Adding a second home: agree how independently it needs to work

Write two versions of the brief

Ask the people who would live in each home to write a short description of an ordinary weekday. Do this separately first. Include working, cooking, visitors, laundry and time alone. You may discover that everybody likes the idea of living nearby but has a different understanding of what nearby means.

For a hypothetical parent moving onto an adult child's property, sharing a garden might sound lovely. Depending on the main house for laundry could feel quite different. I would discuss those activities individually rather than putting everything under the heading of family living.

• What would you like to do together?
• What should each household be able to do without arranging it with the other?
• Where do the two descriptions disagree?

Give shared spaces an everyday test

For each proposed shared facility, ask what happens when both households want it at once. A common outdoor table may be fine until one household invites friends over while the other wants a quiet evening. That does not necessarily mean building two of everything. It does mean deciding what matters enough to provide separately.

I would also ask who looks after the shared things. If the new home relies on somebody else keeping a gate unlocked, moving equipment or clearing a storage area, show that dependency in the brief. A convenient arrangement should be understood by everyone expected to make it work.

• Who uses it, and when?
• Who cleans, stores or maintains it?
• What alternative is available when it is occupied?

Test one believable change

You cannot design for every possible future. Choose one change that is realistic enough to influence today's decisions. Perhaps the owners might move into the smaller home, or another family member could become its occupant. Ask whether the same arrangement would still feel comfortable.

In the hypothetical parent-and-child example, a shared laundry might work because both households already spend time together. Would the proposal still make sense if they preferred more independence later? Ask the designer to test a separate laundry location now, even if you decide not to include it. That comparison makes the compromise visible.

Keep the wish list separate from site evidence

A clear household brief does not establish what the property can accommodate. MBIE's site guidance identifies title restrictions, council information and accurate boundary information as useful parts of evaluating a site. Covenants or easements can restrict its use. I would ask the appropriate advisers to explain those matters alongside the design investigation.

Take the brief to your designer and ask which assumptions need planning, surveying, engineering or legal advice before you develop the preferred option. Ask for the current approval requirements for your particular proposal, rather than assuming another property's outcome applies.

Dean's published feedback about his extension and infill projects highlights being listened to during design. That is a useful quality to look for here: the team needs to understand the households' intentions before translating them into rooms.

• Which parts of our brief appear achievable?
• Which depend on information we do not yet have?
• What should we investigate before choosing a layout?

Bring a short agreement to the first conversation

Put the intended occupants, essential independent facilities, agreed shared spaces and one future scenario on a single page. Leave disagreements visible. They are useful design questions, not something you need to solve before contacting a designer.

Bring that page, your address and any existing plans to an initial conversation. We can discuss the next investigations and how to turn your expectations into a brief for both homes.