Pre-construction Beginner

Building Project Planning: Define Your House Step by Step

10 min read

Why You Should Frame Your Project First

Building a house is probably the most significant project of your lifetime. Yet many future homeowners dive in without taking the time to define precisely what they want. The result: costly back-and-forth with the architect, mid-build changes and a budget that spirals out of control.

Framing your project upfront saves time, money and peace of mind.

THE 6 AXES OF YOUR PROJECT Floor area (m²) Budget (€) Room count Single / Two storey Energy (RE2020) Archi. style Low High Adjust each slider to your priorities to shape your ideal project
flowchart TD A{Single storey or multi-storey?} A --> B{Large plot > 500 m²?} B -->|Yes| C{Reduced mobility / seniors?} B -->|No| D{Tight budget?} C -->|Yes| E[SINGLE STOREY] C -->|No| D D -->|Yes| F[GROUND + ATTIC] D -->|No| G{Need > 120 m² floor area?} G -->|Yes| H[TWO STOREYS] G -->|No| E style A fill:#0F4C81,stroke:#0F4C81,color:#fff style B fill:#FDFCF9,stroke:#C67A3C,color:#0F4C81 style C fill:#FDFCF9,stroke:#C67A3C,color:#0F4C81 style D fill:#FDFCF9,stroke:#C67A3C,color:#0F4C81 style G fill:#FDFCF9,stroke:#C67A3C,color:#0F4C81 style E fill:#56C6A9,stroke:#56C6A9,color:#fff style H fill:#F58220,stroke:#F58220,color:#fff style F fill:#FDB813,stroke:#FDB813,color:#fff

Step 1: Analyse Your Family’s Needs

Start by asking the right questions. How many people will live in the house? Are you planning to expand the family? Do you need a home office, a master suite, a guest bedroom?

Question Why it matters
Current number of occupants Size the living areas
Family evolution over 5-10 years Anticipate extra bedrooms
Regular remote work? Plan a sound-insulated office
Reduced mobility needs? Accessibility, single-storey, wider doors
Pets? Garden access, utility room, storage

💡 Tip — Do this exercise as a family. Every household member should be able to express their needs. Write everything down, even what seems minor — regrets often hide in the details.

Step 2: Define the Floor Area and Room Count

The habitable floor area is a key cost driver. Common benchmarks are:

  • Couple with no children: 70 to 90 m²
  • Family with 1-2 children: 90 to 120 m²
  • Family with 3+ children: 120 to 160 m²
  • House with master suite and office: 140 to 180 m²

Don’t forget ancillary spaces: garage (15-30 m²), pantry (4-8 m²), utility room (4-6 m²). They may not always count towards habitable area but they do affect the budget.

Step 3: Choose Your Architectural Style

Your house style depends on personal taste, but also on local planning regulations. Here are the main families:

  • Contemporary: clean lines, flat roof, large glazing
  • Traditional: pitched roof, render, regional tiles
  • Bioclimatic: south-facing, compact, natural materials
  • Timber frame: fast construction, excellent thermal performance
  • Regional vernacular: respecting local architectural codes

⚠️ Warning — Some municipalities impose strict constraints: render colours, roof pitch, roofing materials. Check the local plan before falling in love with a style.

Step 4: Single Storey or Two Storeys?

This choice affects budget, comfort and the building footprint.

Criterion Single storey Two storeys
Footprint Large (wide plot needed) Reduced
Cost per m² Slightly higher (foundations, roof) Slightly lower
Accessibility Ideal for reduced mobility Stairs required
Privacy All rooms on one level Natural day/night separation
Heating Easier to heat evenly Upper floor warmer, ground floor cooler

Step 5: Set a Realistic Target Budget

Your budget must cover all cost items, not just the build:

  • Land + legal fees (7-8 %)
  • Construction (house + site works)
  • Professional fees (architect, engineers)
  • Utility connections (water, electricity, drainage)
  • External works (fencing, patio, planting)
  • Fitted kitchen, wardrobes
  • Contingency (8-10 % of total)

💡 Tip — Start from your borrowing capacity (check with your bank or mortgage broker) and deduct the land cost. What remains is your construction budget. Not the other way around.

A Method for Prioritising

Classify each item in your programme into three columns:

Essential Desirable Optional
4 bedrooms Master suite Swimming pool
Double garage Adjoining pantry Advanced home automation
Garden > 300 m² Covered terrace Bioclimatic pergola

This grid will serve as your negotiation baseline with your builder or architect. If the budget is tight, you’ll know immediately what can be deferred.

Project Definition Checklist

  • Every household member’s needs listed
  • Target habitable area defined
  • Number and purpose of each room specified
  • Architectural style chosen (and compatible with local plan)
  • Single-storey / two-storey decision made
  • Total budget calculated (land + build + extras)
  • Priorities ranked (essential / desirable / optional)
  • Borrowing capacity confirmed with the bank

Key Takeaway

Defining your building project means laying solid foundations — figuratively speaking. The clearer and more structured your brief, the better professionals can propose solutions that fit your timeline and budget. Don’t skip this step.