Two-Storey Extension Questions Checklist

Walk to the top of the existing stairs and write down where a door into the new rooms could physically go without taking space from a bedroom you rely on.

The route in is the constraint that decides whether a two-storey addition works at all, and it is visible to an owner long before any drawing exists.

Note how narrow the existing landing gets at its tightest point, and whether a radiator, a cupboard door or a hatch already restricts it.

A landing that already feels tight will not absorb a new doorway and a new circulation route without something being given up.

Record whether the loft hatch, airing cupboard or boiler cupboard sits exactly where a new opening off the landing would want to be.

These are the fittings that quietly occupy the only sensible position, and relocating them is a separate piece of work with its own constraints.

Consider whether the new upper rooms would have to be entered through an existing bedroom, and write down whether whoever sleeps there finds that acceptable.

A room reached through another room changes how it can be used and who can use it, and households should settle that between themselves early.

Ask a qualified professional what altering the landing or the floor structure would involve before assuming a new doorway can simply be formed.

Openings in an upper floor and its supporting walls raise questions an owner cannot answer by looking, however obvious the position seems.

Whether an opening can be formed in an existing wall or floor is a judgement for a suitably qualified structural professional on site.

Write down how the household actually moves around upstairs at night, including who shares a bathroom and whose door people have to pass.

Adding rooms upstairs changes the traffic pattern, and the awkward version is only obvious once somebody describes the routine out loud.

Photograph the existing roof from the front, the rear and the far end of the garden so the ridge line and eaves line are recorded before anything is proposed.

These images are the first thing a designer will want, and taking them yourself means the conversation starts from what is there rather than memory.

Note whether the neighbouring houses form a continuous roofline, and where earlier additions along the row have already interrupted it.

How the row reads is often central to how a proposal is received locally, and owners can observe it without any professional input.

Consider whether you would accept a new roof set below the existing ridge, and write down how much the resulting appearance matters to you.

Setting a roof down is a common way of resolving the join, and knowing in advance whether you mind saves a redesign later.

Ask how the new roof would meet the existing roof, and what that junction means for gutters, valleys and the rooms directly beneath it.

Roof junctions collect water and are where problems tend to appear, so the detail matters more than the shape drawn on an elevation.

How two roofs are joined and drained is for a qualified designer and roofing professional to resolve for your specific roof.

Record whether the addition would sit over an existing single-storey structure, and treat whether that is possible as a completely open question.

An existing low addition was built for the loads it carries now, and nothing about its appearance indicates what else it could take.

Whether an existing single-storey structure or its foundations can carry another storey must be established by a qualified structural professional.

Note where the chimney stack sits and whether a new roof would run into it, pass beside it or leave it standing awkwardly.

Stacks are frequently left off early sketches and then become the detail that reshapes the roof at the last moment.

Look out from a nearby existing upstairs window at roughly the height the new windows would sit, and note what you can see into from there.

This is the closest an owner can get to the future view, and it usually reveals more than a plan or an elevation ever will.

Write down which neighbouring windows, gardens and seating areas would fall within view from a new upper room.

Outlook and overlooking generate most neighbour concern, and knowing about them early gives a designer room to respond rather than react.

Consider whether a window facing a boundary would need to be obscured or set high, and raise it as a question rather than deciding it yourself.

Requirements on windows facing boundaries vary by location and by property, so this belongs firmly in the question column.

What is acceptable for a window facing a boundary is for the local authority and a qualified professional to confirm for your property.

Note where the sun reaches the proposed upper rooms in the morning and in the evening, using observation from the existing upper floor.

Bedrooms that bake in the evening sun are a common complaint, and orientation is something an owner can record accurately without help.

Record whether the new windows would need to match the pattern and proportion of the existing ones, and how strongly you feel about that.

Matching or deliberately contrasting is a design decision that is far simpler to state as a preference at the outset than to argue over once elevations exist.

Ask how each upper window would be cleaned and how any opening light would be reached once the addition exists.

Windows above a low roof or tight to a boundary can be very difficult to reach afterwards, which occasionally changes the type chosen.

Access and working at height are matters for the professionals involved; do not plan on reaching upper glazing yourself.

Write down what you actually know about how the house is built beneath the proposed addition, and mark clearly every point where you are guessing.

Separating knowledge from assumption is genuinely useful to a professional and stops a conversation being built on something nobody checked.

Ask a qualified structural professional what would need to be established about the existing foundations before a second storey is considered at all.

The answer usually determines the order of the whole project, because design work committed before it can be wasted.

Foundation adequacy is never a matter of appearance or of what a neighbour did; only site-specific assessment can address it.

Note where the internal walls run on the ground floor beneath the proposed upper rooms, including any walls that have already been removed.

Previous removals matter a great deal here, and owners are usually the only source of information about work done before they moved in.

Record any previous structural work on the property, including beams put in for earlier openings, and gather whatever paperwork still exists.

Earlier work was designed for the loads present at the time, and its paperwork saves a professional from starting entirely from scratch.

Ask what investigation would be needed, who arranges it and at what stage, rather than assuming the existing structure can simply take more.

Knowing the sequence helps you understand why a professional may not commit to anything until the investigation is complete.

Do not proceed on any assumption about structure; take every point in this section to a suitably qualified structural professional.

Consider what your position would be if the answer is that significant work is needed below, and write that down before you are under pressure to decide.

Deciding your limit in advance is the most useful thing an owner can do, because the moment of the answer is a poor moment to think clearly.

Write down whether the new floor is intended to contain a bathroom or shower room, because that decides whether drainage has to reach it at all.

This is a brief decision rather than a design one, and it changes the position of the new rooms more than almost anything else.

Note where the existing soil stack runs on the outside of the house, and whether the addition would enclose it, cover it or require it to move.

The stack position is the anchor for any new wet room, and it is easily observed by an owner from the garden.

Altering or enclosing a soil stack is work for a qualified professional and may involve the relevant drainage authority.

Consider how a new bathroom above a living room or a study would sound from below, and whether that is a room you sit quietly in.

Water noise through a floor is one of the most common regrets after an upstairs addition, and it is easier to plan around than to fix.

Ask what the hot water arrangement would need in order to serve an extra bathroom, and treat the answer as a professional judgement.

Adding a bathroom adds demand at exactly the times the household already competes for hot water.

Hot water and heating capacity must be assessed by a suitably qualified professional for your specific installation.

Record whether the new wet room would have an external wall for ventilation, or whether it would sit internally within the plan.

An internal wet room brings extract and ventilation requirements that influence where it can be placed.

Note where the existing bathroom sits and whether placing the new one nearby is possible without spoiling the arrangement of bedrooms.

Grouping wet rooms usually simplifies the pipework conversation, but it competes directly with where the bedrooms want to be.

Walk the perimeter and write down where scaffolding could physically stand, including whether any part of it would need to cross a neighbouring garden.

Scaffolding for work at this height needs more room than owners picture, and the position that works may be the one strip of ground you do not control.

Note which windows and doors would sit behind scaffolding, and whether any of them is the way the household normally gets in and out.

Losing the usual entrance for a stretch of the work reshapes daily life more than owners anticipate.

Consider how the house would be kept weathertight while the roof is open, and ask directly who is responsible for that.

This is the single largest risk to the existing house during a two-storey addition, and responsibility should be agreed rather than assumed.

Temporary protection and weathertightness during work are the responsibility of the professionals carrying it out; agree it in writing beforehand.

Record where a lorry could stop and how far materials would have to be carried to reach the working area from there.

Carrying distance affects how a job runs and is worth flagging early, particularly on a narrow street or a shared drive.

Ask what happens to the aerial, satellite dish or any cable fixed high on the wall being worked on, and who deals with each one.

Each of these belongs to a different provider or trade, and they are only irritating when discovered on the morning they are in the way.

Write down how security would be handled while scaffolding stands against upstairs windows, and check what your insurer expects to be told.

Insurers usually want notice of building work, and scaffolding is often specifically relevant to what they ask about.

Decide and record whether you would move out while the roof is open, and write down what would trigger that decision rather than leaving it open.

Households that have not set a trigger tend to stay too long, and the decision is much harder to make once conditions are already bad.

Note which bedrooms would be unusable at each stage of the work, and write down where the people who sleep in them would go.

Bedroom loss is the practical difference between a two-storey addition and a ground-floor one, and it is regularly underestimated.

Consider what happens to everything stored in the loft if the roof space is opened up or altered, and where it would go instead.

Loft contents have to leave before work starts, and there is rarely anywhere obvious for them in an already crowded house.

Write down how dust from work overhead would reach the rooms below, and which possessions you would rather remove from the house entirely.

Dust from work at ceiling level travels through a house in a way that surprises people who have only lived through ground-floor work.

Ask who is responsible for protecting the existing staircase, carpets and ceilings while work happens above them, and get that agreed in writing.

The stair is on the route for every load carried up, and protection arranged after the first damage is too late.

Protection of existing finishes is a matter to agree in writing with the professionals doing the work before anything begins.

Record whether anyone in the household works from home, and what continuous noise directly overhead would mean for that arrangement.

Noise from above is harder to work through than noise from an adjoining room, and it is worth planning around rather than discovering.