Product Knowledge

Frame Packers for Door and Window Installation: Which Sizes Should You Buy?

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When fitting doors and windows, frame packers are used to level, align, support, and secure the frame before final fixing. They help keep the frame plumb, square, and stable, especially when the opening is uneven or when there are gaps between the frame and the surrounding structure.

For professional installers, buying the right frame packers is important. The wrong size can slow the job down, make alignment harder, or force the installer to improvise with unsuitable materials.

If you install windows and doors regularly, you should keep a practical range of frame packers in stock, especially the thicknesses and sizes you use most often.

What Are Frame Packers Used For?

Frame packers are used when installing or adjusting the frame itself. This is different from glazing packers, which are mainly used to support and position sealed glass units inside the frame.

Frame packers are commonly used for:

  • door frame installation
  • window frame installation
  • keeping frames plumb and level
  • packing behind fixing points
  • sill and threshold support
  • correcting uneven openings
  • supporting frames before final fixing
  • helping prevent twisting or distortion
  • general construction and joinery adjustments

The main job of a frame packer is to provide firm, consistent support between the frame and the surrounding structure.

Frame Packers vs Glazing Packers

Frame packers and glazing packers are not the same product.

Frame packers are used around the door or window frame. They help position and support the frame during fitting.

Glazing packers are used around or beneath the sealed glass unit. They help support and align the glass inside the frame.

Installers often need both.

Use frame packers when you are fitting, levelling, or fixing the frame.

Use glazing packers when you are supporting or positioning the glass unit.

Why the Correct Frame Packer Size Matters

Choosing the correct frame packer size matters because the packer needs to support the frame properly without creating pressure in the wrong place.

If the packer is too small, it may not provide enough bearing area.

If the packer is too large, it may be awkward to position or unnecessary for the fixing point.

If the thickness is wrong, the frame may not sit correctly, which can affect the final installation.

The aim is to choose a frame packer that matches:

  • the size of the gap
  • the position of the fixing
  • the frame material
  • the load being supported
  • the type of door or window
  • the opening condition

For trade work, it is better to keep a range of sizes available instead of relying on one product for every job.

The Main Frame Packer Sizes Installers Should Consider

Frame packers are available in different widths, lengths, and thicknesses. The correct size depends on where the packer is being used.

At GlazingPacker, the frame packer range includes standard frame packers and specialist options for different fitting situations.

The main sizes to consider include:

For many window and door installers, 53×62mm frame packers are a strong general-purpose choice because they offer a good balance of coverage and control.

53×62mm Frame Packers

53×62mm frame packers are a useful mid-size option for everyday window and door frame work.

They are suitable for:

  • window frame levelling
  • door frame alignment
  • medium-sized uPVC frames
  • timber frames
  • aluminium frames
  • fixing point support
  • sill and lintel packing
  • threshold alignment

This size is useful when you want a firm bearing surface without using a packer that is too long or too small for the job.

For many installers, 53×62mm frame packers are a good first frame packer size to keep in stock.

When to Use Smaller Frame Packers

Smaller frame packers are useful when the fixing point or available space is more limited.

They can be useful for:

  • tighter installation areas
  • smaller support points
  • compact frame sections
  • adjustment around fixing points
  • light frame alignment work

A smaller frame packer can be easier to place where a larger packer would be awkward.

However, installers should avoid using a packer that is too small for the load or support requirement. The frame still needs stable, non-compressible support.

When to Use Larger Frame Packers

Larger frame packers are useful when the installation needs more bearing area, stronger support, or better spread behind the frame.

They can be useful for:

  • wider gaps
  • larger frames
  • heavier doors
  • bigger window frames
  • sill support
  • threshold support
  • uneven openings
  • structural fixing points

A larger packer can help spread pressure more evenly and provide more stable support at important fixing points.

Which Thicknesses Should You Buy?

For frame installation, thickness is usually just as important as the packer footprint.

The main thicknesses to consider are:

  • 1mm
  • 2mm
  • 3mm
  • 4mm
  • 5mm
  • 6mm
  • 10mm

Different thicknesses are used for different levels of correction.

The most useful everyday thicknesses are usually:

  • 3mm
  • 4mm
  • 5mm

Smaller sizes are useful for fine adjustment, while larger sizes are useful for bigger gaps and heavier support.

1mm Frame Packers

Use 1mm frame packers for fine alignment and small final adjustments.

They are useful when the frame is already close to the correct position and only needs a light correction.

Common uses include:

  • final positioning
  • fine adjustment around fixing points
  • small gap correction
  • minor frame alignment work

1mm packers are useful to keep available, but they are usually not the main bulk-buying thickness.

2mm Frame Packers

Use 2mm frame packers for light levelling and minor spacing corrections.

They are useful for:

  • slightly uneven reveals
  • small frame adjustments
  • light support behind fixing points
  • minor alignment corrections

2mm packers give installers more correction than 1mm without jumping straight to a standard support thickness.

3mm Frame Packers

Use 3mm frame packers for standard everyday frame packing.

This is one of the most useful thicknesses for window and door installation because it covers many normal fitting situations.

Common uses include:

  • general frame levelling
  • standard fixing point support
  • routine door and window installation
  • moderate adjustment during fitting

For most installers, 3mm should be one of the first frame packer thicknesses to keep in stock.

4mm Frame Packers

Use 4mm frame packers when more correction is needed than a 3mm packer provides.

They are useful for:

  • medium gaps
  • uneven brickwork
  • slightly irregular reveals
  • added support at fixing points
  • frame alignment where 3mm is not enough

4mm is a very useful middle thickness and should be part of a practical installer stock setup.

5mm Frame Packers

Use 5mm frame packers for larger gaps and stronger support.

They are useful for:

  • heavier uPVC frames
  • timber door and window frames
  • larger gaps behind frames
  • load-bearing fixing points
  • stronger support positions

5mm is one of the most important trade thicknesses because it provides a noticeable correction while still being practical for everyday installation work.

6mm Frame Packers

Use 6mm frame packers when the job needs increased support or base packing.

They are useful for:

  • bottom frame support
  • sill packing
  • threshold packing
  • heavier door installations
  • larger correction points

6mm packers may not be used on every job, but they are important to keep available for heavier or more uneven installations.

10mm Frame Packers

Use 10mm frame packers for maximum adjustment and heavy-duty support.

They are useful for:

  • large gaps behind frames
  • severely uneven openings
  • high load-bearing support points
  • bigger corrections
  • heavy doors or larger frames

10mm should not be treated as an everyday adjustment size, but it is very useful when the opening is badly uneven or when significant packing is required.

Which Thicknesses Should Installers Stock First?

If you are building frame packer stock from scratch, start with the thicknesses that cover the widest range of work.

A good starting setup would be:

  • 3mm for standard frame packing
  • 4mm for moderate correction
  • 5mm for larger gaps and stronger support

Then add:

  • 1mm and 2mm for fine adjustment
  • 6mm for sill, threshold, and heavier support
  • 10mm for large gaps and heavy-duty correction

This gives installers a practical working range without overbuying every size immediately.

Frame Packers for Door Installation

Door frames often need careful packing because they must remain plumb, level, and square. If the frame is not packed correctly, the door may rub, swing incorrectly, fail to latch properly, or move over time.

Frame packers are useful for:

  • hinge-side support
  • lock-side alignment
  • threshold packing
  • keeping the frame square
  • supporting fixing points
  • correcting uneven reveals
  • preventing frame twisting

For door installation, installers should keep stronger support thicknesses available, especially 5mm, 6mm, and 10mm, because door frames can involve heavier loads and more demanding fixing points.

Frame Packers for Window Installation

Window frames also need accurate packing so they sit level and square within the opening.

Frame packers are useful for:

  • side fixing points
  • head and sill alignment
  • levelling the frame
  • correcting uneven brickwork
  • preventing distortion during fixing
  • supporting the frame before final securing

For window installation, the most useful thicknesses are usually 3mm, 4mm, and 5mm, with 1mm and 2mm used for fine adjustment.

Frame Packers for uPVC Frames

uPVC frames need stable support around fixing points to prevent distortion or twisting during installation.

For uPVC frame work, a practical stock setup would include:

  • 3mm for standard support
  • 4mm for moderate adjustment
  • 5mm for larger gaps
  • 1mm and 2mm for fine correction
  • 6mm and 10mm for heavier support or uneven openings

Installers should avoid overtightening fixings against unsupported gaps. Proper frame packing helps maintain the shape of the frame during and after installation.

Frame Packers for Timber Frames

Timber frames also benefit from proper plastic frame packers, especially where the opening is uneven or where the frame needs consistent support.

For timber frames, frame packers can help with:

  • levelling
  • sill support
  • threshold alignment
  • fixing point support
  • correcting irregular openings
  • preventing movement during fixing

Plastic frame packers are a better option than improvised timber shims because they provide consistent thickness and are easier to identify on site.

Frame Packers for Aluminium Frames

Aluminium frames often require accurate positioning because the systems can be rigid and precise.

Frame packers are useful for:

  • fine alignment
  • supporting fixing points
  • correcting small variations
  • keeping the frame square
  • preventing stress from uneven fixing

For aluminium frames, installers should keep 1mm and 2mm for fine correction, along with 3mm, 4mm, and 5mm for normal support.

Should You Buy Frame Packers in Bulk?

Yes, if you install doors and windows regularly.

Frame packers are consumables. They are used across many jobs, and running out of the correct thickness can slow installation work down.

Bulk buying makes sense for:

  • window installers
  • door installers
  • glazing companies
  • builders
  • contractors
  • joiners
  • maintenance teams
  • companies with multiple vans

Buying in packs of 1000 helps keep stock available and reduces the need for last-minute buying.

Recommended Frame Packer Stock for Installers

For a self-employed installer or small team, a practical starting stock would include:

  • 53×62mm frame packers in 3mm, 4mm, and 5mm
  • 1mm and 2mm for fine adjustment
  • 6mm for sill and threshold support
  • 10mm for larger gaps and heavy-duty correction

If you regularly work with different frame sizes or larger openings, add other frame packer footprints such as longer or wider packers to suit the job.

Recommended Frame Packer Stock for Door Installers

For door installation, prioritise:

  • 5mm for stronger support
  • 6mm for sill and threshold packing
  • 10mm for larger gaps
  • 3mm and 4mm for standard alignment
  • 1mm and 2mm for fine adjustment

Door installers should not rely only on lighter adjustment sizes because door frames often need stronger support.

Recommended Frame Packer Stock for Window Installers

For window installation, prioritise:

  • 3mm for everyday frame packing
  • 4mm for moderate correction
  • 5mm for larger gaps
  • 1mm and 2mm for fine adjustment
  • 6mm for base support
  • 10mm for larger gaps where required

Window installers may use 3mm, 4mm, and 5mm most often, but the larger sizes are still useful when openings are uneven.

Frame Packers to Keep Alongside Glazing Packers

Frame packers should be stocked alongside glazing packers, not instead of them.

A complete installer stock setup should include:

  • frame packers for door and window frame fitting
  • flat glazing packers for sealed unit support
  • bridge packers where drainage and ventilation beneath the sealed unit matter
  • wedge packers for fine adjustment

This gives installers the correct product for the frame and the glass.

Common Buying Mistakes to Avoid

Avoid these common mistakes when buying frame packers:

  • buying only one thickness
  • not keeping fine adjustment sizes
  • forgetting 6mm and 10mm for larger gaps
  • using glazing packers where frame packers are more suitable
  • using timber or cardboard shims instead of proper plastic frame packers
  • choosing a packer footprint that is too small for the support point
  • not keeping enough stock in the van
  • failing to restock before larger jobs

A good frame packer stock setup should be based on the type of work you do regularly.

Why Plastic Frame Packers Are Better Than Improvised Shims

Some installers still use timber offcuts, cardboard, or random plastic pieces as makeshift shims.

That may seem convenient, but it is not ideal for professional installation.

Purpose-made plastic frame packers offer:

  • consistent thickness
  • stable support
  • quicker size identification
  • cleaner installation
  • better moisture resistance
  • no cutting or shaping required
  • more predictable results

For door and window installation, proper frame packers help reduce fitting problems and improve consistency across jobs.

Simple Buying Guide

Use this simple buying guide:

  • Buy 1mm and 2mm for fine adjustment.
  • Buy 3mm for standard frame packing.
  • Buy 4mm for moderate correction.
  • Buy 5mm for larger gaps and stronger support.
  • Buy 6mm for sill, threshold, and heavier support.
  • Buy 10mm for large gaps and heavy-duty correction.

For the packer footprint, choose a size that provides enough support for the frame and fixing point without being awkward to position.

Final Thoughts

Frame packers are essential for accurate door and window installation. They help installers keep frames level, plumb, square, and properly supported before final fixing.

For most installers, the best frame packer stock should include:

  • 3mm, 4mm, and 5mm for everyday installation work
  • 1mm and 2mm for fine adjustment
  • 6mm for sill, threshold, and heavier support
  • 10mm for large gaps and heavy-duty correction

For a strong general-purpose option, 53×62mm frame packers are a useful size to keep in stock for medium-sized window and door frame work.

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