Extending a Previously Extended Building Checklist

Walk the building and write down how many separate pieces of construction you think it consists of, naming each one in a way you will use consistently afterwards.

Consistent names for the original house, the older addition and the newer one make every later note, photograph and message about the project unambiguous.

Against each part, write how you know when it was built — deeds, purchase paperwork, a previous owner, a neighbour's memory, old photographs — and how confident you are.

The source matters more than the date, because an engineer can weigh a document differently from a recollection, but only if the two are distinguishable.

Look through any old photographs of the property you or your family hold, and note anything visible in them that no longer exists or has since been built over.

Photographs taken for other reasons are often the only surviving record of what a building looked like before an addition, and nobody thinks to look at them.

From the garden, photograph each elevation and note where brickwork, render, roof line or window pattern changes, marking each change on the photograph.

Changes in the outside face are the most reliable way of showing a designer where one build stops and another starts before anything is opened up.

Walk through the inside and note every step in the floor, change in ceiling height and change in door head height, recording which rooms each occurs between.

These changes usually mark the boundary between builds, and they also constrain what a new addition can connect to without further level changes.

Write a short list of the parts of the building whose age or construction nobody can describe, and keep that list visible in the file rather than buried.

An explicit list of unknowns is more useful to a professional than a confident account that turns out to be partly guesswork.

Go through the file from when you bought the property and copy out anything that refers to alterations, additions or work carried out by a previous owner.

Purchase enquiries frequently record what a seller said about earlier work, and that wording is dated and attributable in a way that later conversation is not.

Look for drawings from the earlier work, including plans, sections and any engineer's sketches, and photograph or scan each sheet including its title block.

The title block carries the revision and the date, which is what tells a later reader whether the drawing shows what was actually built.

Collect any completion paperwork, notices or letters relating to the earlier work, and note what exists and, just as clearly, what does not.

A written note that no paperwork survives for a particular addition is itself a fact your professionals need, and it is better stated than implied.

Gather guarantee documents, product literature and installer paperwork left behind for anything in the earlier addition, including roofing, glazing and any damp treatment.

These documents name parties, dates and sometimes construction details, and they often survive when nothing else from the project does.

Note who handed each document to you and when, and write down whether anything was described as missing at the time of the handover.

Knowing that a set of drawings was already incomplete when you received it stops a later search for something that has not existed for years.

Put everything into one file, paper or digital, with a contents sheet and the date you assembled it, and keep adding to that same file.

A single dated file is what makes this useful to somebody else; a collection of documents in different places is not the same artefact.

Mark on a sketch plan every line where one build meets another, inside and outside, and photograph each of those lines where it is visible.

A marked plan turns a vague sense that the back of the house is newer into something a designer can work from without a second visit.

Photograph and date any crack, gap or separation you can see at a junction, describing where it is without offering any view on what caused it.

Junctions are where differential movement shows, and a dated photographic record is the observation a qualified structural engineer can actually use.

Recording a crack establishes nothing about its cause or significance; only a qualified structural engineer can assess that on the specific building.

Note how the roof of each part meets the next, including any valley, abutment or change of roof shape, and photograph each from the ground or a window.

Roof junctions between additions are where water problems concentrate, and a new addition frequently lands on or near one of them.

Record whether the floor level changes at each junction and by roughly how much in terms of steps, without attempting to measure it precisely.

Level differences between builds constrain how a further addition connects, and they are much easier to note now than to discover during design.

Look at the ground outside where the builds meet and note the levels, any paving laid up against the wall and anything covering a vent or an opening.

Ground raised during earlier work is one of the things most often inherited without anyone realising, and it is visible from the garden.

Note what you can see of how the two builds are joined where it is visible, and record it as an observation rather than as a description of the whole junction.

What is visible at one point is not evidence about the rest of the junction, and saying so in your notes keeps the record honest.

Identify which walls were once outside walls, mark them on your sketch plan, and note anything you can see on them that suggests their former life.

A wall that used to face the weather carries features the newer rooms do not, and its position is one of the first things a designer needs.

Note any opening that appears to have been filled in — a former back door, a window, an air brick — and photograph both faces where you can reach them.

Filled openings are common at the junction between builds and they matter to anyone thinking about forming a new opening nearby.

Look for air bricks, vents or weep openings on what is now an internal wall, and write down where each one is and whether anything has been done to it.

Openings that were built to stay open are routinely enclosed by an addition, and the record of where they were is usually lost with them.

Do not block, open or alter any vent or air brick to find out what it does; raise each one with a qualified professional instead.

Note where you can see a line in the brickwork near the base of what is now an internal wall, recording the observation without interpreting it.

How the damp-resisting arrangement of the original building relates to the newer floor is a professional question, but the observation is yours to make.

Record whether any chimney, flue or stack passes through or near the earlier addition, including anything visible in a loft or above the roof line.

Flues travel through buildings in ways that are not obvious from any single room, and an addition frequently sits against one.

Write down the things you suspect are behind the earlier work but cannot see, and leave each recorded as an open question rather than a conclusion.

An unanswered question written down is more useful to a professional than a guess, and it makes the scope of any survey clearer.

Walk the outside of the property and photograph every drainage cover, gully and grating you can find, noting which part of the building each sits against.

Covers are the visible evidence of a buried network, and their positions relative to the different builds are what a designer works from first.

Note whether any chamber or gully appears to sit beneath an earlier addition or inside the building, and record what you have been told about it.

Building over drainage is a well-known situation with its own procedures, and knowing early whether it already happened here changes the design conversation.

For each part of the building, note where rainwater leaves the roof, where the downpipe goes, and whether it disappears into the ground or runs across a surface.

A further addition often lands exactly where the previous one discharges, and tracing it now avoids designing a building over the answer.

Photograph where the water, gas and electricity supplies enter the building and where the meters are, noting whether any of them sits in the earlier addition.

Supplies that were moved during previous work are often in inconvenient places, and their position constrains what can be built where.

Meters, supply entries and appliance connections may only be altered by the suitably qualified and registered party responsible for each one.

Note where soil and waste pipes run on the outside of the building and where they turn down into the ground, photographing each one in position.

Waste runs have very little freedom of movement, so knowing where they are before a layout is drawn saves the layout being redrawn.

Write down which parts of the drainage and service routes nobody can describe, and keep that as an explicit question for whoever surveys the site.

Naming the gaps is what turns a survey brief into something specific rather than a general request to have a look.

Write down what you or anyone else has assumed about the earlier addition's structure, and mark each assumption clearly as an assumption rather than a fact.

Assumptions harden into accepted facts very quickly once a project starts, and labelling them at the outset is the only reliable protection.

Note whether anything in the paperwork describes the foundations of the earlier addition, and if nothing does, record that absence explicitly.

Foundation information about an existing addition is rare, and knowing it is absent shapes what investigation the project is likely to need.

If the proposal involves building above an earlier addition, record what is known about that roof and what would have to be established about it.

A roof built to keep weather out is a different thing from a floor built to carry a room, and the difference is the whole question.

Whether an existing structure can carry new work is a determination for a qualified structural engineer on this specific building.

Note which walls a new addition would be attached to, and record what you know about each one and how you know it.

Which wall carries the new work is among the first questions an engineer asks, and preparing an honest answer saves a return visit.

Note what similar properties nearby have had done, recording it as background rather than as an indication of what is possible on this building.

Houses in a row were often extended at different times by different people, so what happened next door may have no bearing here at all.

Ask what would have to be opened up to answer the structural questions, who arranges that, and at what point in the process it would happen.

Owners who expect one visit to produce one answer are the ones most thrown when investigation turns out to be a separate stage.

Go through the file and mark each item as a document, a photograph, something you observed yourself, or something you were told by somebody else.

This single distinction is what allows a professional to weight what you have given them, and it takes an afternoon to apply.

Put a date on every note and photograph, including the ones you made yourself, and record when each conversation you are reporting took place.

Undated observations lose most of their value, because nobody can tell whether a crack was photographed before or after the last dry summer.

Draw one rough plan of the building with the different builds, the junctions, the drainage covers and the level changes all marked on it.

A single annotated plan is what makes a file navigable, and it is the document a designer will actually put on the table.

Put the list of things nobody can answer at the front of the file rather than at the back, so it is the first thing a professional reads.

The unknowns are the reason this file exists, and burying them behind the documents undoes the point of assembling it.

Keep the file open as the project proceeds, adding dated photographs each time something is uncovered, before it is closed up again.

The moments when an existing building is visible are brief and never repeated, and this is the only opportunity to record them.