May 4, 2023

Types of shims

Shims are essential in the window and door installation industry. These thin pieces of material fill small gaps or spaces between two objects. But there’s more to shims than meets the eye! They come in a variety of styles and materials.

It’s a good thing they do, because in the window and door replacement world, nothing is square. As installers go to retrofit new, modern, energy-efficient windows and doors into older homes, they run into frequent problems with aging buildings, sagging sills, and non-square openings. The new windows and doors come from the factory square. So, it’s a square peg and round hole scenario if you will.

Here are just a few of the most common types and some of the benefits of each.


Wooden shims

As indicated above, the most common form of shim is wooden — the classic 8-inch tapered. Why is it used so frequently? It’s …

  • Economical
  • Easy to cut to make them flush
  • Thin-tipped with a consistent taper
  • Pre-dried to reduce contraction after installing
  • Available in convenient contractor packs to easily carry and store on the jobsite

But, wood can rot or decay over time as well as shift, expanding and contracting along with the weather.


This style is made from a combination of recycled wood fibers and plastic resin. This combination makes the shim more durable and resistant to rot, swelling, and splitting, especially compared to the traditional wooden ones.

Wood-composite shims
  • Easy to snap to the desired length
  • 100% water, rot & insect proof
  • Great for exterior use
  • Higher load-carrying capacity than wood shims
  • Splinter-free via pre-scored lines
  • Available in convenient contractor packs


There are two types of specialty shims we see often in the window and door installation industry: horseshoe and stackable shims.


Horseshoe shims

It may seem obvious, but this style is shaped like a horseshoe. Horseshoe shims are typically made from plastic or other synthetic materials. But the biggest advantage is using them for irregularly-shaped windows and doors. In addition, they’re …

  • Available in interlocking & non-interlocking styles
  • Fit around bolts or other fasteners
  • Made of recycled plastics, rot & split proof
  • Many sizes to choose from


Also obvious, this style can be stacked or layered on top of one another. These shims are typically made from plastic or other synthetic material and interlock to make them more secure. These shims are …

Stackable shims
  • Easy to snap for length
  • Adjustable height for challenging installations
  • Fits around bolts or other fasteners
  • Made of high-impact plastics for load-bearing applications
  • 100% rot & waterproof
  • Used for leveling windows & doors

Get the shim that’s right for your job

No matter the job, there’s a shim that will work. Although we’ve covered the most-used shims, we have a variety available to get your tough jobs done. Best of all, the Elevated team can recommend other products and solutions, including sealant and Sawzall blades. We’re your partner to help keep your jobs running better and faster. At the end of the day, we make you and your company more efficient and effective.

Jon Rhodig
Author: Jon Rhodig
Jon Rhodig is our Product Specialist. He’s been with the company for 18+ years, starting as the warehouse/logistics manager. After several years in the warehouse, he moved into customer service and sales support where he assisted not only our customers but our energetic sales team. Jon has an appetite for knowledge and product applications, which is how he was promoted to address product application questions. In his free time, he enjoys riding motorcycles, model building, and auto repair.
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