A step on a floor plan is a small mark. In daily life it decides how you carry supper outside, where the garden begins and whether two spaces feel connected at all.

That is what makes Pend’s Newhaven extension interesting. At this Georgian townhouse in Edinburgh, the garden falls away from the house and the lower ground floor was partly submerged. An old conservatory stood between the kitchen and the garden. The problem was not simply a shortage of glass.

Pend replaced that awkward arrangement with a new volume that works with the levels. A stepped profile brings eastern and southern light to a home office; a winding garden path negotiates the changing ground. The house and landscape are considered together.

When discussing an extension, it is easy to spend the meeting looking down at a floor plan. Ask to see a section as well: a drawing that slices through the building and shows floors, ceilings, ground and openings from the side.

It can make a difficult site much easier to understand. Where will you be standing when you look outside? Does the garden rise above the room or fall below it? Where do the steps start, and what will you see before reaching them?

These questions are useful even for a modest rear addition. An extra metre of floor area is not the only way a project can improve a room. The position of an opening or a change in the route may make the existing space more enjoyable.

The existing curved stone gable gives Pend a shape to work with. A circular window and rooflight echo it, while long-format brick relates to the mixed brickwork of the boundary wall.

This is an appealing way to make a new part belong without pretending it is old. For another house, the starting point might be a repeated arch, the tone of local brick or the proportions of an existing window. It need not mean reproducing every historic detail.

Before ordering materials, look at samples against the actual building in different light. A finish chosen in isolation can be much louder when it covers an entire wall. A restrained palette gives the older fabric room to remain interesting.

Do not leave the first few metres outside the new doors as a problem for later. They are part of how the extension will work.

Think through an ordinary journey with a tray, a watering can or a child beside you. Ask where you can stop, turn and put something down. If step-free access is a priority, make that explicit at the outset; an attractive stepped garden is not automatically an accessible one.

On a sloping site, discuss drainage, any retaining work and the relationship between outside ground and the building with the design team. A winding path may make a route feel natural, but it does not remove the need to resolve those technical details.

No build cost or floor area is given on Pend’s project page. This is a design lesson, not a price per square metre to apply to another extension.

The useful commission for an architect is more precise than “make it open-plan”. Describe where the house feels awkward now, which rooms need daylight and how you want to move between them and the garden. Ask the drawings to answer those problems.

Newhaven’s reward is a more coherent sequence of spaces. More glass might have been the obvious request. A better relationship with the ground was the more interesting answer.