Nail plates, cyclone washers and fixing schedules for timber frames

You cannot check a connection you cannot see. The fixing schedule exists so that every nail plate, strap, bolt and washer in a timber frame is specified before the frame goes up, and verified before it is covered. On a residential job in NSW, the schedule is usually a table on the structural drawings or a separate document issued by the engineer. It tells you what connector goes where, what fastener holds it, and what the connection is designed to resist. It is not a suggestion. It is the instruction set for the frame.

Supervisors get caught on this because the frame goes up quickly and the sheeting follows close behind. By the time the plasterboard is on, the only evidence of a missing cyclone washer is a photograph someone took months earlier, or a defect notice from an inspector who found it during a later stage. The commercial reality is that fixing defects are cheap to prevent and expensive to rectify. A nail plate that costs a few dollars and a minute to install becomes a lining removal, a repair and a variation if it is discovered after sheeting.

This article is about using the fixing schedule as a site document. It covers what to look for at the frame stage, how to verify nail plates and cyclone washers, and how to hand over a frame that will pass inspection without argument. The focus is on the moment before sheeting, when everything is still accessible and the cost of getting it right is minimal.

What the fixing schedule actually controls

The fixing schedule is the bridge between the engineer’s design and the trades on site. It takes the loads the frame must resist — uplift, racking, gravity, wind — and translates them into specific hardware at specific locations. For a timber-framed house, that usually means a mix of nails, screws, bolts, straps, nail plates and washers. Each item has a purpose, and each has a specification: type, size, material, coating, and the number required per connection.

The schedule should nominate the connector for each junction: wall to slab, wall to wall, roof to wall, bracing to frame, and any point where a member is notched, cut or loaded in a way that needs reinforcement. It should also nominate the fastener that fixes the connector, because a strap is only as good as the nails holding it. If the schedule says a strap is fixed with a certain number of nails of a certain diameter, that is the requirement. Substituting a shorter nail, a different gauge or a screw changes the capacity of the connection.

Nail plates appear in the schedule for two reasons. The first is protection: a nail plate stops a service or a subsequent fixing from penetrating a member in a critical zone. The second is structural: a nail plate can reinforce a member that has been notched or drilled, or tie a joint that would otherwise split. The plate must be the specified gauge and must be fixed with the specified nails. A plate held on with a couple of staples is not a nail plate in the structural sense.

Cyclone washers are a specific type of load-spreading washer used under fastener heads in timber connections. They increase the bearing area of the head, which reduces the risk of the fastener pulling through the timber under wind uplift or cyclic loading. They are common in cyclonic regions, but they also appear in non-cyclonic areas where the engineer has specified them for a particular connection. If the schedule calls for a cyclone washer, the connection is relying on it. Omitting it or installing it upside down changes the behaviour of the joint.

Why the schedule is a site document, not a filing cabinet ornament

Many supervisors treat the fixing schedule as part of the drawing set that lives in the site office. It gets filed, maybe printed once, and then the frame is built from habit and experience. The problem is that habit and experience are not the same as the current engineer’s design. A frame that was built a certain way on the last job may not match the requirements on this one, especially if the wind classification, the roof design or the bracing layout has changed.

The fixing schedule is a site document because it has to be used on site, at the frame, before sheeting. The most effective way to use it is to walk the frame with the schedule in hand, junction by junction, and tick off each connection as it is verified. That walk is not a substitute for the carpenter’s work; it is a check that the work matches the design. It also creates a record. A schedule with ticks, initials and dates is evidence that the connections were checked before they were covered.

On a busy site, the frame stage is a bottleneck. The carpenters want to finish and move on; the roofers and the electricians are waiting; the plasterers are booked. The pressure is to sheet as soon as the frame is straight and the bracing is on. That pressure is exactly why the fixing schedule needs to be part of the frame inspection routine. If it is left until after sheeting, the only way to verify a connection is to remove the lining. That is a cost and a delay that no one wants.

Nail plates: what to check before the lining goes on

Nail plates are the most commonly misunderstood fixing on a timber frame. They are not just a piece of metal that stops a nail from hitting a pipe. In a structural context, they are a specified component with a gauge, a coating and a fixing pattern. The schedule should tell you where they are required and what they are fixed with. If it does not, ask the engineer. Do not guess.

Start with the location. Nail plates are typically required where a service passes through a member, where a member is notched or drilled, and at certain joints where the engineer wants to prevent splitting or reinforce a tension zone. The plate must cover the area it is intended to protect. A plate that is too short or misaligned leaves part of the member unprotected. The plate must also be oriented correctly; some plates are asymmetric and only work one way.

Next, check the fixing. The schedule should specify the nail type and the number of nails. In general, the nails should be the same material and coating as the plate to avoid galvanic corrosion, and they should be long enough to penetrate the member without protruding through the other side. Staples, screws and clouts are not interchangeable with the specified nails unless the engineer has approved the substitution. A plate fixed with the wrong fasteners may have a fraction of the intended capacity.

Finally, check the coverage. It is common to find a nail plate that has been installed but then covered by a subsequent trade, or a plate that has been removed to run a cable and not replaced. The frame stage is the last chance to catch this. Once the plasterboard is on, a missing or damaged plate is invisible. The cost of replacing it later is the cost of cutting and patching a wall.

Cyclone washers and load-spreading washers: the details that get missed

Cyclone washers are a small item with a large consequence. They sit under the head of a bolt, screw or nail and spread the load into the timber. Without the washer, the head of the fastener can crush the timber or pull through under load. With the washer, the load is distributed over a larger area, which is why they are specified in connections that experience uplift or reversal of load.

The schedule should tell you where cyclone washers are required and what size they are. On site, the checks are simple but easy to skip. First, confirm the washer is present. A missing washer is a connection that does not meet the design. Second, confirm it is seated flat against the timber and under the head of the fastener, not on top of a batten or a packer unless the design allows it. Third, confirm it is not deformed. A washer that has been over-tightened and dished may not perform as intended. Fourth, confirm it is the correct type. A standard flat washer is not a cyclone washer; the difference is in the thickness and the load-spreading geometry.

It is also worth checking that the fastener itself is the specified type. A cyclone washer on the wrong bolt is still the wrong connection. The schedule should nominate the bolt grade, diameter and length, and the washer that goes with it. If the washer and the bolt are mismatched, the assembly may not achieve the design capacity. This is the kind of detail that a frame inspection will pick up, and it is much cheaper to fix before sheeting than after.

Reading the schedule on site: a practical method

The most reliable way to verify a frame is to work through the schedule systematically. Start with the bracing. Bracing connections are critical because they resist racking, and they often use straps, bolts and washers. Check that each bracing member is connected as specified, with the correct number of fasteners and the correct washers. Then move to the wall-to-slab connections. These are often bolted or strapped, and they are a common location for cyclone washers. Check that the bolts are the specified type and that the washers are present and seated.

Next, check the wall-to-wall and wall-to-roof connections. These are where uplift loads are transferred, and they often use straps and nail plates. Check that the straps are the specified length and gauge, that they are fixed with the specified nails, and that they are not bent or damaged. Then check the lintels and the beams. These members often have specific fixing requirements at their bearings, and the schedule will tell you what they are. Finally, check the areas where services penetrate the frame. Nail plates should be installed where required, and they should be intact.

As you go, mark the schedule. A simple tick or initial next to each item is enough. If you find a defect, record it and get it fixed before sheeting. If you find a substitution, record it and get the engineer’s approval in writing. The schedule then becomes a record of the verification, not just a design document. That record is valuable if there is a dispute later, and it is valuable for your own quality system.

Worked example: a frame in western Sydney

A builder in western Sydney is putting up a timber-framed house on a slab. The engineer’s fixing schedule specifies cyclone washers on the wall-to-slab bolts and on the bracing connections, and nail plates at several locations where services pass through top plates. The frame goes up quickly, and the carpenters are ready to sheet. The supervisor decides to do a quick walk before the plasterboard is delivered.

On the walk, the supervisor notices that the wall-to-slab bolts are fitted with standard flat washers, not cyclone washers. The bolts are the correct type, but the washers are wrong. The supervisor also finds two nail plates that have been installed with staples instead of the specified nails, and one location where a nail plate is missing entirely because a plumber moved a pipe and did not replace it.

The supervisor stops the sheeting. The washers are replaced with the specified cyclone washers, the stapled plates are re-fixed with the correct nails, and the missing plate is installed. The cost is a few hours of labour and a small amount of hardware. If the sheeting had proceeded, the washers would have been hidden behind the wall lining, and the defect would likely have been picked up at the frame inspection or later. At that point, the fix would involve removing plasterboard, repairing the lining, and possibly a delay to the handover. The supervisor’s walk cost a morning; the alternative would have cost a week.

The example is not unusual. Substitutions happen because the right hardware is not on site, or because a trade is used to doing it another way. The fixing schedule is the tool that catches these substitutions before they are covered. It is also the tool that protects the supervisor, because it shows that the connections were checked against the design.

Documenting the verification and handing over a clean frame

Verification is only as good as its record. A schedule with ticks is useful, but a schedule with photographs is better. Photograph each connection type before sheeting, with a tape or a scale in the frame so the fixing can be identified. Photograph the nail plates, the washers and the straps. Store the photographs with the schedule and the engineer’s details. If a question arises later, you have evidence of what was installed.

It also helps to note any approved substitutions. If the engineer approves a different washer or a different nail, keep the written approval with the schedule. Verbal approvals are difficult to rely on later. The same applies to any changes on site. If a service is moved and a nail plate is relocated, record it and get it checked. The frame is a system, and a change in one place can affect another.

When the frame is ready for inspection, the supervisor should be able to hand over the schedule, the photographs and a clear statement that the connections have been verified. That package makes the certifier’s job easier and reduces the risk of a defect notice. It also makes the supervisor’s job easier, because the frame is signed off before it is covered. The alternative — discovering a missing washer after the lining is on — is a cost that no one wants to carry.

Where the fixing schedule fits in the broader frame inspection

The fixing schedule is not a standalone document. It sits alongside the bracing plan, the lintel details and the general structural notes. On a residential project, the frame inspection is the point where the certifier checks that the frame complies with the approved plans and the relevant standards. The fixing schedule is part of that check. If the connections are wrong, the frame may not comply, and the certifier can require rectification before proceeding.

For supervisors, the frame stage is also a chance to check other items that will be covered later. The article on slab edge thickness and setdowns explains how the slab details affect the frame, and the article on formwork stripping times covers the timing of the slab. These are related because the frame sits on the slab, and the connections between the two are part of the fixing schedule. Getting the slab right makes the frame connections easier to install and verify.

It is also worth remembering that the fixing schedule is not just for the frame. It can cover the roof connections, the bracing and the tie-down. On a timber-framed house, the roof-to-wall connection is often the most critical for wind uplift, and it is often the hardest to inspect after the roof is on. The frame stage is the best time to check it. If the schedule specifies cyclone washers or straps at the roof-to-wall connection, verify them before the roof is sheeted.

Common mistakes and how to avoid them

The most common mistake is assuming that the carpenter knows the schedule. Carpenters are skilled, but they are not necessarily reading the structural drawings on every job. The supervisor should walk the frame with the schedule and point out the specific connections. A short toolbox talk before the frame starts can prevent most substitutions. Show the crew the schedule, show them the hardware, and explain what is required.

The second mistake is not having the right hardware on site. If the specified washers or nail plates are not available, the crew will use what is in the shed. The supervisor should check the hardware delivery against the schedule before the frame starts. If something is missing, order it. Do not let the frame proceed with substitutions that will need to be undone.

The third mistake is leaving the verification until after sheeting. Once the lining is on, the cost of verification goes up dramatically. The supervisor should schedule the fixing check as a hold point. No sheeting until the connections are verified. That hold point is a simple control that protects the programme and the budget. It also protects the supervisor from being blamed for a defect that was hidden.

Finally, do not rely on memory. The fixing schedule is a document. Use it. Tick it. Photograph it. File it. The effort is small compared to the cost of rectifying a hidden defect. For more on how CPD for NSW builders covers these site verification practices, see the guide to NSW builder CPD and the course catalogue. The PointCPD home page has the full list of courses, including those that cover timber framing and structural connections.

Frequently asked questions

What is a fixing schedule?

A fixing schedule is a document, usually prepared by the structural engineer, that lists the connectors, fasteners and washers required for each connection in a timber frame. It tells you what to install and where. It is a site document because it must be used during construction, before the frame is covered.

Why are cyclone washers specified?

Cyclone washers spread the load from the fastener head into the timber, which reduces the risk of the fastener pulling through under uplift or cyclic loading. They are specified where the connection needs that additional bearing area. If the schedule calls for them, they are part of the design.

Can I use standard flat washers instead of cyclone washers?

No, unless the engineer has approved the substitution in writing. A standard flat washer does not have the same load-spreading geometry as a cyclone washer. Using the wrong washer changes the capacity of the connection and may not comply with the design.

What do I do if the nail plates are missing?

Install them before sheeting. If the frame is already sheeted, you will need to expose the area, install the plate and repair the lining. The cost is much higher after sheeting, so the best approach is to check the frame before the lining goes on.

Who is responsible for verifying the fixing schedule?

The site supervisor is responsible for verifying that the work matches the schedule. The carpenter installs the fixings, but the supervisor checks them. The certifier may also inspect the frame, but the primary verification happens on site before sheeting.

How do I record the verification?

Tick or initial the schedule as you check each connection, and take photographs before sheeting. Keep the schedule and the photographs with the project records. If there are approved substitutions, keep the written approval as well. This record is useful for quality assurance and for any later dispute.

Questions builders ask

• Fixings
• Framing
• Structural
• Timber

Published 7 July 2026. General information for builders, not legal, financial or engineering advice for a specific job. Check current requirements with the relevant regulator or standard before relying on them.