Every year, piling rigs fall over on UK sites. Near misses caused by the ground surface are more common still.
The Working Platform Certificate exists because of that. Developed by the Federation of Piling Specialists in partnership with the HSE, it has been credited with a significant reduction in rig overturning incidents over the past two decades — largely by forcing a conversation that used to happen by assumption.
The FPS issued an updated edition, WPC/4e, in July 2025, released publicly that autumn. If your procedures still reference an older version, they are out of date.
This article covers what the certificate is for, who signs it, what the current edition asks for, and where the process still goes wrong in practice.
The WPC is a formal confirmation, signed by the Principal Contractor, that the working platform has been properly designed and constructed, and that it will be inspected and maintained for the plant operating on it.
Two things it is not.
It is not a transfer of responsibility. The certificate does not move liability from one party to another. It records that competent people have been appointed to design, construct and maintain the platform. It deliberately does not specify who carries out those activities — that remains a matter for agreement between the main contractor and the specialist contractor.
It is not a visual assessment. Judging a platform's adequacy by looking at it is precisely the historic practice the certificate was created to stop. A platform can look entirely sound and be inadequate for the rig about to track onto it.
The certificate is handed to the piling contractor before work starts on site. In FPS terms it applies wherever a rig or attendant plant operates — not only to piling, and not only to FPS member sites. It is used industry-wide.
The mechanism is accountability. Before the WPC, the platform was often nobody's clearly-owned problem: the main contractor assumed the specialist would assess it, the specialist assumed it had been designed for them.
Requiring a named designer and a Principal Contractor's signature closes that gap. Someone has to know the answer before the rig arrives.
The 2025 edition brings more detail to design, verification and ongoing maintenance. The practical changes fall into three areas.
The certificate now asks for more comprehensive information about the design basis, including:
This matters because the older practice of stating a thickness and a material type left too much unsaid. A platform design that depends on geogrid reinforcement is not the same platform if the geogrid is omitted or placed wrongly, and the certificate should now make that dependency visible.
The revised inspection log is built around weekly checks, with additional inspection and recorded repair after events that change the platform's condition — heavy rainfall, flooding, or excavation through the platform surface.
This is the single change most likely to affect day-to-day site practice. It moves the platform from something certified once at the start to something with an ongoing, documented condition record. If your site is not currently keeping a weekly platform inspection log, that is now a gap.
The edition places greater emphasis on designs that are safe and efficient while being conscious of both cost and carbon — which in practice means the use of recycled aggregate is being taken seriously rather than treated as a substitution nobody wants to discuss.
Recycled material can perform perfectly well in a platform. It can also vary in grading, contain contaminants, and behave differently under trafficking. The point is that its performance is a design consideration to be stated, not an on-site substitution made to save a delivery cost.
A commercial scheme with a rotary bored piling package. The platform is designed and built in early spring, certified, and handed over. Piling starts.
Four weeks in, three things have happened.
Obstructions were encountered. Two pile positions hit buried concrete from a previous structure. Both were excavated out and backfilled. Neither was recorded as a platform repair.
It rained for nine days. Water ponded across a low corner of the platform where the falls were never quite right, and the surface has begun to rut where the rig tracks between positions.
The programme changed. A larger rig was brought in to meet the revised sequence.
Every one of those invalidates the original certificate in some way, and none of them announced itself.
The excavated obstructions are the most dangerous. A loosely backfilled hole leaves a soft spot, and a soft spot of around a square metre is enough to unbalance a rig that is otherwise perfectly stable. The platform looks continuous. It isn't.
The weekly inspection log exists to catch exactly this sequence. Not because anyone was negligent, but because platform condition degrades through ordinary site activity, and nobody notices a cumulative change unless someone is looking on a schedule and writing it down.
Signing on a visual inspection. The platform looks fine, the ground is firm underfoot, the certificate gets signed. Adequacy for a 90 tonne rig cannot be assessed by walking on it.
Not challenging the design. The certificate process works when the design is checked and challenged — including the installation, and any change that occurs during the works. A design that nobody interrogated is a design nobody has confirmed.
Backfilling obstructions without recording it. This is the classic route to a rig overturning on a platform that was correctly designed and correctly built.
Stopping the platform at the structure line. Good practice is to extend the platform at least 2 m beyond the pile position or building edge, so the rig and attendant plant have safe working area. Where working within that zone is unavoidable, the designer needs to be told, not worked around.
Letting the platform hold water. Standing water and slurry conceal recently constructed piles, trip hazards, excavations and services. Free drainage is a safety requirement as much as a durability one.
Undefined platform limits. The extent of the certified platform must be clearly identified on the certificate and physically demarked on site. This matters most when material is removed from an area the specialist contractor was previously using — the boundary moves and nobody marks it.
Forgetting pedestrian use. The platform is an access route as well as a plant surface. It needs to be safe to walk on, free of trip hazards such as protruding reinforcement, and free of harmful materials — particularly anything that becomes airborne in dry conditions.
Treating a change of plant as a logistics decision. A different rig is a different design case. The certificate covers the equipment listed on it.
It is a document signed by the Principal Contractor confirming that a working platform has been designed and constructed by competent persons, and will be inspected and maintained, so that specified plant can operate on it safely. It was developed by the FPS with the HSE and is used across the UK construction industry.
The Principal Contractor signs it. They must be satisfied that a competent designer has been appointed before doing so. The certificate is then provided to the piling or specialist contractor before work begins on site.
It is not itself a statutory document, but it is the recognised industry mechanism for discharging duties that are legal — providing safe plant and a safe place of work, and the Principal Contractor's duties under CDM 2015. In FPS terms it applies wherever a rig or attendant plant operates.
No. The certificate explicitly does not seek to transfer responsibilities. It confirms that competent persons have been or will be appointed to carry out design, construction and maintenance. Who performs those activities is a matter for agreement between the contracting parties.
The 2025 edition adds more comprehensive design data — plant configuration, platform material, drainage provision and geotextile reinforcement — and incorporates a revised inspection log based on weekly checks with recorded repairs after events such as heavy rainfall, excavation or flooding. It also gives greater attention to recycled aggregate performance and to cost and carbon in design.
The current certificate is built around weekly inspection, with additional checks and recorded reinstatement after any event that changes the platform's condition — heavy rain, flooding, or excavation through the surface. A change of plant requires reassessment rather than inspection.
Not without reassessment. The certificate relates to the equipment listed on it. A heavier or differently configured machine is a new design case, and the fact that the platform appears undamaged is not evidence that it is adequate.
That excavation creates a potential soft spot, and a soft spot of around a square metre can be enough to overturn a rig. It must be reinstated to the platform specification and recorded in the inspection log — not simply backfilled with whatever came out of it.
The Working Platform Certificate works because it forces a specific question to be answered by a named person before a rig arrives: has this platform been designed for this machine, built to that design, and will it be maintained?
WPC/4e sharpens that in three ways — more design data, so the basis of the design is visible; weekly inspection, so degradation gets caught; and explicit attention to material performance and drainage, so the assumptions behind the design survive contact with the site.
Most of what still goes wrong is not exotic. It is an obstruction backfilled and not recorded, a platform that ponds water, a boundary nobody marked, or a bigger machine arriving on a design that was never intended for it.
Check which edition your procedures reference, and check whether anyone is actually filling in the inspection log.
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