Levelling Shims: The Unsung Heroes of Perfect Construction | Brilliant Ideas Brilliant Ideas | Levelling Shims: The Unsung Heroes of Perfect Construction

In the construction industry, precision and stability are paramount. When building structures, especially those made of steel and concrete, even a small misalignment can lead to significant issues down the line.

Enter levelling shims, the unsung heroes that help ensure everything lines up perfectly. These small but mighty tools, often overlooked in the grand scheme of construction projects, play a vital role in ensuring surfaces are level and components fit together seamlessly.

Whether you’re a seasoned professional or new to the world of construction, this comprehensive guide will delve into the world of levelling shims, unpacking their purpose, composition, and why they’re indispensable in modern construction.

Dive in to understand the science and art behind these essential construction components, and discover how we are revolutionising the industry with our innovative Stacker Packers.

What is a levelling Shim?

Levelling Shims or Levelling Packers are small square elements used to level surfaces in construction, usually precast concrete components such as stairs and terracing which are supported by a steel frame structure. They are also used to level modular elements like pods and cabins.

They are categorised into two functions. Non-loadbearing and loadbearing, with the later making the material selection crucially important. Non-loading bearing shims are generally made from recycled plastic which doesn’t offer any assurances in relation to structural properties.

The brand name for the engineered levelling Shims we develop at Brilliant Ideas Ltd is Stacker Packers. Manufactured and tested in the UK, they’re made from virgin High Impact Polystyrene (HIPS), complete with UV stabilisers.

The addition of UV stabilisers overcomes the yellowing and brittleness associated with prolonged exposure to UV rays of unmodified HIPS. This is critical to the Shims performance, which enables them to be classified as loadbearing shims, making them a sound alternative to steel shims.

Close of up of one of our Levelling Shims (Stacker Packers)

What is the purpose of Shims?

The purpose of shims is to pack tolerance gaps between two elements, ensuring the final level is sited within acceptable level tolerances.

With all construction projects, manufacturing and installation tolerances are normal, which is why tolerance gaps are detailed at the design stage. If you try building a structure without these gaps, you’ll find the various elements will not fit together, which is why shims are necessary.

For example, with precast concrete terracing, you may have a nominal tolerance gap of 20mm, but due to manufacturing and installation tolerances the gap could end up being anywhere from 5mm and in extreme cases, up to 50mm.

That’s why Shims come in different depths to be able to facilitate whatever the final gap is before the concrete precast component, bathroom pod or whatever is being levelled, is landed in its final position.

What are levelling shims made of?

Levelling Shims which are most in demand on construction sites are typically made of steel and plastic.

Steel Levelling Shims

Steel Shims are generally used only when they are required to be loadbearing, and when the element or load they’re supporting is high. If they are not treated and or protected they can also rust, leading to issues with durability and maintenance.

Steel shims don’t interlock, so they can slip out of position whilst the element that is being supported is being installed. They are also expensive and heavy compared to plastic load bearing shims.

Plastic Levelling Shims

Plastic shims are made from various types of polymers, which means their functionality varies. Recycled plastic shims are the most widely used in the industry but these should not be used as load bearing shims as the source/blend of the recycled materials is not controlled. Laboratory structural tests has shown a wide range of results, concluding that the structural integrity cannot be guaranteed.

For plastic shims to be classed as load bearing shims, they have to be made from certified virgin material combined with certified laboratory tests – with the results being consistent and uniformed.

Load bearing plastic shims should also come with UV Stabilisers, which overcomes the yellowing and brittleness associated with prolonged exposure to UV rays of unmodified polymers.

Plastic shims are cheaper and lighter than steel shims, with the latter making them easier and safer to move around site.

Stacker Packers come with a unique interlocking design. This ensures the shim stack remains stable and locked into placed during the installation process, also allowing final adjustment away from the trapping zone by utilising the interlocking side profile.

During our design phase, we reviewed the material within standard Shims and found that in most cases, manufacturers use a variety of relatively low quality, recycled, substandard materials. These materials are often combined with a blowing agent to keep the cost down, which results in formed air voids within the material – which has no compressive strength.

To read more about our testing data for Stackers and its competing system, click here.

Photo showing Stacker Packers positioned onto steel angle which is bolted into a precast concrete wall element, this is prior to a precast concrete terracing element being installed

Who uses levelling Shims?

Levelling Shims are predominantly used by steelwork contractors and specialist installation companies. For a Shim to be classed as load bearing, they have to be certified. Brilliant Ideas Stacker Packers are load bearing and certified.

Stacker Packers are trusted by some of the leading steelwork contractors and structure design consultants, including Billington Structural Steelwork, Severfield, Coventry Construction, Hambleton Steel, J & D Pierce Contracts, Midland Structures, B & K Structures and Kelvin Power.

Projects include – Premier league football stadiums, La Sagrada Basilica in Barcelona, Wimbledon Court One and Sandwell Aquatics (Commonwealth Games, 2022).

If you’re using a competing system, we’d recommend you ask your supplier:

  1. For a copy of their testing report to be sure the Shims are certified.
  2. If their manufacturing process is ISO9001 certified.
  3. If their material comes with UV Stabilisers.

Where do you use Shims?

Shims are widely used to level/support precast concrete components – especially in the construction of sports and entertainment stadiums and arenas where you have steel frame Raker beams with precast concrete terracing, stairs, balcony walls and walkways.

They’ve also started to be used under steel column bases, albeit they’re not used to transfer the permanent condition of loading because the grouting of the column bases deals with that in the final state. This is great example of where load bearing plastic shims are an ideal alternative to steel shims.

They are used on modular structures, such as bathroom pods in multi-occupancy residential dwellings, cladding and curtain walling.

Some steel contractors have realised that plastic Shims work as well as steel Shims. Plastic Shims are much lighter – Stacker Packers weigh up to 12kgs per box, whereas the equivalent steel shims would weigh 180kgs so they wouldn’t be transportable by hand, making distribution across sites challenging. Plastic Shims are also cheaper, and importantly, more sustainable.

Positioned on the precast concrete terracing upstand supporting the precast concrete terracing horizontal going element

What size Shims do I need?

The size of Levelling Shim you need, really does depend on your application. There’s a certain amount of variation in all manufactured parts. Tolerances are used to control these variations.

Stacker Packers are modular and available in 2mm, 3mm, 5mm and 10mm. And because they have interlocking profiles, the Shims can be mixed up to create the desired packing height to suit the task in hand.

The flexibility of Stackers also allows them to be clipped together to adjacent shims to form a bigger bearing area. Our on-plan system creates two standard sizes: 35mm x 35mm and 70mm x 70mm – but tailored bearing areas can also be created to further increase the length and width to give even greater stability.

How should shims be installed?

Levelling Shims should be installed with safety and stability in mind, and without putting the hand in the trapping zone. One of the unique features of our Shims is that the system can be adjusted from the side without the hand being in the trapping zone because they have a unique side profile. With other systems this isn’t possible.

Once the packing zone has been determined by the setting out engineer on site, the Shims are then placed at the packing locations that should have been determined at design stage. By placing Shims in advance of the component being landed, final adjustment is minimal and can be done safely.

Stackers have inbuilt dowels which allow them to interlock horizontally and vertically, forming a safe and stable structure, which doesn’t slip against each other under load.

How big are levelling shims?

Levelling shims vary in size and shape – square, rectangular, horseshoe and double-horseshoe. They can be custom made using different dimensions and materials depending on your application.

On a recent premier league football ground project, our customer required a 35mm x 70mm bearing area. We achieved this by interlocking two 35mm Shims together.

We’ve also worked on a project where our customer required a load bearing 150mm x 150mm Shim plan, and we proposed interlocking four of our 70mm x 70mm Shims together to give an overall footprint of 140mm x 140mm, which was accepted by the structural engineer on the project.

Are shims permanent?

Shims are permanent. But what is absolutely fundamental is why they are permanent. Stacker Packers are permanent because the material is certified and comes with UV Stabilisers. This isn’t the case with all Levelling Shims.

Standard shims, for example, are made from recycled plastic and from the literature and test reports we’ve seen, the results are highly variable because they’re made from unknown recycled material. As Shims are permanently in the shade, there’s this myth that they’re not exposed to UV rays. But that’s not true, because the fundamental part of the Shim is exposed.

Because Stacker Packers are made from a high-quality material, it does make them more expensive than traditional Shims, but still more commercially viable when compared to steel shims. We’re not aware of any competing system that has a UV inhibitor, as nothing has been declared in any literature we’ve read.

Photo showing the precast concrete terracing elements (terracing, vomitory walls, rear walls and step block), which are all supported directly off our Stacker Packers, which are then supported off either steel beams or precast concrete elements

How much weight can a shim hold?

The weight that a Shim can hold depends on your application and how much compressive strength you need.

Our Shims have been independently verified by two testing houses to ensure consistency of results.

HCC County Highways Laboratory carried out simple compression tests and TWI Ltd carried out compression tests whereby the stress/strain relationship was analysed and recorded during the test. Shim stack heights ranged from 25mm to 100mm.

Under a 14.65T load test, the 50mm stack height from HCC and TWI recorded post-test vertical deformation at -0.38% and -0.36% respectively, which we think is a fantastic in terms of consistency because it gave us a variance of -01%. That’s a vertical deformation of .19mm which means we’re at a stack height of 49.81mm from 50mm stack height, which is phenomenal.

We recommend for shim stacks up to 50mm high the Stackers compressive strength value should be taken as: 30N/mm² (under factored loads). The competing system on the market is made from High Impact Polystyrene (HIPS).

In testing, the competing Shims were taken up to circa 148kN (15.08T). The load vs displacement results strongly suggests the stack would show permanent damage at around the 85kN (8.66T) mark, and serious deformation at 100kN (10.19T). The vertical deformation of this competing system was 19.40% (9.70mm)

Photo showing both steel and concrete raker beams, which support the precast concrete terracing units, the interface between the raker beams and terracing units will be where the Stacker Packers are used

Are Shims the same as Packers?

Yes – Shims are the same as Packers.

Stacker Packers is the brand name for Brilliant Ideas Ltd, engineered levelling shims.

Steel Shims – a sledgehammer ‘To Crack a Nut’?

We’ve talked a lot about steel shims and plastic shims – so, we’d like to leave you with this thought.

When shims are required to be load bearing, the industry ‘go to’ solution is steel, as they inherently have a very high compressive strength and are readily available in various sizes and thicknesses. But Brilliant Ideas plastic system is load bearing too – as it’s made from certified virgin High Impact Polystyrene (HIPS), complete with UV Stabilisers, and fully tested.

Unlike steel shims our system interlocks, making them easier and safer to use. Plus, there are significant weight advantages, so moving them around site can be done by the site operative.

Our system is rated at 30N/mm² (under factored load) which equates to over 14T over the 70mm x 70mm area, which is our standard shim size – so why not use them on your next project where the load condition permits.

For more information, call the Brilliant Ideas team on 01335 345111 or email enquiries@brilliantideasltd.co.uk