Square Washers

Square Washers for Australian Timber Framing and Structural Fastening

Square washers are flat washers with a square outer perimeter rather than the standard round profile — providing a larger bearing area on softer substrates like timber, where the larger footprint distributes bolt load and prevents the bolt head from pulling through. For Australian timber framing, structural construction, and large-bolt fastening into soft materials, square washers are the everyday choice. AIMS Industrial supplies square washers in the metric and imperial sizes Australian construction and trade users need.

Where square washers earn their place

• Timber framing and structural work — large bolts into timber where the bolt head would otherwise pull through
• Coach bolt installations — under coach bolt heads in timber connections
• Bridge and infrastructure — heavy bolt fastenings in structural applications
• Roof and ridge fastenings — where bolts pass through timber and require load distribution
• Foundation and ground-anchor work — bolted connections to soft substrates

Why square versus round washers

Round washers are the standard everyday washer — simple, inexpensive, and adequate for most fastenings into hard substrates. Square washers earn their place when:

• The substrate is soft — timber, plastic, or soft metal where load distribution matters
• The substrate has grain — timber where rotation under torque could split the substrate (the square washer's flat sides resist rotation)
• The bearing area must be larger than a standard round washer provides — for very high loads or oversized clearance holes
• The application is structural — where building codes specify washer dimensions for timber connections

Sizing

Square washer sizing has two main dimensions: the inside hole diameter (matched to the bolt size) and the outer square dimension. Common metric sizes range from M10 through M24, with imperial sizes from 1/4 inch through 1 inch. Thickness varies with size — typical 3-6mm for general use, thicker for very heavy structural applications. Match the washer to the bolt size and the load distribution requirement.

Materials and finishes

• Hot-dip galvanised steel — the standard for outdoor and timber-frame structural work
• Zinc-plated steel — for indoor and protected applications
• Black mild steel — for paintable surfaces and where finish coatings will be applied
• Stainless steel 304 and 316 — for marine, food-grade, and aggressive environments

Australian timber framing standards

Australian Standard AS 1684 (Residential Timber-Framed Construction) and related codes specify washer dimensions for various structural timber connections — washer outer dimensions and thickness must match the requirements for the specific connection type. For load-bearing timber connections, refer to the structural drawings and AS 1684 specifications; don't substitute smaller or thinner washers in structural applications.

Brands stocked at AIMS

Hobson and Bremick cover the square washer range across metric and imperial sizes in galvanised, zinc-plated, black, and stainless finishes. Bulk packs are available for fitout and structural work; trade pack quantities for general workshop use.

Companion ranges at AIMS

Square washers sit alongside our broader fastener range — see coach bolts, mudguard washers, safety washers, and spring lock washers for the related products.

Need help speccing square washers for timber framing or structural work? contact our team — we'll match by bolt size, outer dimension, and material.