To calculate the initial budget of a renovation, define the scope room by room, separate wet areas from dry rooms, estimate construction, joinery and furniture as three distinct blocks, add indirect costs such as debris removal, reports and temporary housing, and set aside 10% to 15% for contingencies.
Every renovation budget begins before a design exists — which is precisely why it overruns. A simple initial estimating method avoids the gap between expectation and reality.
Step 1 — Scope room by room
List each room and classify the intervention: keep, update finishes or rebuild entirely. That table is the basis of everything that follows.
Step 2 — Separate the wet areas
Bathrooms, kitchen and utility room concentrate services, waterproofing and surfaces. As the number of wet areas touched grows, cost grows disproportionately to floor area.
Step 3 — Three cost blocks
- Construction: demolition, masonry, services, surfaces, painting, window frames.
- Joinery and stone: usually the single largest item in an interiors renovation.
- Loose furniture, decorative lighting, curtains and soft furnishings.
Separating the three blocks allows the scope to be adjusted without losing the result — they can be phased over time.
Step 4 — Indirect costs
- Debris, skips and protection of communal areas.
- Technical reports, building fees and approvals.
- Temporary housing and furniture storage.
- Design and site-supervision fees.
Step 5 — Contingency and payment schedule
Set aside 10% to 15% for contingencies and spread payments across a physical-financial schedule aligned with the construction stages. A renovation paid in predictable blocks does not stall halfway.
A budget is not a number: it is a document that evolves from the preliminary study to the finishes schedule.
With the construction documents and specifications schedule in hand, you can request comparable quotes from three contractors — and only then does the number become a commitment.
