Estimating your renovation budget: a practical step‑by‑step guide

Why your renovation budget is crucial in a buy or rent decision

A renovation budget is often underestimated, yet it can easily reach 5–30% of the property price. Whether you’re wondering if you should buy or rent, the renovation cost radically changes the true cost of owning and the time needed to break even versus renting.

On a simulator like buy-or-rent.net, the montant_travaux (renovation amount) parameter lets you include these costs in the full calculation: mortgage payments, available cash, alternative investment returns, etc. Ignoring it means your buy or rent comparison is simply wrong.

Step 1: understand the main categories of renovation work

To estimate your renovation budget properly, start by classifying the works:

• Light refresh: paint, basic flooring, minor fixes (typically €80–250/m²).
• Interior renovation: kitchen, bathroom, partial electrical work (€250–800/m²).
• Heavy renovation: layout changes, full rewiring, plumbing, windows (€800–1,500/m²).
• Energy / efficiency upgrade: insulation, heating system, high‑performance windows (often an extra €300–700/m² depending on scope).

These are 2024 national averages for licensed contractors, VAT included. In major metro areas (e.g. Paris, London), add roughly 10–20% versus smaller cities.

Step 2: calculate a basic renovation budget per m²

Let’s use concrete examples to structure your renovation budget before you decide to buy or rent.

Example 1: 60 m² flat, light refresh

• Painting walls/ceilings: €40/m² of floor area ≈ €2,400.
• New laminate flooring in entry/living/bedrooms: €35/m² installed × 45 m² ≈ €1,575.
• Minor electrical updates (sockets, lighting): ≈ €800.

Estimated renovation cost: about €4,800, i.e. €80/m² of living area.

If the property price is €220,000, the renovation cost already adds just over 2% of the purchase price. In a buy or rent simulator, this €4,800 must be entered in the montant_travaux field.

Example 2: 100 m² house with heavy renovation

• Full electrical rewiring: €120/m² × 100 m² = €12,000.
• Plumbing + new bathroom: €8,000.
• Mid‑range fitted kitchen: €9,000.
• Double‑glazed windows (8 units @ €750): €6,000.
• Loft insulation: €50/m² × 60 m² loft = €3,000.
• Painting + new floors: €120/m² × 100 m² = €12,000.

Total renovation cost ≈ €50,000, or €500/m². On a house bought for €260,000, your global budget jumps to €310,000 before notary and agency fees. Here again, montant_travaux becomes a key variable to understand whether it makes more sense, for you, to buy or rent.

Step 3: don’t forget the hidden renovation costs

The renovation budget is not just the main contractor quote. To avoid nasty surprises, systematically add:

• Architect / project manager fees: typically 8–12% of the pre‑tax works cost for a full service.
• Technical surveys (structural, energy, asbestos, lead): €500–2,000 depending on the project.
• Demolition and waste removal: €30–80/m² of affected area.
• Access constraints in buildings (no lift, narrow staircase): +5–15% on some trades.
• Planning permission / prior declaration: admin fees + professional fees (€300–1,500).
• Furniture and appliances if starting from scratch: often €3,000–10,000.

A prudent rule of thumb: add 10–15% contingency on top of the initial renovation cost. A €40,000 quote becomes a realistic budget of €44,000–46,000.

Step 4: how renovation costs affect your financing

Your renovation budget has a direct impact on how you finance the project and therefore on the buy or rent comparison. You typically have three options:

1. Include renovation in the mortgage

You finance purchase + renovation in a single home loan. Example:

• Purchase price (flat): €220,000.
• Renovation cost: €30,000.
• Notary fees (older property, 7.5%): ≈ €16,500 (on the price only).
• Agency fees: 4% ≈ €8,800.

Total financed amount ≈ €275,000. With a loan rate of 3.6% over 25 years and borrower insurance at 0.30%, you get roughly:

• Monthly mortgage (excluding insurance): ≈ €1,390.
• Insurance premium: ≈ €69/month.
• Total monthly payment ≈ €1,460.

Without the €30,000 renovation (i.e. €245,000 financed), the total monthly payment would be around €1,300. Your renovation budget therefore raises your monthly outgoings by roughly €160.

2. Pay for renovation from savings

You use cash to cover the €30,000 renovation, but you give up the investment rate you could have earned by keeping that money invested (say 4%/year in diversified ETFs).

After 10 years:

• €30,000 invested at 4%/year ≈ €44,400 (compounded).
• €30,000 spent on renovation = €0 financial capital, but a more valuable and comfortable home.

In a buy or rent calculator, this trade‑off between montant_travaux and investment return is exactly what gets modelled.

3. Separate renovation loan

You can also take a dedicated renovation loan over 10 years, usually at a slightly higher rate than the main mortgage. Simplified example:

• Main mortgage: €245,000 at 3.6% over 25 years.
• Renovation loan: €30,000 at 4.5% over 10 years.

The renovation loan payment will be about €310/month for 10 years, on top of your main mortgage. Again, the renovation cost heavily affects your disposable income and thus your buy or rent decision.

Step 5: energy renovation, DPE and property value

Energy‑efficiency works are a special case in your renovation budget, but critical for buy or rent analysis, especially in Europe where energy labels (DPE, EPC) drive both comfort and resale value.

Example: upgrading from an F to a C energy rating

• Loft insulation: €3,000.
• Internal wall insulation: €12,000.
• Switching gas boiler to heat pump: €12,000.
• High‑performance windows: €8,000.

Total energy renovation cost ≈ €35,000.

Assume this leads to:

• Heating/electricity savings: €1,500/year.
• Higher resale value: estimated +€20,000.

Over 10 years, energy savings alone total €15,000. Combined with the potential value uplift, you recoup a large share of the renovation budget. But this only holds if you stay long enough in the property – a central question when you compare buy or rent scenarios.

Step 6: compare buy or rent with and without renovation

To see the impact of the renovation budget, let’s contrast two simplified 15‑year scenarios.

Scenario A: you buy and renovate

• Purchase price: €260,000.
• Renovation cost: €40,000.
• Notary fees (older property, 7.5% on €260,000): €19,500.
• Agency fees: €10,000.
• Property tax: €1,200/year, increasing 2%/year (property tax revaluation).

Total financed amount: €329,500 (ignoring down payment) at 3.6% over 25 years, insurance 0.30%:

• Total monthly payment ≈ €1,750.
• Average annual property tax over 15 years ≈ €1,400.

Over 15 years, you pay roughly €315,000 in mortgage payments + €21,000 in property tax. In return, you own a renovated property.

Scenario B: you rent and invest the renovation money

• Initial rent: €1,150/month, indexed to inflation/IRL at +2%/year.
• No renovation budget, no property tax.
• You invest €40,000 (the renovation budget you did not spend) at 4%/year.

After 15 years:

• Financial capital ≈ €72,000 (from €40,000 invested at 4%).
• Total rent paid ≈ €250,000 (including yearly increases).

Depending on property price trends, interest rates and inflation, either scenario can be better. That’s why there is no universal answer to whether you should buy or rent: it depends on your situation, your renovation plans and your assumptions about the future.

Step 7: a practical method to estimate your renovation budget

To avoid underestimating your renovation cost, follow this step‑by‑step checklist.

1. Detailed viewing and measurements

• Measure each room (length × width) to get accurate areas.
• List everything to be replaced: flooring, paint, windows, kitchen, bathroom, heating, electrics.
• Take photos of key technical points (fuse box, radiators, windows, ceilings).

2. First estimate using €/m² ranges

• Simple refresh: €100–200/m².
• Partial renovation: €300–600/m².
• Heavy renovation: €800–1,500/m².

Apply low and high values to the living area to get a renovation budget range. For instance, 70 m² × €400–700/m² = €28,000–49,000.

3. Get multiple detailed quotes

• Ask at least 2–3 contractors per major trade (electrics, plumbing, windows).
• Check that VAT, labour, materials and waste removal are all included.
• Focus your negotiations on the most expensive items (kitchen, bathroom, windows).

4. Add contingency and account for inflation

Between signing the purchase agreement and starting works, prices can rise (inflation, materials, labour). Add:

• +10–15% for technical surprises.
• +5–10% if works will start in more than 12 months.

The final figure is what you should input as montant_travaux in the buy or rent simulator for a realistic comparison.

Step 8: how renovation costs shape your buy or rent strategy

Your renovation budget acts as a lever on several key variables:

• Minimum holding period needed to amortise notary fees, agency fees and renovation works.
• Implied rental yield if you later decide to rent out the property.
• Borrowing capacity, as higher monthly payments increase your debt ratio.
• Trade‑off with financial investments: the more you spend on bricks, the less you invest at a given return rate.

A large renovation cost can make buying unattractive if you plan to move again within 3–5 years. Conversely, over 15–20 years, those works can be fully amortised, especially if they improve the energy rating and resale value.

Conclusion: renovation budget, a critical parameter to simulate

Estimating your renovation budget correctly is essential to compare buy or rent options objectively. The montant_travaux changes:

• the total cost of the operation (purchase + renovation + notary + agency fees),
• your monthly mortgage outgoings and savings capacity,
• the optimal holding period before selling,
• the balance between property and financial investments.

There is no one‑size‑fits‑all answer to whether you should buy or rent: it depends on your personal situation, renovation plans, time horizon and risk profile. All numbers and examples here are general illustrations, not personalised financial advice.

To go further, test different scenarios (with or without renovation, higher or lower renovation budget, different investment returns) using the dedicated simulator: Simulate your situation on buy-or-rent.net.