Do Carriage Bolts Need Washers?

Carriage bolts are commonly used in wood-to-wood and wood-to-metal connections, especially in furniture, fencing, and light structural assemblies. During installation, one practical question often comes up: do carriage bolts need washers, or can they be used without them?

As a fastener manufacturer, Xinchi Fastener Factory usually explains it like this: it depends on the application, but in most real working conditions, washers are strongly recommended because they improve stability and surface protection.

Carriage Bolts

Do Carriage Bolts Need Washers in Real Applications?

In theory, carriage bolts can be used without washers. The square neck under the head is designed to lock into wood and prevent rotation, so the bolt can still function on its own.

But in actual use, things are a bit different.

Without washers, the nut side (and sometimes the material surface) may gradually sink into the wood under pressure, especially when the joint is under load or exposed to vibration. Over time, this can lead to loosening or surface damage.

That’s why in most carriage bolt applications, installers prefer adding at least one flat washer under the nut. It helps spread the load more evenly and reduces pressure on the material, especially in softer wood.

Carriage Bolts

Carriage Bolt Washer Types and How to Choose

Choosing washers for carriage bolts is not complicated, but it does affect performance.

In most cases, a flat washer is used on the nut side to distribute force and protect the surface. For outdoor structures or environments with vibration, a lock washer or spring washer may also be added for extra holding security.

For wood applications, a larger outer-diameter flat washer is often a better choice because it helps reduce indentation into soft materials. For metal assemblies, standard flat washers are usually enough as long as the torque is properly controlled.

A simple rule: match the washer size to the bolt size and the material strength.

carriage bolt

Installation Tips for Carriage Bolts with Washers

When installing carriage bolts, the washer is typically placed under the nut, while the bolt head sits flush against the material surface. The square neck grips the wood and prevents rotation, so no extra holding tools are needed on the head side.

During tightening, avoid over-tightening—especially in wood. Excess force can compress the fibers and actually reduce long-term holding strength. A properly selected washer helps distribute pressure and keeps the joint stable over time.

carriage bolt

When Carriage Bolts May Not Need Washers

There are situations where washers can be skipped, although they are less common.

For example, in light-duty indoor assemblies where loads are minimal, or when fastening into dense hardwood or metal plates, some installers choose to omit washers for faster installation or a cleaner appearance.

However, these cases are more of an exception. In outdoor structures, load-bearing joints, or anything exposed to vibration, using washers is still the more reliable choice.

Xinchi Fastener Factory Carriage Bolts Manufacturing Strength

Behind consistent performance, manufacturing capability plays an important role.

Xinchi Fastener Factory was established in 2007 and has built solid production capacity in carriage bolts and other fastening products. The factory is equipped with 102 cold heading machines, with a daily output exceeding 10 million pieces, supporting stable supply for large-volume orders.

The production base covers 30,000 square meters, including two six-story workshop buildings, designed for efficient workflow and strict quality control.

Xinchi Fastener Factory

As a trusted fastener supplier, Xinchi offers a wide range of high-quality fasteners, including nuts, screws, bolts, rivets, and washers. With years of experience in fastener manufacturing, Xinchi focuses on stable quality, high-volume delivery, and customized fastening solutions for global customers.