House size is the number decided earliest and on the least information. Somebody said that 150 square metres suits a family of four, and the number sticks. Yet square metres say nothing about whether a house works: the same family can live well in 130 and feel cramped in 180 if the layout is poor.

Below are eight questions that reach a number from how a family actually lives. Size drives the build budget and the running costs, and both are covered here.

1. Start from a list of rooms, not a number

Write down rooms rather than square metres: bedrooms, bathrooms, a study or not, a sauna, a utility room, a technical room, storage by the hall. The architect turns that list into a layout, and the layout produces the number. Measuring the rooms in your current home that feel right, and those that do not, sharpens it.

Starting from a number usually ends with a room dropped for budget reasons — most often the storage or technical room, whose absence is noticed in the first year. The full checklist is in our article on the house floor plan.

2. How many bedrooms are actually needed

Bedrooms are the most direct driver of floor area: one room for each person who sleeps in the house, plus one if guests come regularly or somebody works from home. Two children who share a room now will want separate rooms in ten years; two who want separate rooms now may leave home in five.

So plan rooms whose purpose can change: a child’s room has to become a study, and a study a guest room, without removing walls — which means rooms of roughly equal size, each with a window and wardrobe space.

3. Bathrooms and the morning rush

Bathrooms affect area and price more than any room except the kitchen, and the calculation is in people, not square metres: how many get ready at the same time. For a family of four, two bathrooms, or a bathroom plus a separate WC, is the usual minimum.

This is also where size should not be saved: adding one later means changing the plumbing and the ventilation, which is effectively a rebuild. The ventilation of these rooms is covered in our article on ventilation in a detached house.

4. Storage: the square metres nobody counts

The technical room, hall storage, a wardrobe, a cleaning cupboard and somewhere for seasonal items add up to a real share of the floor area. Unplanned, they end up in the living room, so list what needs a place and check each has one on the drawing.

Storage can also sit outside the house: an outbuilding, carport or garage gains space more cheaply than living area, needing neither the same insulation nor finishing. The options are in our article on garage construction, a carport or an outbuilding.

5. The home office and how working from home changes the space

One person working from home a couple of days a week manages with a corner of the living room; two people taking calls every day need two rooms with doors. That is around twenty square metres that must come from somewhere, so if the calls cannot share a room, the study belongs in the layout rather than in hope. Room flexibility is covered in our article on house designs: standard or custom.

6. What square metres cost in the budget

A larger house costs more, but not linearly. The foundation, roof, kitchen, bathrooms, technical systems and connections are largely fixed costs, so the price per square metre of a larger house tends to be lower even though the total is higher. That logic is explained in our article on the price per square metre of a house.

Two parts of our own budgets show it: good interior finishing starts from 400 €/m² + VAT and comes down per square metre on larger houses, while in-house electrical work starts from 26 000 € + VAT and depends more on the technical solution than the area. The exact figure for your house comes in a more precise offer after a consultation.

7. Running costs: what each square metre costs a year

Every square metre also costs after you move in: heating, ventilation, lighting, cleaning, maintenance. Per square metre the heating cost is small in a well insulated house, but not zero, and over thirty years it adds up. The solution matters as much as the area — an air-water heat pump, ground source heating and solar panels can be combined, and cooling added where wanted. See our article on an energy class A house; comparative statistics on dwellings are published by Statistics Estonia.

8. Can the house be extended later

Yes, if it has been allowed for. Extending means a new design, a new permit and a new build, and an extended square metre usually costs more than one built at the start; the plot conditions, above all the permitted footprint, may rule it out. For scale, design work with us takes one to three months and the permit two to three months in practice.

The two practical hedges are flexible rooms and an outbuilding or second phase marked on the site plan from the start. The opposite mistake is building in reserve: rooms nobody uses cost money to build, heat and clean, and a guest room slept in twice a year could be a daily study.

Living room and kitchen: where square metres can be saved

When the number comes out above the budget, the layout helps more than the floor area. An open main space combining living room, dining area and kitchen feels larger than three separate rooms of the same total area, especially with daylight from two directions. Ceiling height works the same way and costs less than adding area, as our article on large windows and high ceilings shows.

House size and the plot

The plot has a vote too. A detailed plan or the design conditions may restrict the footprint, the building area and the number of storeys, whatever the family wants, and on a small plot the same living area may require two storeys. The garden is the second factor: the larger the house, the smaller what is left of it. See our article on a single storey house or two storey.

How to compare houses whose floor areas differ

Houses are measured differently, so always ask which area is quoted — heated, net internal or gross — and whether a terrace, garage or technical room is counted. Two figures twenty square metres apart may describe the same house, so compare the lists of rooms instead.

Summary

Bedrooms, bathrooms, a home office, storage and the technical room set the area; the rest is the work of the layout. Build the house size the family actually uses and put the difference into quality.

If you would like to know what suits your family, send us your own list of rooms through the contact page and we will turn it into a concept design and tell you how many square metres it comes to.