28mm Flat Plastic Packers – Precision Shims for Windows, Doors & General Construction

28mm Flat Plastg and aligning windows, doors, frames, battens and units fast, reliable and compliant with modern building standards. Manufactured from high‑density, moisture‑resistant plastic, they offer consistent thickness, excellent compressive strength and long‑term stability in both domestic and commercial environments.

Perfect for uPVC, aluminium and timber installations, these packers remove the guesswork from shimming, helping you deliver accurate, repeatable results on every job.

Detailed 28mm Flat Plastic Packers Description & Use Cases

These 28mm Flat Plastic Packers are designed for professional trades and serious DIYers who need reliable, code‑compliant shimming across a range of applications.

Common Use Cases

1. Window & Door Installation (uPVC, Timber & Aluminium)
– Used to support and align frames before fixing into brick, block or timber openings.
– Ideal for achieving the correct frame position required to comply with Approved Document L (thermal performance) and Document M (accessibility) where accurate thresholds and levels are critical.
– Provide stable backing beneath jambs and sills when fixing through to C24 structural timber or masonry.

2. Timber & Joinery Works
– Perfect for packing under door linings, studwork, partitioning and timber grounds.
– Maintain alignment when fixing into C16 or C24 timber studs, avoiding compression and long‑term movement.
– Can be stacked to create accurate spacing for architraves, skirting, panelling and cladding.

3. Kitchens, Bathrooms & Interior Fit‑Out
– Used for levelling kitchen carcasses, worktops and bathroom furniture against uneven walls or floors.
– Moisture‑resistant properties make them particularly suited to wet areas, reducing the risk of rot compared with timber shims.
– Help achieve accurate reveal gaps and shadow lines for a high‑end finish.

4. Flooring, Decking & Sub‑Frames
– Suitable for packing decking bearers, joists and sub‑frames, ensuring accurate falls and levels.
– Can be used under floor battens over concrete slabs to create consistent height and protect timber from direct slab contact.

5. Cladding, Rainscreen & Facades
– Provide stable packing behind cladding rails and brackets to maintain plumb and line.
– Plastic composition prevents moisture bridging and rot, contributing to the performance of ventilated rainscreen systems.

Installation Tips & Best Practice

To maximise performance and ensure compliance with good building practice:

1. Surface Preparation
– Ensure surfaces are clean, free from dust, debris and loose material.
– When packing against masonry, brush away loose grit and, where necessary, spot‑prime friable surfaces for better grip.

2. Positioning the Packers
– Place packers at load‑bearing points – typically near fixing positions, corners and hinge sides on doors and windows.
– For timber frames (C16/C24), position packers directly in line with structural studs or lintels to transfer load effectively.

3. Stacking & Building Up Thickness
– Combine multiple packers to achieve the exact gap required (e.g. 1mm + 2mm + 5mm).
– Avoid excessive stacks where a single thicker packer is more appropriate. As a guide, try not to exceed 3–4 packers in one stack for high load points.

4. Fixing Through Packers
– Drill and fix directly through the packer using appropriate screws/plugs for the substrate (e.g. frame fixings into masonry, wood screws into timber).
– Tighten fixings evenly to prevent twisting or bowing of frames; do not over‑tighten against brittle substrates.

5. Compliance & Standards
– Use packers to help maintain correct frame squareness and reveal dimensions, supporting compliance with:
– BS 8213‑4 – Code of practice for the survey and installation of windows and external doorsets.
– EN 14351‑1 – Performance characteristics for windows and external pedestrian doorsets (relies on correct installation).
– Where required, consult your system supplier’s installation manual – packers are recognised as standard practice for achieving performance values in tested window and door systems.

*(Note: While plastic packers themselves may not carry a dedicated EN standard, they are widely used in systems tested to standards such as EN 14351‑1 and within installations following BS 8213‑4 and local Building Regulations.)*

Technical Specifications

– Width: 28mm (flat profile)
– Typical Length: Approx. 50–100mm (check product variant)
– Available Thicknesses: Commonly 1mm, 2mm, 3mm, 5mm, 6mm (thickness may vary by set)
– Material: High‑density, rigid plastic (polypropylene or equivalent)
– Compressive Performance: Designed to resist compression under typical frame and joinery loading
– Moisture Resistance: Non‑absorbent, rot‑proof, corrosion‑free, suitable for internal and external use
– Compatibility: Suitable with C16/C24 structural timber, uPVC, aluminium, steel and masonry substrates
– Colour: Often colour‑coded by thickness for fast identification (e.g. 1mm = white, 2mm = blue, etc., depending on manufacturer)

Always refer to the specific product label or data sheet for exact dimensions and pack quantities supplied.

28mm Flat Plastic Packers Features & Customer Benefits

– 28mm Flat Bearing Surface
– Provides generous contact area, reducing point loading and improving stability under windows, doors and frames.
– Helps maintain squareness and plumb for better operational performance of sashes and doors.

– High‑Density Plastic Construction
– Will not rot, rust, swell or delaminate, even in damp or exposed locations.
– Maintains its thickness under long‑term load, preserving levels and alignment.

– Precision Thickness & Colour Coding
– Consistent, factory‑controlled thickness enables quick, accurate adjustments.
– Colour‑coding (where supplied) makes it easy to grab the right size without constant measuring.

– Stackable & Easy to Trim
– Can be layered to achieve precise build‑ups; simple to cut with a saw or knife for custom shapes.
– Versatile for awkward spots behind battens, clips and brackets.

– Trade‑Quality, Time‑Saving Solution
– Eliminates the need for improvised shims, saving time and delivering a neater, more professional result.
– Widely used by joiners, carpenters, glaziers, shopfitters and general builders.

28mm Flat Plastic Packers  FAQs

Q1: What are 28mm Flat Plastic Packers used for in window and door installation?

A: 28mm Flat Plastic Packers are primarily used to level, support and align window and door frames during installation. They are placed at key load points – such as corners, hinge sides and mullions – to ensure the frame sits plumb, level and square before fixing. This helps the installation meet the expectations of BS 8213‑4 and supports the performance of windows and doors tested to EN 14351‑1.

Q2: Are plastic packers better than timber shims for C24 timber frames?

A: Yes, in most cases. When working with C24 structural timber, plastic packers offer several advantages over timber shims:

– They do not absorb moisture, so they won’t swell, rot or compress.
– Their thickness is consistent, making accurate levelling easier.
– They maintain long‑term performance, even in damp conditions like floors, bathrooms or external openings.

Timber shims can be used, but for longevity, consistency and moisture resistance, plastic packers are generally the better choice.

Q3: Have these plastic packers been tested to any standards?

A: Plastic packers are generally considered an ancillary installation aid rather than a standalone structural product, so they are not usually certified under a dedicated EN standard. However, they are widely used within window and door systems tested to EN 14351‑1 and installations following best practice guidance such as BS 8213‑4.
If you require specific certification, please check our product documentation or contact us for any available test data or technical statements from the manufacturer.

Q4: How do I choose the right thickness of 28mm Flat Plastic Packer?

A: First, measure the gap between the frame (or item being installed) and the substrate. Then:

1. Select the closest packer thickness (e.g. 3mm).
2. If needed, stack multiple packers to build up to the exact measurement (e.g. 3mm + 2mm for a 5mm gap).
3. For heavy load points, use the fewest packers possible in the stack, choosing thicker ones where you can.

Colour‑coded sets make this much quicker on site and help reduce packing errors.

Q5: Can 28mm Flat Plastic Packers be used for external decking, cladding or rainscreen systems?

A: Yes. These packers are moisture‑resistant and non‑corrosive, making them suitable for:

– Packing and levelling decking joists and sub‑frames.
– Installing timber or composite cladding where precise stand‑off from the substrate is needed.
– Helping create and maintain ventilated cavities behind rainscreen systems (within the system designer’s guidelines).

Always ensure the design complies with the relevant structural and fire performance requirements, and follow the cladding or decking manufacturer’s own installation instructions.

Q6: What is the difference between plastic packers and glazing packers?

A: The term “plastic packer” is broad and can include general purpose shims and glazing packers. Glazing packers are specifically sized and shaped for positioning glass units within frames. 28mm Flat Plastic Packers are more general‑purpose shims, ideal for frames, battens and general construction. For critical glass positioning, use packers recommended by the window or glazing system manufacturer, which may include specialised glazing blocks.

Q7: Can I cut or drill 28mm Flat Plastic Packers to fit around fixings?

A: Yes. They can be cut with a handsaw, utility knife or snips and can be drilled through with standard drill bits. Many installers simply screw directly through them when fixing frames or battens. Just ensure cut edges remain flat and that the packer still provides full support at the load point.