Using the right shims are crucial to getting it right the first time. Whether you’re levelling steel beams, adjusting precast panels, or installing heavy machinery, the right combination of plastic or metal shims will keep everything secure, aligned, and compliant.
In this guide, we’ll show you how to choose the best shim type, material, and size for your job, so you can avoid rework and meet spec on site.
Need a quick recommendation? Call us on 02 4646 1166 before you order.
Packers and shims compared: type, material, applications and when to use
| Shim type | Material options | Typical applications | Sizes available | When to use |
| Slotted shims | Stainless steel, mild steel, brass, plastic | Bolt and anchor positions, steelwork baseplates, frame fixings | Range of thicknesses, slot sized to common bolt diameters | When you need to add or remove a shim around an existing bolt without undoing the fixing |
| Packing shims | Stainless steel, mild steel, plastic | General spacing and levelling, precast panels, structural packing | Multiple thicknesses, stackable | Filling and levelling a gap where load is spread across a flat area |
| Custom shims | Any stocked material: stainless, mild steel, brass, copper, plastic | Non-standard gaps, bespoke profiles, tight tolerances | Made to your drawings or samples | When a standard size or shape will not fit the gap |
| Pre-cut shims and kits | Stainless steel, mild steel, plastic | Fast site work, machinery alignment, repeat packing tasks | Assorted thicknesses supplied in a kit | When you want a ready range of thicknesses on hand to avoid delays on site |
What Are Packers and Shims Used For?
Levelling materials are small but vital components used to fill gaps, level surfaces, align elements, and distribute loads across structural and non-structural installations. They’re everywhere, from steel and concrete construction to window installations and flooring prep.
Depending on the job, you might use:
- Plastic shims for moisture resistance and ease of handling
- Steel shims for strength under load
- Brass shim sheets or copper shims for conductivity or specialist applications
- Custom shims for non-standard gaps or bespoke adjustments
What to Consider When Choosing Packers and Shims
1. Material
The first decision is what material suits your job:
- Plastic shims: Lightweight, rot-proof, and easy to stack. Great for general construction, facade works, and areas exposed to moisture.
- Metal packers and shims: Stainless steel, brass, copper, and mild steel. For heavy loads, machinery alignment and precise adjustments.
- Pre-cut shims: Supplied in shim kits, save time on site and ensure consistency when packing or aligning.
2. Load-Bearing Requirements
For structural works or any load-critical application, steel shim stock or a stainless steel shim kit will outperform plastic or timber options. Use slotted shims for positioning around bolts or anchor points where lateral movement isn’t acceptable.
3. Environmental Conditions
Working in wet areas, outdoors, or coastal environments? Go for:
- Plastic shim packs in UV-stable materials
- Stainless steel shims for corrosion resistance
Avoid timber shims in these conditions; they absorb moisture and can deteriorate quickly.
4. Precision and Flexibility
Need to dial in perfect levels or work around existing fasteners? Look for:
- Shim kits with multiple thicknesses
- Slotted shim kits for bolts and anchors
- Custom shim manufacturing where exact tolerances are needed
5. Installation Ease
Plastic packers and shims are often colour-coded by size, pre-cut, and ready to go. Ideal for fast-paced jobs. Steel packers take more effort but offer unmatched strength and durability.
Step-by-Step: How to Choose the Right Shim
- Assess your project – Think load, environment, and alignment needs. Are you lifting, levelling, spacing or adjusting?
- Match the material – Use metal packers and shims for strength or plastic shims for fast, moisture-resistant installs.
- Measure your gaps – Have multiple shim thicknesses on hand to avoid delays on site.
- Consider kit options – A metal shim kit or plastic shim pack keeps everything in reach and saves time.
- Buy from a trusted source – At PP Shim, we supply precision shims, custom options, and off-the-shelf kits for jobs across Australia. Our team can guide you to the right product, fast.
Need Help Choosing the Right Shim?
With years of on-site experience and a full range of steel packers, plastic levelling kits, and precision-engineered custom options, PP Shim supports builders, engineers, and project managers across Australia.
We offer fast, nationwide delivery and stock stainless steel supports and site-ready plastic packers for commercial and industrial construction. Contact us online for advice, specs, or to place an order.
Frequently Asked Questions
What’s the Difference Between a Packer and a Shim?
They’re often used interchangeably, but typically, packers are pre-sized spacers, and shims offer finer adjustments and can be stacked or cut to size.
Do I Need Metal or Plastic Shims?
If your application involves heavy loads or outdoor exposure, metal shims (stainless steel or brass) are usually the better choice. For fast, low-load installs, plastic shim packs are perfect.
Can You Supply Slotted Shims or Custom Shapes?
Yes, we offer slotted shim kits for bolt installations and custom shim solutions made to your specs.
Which shims should I use behind frame fixings or for levelling?
For packing behind window and door frame fixings, a flat or slotted shim sits cleanly against the fixing and spreads the load without distorting the frame. Slotted shims help here because the slot lets you locate the shim around a bolt or screw without removing the fixing. For levelling steel beams, precast panels or machinery, load-bearing steel packers in the right thickness give a firm, stable seat.
How do I work out the right shim thickness?
Measure the gap at its widest and narrowest points, since few gaps are perfectly even. Build up to the target with a combination of thicknesses rather than forcing a single oversized shim, which gives a more stable stack and a more accurate final level. A shim kit with a range of thicknesses on hand avoids return trips when the gap isn’t what the drawings suggested.
Can I mix shim materials in the same stack?
Yes, within reason. It’s common for a steel shim to carry the load while a thin plastic shim takes up a small remainder. Watch two things: galvanic corrosion if dissimilar metals sit together in a damp location, and total load, since the weakest material in the stack sets the limit. For load-critical work, keep the load-bearing layers in steel.
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