Where the Envelope Meets the Ground

The continuity record describes the failure in its clearest form. The barrier under the slab stops at the slab edge, the course within the wall starts above it, and the space between them is an uninterrupted path from the ground into the wall regardless of how well either product performs across its own area. The lap that joins them is formed at the moment when neither trade regards the work as theirs.

It then names why this is worth stating at all: if that lap is missed, both components remain intact and both continue to perform across their own area, while the assembly as a whole has a continuous path from the ground into the wall. The record calls it the clearest case in the library of a complete component producing an incomplete system.

The position of the course relative to the external ground and the internal floor decides whether the barrier is being asked to interrupt an upward path or to hold back water standing against the wall above it, and the record says those are different demands. That is the sentence with the longest reach in this guide, because it means the barrier's job can change without anyone touching the construction.

The record says so explicitly: later landscaping that raises external ground can change which of the two applies. It also notes that external drainage and the barrier work against the same water from opposite sides, so where ground falls, land drainage and granular zones are absent or later altered, the same barrier is asked to hold back standing water, which is a materially different requirement and one that belongs with a qualified professional.

An insulated render facade has to begin somewhere, and the record describes that as a design problem in its own right. It has to start above splash and standing water on a supported, shedding edge that protects the exposed lower face of the insulation, and the record calls the base the place where every weakness meets: the lowest exposed edge of a soft board, the place splash arrives, the level at which any damp-proof provision in the wall passes, and the point where a starter profile has to hold the build-up, shed water clear and resist knocks.

It also names the consequence of getting it wrong, and it is not cosmetic. Water enters the back of the insulation and travels behind the render, where no external repair can reach it, and a stained band above ground level usually points backwards to the starting detail.

A bonded tile or stone facade has no cavity, and the record says that single absence explains most of the assembly's behaviour. With no drained space, water has only two routes, through the surface into the bed or down the face to the bottom edge, which makes the grouting and the base termination the whole of the water strategy and makes freezing conditions a question about what is behind the units rather than about the units themselves.

A brick slip facade is different again. The record's boundary test is set at the bottom of the wall: a veneer stands on something, a footing, a plinth or a supporting angle, while a slip facade has no continuous bearing line and its weight is distributed into fixings all the way up the elevation. How corners, reveals and the base are formed, and what supports those special pieces, is described as usually the hardest part of the setting out.

The direct-applied render record asks how the render terminates near the ground relative to paving and the wall's damp-proof provision, and calls it a moisture decision made early. It also notes that one render can be doing several different jobs on one building, taking splash and abrasion over a plinth while doing far less on a sheltered return, and that the differences are handled at the edges rather than in the coats.

There is a broader warning in the same record about the whole of this line. A cracked render is worse than no render where water can enter and then cannot leave, because the coats now shelter a wetted wall from the drying it once had. At the base, where the wall is wettest, that trade is at its sharpest.

The cavity tray record identifies the base of the cavity as the one interruption that belongs elsewhere, because there water falling inside the cavity and moisture rising from the ground arrive at the same element, and the continuity system owns it. The continuity record describes the same meeting from its side and asks which layer intercepts what, and where each discharges.

The cavity wall record adds the component that sits in that corner and the way it fails. Closers sit where three demands meet: stopping air moving through the void, shortening the thermal path around the insulation, and not reconnecting the leaves for moisture. A closer that answers the first two by packing the gap with something conductive or absorbent has met them at the expense of the third, which is why the wall base is so often where internal staining appears first.

At a threshold, everything a step would otherwise have solved has to be solved by other means. The record lists structure, floor build-up, wall base, external paving, drainage, the door frame and the door's operating seals all terminating within the width of one doorway, each designed by somebody looking at a different drawing.

It also states the property that makes an upstand valuable and fragile at the same time. An upstand is passive protection: it works by height and gravity rather than through a connection or a clearing regime, so what it depends on is not upkeep of the upstand but the external level staying below its top, which later paving, decking, a raised bed or accumulated silt can change.

The continuity record describes the conditions this line is made in. It is built at the busiest and least tidy stage of a project, under weather, alongside groundworks and often before a drawing package is complete, and the connections it depends on are made before anyone is watching them closely. Barriers at this level are laid early and then walked over, loaded, drilled and covered by other trades, so damage happens before completion and is concealed by the construction that follows it.

And almost none of it remains reachable. The record says so, and draws the practical conclusion: anything that could reasonably be inspected later, such as external levels and drainage, carries a disproportionate share of the attention. A record of where the barrier runs, what it is and how it was connected is what allows a later alteration, a new opening, a raised patio or an added service, to be judged rather than guessed at.