Specifying Shims

Selecting and Specifying Shims

In general, solid shims are used as leveling aids to hold objects in place until they are permanently attached with fasteners, welds, grout, adhesive, or another method. Although shims are just considered accessories, they are an important part of many construction projects. The proper selection and specification is crucial in the project’s build and longevity.

Understanding the role of the alignment shim in the system that it will serve allows a design professional and/or architect to choose the best solid shim material, style, and size. For example, if load-bearing is an important aspect, completely solid, not hollow, shims are ideal for optimal support.

When submitting a quote or requesting more information, take into account execution requirements, material properties as well as any additional specifications necessary to assure proper performance for project conditions. If a specific shape or size of shim is required, custom leveling and alignment shims are available. Read on for additional information on how to make sure you are purchasing the right shim for your construction application.

Execution Requirements

Describing your execution requirements in a results-oriented way ensures the shim fits your industry and job applications. Example requirements to specify when describing your needs include:

• “The shims should not remain permanently exposed to view, sun, or weather.”
• “For shimming mortar or grout joints, hold the plastic shims back from the face of the panel by at least two times joint width.”
• “When shimming sealant joints, shims should not intrude into the depth required for the specified sealant and backer rod.”
• “For movement joints in stone flooring, remove alignment shims progressively as the sealant is installed.”
• “To install shims to shed water, U-shaped shim, horseshoe shim, and key slot shim openings should face down in cladding outside the weather barrier.”
• “Do not shim certain secondary structural members or cladding members more than a certain size without written acceptance by the architect or the engineer.”

Material Properties

As there are so many different functions that shims can be used for, the material determines if it is right for the application. Common alignment shim materials include wood, plastic, and metal, and each has its advantages and drawbacks. To discover which shims are ideal for your application, read the Different Shim Materials: Wood vs Metal vs Plastic article.

Each shim type is made from a variety of materials for different uses. For example, plastic shims are commonly manufactured from materials like Polypropylene (PP), High-Impact Polystyrene (HIPs), and ABS. This makes plastic shims ideal for construction applications such as in-house restorations, window and door replacement, as well as outdoor construction such as precast and tilt-up.

Selecting a Shim Manufacturer

For more details on common applications for plastic shims to determine if they are the correct shim choice, take a look at the Common Types of Construction Work Using Plastic Shims article or the list of industry applications and which plastic shims are ideal for each.