How to Choose the Right Thickness for 30mm Flat Glazing Packers

30mm flat glazing packers are used when installers need a wider support surface than standard narrower packers provide. They are useful for wider glazing rebates, heavier sealed units, deeper channels, conservatories, curtain walling, and general window and door glazing work.

But once you have chosen the 30mm width, you still need to choose the correct thickness.

The width gives the sealed unit a broader bearing surface. The thickness controls how much lift, spacing or correction is applied during installation.

At GlazingPacker, we stock 30mm × 100mm flat glazing packers in packs of 1000, available in 1mm, 2mm, 3mm, 4mm, 5mm and 6mm thicknesses.

This guide explains what each thickness is used for and which sizes installers should buy first.

Quick Thickness Selector

Use this quick guide when choosing 30mm flat glazing packers:

Thickness	Colour	Best used for
1mm	Green	Fine correction and final positioning
2mm	Black	Light spacing and small adjustments
3mm	White	Everyday glazing support
4mm	Grey	Medium adjustment and moderate gaps
5mm	Blue	Larger spacing and stronger support
6mm	Red	Maximum standard adjustment and heavier support points

For most installers, the best starting thicknesses are usually 3mm, 4mm and 5mm.

The 1mm and 2mm sizes are useful for fine adjustment, while 6mm is useful for larger gaps, deeper rebates and stronger support.

Why Thickness Choice Matters

The correct thickness helps the sealed unit sit in the right position without creating unnecessary pressure on the glass edge, gasket or frame.

If the packer is too thin, the unit may not be supported correctly.

If the packer is too thick, it may lift the unit too much, create pressure, or make the installation harder to align.

The aim is to choose the packer thickness that gives enough support without over-packing the unit.

This is especially important with 30mm packers because they are often used in wider or more demanding glazing situations.

Width and Thickness Do Different Jobs

It is useful to separate the two decisions.

The 30mm width gives a wider bearing surface.

The thickness gives the amount of adjustment.

For example, a 30mm 3mm packer and a 30mm 6mm packer have the same support width, but they do very different jobs.

A 3mm packer is usually for standard support.

A 6mm packer is for larger spacing, stronger lift or deeper correction.

That is why installers should not choose thickness based only on what is already in the van. The thickness should match the actual gap, support point and installation requirement.

1mm 30mm Glazing Packers

Use 1mm 30mm glazing packers when the unit only needs a very small adjustment.

This is the fine correction thickness. It is useful when the sealed unit is already close to the correct position and only needs slight levelling or finishing adjustment.

Typical uses include:

• fine levelling
• final positioning
• correcting very small gaps
• adding a small amount of lift
• combining with other thicknesses for precise adjustment

A 1mm packer is not usually the main support size on wider glazing jobs. It is mainly used when accuracy matters and a thicker packer would be too much.

When Installers Should Buy 1mm

Buy 1mm 30mm packers if you want proper adjustment stock for wider glazing work.

They are useful for installers who want to avoid forcing a 2mm or 3mm packer into a space that only needs a small correction.

For most trade buyers, 1mm should be stocked in lower quantities than 3mm, 4mm and 5mm, but it is still worth keeping available.

2mm 30mm Glazing Packers

Use 2mm 30mm glazing packers for light spacing and minor correction.

This thickness is useful when 1mm is not enough, but the job does not need a standard 3mm packer.

Typical uses include:

• small glazing gaps
• minor unevenness
• light support under sealed units
• small alignment corrections
• combining with 1mm or 3mm packers

2mm is a useful adjustment thickness because it gives slightly more lift while still allowing controlled positioning.

When Installers Should Buy 2mm

Buy 2mm 30mm packers if your installation work often needs small but noticeable corrections.

This thickness is especially useful for repair work, replacement glazing, older frames, and jobs where the unit needs careful positioning.

Like 1mm, 2mm is usually adjustment stock rather than the main high-volume thickness.

3mm 30mm Glazing Packers

Use 3mm 30mm glazing packers for standard everyday support where a wider flat packer is required.

This is one of the most useful thicknesses in the 30mm range. It gives enough support for many routine glazing jobs without being too thick.

Typical uses include:

• standard glass positioning
• general window glazing
• door glazing
• sealed unit support
• everyday site use
• wider glazing rebates where standard support is needed

If you are buying 30mm packers for the first time, 3mm should usually be one of the first thicknesses you order.

When Installers Should Buy 3mm

Buy 3mm 30mm packers in bulk if you regularly work with wider support points but still need a practical everyday thickness.

For many installers, 3mm will be one of the most-used sizes because it works well for standard glazing support.

It is a good core stock size for vans, workshops and warehouse stock.

4mm 30mm Glazing Packers

Use 4mm 30mm glazing packers when the job needs more correction than 3mm provides.

This is a useful middle thickness. It gives more lift and spacing than 3mm, but it is not as heavy as 5mm or 6mm.

Typical uses include:

• medium gaps
• slightly uneven rebates
• additional support under heavier sections
• balancing the unit during installation
• jobs where 3mm is slightly too thin
• wider support points needing moderate correction

4mm is a very practical trade thickness because many jobs need more than fine adjustment but less than heavy spacing.

When Installers Should Buy 4mm

Buy 4mm 30mm packers in bulk if you want a strong middle option for wider glazing jobs.

For trade buyers, 4mm should often be treated as a core working thickness, especially if you install across different frame types and site conditions.

It is useful for installers who do not want to jump from 3mm straight to 5mm.

5mm 30mm Glazing Packers

Use 5mm 30mm glazing packers when the installation needs stronger spacing support.

This thickness is useful for larger gaps, heavier sealed units and support points where 3mm or 4mm is not enough.

Typical uses include:

• larger glazing gaps
• heavier sealed units
• base support points
• firmer lift or spacing
• wider glazing rebates
• more demanding window and door glazing work

For installers working with larger sealed units, 5mm is one of the most important thicknesses to keep in stock.

When Installers Should Buy 5mm

Buy 5mm 30mm packers in bulk if your work includes heavier glass, deeper rebates, conservatories, curtain walling or larger window and door units.

5mm gives noticeable support while still being easier to control than the maximum 6mm thickness.

For many trade buyers, 5mm will be one of the faster-moving 30mm sizes.

6mm 30mm Glazing Packers

Use 6mm 30mm glazing packers when the job needs the largest standard adjustment in this range.

This is the thickest 30mm flat glazing packer option and should be used where substantial spacing or strong support is required.

Typical uses include:

• large spacing requirements
• base packing
• load-bearing support areas
• uneven openings
• deeper rebates
• heavier glazing conditions
• stronger bearing points

6mm is useful, but it should not be used simply because it is the thickest option. Use it where the installation genuinely needs that level of correction or support.

When Installers Should Buy 6mm

Buy 6mm 30mm packers if your jobs regularly involve larger gaps, uneven openings, deeper rebates or heavier sealed units.

For many installers, 6mm will not move as quickly as 3mm, 4mm or 5mm, but it is still important to keep available.

It is best treated as larger-gap or stronger-support stock rather than everyday stock.

Which 30mm Thicknesses Should Installers Buy First?

If you are adding 30mm flat glazing packers to your stock for the first time, start with the thicknesses most likely to be used regularly.

The best starting point is usually:

• 3mm for standard support
• 4mm for medium correction
• 5mm for stronger support

Then add:

• 1mm for fine adjustment
• 2mm for light correction
• 6mm for larger gaps and heavier support

This gives you a practical working range without buying every thickness in equal quantities.

Stock Priority for Trade Buyers

For trade buyers, it helps to divide the range into three stock groups.

Stock priority	Thicknesses	Why they matter
Core stock	3mm, 4mm, 5mm	Most useful for regular support and correction
Adjustment stock	1mm, 2mm	Needed for fine control and small corrections
Specialist support stock	6mm	Useful for larger gaps, deeper rebates and stronger support

Most installers should keep more stock of 3mm, 4mm and 5mm than the lighter adjustment sizes.

Choosing Thickness by Job Type

Different glazing jobs may need different thicknesses.

Standard Window Glazing

For standard window glazing, start with 3mm.

Use 4mm if the gap is slightly larger or the rebate needs more correction.

Use 1mm or 2mm for small finishing adjustments.

Door Glazing

For door glazing, 3mm and 4mm are useful starting points, but 5mm may be needed where the unit is larger or heavier.

Use 6mm only where the support point genuinely needs larger spacing.

Conservatory Glazing

Conservatory work can involve varied sections and larger panels.

A useful 30mm stock setup for conservatories would include 3mm, 4mm and 5mm, with 1mm and 2mm for adjustment and 6mm for larger corrections.

Curtain Walling and Commercial Glazing

For curtain walling and commercial glazing, 5mm and 6mm may become more important where the units are heavier or the support points are more demanding.

However, installers should still keep 3mm and 4mm available for standard support and moderate correction.

Repair and Replacement Work

For repair and replacement glazing, fine adjustment is often important.

A good repair stock setup should include 1mm and 2mm, along with 3mm, 4mm and 5mm for regular support.

This helps installers deal with older frames, inconsistent rebates and unknown site conditions.

Should You Buy a Full Thickness Set?

A full thickness set can be useful if you want every 30mm thickness available for different site conditions.

A full 30mm setup gives you:

• 1mm for fine correction
• 2mm for light spacing
• 3mm for standard support
• 4mm for medium adjustment
• 5mm for larger spacing
• 6mm for maximum standard correction

This is useful for installers who handle varied jobs and do not always know the exact support requirement before arriving on site.

When a Full Set Makes Sense

A full thickness set is a good choice if:

• you are building stock for the first time
• you install different window and door systems
• you work on conservatories or curtain walling
• you handle repair and maintenance work
• you want every van to carry a complete range
• you want to reduce improvisation on site
• you do not yet know which thicknesses will move fastest

A full set gives installers more flexibility and reduces the risk of not having the right thickness available.

When Single Thickness Packs Make Sense

Single thickness packs are better when you already know your usage pattern.

For example, if your team regularly runs out of 30mm 4mm packers, it makes sense to reorder that thickness separately.

Single thickness packs are useful for:

• restocking fast-moving sizes
• reducing slow-moving stock
• managing multiple vans
• buying based on real usage
• keeping warehouse stock organised
• topping up core thicknesses

The best approach is often to build a full working range first, then reorder the fastest-moving sizes individually.

Should You Stack Packers?

Sometimes installers use more than one packer together to achieve a precise thickness.

For example, a 2mm and 3mm packer can be used together to create 5mm of adjustment.

This can be useful for fine control, but stacking should be done carefully. The packers should sit flat, stable and properly supported.

Avoid unnecessary stacking when a single correct thickness is available.

A clean, stable support point is better than a messy stack of several packers.

Common Thickness Mistakes to Avoid

Avoid these mistakes when choosing 30mm glazing packer thicknesses:

• using 6mm when the job only needs light adjustment
• buying only one thickness for every job
• ignoring 1mm and 2mm fine adjustment sizes
• relying only on 3mm when heavier support is needed
• stacking several packers instead of using the correct thickness
• using 30mm packers where a narrower width would fit better
• using flat packers where bridge packers are required
• using timber, cardboard or improvised shims instead of proper plastic packers

The correct thickness should match the job, not just the packer that happens to be closest to hand.

Simple Buying Guide

Use this guide when choosing 30mm glazing packer thicknesses:

• Buy 1mm for fine correction.
• Buy 2mm for light spacing.
• Buy 3mm for everyday glazing support.
• Buy 4mm for medium adjustment.
• Buy 5mm for larger spacing and stronger support.
• Buy 6mm for deep rebates, larger gaps and heavier support points.

For most installers, the first bulk order should focus on 3mm, 4mm and 5mm.

Then add 1mm, 2mm and 6mm for complete coverage.

Final Thoughts

Choosing the right thickness for 30mm flat glazing packers depends on how much spacing, lift or support the installation needs.

For most trade buyers, the key 30mm thicknesses are:

• 3mm for everyday wider support
• 4mm for medium correction
• 5mm for stronger support

Installers should also keep:

• 1mm and 2mm for fine adjustment
• 6mm for deeper rebates, larger gaps and heavier support points

A 30mm flat glazing packer gives installers a wider bearing surface, but the thickness still needs to be chosen carefully. The best result comes from matching the correct width and thickness to the frame, sealed unit and support requirement.

Explore our 30mm flat glazing packers in packs of 1000 or choose the full thickness set if you want the complete 1mm to 6mm range.