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Writing a pedestal system into the specification

A work-section outline for pedestal decks, with each requirement traced to the document that imposes it. It is written for architects, specifiers and contractors drafting the scope of works.

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Writing a pedestal clause that traces back to something

A pedestal system gets into a scope of works the same way any other product does: as a clause that names what must be supplied and leaves the installer no room to interpret it differently. Most pedestal clauses in circulation are written by the manufacturer whose product they describe, and a clause written to sell a product reads differently from one written to impose a requirement. The two are not always the same document.

What a compliant-looking clause is supposed to do

A specification clause should trace back to something. Load capacity should trace to the imposed load the structure must carry. Fire performance should trace to the reaction to fire classification the build-up requires. Fixing and spacing should trace to the product standard or warranty requirement that governs the slab type. Where a clause states a figure or a requirement with nothing behind it, there is nothing for a building control body or a warranty surveyor to check it against.

Where the gaps tend to sit

A manufacturer-authored clause usually describes the manufacturer's own product correctly. What it tends to leave out is the requirement that sits a step away from the product itself: a spreader plate required by a warranty body rather than by the pedestal manufacturer, a rule against fixing through the membrane that comes from the waterproofing side of the build-up, or a wind-uplift calculation that the pedestal's own load figure does not cover. Omissions like these are not usually visible from reading the clause in isolation. They show up when the clause is checked against the warranty or standard it is meant to satisfy, line by line.

What to require instead

  • Check each clause against the document it claims to satisfy.
  • Ask whether a requirement sits with the pedestal supplier, the waterproofing designer, or the warranty provider, and confirm the clause names whichever one it is.
  • Where a figure appears without a unit, a test house or a standard behind it, treat the clause as incomplete until the supplier confirms all three in writing.

You can check the governing figures for your build-up against load requirements and slab thickness and spacing provisions, and set the two compliance routes for fire classification against what a clause assumes in the regulation itself.

Checking a supplied clause

What a manufacturer-authored pedestal clause commonly leaves out

A clause copied from a manufacturer's catalogue usually describes the product well and the surrounding requirements poorly. Run it against these points before it goes into the specification.

  • A spreader plate under the pedestal base

    LABC Warranty sets out a spreader plate requirement under the pedestal base on certain substrates, and a clause built around one system's standard fixing does not always carry it forward.

  • A rule against fixing through the membrane

    LABC Warranty's position against fixing pedestals through the waterproofing membrane can be absent from a clause written to showcase a particular fixing method.

  • A wind-uplift calculation and who carries it out

    A clause can describe a pedestal product fully while leaving open whether a wind-uplift calculation has been done for the layout, and by whom.

  • The standard and test house behind any stated load figure

    A load capacity stated without the standard it was tested to and the test house that carried out the test cannot be checked against a figure from another manufacturer.

  • Which fire-class route the clause relies on

    Approved Document B Volume 1 paragraph 10.10 sets out two separate routes to a fire-class outcome, and a clause that states a classification without naming the route leaves that route to be assumed.

  • Pedestal spacing tied to the slab actually specified

    A generic spacing figure means little unless it is tied to the thickness and type of slab named elsewhere in the specification.

A clause that covers every point here still needs checking against the document that imposes each one. Presence in the clause is not the same as confirmation in writing.