How To Screed Around Columns On Large Commercial Sites

Large commercial floor screeding projects rarely involve a simple, uninterrupted expanse of floor.

In practice, most significant commercial and industrial sites contain columns, service risers, plant bases, machinery plinths, partition walls and a range of other obstructions that the screeding team must work around carefully to achieve a consistent, level finish across the entire floor area.

Getting this right requires careful planning, the right materials and a level of practical skill and experience that goes well beyond what is needed on a straightforward domestic or small commercial installation.

Why Obstructions Create Challenges For Screeding

Every obstruction on a commercial floor creates a potential weak point in the screed if it is not handled correctly. Columns, in particular, present several distinct challenges.

They interrupt the flow of liquid screed, create corners and junctions where the screed must be carefully detailed and introduce points where thermal movement during curing and in service can cause cracking if expansion is not adequately provided for.

Beyond the structural challenges, obstructions also affect the logistics of the screeding operation itself. On a large site where liquid screed is being pump-applied at speed, any obstruction that interrupts the flow of material or requires the team to slow down and work more carefully has the potential to create cold joints, level inconsistencies or surface defects if not managed correctly.

Expansion Strips Around All Obstructions

One of the most critical details in screeding around any fixed obstruction is the installation of perimeter expansion strips before any screed is poured.

Just as expansion strips are required at the perimeter of the floor against all walls, they must also be applied around every column base, service riser, plant plinth and any other fixed element that penetrates or sits on the floor slab.

These strips serve two purposes. They isolate the screed from the obstruction, allowing both elements to move independently in response to thermal changes and shrinkage during curing without transmitting stress across the junction.

They also define the interface between the screed and the obstruction clearly, producing a clean, consistent detail that can be finished neatly once the screed has cured.

Failing to install expansion strips around columns and obstructions is one of the most common causes of localised cracking on commercial screeded floors, and it is a detail that should never be omitted regardless of programme pressure.

Managing Liquid Screed Flow Around Columns

When pump-applied liquid screed is used on a large commercial site, its self-levelling properties are one of its greatest advantages. However, these same properties mean that the screed will flow around and under obstructions if not carefully controlled, and that the level on one side of a column may differ from the level on the other side if the pour is not managed correctly.

Experienced screeding teams plan the sequence of the pour carefully to make sure that screed reaches all areas around each column without creating trapped air pockets or areas where the material cannot flow freely.

On sites with a high density of columns or other obstructions, the pour sequence may need to be adjusted significantly from what would be used on an open floor, and additional operatives may be needed to work the screed into tight corners and confined areas as the pour progresses.

Checking Levels Around Obstructions

Achieving a consistently level finish around columns and obstructions requires careful monitoring during and after the pour.

Level pegs or laser screed guides should be set at regular intervals throughout the floor area, including on both sides of every column, to give the team reference points that allow them to confirm the screed is reaching the correct level as the pour progresses.

After the screed has been placed, a final check of levels around all obstructions should be carried out before the material begins to set, so that any areas that are high or low can be adjusted whilst the screed is still workable.

Once liquid screed has begun to cure, corrections become significantly more difficult and may require grinding or the application of additional material.

Day Joints & Pour Sequencing

On very large commercial sites, the floor area may need to be screeded in sections over multiple days, with day joints formed where one pour ends and the next begins. Where these day joints fall near columns or other obstructions, their positioning needs to be carefully considered to avoid creating a joint in a location that will be subject to point loading or where the joint detail will be difficult to execute cleanly.

Planning the pour sequence to keep day joints away from column bases and other stress concentration points, and to the details agreed with the structural engineer and main contractor, is an important part of the pre-pour planning process on any complex commercial project.

Service Penetrations / Cast-In Elements

Many commercial floors contain service penetrations, cast-in conduits, drainage channels and other elements that pass through the screed.

Each of these requires careful detailing to make sure the screed is correctly supported at the edges of the penetration, that water cannot track beneath the screed at these points and that the finished surface around each penetration is level and clean.

Where drainage channels or other linear elements run across the floor, they must be set to the correct level relative to the screed and firmly fixed in position before screeding begins, as any movement during the pour will result in level inconsistencies that are difficult to correct afterwards.

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