Washers are small components, but they play a big role in the performance of bolted joints in building projects. The right washer type can protect surfaces, distribute load, improve preload control, and help connections survive vibration and outdoor exposure. The wrong washer type — or no washer at all — can lead to crushed coatings, loosened bolts, and premature corrosion.
For engineers, contractors, and purchasers, understanding washer types is essential for reliable steelwork, timber connections, and façade or roofing systems. This article explains common washer types, how they are used in building projects, and what to discuss with your fastener supplier when preparing specifications and RFQs.
1. What Does a Washer Do in a Bolted Joint?
A washer is a thin plate with a hole that sits between the nut or bolt head and the surface being clamped. Even a simple flat washer can provide several important functions:
- Distribute load over a larger area so that the contact pressure is lower.
- Protect softer materials such as timber, aluminium, or coatings from damage.
- Provide a better bearing surface when the base material has oversized or slotted holes.
- Help control friction under the rotating nut or bolt head, improving torque–tension consistency.
- Support locking elements or combined sealing systems in roofing and cladding.
Standardized plain washers are defined in international standards such as ISO 7089 for normal-series product-grade-A plain washers with specified hardness classes.国际标准化组织 In structural building projects in Australia and New Zealand, washers are also part of high-strength bolt assemblies defined in AS/NZS 1252.新西兰标准
2. Common Washer Types Used in Building Projects
There are many specialized washers, but most building projects use a manageable set of washer types. Below are the most common groups and where they are typically used.
2.1 Plain flat washers
Plain flat washers are the simplest and most widely used washer type. Key features:
- Flat ring with a central hole matched to the bolt or screw size.
- Available in normal and large outer diameter series.
- Hardness class chosen to match the strength of the bolt and nut.
Typical uses:
- General structural steel connections.
- Anchor bolt assemblies in base plates.
- Brackets, purlin connections, and equipment mounting.
For many building projects, plain washers according to ISO 7089 or similar standards are used with hex bolts and nuts.国际标准化组织 You can find typical plain washer ranges together with bolts and nuts at
https://linkworldfast.com/product-category/bolts-nuts-washers/
2.2 High-strength structural washers
High-strength structural washers are designed to work as part of preloaded bolt assemblies in steel structures. Compared with commercial plain washers, they usually have:
- Higher hardness and strength.
- Larger outer diameter to distribute load and cover oversized holes.
- Tight dimensional tolerances compatible with structural bolt standards.
In Australia and New Zealand, structural washers for high-strength assemblies are covered by AS/NZS 1252 together with the matching bolts and nuts.新西兰标准 Technical notes from local steel institutes also explain how these washers perform in preloaded connections.steel.org.au+1
Structural washers are used in:
- Primary steel frames in buildings and bridges.
- Braced frames and moment-resisting connections.
- Connections where bolt preloading is required for slip resistance.
2.3 Spring and split lock washers
Spring washers (often split lock washers) are designed to provide some resilience in the joint and increase friction against loosening. They are:
- Shaped as a helical split ring that flattens when tightened.
- Often used in small machinery, light steelwork, and non-critical connections.
In modern structural practice, spring washers are less popular for high-strength connections because design standards and research have shown that proper preloading and suitable friction surfaces are more reliable than relying on split washers for loosening resistance. However, they are still widely used for secondary brackets, equipment mounting, and general-purpose applications.
2.4 Large OD and square plate washers
For connections in timber, thin sheet, or soft materials, larger washers distribute load over a broader area. Types include:
- Large outer diameter round washers, sometimes referred to as “penny washers”.
- Square plate washers with a central hole and chamfer, commonly used with anchor bolts in base plates or timber frames.
These washers reduce the risk of crushing timber fibers, deforming thin sheet metal, or pulling heads and nuts into oversized holes. They are common in:
- Timber framing and hold-down connections.
- Masonry and concrete anchoring with cast-in or post-installed anchor bolts.
- Roof and façade sub-structure where thin sections are clamped.
2.5 Sealing and bonded washers
In roofing, cladding, and façade applications, sealing washers combine a metal backing with an elastomer element (e.g. EPDM). Features:
- Metal washer (often stainless or galvanized) forms the structural bearing surface.
- Bonded rubber or elastomer provides a seal against water ingress.
- Often used with self drilling screws for metal roofing and wall panels.
Bonded washers are essential in weather-exposed joints because they keep water away from the screw penetration and reduce the risk of leaks and corrosion around the fixing.
2.6 Serrated washers and locking washers
Serrated washers have teeth or serrations that bite into the contact surfaces to increase friction and resist loosening. They are used in:
- Railings, stair connections, and vibrating equipment.
- Safety-critical connections where loss of preload is a concern.
When using serrated washers, it is important to understand that they can damage coatings, especially galvanizing or paint, and may not be suitable where corrosion protection relies on intact coating systems. Guidance on bolting and corrosion protection from galvanizing associations points out the importance of compatible washers and surface conditions in hot dip galvanized joints.设计手册+1
3. Materials and Coatings for Washers in Construction
The material and coating of a washer should be consistent with the bolts, nuts, and structural members in the connection. Mismatched materials can lead to galvanic corrosion or uneven performance.
3.1 Carbon steel washers
Most plain and structural washers are made from carbon steel. Key considerations:
- Hardness must be appropriate for the bolt strength; high-strength bolts need hardened washers to avoid embedding.
- Coatings include electroplated zinc, mechanical galvanizing, hot dip galvanizing, or zinc flake systems.
- For outdoor AU/NZ projects, hot dip galvanizing or zinc flake coatings are often used to align with the corrosion protection of structural steelwork and fasteners.Galvanizers Association of Australia+1
3.2 Stainless steel washers
Stainless steel washers are used where corrosion resistance is more important than high preload, such as:
- Coastal and marine environments.
- Stainless steel handrails, balustrades, and façades.
- Food processing or chemical plant equipment.
The stainless grade (for example A2/304 or A4/316) should match or exceed the corrosion resistance of the screws and bolts in the joint.
3.3 Non-metallic and insulating washers
Non-metallic washers, such as nylon or fiber, may be used:
- As insulating washers between dissimilar metals to reduce galvanic corrosion.
- To provide noise and vibration damping in lightweight assemblies.
- In specific architectural details where metal contact must be avoided.
In structural connections, these washers are usually used together with metallic washers that carry the primary load.
4. Selecting Washer Types for Common Building Connections
Different parts of a building see different loads and environments. Below are practical suggestions for choosing washer types in typical applications.
4.1 Structural steel bolted connections
For primary structural steelwork using high-strength bolt assemblies, typical practice in AU/NZ is:
- Use hardened structural washers that match the bolt standard (such as AS/NZS 1252 assemblies).新西兰标准+1
- Place washers under both the bolt head and nut where required by the design standard or installation method.
- Choose coatings (e.g. hot dip galvanizing) that are compatible with the structural steel coating system.
For secondary steel such as purlins, cleats, or non-preloaded connections, commercial plain washers may be acceptable, but they should still have suitable hardness and compatible coatings. You can source these washers along with bolts and nuts from categories like
https://linkworldfast.com/product-category/bolts-nuts-washers/
4.2 Concrete and masonry anchoring
When using anchor bolts in base plates or masonry:
- Use large OD or square plate washers to distribute loads into the concrete or masonry.
- Ensure the washer thickness is adequate so that it does not deform under tightening.
- For cast-in anchor systems, check the washer and plate dimensions against the base plate hole layout.
These connections often rely on galvanized or zinc flake coated washers and nuts to match the durability of the anchor and the surrounding structure.
4.3 Timber construction
In timber framing, hold-downs, and connection plates:
- Large round or square washers help spread the load over the timber fibers.
- Hardened washers may be required where high-strength bolts are used and deformation must be limited.
- For outdoor or weather-exposed timber, washers should use corrosion-resistant coatings that match the bolts.
4.4 Roofing and cladding
For metal roofing and wall cladding fixed with self drilling screws:
- Bonded sealing washers are critical to prevent leaks.
- The metal backing should be compatible with the roofing material (for example, stainless or coated steel).
- The elastomer (often EPDM) must be UV and weather resistant.
These assemblies are usually supplied as complete screw + washer combinations. You can find related fasteners under screw categories such as
https://linkworldfast.com/product-category/screws/
4.5 Equipment and services installation
For mechanical and electrical equipment mounted on structural steel:
- Plain washers help protect painted or galvanized surfaces when brackets are bolted on.
- Spring or serrated washers may be added for vibration control, but their effect on coatings should be considered.
- In some cases, combined washer and locking elements (such as serrated flange nuts) provide a more robust solution than separate spring washers.
5. Practical Checklist for Specifying Washers in RFQs
When you send RFQs for washers and associated fasteners, a clear specification helps your supplier respond quickly and propose suitable options. Consider including the following points.
5.1 Technical details
- Washer type: plain, structural, spring, large OD, square plate, bonded sealing, serrated, or other.
- Size range: nominal bolt size (e.g. M12, M16) and standard series (normal or large OD).
- Thickness and hardness where relevant.
- Material: carbon steel, stainless steel grade, or special material.
- Coating: zinc plated, mechanical galvanized, hot dip galvanized, zinc flake, or other.
- Applicable standards: for example ISO 7089 for plain washers, AS/NZS 1252 for structural assemblies, or project-specific documents.国际标准化组织+1
5.2 Application information
- Whether the washers are for primary structural connections or secondary fixings.
- Environment: indoor, outdoor, coastal, industrial, or high-humidity areas.
- Any design standards or corrosion categories used for the project.Galvanizers Association of Australia+1
- Whether washers will be used with preloaded bolts, expansion anchors, or other systems.
5.3 Logistics and packaging
- Expected annual quantity and order size.
- Requirements for small packing, labels, barcodes, or project kits.
- Whether you need mixed packs of bolts, nuts, and washers for each connection type.
A supplier that combines its own cold forming capability with a network of partner factories can often supply washers together with matching bolts, nuts, screws, and related metal parts in one package. You can see the broader product scope at
https://linkworldfast.com/products/
and organisation information at
https://linkworldfast.com/about-us/
6. Conclusion: Choosing the Right Washer Types for Your Building Project
Washers may be small components, but they strongly influence the performance and durability of bolted joints in building projects. Plain flat washers, structural washers, large OD washers, bonded sealing washers, and locking types all have their own roles. The key is to match washer type, material, and coating to the connection design, environment, and installation method.
When you plan your next building project, review each major connection group — structural steel, anchors, timber, roofing, and equipment — and check whether the washer specification is clear and consistent with the bolts and screws used. Align your requirements with relevant standards and local corrosion guidance, and discuss practical options with your fastener supplier.
If you are preparing a list of washers, bolts, nuts, screws, rigging items, or other fastening solutions for building projects, you are welcome to explore:
https://linkworldfast.com/
For detailed categories and customized parts, visit:
https://linkworldfast.com/products/
When you are ready to talk about drawings, washer types, coatings, and packing for your project, you can send your enquiry through:
https://linkworldfast.com/contact/