Finish Architectural Knowledge Base
What are Window Shims: Plastic vs Metal?
Window shims are essential components in the installation of windows, playing a crucial role in ensuring that windows are securely placed, level, and function correctly. Commonly, metal and plastic are two materials that are used to manufacture window shims, ensuring a high-quality installation. However, it must be emphasised that fire compliant, metal window shims are rapidly replacing unsuitable plastic shims.
Notably, since the Grenfell Tower incident in 2017, metal window shims are commonly used in buildings, as opposed to plastic ones. This is due to one of the design and installation failures being the gaps left in the original concrete columns after a new window installation. Additionally, new building regulations require non-flammable A1 shims, meaning that plastic window shims are no longer suitable.
“The detailing created around the old and new windows meant that the materials, and the arrangement of those materials, increased the likelihood of a fire breaking out of the flat and increased the likelihood of that fire breaking into the large cavities contained within the cladding system.” - Construction News
These small, wedge-shaped pieces are typically inserted between the window frame and the surrounding structure, providing the necessary adjustments to compensate for any irregularities in the wall or window frame. Without shims, even the slightest misalignment can lead to a host of issues, including drafts, leaks, and compromised structural integrity.
What is a Window Shim?
Shims are thin pieces of material, often made from plastic, wood or metal, used in construction to fill gaps and provide support or alignment. Their primary purpose is to adjust the height, level, and alignment of various structures, including window and door frames. In this context, shims are essential for ensuring that the window is plumb and correctly aligned within its frame. This helps prevent air and water leaks, which can lead to rot.
When installing a window or door, it is crucial to check that the window is level and adjust as necessary. To do this, installers use shims to fill any excess space along the sides of the window. For example, if one side is lower than the other, a metal shim can be placed under the lower side, while a wood shim might be used for added stability.
By using the right type of shim, whether plastic, wood, or metal, builders can ensure that their cabinet installations or door frames remain stable and well-aligned. Professionally installed shims, with the safest non-flammable materials, help maintain the structural integrity of the window or door, ensuring that it operates smoothly and efficiently throughout its lifespan.
Difference Between a Window Shim and Window Packer
The differences between a window shim and a window packer are significant in the context of window installation. Shims are typically small, tapered pieces of material, such as plastic shims or wood shims, used to fill gaps and ensure that the window is plumb and level within the frame.
In contrast, packers in construction are often made of more robust materials, such as a metal shim, and are used for more substantial gaps. They are typically employed in situations requiring greater load-bearing capabilities, like door frames or cabinet installations.
The Installation Process: How to use Window Shims
Installing a window or door requires careful attention to detail, particularly when it comes to ensuring that the frame is level and plumb. Start by placing the window into the rough opening and checking that the window is plumb. To re-emphasise however, utilising fire compliant metal shims are now the safest option since A1 graded, non-flammable metal shims are required under new building regulations.
It’s essential to place shims on the sides of the window to ensure proper alignment. Gently tap the shim with a hammer until the window is level, ensuring that it fits snugly against the casing without any excess shim sticking out that could cause rot over time.
Once the window is properly aligned, secure it in place by nailing or screwing through the frame into the wall studs. If you are using metal shims, they can provide additional stability, but be cautious not to use too many, as excess shim can lead to complications down the line. For added assurance, it's advisable to check that the window opens and closes smoothly, ensuring that it complements any adjacent cabinet or door frames.
Mistakes Commonly Made when using Shims
Over-shimming and Incorrect Shim Placement
One of the most common mistakes when using shims during window installation is over-shimming. This occurs when excessive shims are placed inappropriately, leading to an uneven frame. It's essential to check that the window is plumb by ensuring that it sits level on all sides of the window before securing it with a nail or screw to avoid future issues like rot or misalignment.
Using Shims for Permanent Load Support
Common mistakes when using shims for permanent load support can lead to structural issues. In packers in construction, using metal shims may be beneficial for heavy loads, while wood is suitable for lighter applications. Properly placing shims and packers aids in levelling cabinets and door frames, enhancing stability and durability. Always ensure your installation is effective to avoid future complications.
Pros and Cons of Metal and Plastic Window Shims
When considering shims and packers for window installation, it is worth considering the advantages and disadvantages of plastic shims. Plastic shims are lightweight, resistant to rot, and provide a non-corrosive option, making them ideal for areas prone to moisture and they are typically cheaper than metal shims. However, due to their flammability, they are no longer suitable for new building regulations, due to them being affected by extreme temperatures. They also may not provide the same structural stability as metal shims, which can be essential for heavy door frames or large window and door installations.
Additionally, Wood shims are another alternative, often used for certain casing applications, but they can be susceptible to rot over time. Ultimately, the choice between materials depends on specific project requirements.
Best place to buy Metal Window Shims?
At Finish Architectural, you can buy high quality, fire graded metal window shims, ranging from horseshoes and squares to custom designs. Additionally, we offer a wide variety of finishing options for increased durability and additional corrosion resistance.
These shims and packers are crucial for achieving the perfect fit for your window and door frames. The professional team at Finish Architectural is ready to assist you with high-quality shims for any cabinet, window, or door project. Reach out here.
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