When the Product Documentation Is the Governing Document

There is a consistent shape to these questions. They ask whether a specific product will do something in contact with another specific product, or in a specific position, and the answer changes between products that share a description. The transition record states the case directly: because behaviour there depends on primers, substrates and compatibility that vary between products, it is one of the few places where the manufacturer's own literature is the governing document rather than background reading.

Several of them recur across the family. Whether a tape or sealant bonds to the frame material as well as to the wall face. Whether a membrane and its tapes are compatible with the surface beneath. Whether a board can accept a particular render, and in what arrangement. Whether a product may be used where standing water is designed into the roof. Whether a covering can be used at a given pitch and exposure. None of those is answered by a family name.

Wherever something is stuck to something else, the documentation covers a chain rather than a product. The transition record describes it plainly: nothing in a transition bonds to itself, the band adheres to a primer, the primer adheres to a substrate, and that substrate was prepared by a trade which has usually moved on. It adds that a band which bonds readily to a clean face has no bond at all to a release agent, and the drawing shows neither condition.

The liquid membrane record describes the same chain vertically: a sound coating over a poor primer, or a good primer over a friable surface, produces a layer that looks complete and can lift as a sheet later. The adhered facade record describes a chain of bonds from unit to bed to levelling layer to background, where a failure at any one presents identically from the outside. In each case the documentation being asked about is the documentation for the whole chain.

Some assemblies work by a shape that belongs to a manufacturer. The composite panel record states that panel systems are proprietary arrangements, that joint geometry, fixings and closures come from the manufacturer's documentation, and that they are not interchangeable between systems. It describes the manufactured side lap and end joint as having to shed water at the outer face, close the core against a gap and stop the air path at the liner face within one geometry set by the manufacturer.

Curtain walling is described the same way in a narrower respect: because the glazing rebate is drained rather than sealed, where sealant belongs and where it must not go is defined by the system documentation. That is the point at which a well-intentioned site decision, made from general knowledge, can close the route the design depends on.

Several records place the question of where a product may be used with the documentation rather than with the assembly. Whether a covering can be used at a given pitch and exposure is described as a design determination made against the manufacturer's documentation and not a general rule. Whether a waterproofing product may be used where standing water is designed into the roof is stated in the manufacturer's documentation and confirmed by the designer. Whether a board can accept exposure to cavity air and to weather before the cladding is complete is a question for its documentation and for the designer.

Movement capability behaves the same way. The window record notes that sealants and tapes have finite movement capability, which the product literature states and general guidance cannot. That single sentence is why a joint that moves is a documentation question rather than a judgement made from experience of a similar-looking joint.

The records treat a substitution across sources as a change of kind rather than of brand. The rendered insulation record states that the tested combination of board, fixings, base coat, mesh and finish is what the documentation covers, and that mixing components across sources leaves nobody able to say what the assembly is. Its caution note repeats it: mixing components from different sources leaves no one able to describe what the assembly is or what its documentation covers.

The transition record adds the contractual consequence, describing the transition as a place where a substitution is not a like-for-like change. The practical effect is that a swap made for availability or price on site can move the assembly outside everything that was written about it, and nobody notices until an answer is needed and there is none.

The records name the documents to request rather than leaving it open. For a rendered insulation system: whether all the components are part of one documented combination, and what would be recorded for a future repair or claim. For a single ply roof: what documentation will be handed over describing the layers and the details actually installed. For a liquid membrane: what record will be provided of the products used, the coats applied and the areas covered. For a metal component: which process was used, what the supplier states about suitable environments, and the specified remedial treatment for cut edges and site damage.

Timing matters as much as content. The transition record observes that the window in which a detail is verifiable is set by the programme, and the rendered insulation record that recording exactly what was installed is what makes a later claim answerable. Both point to asking before the component is ordered and recording before it is covered.

It is worth being clear about what this does not mean. Documentation answers what a product does in a stated arrangement. It does not decide whether that arrangement suits a particular building, which the records consistently place with the designer, and it does not settle regulated questions, which they place with the relevant authority and with tested assemblies.

So the routing is threefold. A general reference describes how an assembly is organised and what the parts are for. The manufacturer's documentation states what a specific product does, in contact with what, in which positions and within what limits. And a qualified professional decides whether that product in that arrangement suits this building, this climate and this use. Knowing which of the three a question belongs to is most of the work.