cylinder or pipe has a welded or loose 1/2″ (3 gauge) steel baseplate to spread the load and secure it to the floor. A slightly narrower diameter hollow 11-gauge steel cylinder resides within the open end with a heavy jack screw threaded into a heavy metal plug at the upper pipe’s end.

The other end of the jack screw is squared for turning with a wrench or bar, and a heavy 3-gauge metal plate for the top. The inner cylinder has through holes every 6” for a section which allows for gross adjustment. Raising the inner cylinder from the outer one exposes the holes.

A 3/4″ to 1” diameter steel locking pin or bolt is inserted through the inner pipe once it is raised the desired amount. The pin has grooves near each end that hook onto the outer tube and prevent the pin from slipping out.

Jack posts are often used during renovations to temporarily support floors or ceilings or to level sagging joists. It is common to use two or more posts with a temporary beam to lift or support a section too. If using two or more posts, turn each screw a 1/4 turn at a time.

Take your time if lifting floors or ceilings a 1/2″ or more; it may take a week to raise it 1” so as to minimize cracking and nail or screw pops. Jack posts that will be used as permanent supports, need to have a proper 2’x2’ footing pad underneath them and meet code requirements.

Jack posts typically are installed with the wider diameter pipe at the bottom and the jack screw at the top, but they can be used either way. However, it is easier to plumb the post with the screw at the top. Plus, it is easier to turn with a wrench for fine adjustment at shoulder height than at your feet.


  • Adjustable
  • Rust-resistant coating
  • Temporary or permanent
  • Lighter and easy to install
  • Ideal for lifting and supporting sagging joists or beams


  • Some claim it is not sturdy or stable
  • More difficult to plumb true
  • Requires some assembly

What is the Difference Between Lally Column and Jack Post?

Difference Between Lally Column and Jack Post

The terms jack post and lally column are often used interchangeably to mean structural support for beams that span long distances and carry up to two floors. However, when comparing them it is clear there are some significant differences.


A lally column is made from a 3” or 4” hollow 16- to11-gauge carbon steel pipe and filled with high-strength concrete. It may have a 1/2″ steel plate welded to the base and a matching plate with a welded cup for securing it at the top. Some may have a saddle or ‘U’ shaped flange for the top instead.

A jack post has a hollow lower or outer 12-gauge 2-3/4” O.D. carbon steel tube and an 11-gauge 2-1/2” O.D. steel inner tube. There is a top and bottom 3 gauge 3-1/2” by 6” steel plate as well that may be loose or welded in place.

The upper end of the inner tube has a welded high-grade steel plug with a threaded hole for a steel jack screw. There is also a 3/4″ or 1” locking pin. Some manufacturers use 15-gauge steel and smaller diameter tubes for temporary supports.


A lally column is typically permanent. The base can fit into a cup-shaped depression in the center of a 2’x2’ concrete footing pad or rests on a steel plate on the pad. The top may have a plate with a cup, dimples, or a saddle or ‘U’ flange to fasten it to the beam it supports at the top.

The column is often placed to support a structural beam as it is being set or built and helps prevent sagging. Once the concrete floor is poured, the base of the column is encased and fixed, making the column permanent.

A jack post can be either permanent or temporary and often is used to support beams, joists, ceilings, floors, or even walls. Since they are adjustable, they are often used to correct structural members sagging or during renovations as temporary supports.

In some residential construction, they may be used as permanent posts to support structural beams and must comply with building code requirements. However, they need diameters 3” or greater to be used as permanent posts.

Weight Capacity

A true concrete-filled lally column can support more than an adjustable jack post or mono-post. The weight capacity of both a lally column and a jack post depends on the diameter, gauge of steel, and length. The greater the length, the less weight either type can support.

Most manufacturers have load tables for their products as different variables affect load ratings. The load capacity or rating of the beam and the load it needs to transfer to vertical supports will determine the rating of posts or columns and their spacing.

Non-adjustable concrete-filled lally posts can support up to 60,000 pounds depending on the column’s diameter, length, steel grade, and gauge. A 6-foot long 3” diameter lally post typically has an allowable load rating of 18,000 pounds while an 8-foot is rated for 14,900 pounds.

A comparable 4” diameter can carry 29,100 pounds at 6 feet and 25,500 at 8 feet depending on the manufacturer. Improving the steel to Schedule 40 and a 3-1/2” diameter 6-foot lally can support 41,500 pounds and 34,600 pounds at 8 feet.

The weight capacity of an adjustable jack post depends on its diameter, gauge, grade, length, and manufacturer too. A 60” to 96” adjustable post with a 2-3/4” 12-gauge outer tube and 2-1/2” 11-gauge inner tube using 3-gauge top and bottom plates from one manufacturer has a working load limit of 8090 pounds.

Another manufacturer’s jack post that extends from 56” to 76” has a working load limit between 6,360 and 3,720 pounds respectively.

Code Compliance

Before using lally columns or jack posts it is best to check with a Structural Engineer or the local building code or department. Section R407.2 and R407.3 of the 2021 IRC (International Residential Code) identify steel column or post protection and structural requirements.

Permanent steel columns or posts must be Schedule 40 pipe at least 3 inches in diameter. It must be manufactured to meet ASTM A53/A53M Grade B requirements or an approved equivalent.

Girder and beam span are also addressed in the code, as are footings (R403) under support columns or posts. Loads (R301) that beams must support, and in turn, are transferred through support columns or posts are specified too. The placement of columns or posts and their spacing greatly depends on the beam size, span, composition, and loads, and typically requires an Engineer’s involvement.

Posts or columns used for temporary support or bracing need to support the loads required until permanent supports are in place. Although temporary and not specifically addressed in the building code, it is recommended a qualified professional identify the size and spacing, and supervise the installation.

Installation Complexity

The size and placement of a lally column are typically identified on the construction drawings along with the beam it or they must support. Installation is commonly done during the construction phase as the support beam is being placed and prior to the pouring of the concrete floor.

So, installation is rather simple as the lally is centered on the footing pad and under the beam as it is placed or constructed. If too long, the lally column must be cut, if too short, a new one may be required or a thicker steel plate used at the top or bottom, or both. The column must be plumbed longitudinally and laterally to prevent failure under loads.

Jack posts that are 3” in diameter or greater can also be used in place of lally columns to permanently support structural beams provided they are code compliant. They are usually installed in the same manner on footing pads as the beam is placed or constructed. Their advantage though is that they can be more finely adjusted for a perfect fit. They too need to be plumbed perfectly.

Installation complexity increases if a permanent support is to be added to address a sagging joist or beam, or if an existing support needs to be moved or replaced. Permanent supports must have a footing underneath them to transfer the loads; just having them sit on the existing floor isn’t enough support. In most such situations, a building permit is required as is the involvement of a Structural Engineer.

Temporary support posts are commonly used to hold or lift something in place to permit a permanent support structure to be fabricated or placed. It may only involve the use of one jack post but often requires two or more with a temporary beam to support the load. It is also important that the temporary posts be plumb too.


The lifespan of jack posts or lally columns depends on the location and how they are used. Lally columns tend to be permanent structural components, so they should last as long as the house, as should jack posts used as permanent posts. However, dampness and moisture can cause corrosion and damage the structural integrity of the steel. Which is one of the reasons the building code requires the metal to be properly protected against moisture.

Temporary jack posts are just that, temporary. Their lifespan may be decades but they shouldn’t be left in place for more than a couple of months while permanent supports are put in place.


A lally column is commonly used as a permanent support under a structural beam. It can be used as temporary support but since it isn’t adjustable, it is difficult to place and plumb. A jack post is adjustable and may be used as a temporary support for a beam, joist, header, lintel, floor, ceiling, or wall.

Jack posts are often used to lift sagging structural members while a permanent solution is found and installed. Jack posts 3” in diameter or greater can also be used as permanent posts the same as lally columns.

Installation Cost

The cost of installing a lally column or jack post depends on numerous variables. Lally columns tend to be permanently installed as part of new construction. So, are typically contractor purchase cost, labor cost to install, plus the cost of the concrete pad it will sit upon. If the column needs to be cut to fit, that cost is added too.

If you do the work yourself, which isn’t recommended, the cost could be $200 to $500 depending on the diameter and length of the column used. Leaving the job to the professionals could run from $2,000 to $3,000.

The cost of installing a permanent 3” to 4” diameter jack post is similar to that of installing a lally column. Temporary jack posts can range from $50 to $2500 depending on how they will be used, type, specs, and additional materials.

Retrofitting a lally column or permanent jack post can require cutting out a square of the existing concrete floor, removing several cubic feet of material, and pouring a new pad. The cost to do so can easily top $10,000 or more.

Do Lally Columns Need Footings?

A lally column is a permanent structural support and requires a proper footing to be code compliant. The footing is usually a 24”x24” poured pad between 8” to 12” thick with #4 rebar longitudinally and latitudinally through the center. The footing helps spread the weight and pressure of the load from whatever the column supports. Once the concrete floor is poured, the base of the lally is secured.

How Far Apart Should Lally Columns Be?

The distance between lally columns is commonly determined by the sizing of the beam, joist span, spacing, size, and the loads being supported. So, it is usually identified on the drawings by an engineer. Additionally, it depends on the diameter of the lally column and its length. The shorter its length and the greater its diameter, the more weight it can support.

The spacing between lally columns for a three or four-ply 2×12 beam will differ from an LVL or steel I-beam depending on dimensions. The weight of the building being supported is also a factor to consider.

A one-story home vs a two-story one requires different spacing due to increased loads. Plus, the types of finishings and furnishings can add to the load – marble tile floors, concrete countertops, hot tubs, grand pianos, etc.

Lally columns are commonly used in what often becomes a finished basement. They may be required to support a corner of the stair opening as well as the central beam. The spacing between supports may be determined based on rough plans for finishing the basement so the column disappears within a wall.

Typically, the minimum distance between lally columns is 8 feet and the maximum is 26.5 feet, with the average spacing for residential single-family homes being between 10 and 12 feet.

Can Jack Posts Be Permanent?

Can Jack Posts Be Permanent

Jack posts that are at least 3” in diameter and made of heavy gauge steel can be used as permanent supports. If they are used in place of lally columns for structural beams they must also be centered on a poured concrete footing. However, they can also be used to permanently shore up sagging joists, floors, ceilings, or other structural components.

It is recommended that their use and sizing be approved by a Structural Engineer or your local building department to be code compliant.

Written By: Yevgen

YevgenI'm a DIY nut, and the founder and chief editor here at Weekend Builds.
This site is a result of my DIY passion, and to share the joys I have experienced fixing, building, and creating things over the years.

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