Addition Daylight Impact Questions Checklist

Walk through the house and write down every room that would sit behind the new structure rather than beside it, because those are the rooms most likely to change.

Owners picture the bright new space and forget the rooms it would stand in front of, which is where daylight is usually lost.

Note which of those rooms already needs a lamp on during the day, and in what weather, since a room that is marginal now rarely improves.

A room that is already borderline is the one where a small change in daylight becomes a permanent annoyance.

Record what each affected room is used for and at what time of day, since a dim utility corner matters far less than a dim room somebody works in.

Ordering rooms by how they are used shows a designer where daylight is doing real work and where it matters much less.

Write down whether an affected room is used by someone who reads, sews, draws or works closely, and say so plainly when the scheme is discussed.

Close work needs light in a way that general living does not, and it is easy to leave out of a brief.

Note which affected rooms have only one window and which have two or more, because a room with a single source has nowhere else to draw from.

A room with two aspects can lose one and still function; a single-aspect room usually cannot.

Record the rooms you would accept becoming dimmer and the ones you would not, and keep that list where design decisions are actually being made.

Written down early, this list settles arguments later; held in your head, it gets quietly overruled by a drawing.

This is a personal judgement about your own home. Whether any effect on daylight is acceptable in planning terms is for the local authority and a qualified professional to address.

Mark on a rough sketch which existing windows would be built over, built up to, or left sitting inside the new structure.

Giving every window one of three labels turns a vague worry into a list a designer can respond to.

Note any window that would become an internal opening between old and new space, and write down what the room behind it would then be relying on.

A window that opens into a new room is no longer a daylight source; it becomes a borrower like everything else.

Whether an existing opening can be kept, altered or closed up is a structural and consent question for a qualified professional and the local authority.

Record whether a glazed door, fanlight or side panel currently brings light into a hall, landing or stair that has no window of its own.

Circulation spaces often live entirely on borrowed light, and the source is easy to overlook because it is not called a window.

Note which windows face a side passage or a narrow gap, since these often deliver more light than anyone expects until they are gone.

A window onto a passage looks unpromising but may be the only thing keeping a room usable in the middle of the day.

Write down whether any window you would lose is the only one giving a view out, because outlook and daylight are two separate losses.

People often describe a room as dark when what they actually miss is the view, and the two need different remedies.

Note whether an existing rooflight, lantern or glazed roof would be covered by the new structure, and flag it before layouts are drawn.

Overhead glazing delivers far more than its area suggests, so losing one is rarely a small change.

Describe in your own rough terms how far back from the existing rear wall you imagine the new space going, and label it clearly as an estimate.

Writing it down as an estimate keeps it available to change, rather than hardening into a requirement nobody remembers agreeing.

Pace the depth out in the garden with canes or a line, stand at the far end and look back at the house before you settle on the idea.

Seeing the depth on the ground tells you more about what would be shaded than any plan does, and moving a cane is free.

Note which part of the deepened plan would end up furthest from any external wall, and treat that as the place daylight has to be designed for.

The middle of a deep plan is where schemes come unstuck, and naming that spot now is far easier than rescuing it once everything is built.

Write down whether a hall, stair or landing sits in that middle zone, since circulation is often the first thing to go dark and the last thing anyone mentions.

Nobody writes a brief for a hallway, which is exactly why it ends up permanently lit by a bulb.

Ask a designer how the middle of the plan would be lit once the house is deeper, rather than only how the new end of it would be lit.

It is a specific question with a specific answer, and it exposes the weakness of a scheme early.

Only a qualified designer can work out what a deeper plan needs; treat any sketch you make yourself as a question rather than a proposal.

Record whether you would accept a shallower or narrower structure in exchange for keeping daylight in the existing rooms.

This trade sits at the heart of most addition schemes, and deciding your position early stops it being decided for you.

Photograph each affected room from the same spot on more than one occasion, at the same hour, and keep the images together with their dates.

A consistent set of photographs is the only honest record of what you had, and it takes very little effort to make.

Note the weather when each photograph was taken, because a bright overcast sky and a clear low sun give completely different impressions of the same room.

Without the weather noted, your own photographs will mislead you when you look back at them.

Write down which way the rear elevation faces as accurately as you can establish it, and state plainly that it is your own observation rather than a survey.

Orientation frames every daylight discussion, but an owner estimate must be labelled as one so nobody designs from it.

Record where shadow already falls across the garden in the middle of the day and what casts it, whether a fence, a tree or a neighbouring building.

Existing shadow tells you what the new structure would be sitting in, which changes what glazing on that side could deliver.

Note whether a tree, hedge or neighbouring structure has recently appeared or been removed, because your sense of normal may already be out of date.

People compare a proposal against a memory of the house, not against the house as it currently stands.

Write down anything that already bounces light into the affected rooms, such as a pale wall, a light-coloured fence or a glazed structure next door.

Reflected light is easy to lose without noticing, because nobody thinks of a fence as part of the daylight arrangement.

Note where the nearest neighbouring windows sit relative to the proposed structure, and which appear to serve a main room rather than a store or landing.

Raising this yourself, early, is far less painful than hearing it for the first time from the authority or the neighbour.

What weight is given to a neighbouring window is not something owners can settle between themselves; confirm locally what the authority takes into account.

Record whether a neighbour has a conservatory, garden room or glazed door close to the shared boundary.

A glazed structure over the boundary changes the conversation entirely and is often not visible from your own back door.

Write down whether the ground rises or falls towards the boundary, since a difference in level changes how a new roof reads from the other side.

A structure that looks modest from your garden can look considerably taller from a plot that sits lower.

Note whether any opening you are considering would look towards a neighbouring garden or window, and raise privacy with a designer before it is drawn.

Privacy and daylight pull in opposite directions, and that tension is far easier to settle while a sketch can still be redrawn.

Obscured glazing, high-level openings and screening are matters for a qualified designer and for confirmation with the local authority, not for assumption.

Record anything a neighbour has already said to you about light or outlook, with the date, so it is not lost or misremembered later.

An early informal comment often turns out to be the substance of a later objection, in almost the same words.

Note whether a neighbouring property has already been extended and where their structure meets the boundary, without treating it as any indication of what would be acceptable for you.

Nearby work is useful context for a conversation, but it establishes nothing about your own proposal.

Never assume that what stands next door indicates what would be acceptable on your plot; confirm locally what applies to your property.

Decide and record whether daylight from above, from the side, or from both matters more to you, and which you would give up first if something has to go.

Stating the preference before drawings arrive means the trade is made openly rather than settled by whatever is easiest to build.

Note the roof form you have in mind and ask what openings the build-up would allow, rather than assuming a rooflight can go anywhere on it.

The roof shape you like and the openings you want are not independent decisions, though they are usually discussed as if they were.

What a roof can carry and where openings can sit are questions for a qualified designer and engineer, not something to settle from images.

Write down whether a tall opening at the far end of the plan would do more for the dark middle than a wider one at the garden end.

Height often reaches deeper into a plan than width does, but width is what people ask for by default.

Record whether any proposed rooflight would see open sky or mostly face a boundary wall, because those two deliver very different results.

A rooflight boxed in by a neighbouring wall or a parapet can disappoint badly once it is in.

Note which openings you would want to open for air as well as light, and which could be fixed shut without you minding.

Ventilation and daylight get bundled together in conversation and then separated in the order, usually to somebody's surprise.

Write down how much glazing you are actually willing to clean, dress and live behind, not just how much appeals in a photograph.

Large areas of glass bring cleaning, blinds, heat and glare with them, and none of those appear in the image that inspired them.

Gather your dated photographs, window notes and shadow observations into one place before the first design conversation.

A designer can work with an ordinary owner record; they cannot work with a recollection offered halfway through a meeting.

Label each note as either something you have seen or something you have assumed, so nobody treats a guess as a measurement.

Mixed observation and assumption is how an error travels quietly from a first sketch into a drawing package.

Write down the daylight questions you could not answer yourself, so they are asked rather than remembered halfway home.

The questions you leave out of the meeting are the ones that come back as changes later.

Ask what survey information would be needed before any effect on daylight could properly be assessed, and who would arrange it.

Knowing what has to be measured, and by whom, sets expectations before anyone is invested in a scheme.

Any assessment of daylight or overshadowing belongs with a suitably qualified specialist; nothing recorded by an owner substitutes for it.

Note any existing drawings, title plan or previous application documents you hold that show window positions on your property or alongside it.

Old drawings are frequently wrong but still useful, provided everybody knows they are being read as history rather than fact.

Record which daylight outcome would make you rethink the whole scheme, so that test exists before you become attached to a drawing.

A stopping condition written down early is the only one anybody honours once momentum builds.