Boundaries are logistics, not feelings
Families talk about boundaries as if they were emotional skills. In shared households they're mostly logistics: who enters which space, who cooks when, whose guests, whose noise, whose schedule. Vague goodwill (“we'll figure it out”) works for a fortnight. After that, every unspoken assumption becomes a small recurring negotiation, and small recurring negotiations are what wear families down.
The four boundaries that matter most
1. Doors
Agree explicitly which spaces are knock-first, which are invitation-only, and which are genuinely shared. If one generation has a separate annexe or converted floor, treat its front door like a neighbour's: nobody lets themselves in. This single rule prevents more friction than any other.
2. Meals
Eating together every night sounds warm and becomes an obligation. Most successful households land on a rhythm — two or three shared meals a week, the rest independent — and say it out loud so nobody is silently waiting for anybody.
3. Childcare and help
If grandparents help with children, agree the shape of it: which days, which hours, and how either side can decline without a scene. “Whenever you need” sounds generous and quietly becomes unlimited. The same applies in reverse to lifts, errands and care tasks.
4. Money edges
Boundaries fail fastest where money is fuzzy. Who buys shared groceries, who pays when the boiler or furnace dies, what counts as a household expense versus a personal one. Put the recurring ones in a simple written split and revisit it yearly — the site's guide to splitting costs fairly covers the frameworks.
Make the review meeting boring and regular
The best tool available is unglamorous: a short household check-in every month or two, in the calendar, whether or not anything is wrong. When a review is routine, raising an irritation is administration. When there's no routine, raising it is a confrontation — so people don't, until it's big.
Renegotiate when life changes
Boundaries set on moving day are drawn for the people you were on moving day. A new baby, retirement, a health change, a new partner — each redraws the map. Expect to renegotiate at every life event, and say so at the start: “whatever we agree now, we'll redo when things change” makes the first agreement easier to sign up to.
If the friction is about the building rather than the people, layout changes do more than willpower — see privacy by design. And if boundaries keep failing despite honest effort, read when it isn't working.