Extension Roof Form Discussion Preparation Checklist

Stand outside and note what sits on the existing wall between the ground and the first-floor windows, since that band is where a new roof would have to land.

Everything in that band becomes a constraint, and owners can record it accurately without any specialist knowledge.

Write down whether you have a preference between a roof that slopes and one that is essentially flat, and say plainly why you prefer it.

Stating the reason matters more than the preference, because a designer can often satisfy the reason with a different shape.

Note whether a sloping roof would be seen from the garden as a large surface or barely seen at all, given where people actually stand outside.

Roof shape is often argued about in drawings and then invisible in reality, or the reverse, depending on where you view it from.

Record the shape of the existing roof and whether the new roof would sit under it, beside it or independently of it.

The relationship between the two roofs is usually what a designer is really deciding, and owners can describe it in plain terms.

Consider whether you would rather see an overhanging edge with a gutter, or a raised edge that hides the roof surface behind it.

This choice changes the whole character of an extension from outside and is worth having an opinion on before drawings arrive.

Ask what would limit how high the new roof could go at this particular house, and record the answer as a list of separate constraints.

Height is limited by several unrelated things at once, and separating them helps you understand which are negotiable.

What height is acceptable at your property can only be confirmed locally; nothing here indicates what would be permitted or achievable.

Write down which room each upstairs window above the proposed extension belongs to, and how that room is used day to day.

A bedroom window and a landing window carry very different weight when a roof has to pass beneath them.

Note roughly how much bare wall sits between the top of the ground-floor opening and the bottom of the window above it.

That band of wall is the space a roof and its junction have to fit into, and it is often much tighter than owners assume.

Consider whether a new roof arriving close to an upstairs window would change the light or the outlook from that room.

A pale roof surface immediately below a window changes how a room feels, and it is rarely mentioned until it is built.

Ask whether the upstairs window could still be opened and used normally once the new roof is beneath it.

Some arrangements make a window awkward to open or clean, and that is easier to raise now than to remedy later.

Whether an existing window can remain usable, and any escape or ventilation implications, must be confirmed with a qualified professional.

Note whether a low roof beneath a window would create a new way of reaching that window from outside, and write it down as a security question.

Owners think about this after completion far more often than before, when a design response would have been straightforward.

List any vent, flue terminal or extract outlet on the wall above the proposed roof, and photograph each one where it sits.

Terminals above a new roof raise questions about position and access that belong with a qualified professional.

Vents, flues and combustion terminals near a proposed roof are for a suitably qualified professional to deal with; nothing here indicates what is acceptable.

Decide whether you want a level ceiling throughout the new space or a ceiling that follows the roof and rises towards one side.

This is one of the few genuinely irreversible decisions in an extension, and it is often left to be resolved on a drawing.

Note where the lowest part of a sloping ceiling would fall, and what you intend to put underneath it.

Low ceiling edges are fine over a worktop or a bench and difficult over a dining table or a door.

Ask whether any beams, ties or supports would be visible in the finished ceiling, and record what you are told about their position.

Visible structure can be an asset or an intrusion, but it should never be a surprise revealed at first fix.

What structure a roof needs, and where it would sit, is for a suitably qualified structural professional to determine.

Ask what space a chosen roof shape leaves for lighting, ductwork and insulation above the finished ceiling.

Owners choose a ceiling and then discover the lights, extract or heating they wanted has nowhere to sit.

Consider what happens where the new ceiling meets the existing one, and whether you would accept a visible change in level at that line.

The two ceilings are almost never the same height, and how they meet is one of the first things a visitor sees.

Ask how a chosen roof form is likely to behave in heavy rain, since the sound overhead is part of living in the room.

This is a genuine daily experience question, and it varies with construction rather than with shape alone.

Go upstairs and write down which of your own windows would look directly down onto the new roof surface.

Owners choose a covering for how it performs and then look at it every morning from a bedroom window.

Note whether any neighbouring upper window would look down onto the proposed roof, and from roughly what angle.

Roofs that face a neighbour are worth thinking about early, because the appearance question can arise in conversation with them.

Consider what would collect on a low roof given the trees and gutters around it, and whether you could see it building up.

Leaves and debris on a roof you can see are a recurring irritation, and shape influences where they gather.

Note that anything set into the roof would also be seen from above, and decide whether that affects where you want it.

Positions chosen purely for daylight sometimes look arbitrary from the window overlooking them.

Ask whether anything is expected to sit on the new roof, and where it would be positioned relative to the windows above.

Equipment on a flat roof is often located late in the process and ends up directly in the view.

What may be placed on a roof, and whether the roof can carry it, must be confirmed with a suitably qualified professional.

Consider how the roof surface is likely to look once it has weathered, and ask what changes in appearance are normal for the options discussed.

Surfaces looked down on tend to show their age more openly than the same material seen from ground level.

Note which edge of the proposed roof would come closest to a boundary, and what stands on the other side of that line.

Whether the neighbouring side is a garden, a driveway or a blank wall changes the whole conversation.

Consider whether the roof sloping towards or away from the boundary would make any practical difference to the neighbouring side.

Slope direction affects both appearance and where water and snow would go, so it is worth an early opinion.

Ask whether any part of the roof, including its edge, gutter or overhang, would sit above land that is not yours.

Overhanging elements are a common cause of neighbour objection and are easy to design out early.

Whether anything may oversail a boundary is a legal and local matter; confirm it with the appropriate authority or adviser, not from a checklist.

Note at what times of day a taller roof might fall across a neighbouring window or seating area, and raise that as a question rather than as a conclusion.

Raising it before the design is drawn gives a designer room to respond, rather than having to defend a shape already committed to.

Effects on light reaching a neighbouring property are assessed by a qualified professional and the local authority, never concluded by an owner.

Stand where a neighbour would stand and write down what they would actually see of the new roof from there.

This takes minutes and produces a far more honest picture than looking at an elevation drawing.

Confirm locally what the authority needs to know about roof height near a boundary, and note the name of whoever answers.

What a neighbour was told about their own roof is not evidence about yours, and the only dependable answer comes from asking directly.

Nothing about roof height near a boundary can be settled from a general source; put it to the responsible body for your area and record their answer.

Note where the existing roof drains today, tracing each downpipe to where it disappears into the ground.

A new roof usually interrupts this arrangement, and knowing the existing route is the starting point for any conversation.

Ask whether the shape being discussed would create a valley or a concealed gutter, and what looking after it would involve.

Concealed drainage is often the elegant answer visually and the demanding one in maintenance, so both sides should be stated.

How a roof is drained and where water is discharged must be settled by a qualified professional and confirmed against local requirements.

Ask whether the new roof would send additional water into an existing outlet, and whether that arrangement can take it.

Adding roof area to an existing drainage route is a specific question, and owners rarely think to raise it.

Note which trees overhang the proposed roof, and ask which parts of the arrangement would be most likely to block.

Blockage points on a roof you cannot easily reach become a recurring problem rather than a one-off.

Ask what would happen if a gutter or outlet on the new roof blocked, and where the water would go in that case.

The honest answer to this question influences roof form more than most owners realise.

How a roof behaves when drainage blocks is a technical matter for a qualified professional; nothing here indicates what is acceptable.

Consider how anyone would reach the junction between old and new roofs to clear or check it once the extension is finished.

Access for maintenance is decided by roof form whether or not anybody discusses it at the time.

Note that the roof shape decides what glazing is possible overhead, and write down whether daylight from above matters to you.

Owners often choose a roof and then ask for rooflights that the chosen form does not comfortably allow.

Ask how the roof form affects the height available at the opening between the extension and the existing house.

The head height at that junction is one of the strongest impressions of an extension, and roof shape drives it.

Consider whether the roof form makes the extension read as taller or lower from the garden, and which you would prefer.

Perceived height is what neighbours and visitors respond to, and it is not the same as measured height.

Ask what depth the chosen roof build-up needs, and what that does to the height available inside the room.

Roof build-ups take real space, and owners commonly plan the ceiling before knowing what sits above it.

Roof build-ups, insulation and ventilation of a roof void must be specified by a qualified professional for your particular construction.

Write down which roof questions you want answered before the design goes further, and which you are content to leave open.

Naming the open questions is more useful than pretending everything is settled, and it keeps later changes deliberate.

Record the reasons behind the roof form you end up favouring, not just the shape, so the reasoning survives later changes.

When a roof has to change for a technical reason, the recorded intent is what lets a designer protect what mattered.