What Architects Need to Know About Fire Boarding Details

Fire boarding is easy to reduce to a line on a drawing.

A box around a steel column. A layer around a beam. A note calling for 60, 90 or 120 minutes of fire resistance. From a distance, the principle appears simple: enclose the structure with a fire-resistant board and move on.

The detail is less forgiving.

A fire boarding system depends on board type, thickness, fixing centres, support arrangement, joint treatment, corner construction, substrate, section factor and the required resistance period. It must also be buildable within the available space, accessible for installation and capable of tolerating the finishes and interfaces placed around it.

The board is only one part of the protection. The tested encasement is the system.

For architects, this distinction matters because a fire boarding detail can look resolved in section while remaining difficult, or impossible, to install correctly on site.

Fire Boarding Is a Tested Assembly

Fire protection boards are not interchangeable sheets with similar headline ratings.

Their performance depends on the construction in which they were tested or assessed. That may include the number of layers, board thickness, framing arrangement, fixing type, fixing spacing, joint position, corner treatment and the shape and size of the protected steelwork.

The required resistance period does not determine board thickness by itself. The steel section, exposure condition and tested system all influence the specification.

A board suitable for one beam or column arrangement may not be suitable for another. A single-layer system cannot be changed to a different board simply because both products are described as fire-resistant. Nor can fixing centres, joint layouts or corner details be adjusted without checking the supporting evidence.

The relevant question is not whether the board carries certification. It is whether the complete installed encasement matches the tested detail.

Board Thickness Must Come from the System

Board thickness is one of the most visible parts of the specification, but it should never be selected in isolation.

The required thickness may vary according to the fire resistance period, board product, steel section, section factor and number of exposed faces. A large column and a slender beam do not necessarily require the same construction, even when the required resistance period is identical.

Architectural drawings should therefore avoid treating board thickness as a generic project-wide note unless the supporting design confirms that approach.

The specification should identify the approved system and make clear where different thicknesses or layer arrangements apply. Where several steel profiles occur across the building, a schedule may be more useful than a single typical detail.

This also affects spatial coordination. Increasing the board thickness changes the finished dimensions of columns, beam casings, junctions and ceiling zones. If those dimensions are not allowed for early, the fire protection is often left competing with partitions, doors, services and finishes later.

Fire resistance occupies space. The design needs to admit it.

Fixings Are Structural to the System

The fixings in a fire boarding system are not merely there to keep the board tidy.

Their type, length, material, position and spacing contribute to the tested performance. They hold the encasement together while the board is exposed to heat, moisture loss, movement and thermal stress.

Fixing centres that are too wide may allow boards to move or joints to open. Incorrect screw lengths may fail to engage the supporting construction properly. Missing fixings at edges and corners can weaken the enclosure. Substituted framing or channels may not match the approved system.

Architectural details should provide enough information for the installer to understand the intended build-up, but they should not replace the manufacturer’s tested fixing requirements with a general note such as “fix to suit”.

In passive fire protection, “to suit” often means the critical decision has been left to the most pressured point in the programme.

The detail should identify the system. The system should define the fixings.

Joints Need Deliberate Positioning

Every joint is a break in the board surface and therefore part of the fire-resisting design.

The tested system may require joints to be tightly butted, staggered between layers, backed by framing, covered with strips, filled with a specified compound or positioned away from vulnerable corners. Some systems permit particular joint treatments; others rely on the board edges and supporting arrangement alone.

These requirements should be understood before the board layout is drawn.

Random joints may create narrow offcuts, weak edges or difficult fixing conditions. Joints positioned directly at steelwork corners can be harder to secure. Unplanned junctions with partitions, ceilings and service openings may leave gaps that are difficult to complete.

A good boarding detail considers the board module as well as the finished geometry. It asks where the sheets begin and end, where they are supported and how one layer relates to the next.

The finished enclosure may appear seamless. Its performance depends on how the seams were built.

Corners Are Part of the Fire Protection

Corners are often where an apparently simple encasement becomes technically demanding.

A beam or column casing may require butt joints, overlapping boards, proprietary corner channels, cover strips or a particular sequence of fixing. The tested detail determines how the corner is formed and how continuity is maintained.

Poorly considered corners can create several problems. Board edges may lack support. Fixings may be too close to the edge. Joints may open. The finished dimensions may drift. Decorative trims may be introduced that were never part of the tested assembly.

The architectural ambition for a crisp corner is reasonable. But the finish must grow from the fire protection system rather than conceal a weak version of it.

Where a column casing forms part of a visible interior, the design should coordinate fire performance and final appearance from the beginning. Shadow gaps, skirtings, ceiling trims, access panels and decorative finishes all need to meet the encasement without damaging or altering it.

The corner is not where fire protection ends and interior design begins. It is where the two have to agree.

Tested Encasement Must Match the Steelwork

The steel profile matters because different sections heat at different rates.

The relationship between exposed surface area and the volume of steel affects how quickly the section reaches critical temperature. This is often expressed through the section factor. The required boarding system must therefore suit the actual steel member being protected and the number of faces exposed to fire.

A beam enclosed on three sides is not the same condition as a column exposed on four. A steel section built into a wall may require different consideration from one standing independently. Connections, plates, brackets and changes in profile can complicate the encasement.

Architects should avoid drawing an idealised rectangular box without considering what sits inside it.

Connection plates may project beyond the main section. Bolts may reduce clearance. Brackets may interrupt framing. Secondary steelwork may enter the casing. Services may pass close to the enclosure. All of these conditions need enough room for the tested board system to continue.

The fire protection should follow the real steelwork, not the simplified outline used during early design.

Access Must Be Designed Before the Space Disappears

Fire boarding needs working room.

Installers must be able to position boards, form corners, fit framing, reach fixing points and inspect completed joints. If the steelwork sits tight against walls, façades, ducts or ceilings, the approved system may become difficult to construct.

This problem is common where fire protection is treated as a later addition. The structure is designed, services are routed and finishes are coordinated before anyone considers how the board enclosure will be installed.

The remaining gap may look adequate on a drawing but provide no meaningful access on site.

Architects should consider the sequence of installation. Can the board be fitted before the adjacent partition is closed? Can both sides of the beam be reached? Is there enough clearance around connection plates? Will M&E services block fixing positions? Can the completed work be inspected before it is concealed?

Access is not merely a contractor concern. It is part of whether the detail can be built as designed.

Service Penetrations Through Boarding Need Control

Fire board encasements are sometimes penetrated by services, brackets or later fixings.

This should not happen casually.

A tested enclosure is designed to provide continuous protection around the steelwork. Cutting openings through it may expose the section, interrupt the board system or create a detail unsupported by test evidence.

Where services must pass near protected steel, the preferred approach is usually to coordinate routes around the enclosure rather than through it. Where penetration is unavoidable, the detail needs technical review and a suitable approved solution.

The same applies to supports and fixings for other trades. Cable containment, ceilings, signage or decorative features should not be attached through the fire protection without confirming that the system permits it.

A finished board surface can look like convenient construction. It is not. It is safety-critical encasement.

Interfaces with Walls and Ceilings

Fire boarding rarely exists in isolation.

Beam casings meet ceilings. Column encasements meet floors, partitions and raised access systems. Boards pass behind or alongside drylining, façade linings and service zones. These interfaces need clear detailing.

The main question is continuity.

Where the steel protection meets another fire-resisting element, the junction must preserve the required performance. Gaps, unsupported edges and poorly coordinated changes in material can weaken the assembly. The sequence should also allow both systems to be installed without obstructing each other.

A partition should not be used to hide an incomplete column casing. A suspended ceiling should not prevent inspection of a beam enclosure. Decorative finishes should not cover joints before the fire boarding has been checked.

The drawing should show more than the clean line of the finished surface. It should show how the fire protection meets the surrounding construction.

Access Panels and Removable Sections

Some boarded enclosures require access for valves, connections, inspection points or future maintenance. This creates a particular design challenge.

A standard access hatch cannot simply be inserted into a fire-resisting encasement. The panel, frame, fixings and surrounding board detail must maintain the required performance and sit within a tested or assessed solution.

The location also matters. An access panel placed across a critical joint, corner or narrow section of casing may be difficult to support. A removable board fixed with ordinary screws may not provide the required continuity. A panel that is rarely used may still become the weak point in the assembly.

Architects should identify access requirements early and coordinate them with the system manufacturer or passive fire protection specialist. The access detail should be designed, not improvised after the enclosure is complete.

Where access is not essential, the encasement should remain uninterrupted.

Finish Tolerance Must Not Override Fire Performance

Fire boarding often sits beneath a decorative finish, but not every fire protection board is intended to provide a finished architectural surface.

Boards may have different tolerances for joint treatment, sanding, skimming, painting or applied finishes. Additional layers can alter dimensions, affect moisture behaviour or conceal defects before inspection. Some compounds and coatings may need to be compatible with the board system.

The required finish should therefore be agreed alongside the fire protection detail.

Where a high-quality visible finish is required, the system must allow for it without changing the tested assembly. That may mean a separate decorative lining outside the fire protection, a manufacturer-approved joint treatment or additional framing to control tolerances.

The temptation to correct unevenness by sanding board edges, filling large gaps or adding unapproved materials should be avoided. A smooth surface is not a sensible exchange for weakened fire resistance.

The finished appearance matters. It simply comes second.

Coordination with the Structural Engineer

Fire boarding design sits between architecture, structural engineering and specialist fire protection.

The structural engineer identifies the steel sections, loadbearing function and required fire resistance. The fire strategy establishes the performance period. The board manufacturer or specialist system determines the tested encasement. The architect coordinates the resulting thickness, geometry, interfaces and finish.

This information needs to remain aligned.

Changes to the steel profile may change the required protection. Revised connection details may affect the casing dimensions. A change in exposure condition may alter the board system. Architectural changes that reduce clearances may make the approved detail unbuildable.

Fire protection should therefore be reviewed when the steelwork changes. The board specification cannot remain frozen while the structure develops around it.

The design process must treat the encasement as part of the steel package, not an annotation added after coordination.

Inspection and Evidence Before Concealment

Fire boarding is frequently hidden behind finishes or incorporated into walls and ceilings. Once concealed, it becomes difficult to check board thickness, joints, fixings and corner construction.

Inspection should take place while the full enclosure remains visible.

The records should identify the location, protected section, required resistance period, board product, thickness, layer arrangement and installed system. Photographs should show the wider location as well as the fixing and joint details. Any departures from the approved construction should be resolved before concealment.

The evidence trail matters because the board surface reveals very little once decorated. Two enclosures may look identical while being built quite differently beneath the finish.

The Golden Thread depends on that distinction being recorded.

Practical Design Checks for Architects

Before issuing fire boarding details, architects should confirm that:

• The required fire resistance period is clear.

• The actual steel sections and exposure conditions have been identified.

• The board system is supported by suitable test or assessment evidence.

• Board thickness and layer arrangements suit each condition.

• Fixing types, centres and supporting construction follow the tested system.

• Joint positions and treatments are properly coordinated.

• Corner details match the approved assembly.

• Connection plates, bolts and brackets fit within the enclosure.

• There is enough space for installation and inspection.

• M&E services do not obstruct or penetrate the casing without approval.

• Wall, floor and ceiling interfaces maintain continuity.

• Access panels are supported by a tested or assessed detail.

• Decorative finishes are compatible with the fire protection system.

• Inspection and photographic records are required before concealment.

These checks turn a general fire protection note into a detail that can be built and verified.

Why JW Simpkin Treats Boarding as Precision Work

At JW Simpkin, fire boarding is treated as a measured construction system rather than a covering applied around steel.

The work depends on correct materials, thicknesses, fixings, joints, corners and interfaces. It also depends on access, sequencing and coordination with the structure and surrounding trades.

A well-built encasement is quiet. It follows the steelwork closely, meets adjoining construction cleanly and provides the required resistance without drawing attention to itself. That apparent simplicity is the result of disciplined installation.

The board may hide the steel. The evidence should never hide the method.

Conclusion: Draw the Assembly, Not Just the Outline

Fire boarding details often begin with a simple line around a steel section. The completed construction is more exact.

Board thickness, fixings, joints, corners, access, interfaces and finish tolerances all affect whether the system can be installed as tested. Each decision shapes the enclosure and its ability to protect the structure under fire conditions.

For architects, the responsibility is not to design every fixing in isolation. It is to specify the tested system clearly, allow enough space for it, coordinate its interfaces and ensure that the site team can install and verify it properly.

A rectangular outline may describe the shape.

Only the detail describes the fire protection.