Cavity Tray and Abutment Questions Checklist

Walk the proposal through and list every place where something new would meet an existing outside wall, however small the new item is.

A canopy, a flue and a full extension all create the same kind of junction, and the small ones are the ones nobody raises.

Include anything that would be built up against the base of a wall, such as paving, decking, a planting bed or a step.

Work at the bottom of a wall is a junction with the existing construction just as much as a roof arriving part way up it.

Include anything that would be fixed to the wall rather than built against it, such as a canopy, an awning or a bracketed structure.

A fixed item is a different kind of junction from a built one, but both are things arriving on a wall that was not expecting them.

Mark each junction on a photograph of the elevation, so that the list and the building can be looked at together.

A marked photograph is the artefact that gets the junctions discussed, because it makes them impossible to overlook in a meeting.

Note for each junction which wall it lands on, including whether that wall is part of the original building or a later addition.

Walls of different ages may be built differently, so which one a new junction meets is a genuine distinction rather than a detail.

Include anything the project removes from a wall, such as an existing lean-to, canopy or pipe, since taking something off leaves a junction behind as surely as adding one.

Removals are thought of as clearing rather than as work on the wall, so what is left behind at that position is rarely anybody's item.

Write down what you have been told about how the wall is built, who told you, when, and whether they had looked at it.

Descriptions of an existing wall circulate as fact long after the person who first offered one has been forgotten.

Search the property papers for any description of the wall, including survey wording and anything from previous work, and copy it out exactly.

Original wording from a dated document is something a professional can weigh, whereas a summary of it is not.

Photograph the reveals of existing windows and doors in that wall, since what is visible there is an observation you can make without disturbing anything.

Reveals are where a wall is most readable from outside, and photographs of them answer a surprising number of first questions.

What is visible at one opening is not evidence about the rest of the wall; how a wall is built can only be established by survey.

Look along the wall for small openings in the joints above windows, doors and at the base, and photograph any you find with their positions.

These openings are the only visible sign of an arrangement inside a wall, and knowing whether the wall has any is worth recording.

Note anything that suggests the wall has been altered — filled openings, changes in the face, added insulation, a rendered section — and photograph each.

Alterations change what is inside a wall, and they are the reason two walls that look alike can behave very differently.

Where nobody can say how the wall is built, write that down explicitly rather than allowing an assumption to stand in for it.

A stated unknown is what prompts somebody to establish the answer; an unstated one is simply designed around.

Photograph the exact position where the new work would land, from several distances, before anything is removed or changed.

The before photograph is the only description of what was there, and once work starts it cannot be taken again.

Note any existing flashing, metalwork or weathering visible at or near the position, and photograph each one in place.

Existing weathering is frequently removed as part of the new work, and what it was doing is worth a question before it goes.

Look for a line, a chase, a row of filled holes or a change in the wall face suggesting something was once attached there, and photograph it.

Traces of a previous structure indicate that this junction has existed before, which is genuinely useful information.

Photograph and date the inside face of that wall, noting any existing stain, patch or decoration difference before the work begins.

A dated internal record is the only way to distinguish something existing from something that appeared after the work.

Watch what happens at that part of the wall during heavy rain if you can, and note where water runs and where it collects.

An observation made in the rain is worth several made in dry weather, and it is something only an occupier is in a position to do.

Ask whether there is a drawn detail for each junction you listed, and ask to see it rather than being told that it is covered.

Asking to see the detail is the difference between an assurance and a document, and it is an entirely ordinary request.

Ask which package or trade includes each part of the junction, and whether that has been confirmed with the people who will actually build it.

A junction crosses at least two trades, and the item at the boundary between them is the one that ends up in nobody's scope.

Ask in what order the parts of the junction are built and by whom, since one trade is often finished before another arrives.

Provision inside a wall has to be made while the wall is being built, by a trade who will have left before the roof arrives.

Ask what happens if the junction cannot be built as drawn once the existing wall is exposed, and who decides at that point.

Existing buildings reveal themselves during work, and knowing in advance who makes the decision is worth more than the drawing itself.

Ask what happens on the inside of the wall at that junction, including any finish, and who is responsible for it.

The inside face is frequently treated as a decorating matter, and it is the face where a problem at the junction would first show.

Keep the answers, the details you were shown and the names of who is responsible for each junction in one place with the project papers.

These answers are worth very little individually and a great deal as a set, particularly if anything is queried later.

Ask whether the project puts anything into or onto the existing wall, such as insulation or a new finish, and whether that changes what the junction has to do.

Work to the wall itself can change what a junction is dealing with, and it is usually designed by somebody other than whoever drew the junction.

Ask where water collected at the junction is meant to leave the wall, and whether those points will be visible from outside afterwards.

Discharge points that can be seen are the only evidence available afterwards that anything inside the wall is working.

Ask to be shown where those points are once the work is finished, and photograph them with their positions marked on an elevation.

Knowing where they are is what makes it possible to protect them, and nobody will point them out unless asked.

Look at what else the project involves near that position — paving, render, a planting bed, a step — and ask whether any of it would cover those points.

Work by a different trade arriving later is the most common way a discharge point is closed within the same project.

Where the project raises the ground or a surface against the wall, ask what that means for anything at the base of it.

Raising a surface against a wall is an ordinary landscaping decision that changes the position of the wall relative to the ground.

Whether a change in level against a wall is acceptable is a professional determination on the specific building, not something to judge by appearance.

Write down that these openings are meant to be open, and keep that note where anybody later repointing, rendering or painting the wall will see it.

These openings are read as defects and filled by people acting in good faith, and a written note is the only realistic protection.

Ask specifically about what happens where the junction turns a corner or returns along another face of the building.

Corners are where a continuous arrangement has to be re-formed, and they are frequently drawn only as a straight run.

Ask what happens where one part of the junction meets another, particularly where work by different trades comes together.

A join between two correctly built runs can still be a gap if it was formed the wrong way round, which is a design question.

Ask about anything that passes through the junction, such as a flue, a pipe or a cable, and who is responsible at that point.

Something passing through a junction is a second problem inside the first, and it usually belongs to a different trade again.

Flues carry combustion products, and any work affecting one belongs with a suitably qualified and registered professional in that field.

Note whether any junction is at or near a boundary, or involves a wall belonging to somebody else, and raise it before work is planned.

Work on or against a wall belonging to another owner has its own procedures, and it is not a matter to settle between households.

Working on a wall belonging to an adjoining owner may involve obligations that vary by location; confirm what applies with your own adviser.

Ask specifically about any junction landing on an earlier addition rather than on the original building, and what is known about that construction.

Earlier additions are the walls least likely to be documented and most likely to be assumed to match the original house.

Ask when each junction will be built and covered, and put those dates somewhere you will see them so photographs can be taken beforehand.

The window is short and nobody will tell you about it unless you have asked, which is why so few owners have these photographs.

Ask the designer and the builder whether they photograph junctions as they are built, and whether you can have copies.

People working on the junction can photograph it far better than you can from outside, and they are usually willing to share.

Take your own photographs only from where you are permitted to stand, and ask for any view you cannot reach safely.

Asking for a photograph is straightforward and avoids an owner climbing onto scaffolding to get one.

Do not go onto scaffolding, ladders or a roof to photograph a junction; ask somebody working there to take the view for you.

Mark every junction and every discharge point on one photograph of the finished elevation, and keep it with the property papers.

This single annotated photograph is the most useful thing to hand to anybody working on the outside of the building later.

Keep that annotated photograph where you will find it before any future work on the outside of the building, and show it to whoever is doing that work.

Decorators, roofers and landscapers arrive years later with no knowledge of what is in the wall, and this is how they find out.