BienCheck pillar guide
Buying a house without nasty surprises
Written by Mathieu Delranc
Founder of BienCheck · View author profile
A house is the opposite of an apartment. More freedom, more space, but everything is on you. The roof, the boiler, the septic tank, the garden, the gate, the insurance. When something fails, you pay, no vote, no shared bill.
This guide covers everything we'd check before signing for a house, from the foundations to the local plan, including the invisible easements no seller volunteers. The point: spot the real drama before it costs you €40,000 after signing.
What makes a house different
In a house, you're alone at the wheel. No syndic to spread the cost of a roof, no HOA reserve fund. When the roof leaks, it's 100 % yours. When the boiler dies mid-winter, you make the calls and you pay the invoice.
You also decide. Want to extend, plant, replace the gate, swap the heating? Your call, subject to the local plan and any easements. That freedom comes at a price, in attention, in budget, in skills you need to acquire or outsource.
The right house is the one you've inspected on the expensive items before signing, and whose real ten-year cost you've sized up properly.
Structure, roof, framework
This is the line that can wipe out a good deal. A full roof redo runs €12,000 to €35,000 depending on surface and complexity. A framework eaten by woodworm costs more again if structure needs treating and reinforcing.
- Tiles and ridge. Shifted tiles, heavy moss, loose ridge, those are warning signs. A partial redo shows. A full one shows too.
- Framework. Go up into the loft. Look for dark stains (damp), small holes (insects), sagging. A healthy framework is pale, straight, no fine dust.
- Facades. Short horizontal cracks: nothing. Vertical or stair-pattern cracks crossing a lintel: structural movement, get it surveyed.
- Load-bearing walls and floors. Ask for the plans. Past renovation that touched a load-bearing wall without a structural study is a risk.
- Cellar and crawl space. Ventilation, damp marks, cracks, standing water. A musty cellar means trouble.
Damp, foundations, ground
Damp is the number one disease in houses. It comes from the ground (rising damp), from the roof (leaks), or from poorly extracted indoor water vapour (condensation). Each cause needs a different fix and each one is expensive.
Clay shrinkage is another underrated risk. In exposed zones, repeated droughts move foundations and crack walls. It's one of the most expensive claims in the market. Always check Géorisques for the address.
Drainage and utility connections
If the house is on mains drainage, easy. If it's on individual treatment (septic tank, micro-station), it's a whole file. The SPANC report tells you whether the install is compliant. If it isn't, you have one year after sale to bring it up to spec, and that runs €6,000 to €15,000.
Check water, electricity, gas and fibre connections. A house with no fibre in an eligible area catches up fast. A house with no fibre in a non-eligible area can cost you in mobile work setup or comfort.
Energy and EPC in a house
In a house, the EPC is critical. A poorly insulated F or G can cost €3,500 to €5,500 a year to heat, more depending on size and region. Works to move from F to D (external insulation, windows, boiler, ventilation) sit between €25,000 and €70,000.
MaPrimeRénov', the zero-rate eco-loan, energy savings certificates and some local grants can cover 30 to 60 % of the project depending on income. Check before locking your budget.
Land, garden, easements
Walk the whole plot. Check the boundaries with markers or a recent cadastral plan. A neighbour who's been encroaching for 20 years can claim adverse possession. Better to know before signing.
Read the title deed. A right of way, a view easement, a buried utility easement can seriously reduce your rights. A well, a pond, a protected tree create constraints. The notary lists them, you still need to read them.
Local plan, neighbours, projects
Visit the town hall or browse the local plan online. Future development zones around your house can change everything in ten years: an estate, a roundabout, a logistics warehouse, a quarry.
Ask for the planning certificate. It lists the rules for your plot: building footprint, max height, imposed colours, set-back distances. If you dream of an extension, this document tells you whether it's possible.
Pricing it properly
As with flats, start from DVF. But in houses, land effect is huge. Two identical houses on 400 m² or 1,200 m² of land aren't worth the same. Compare like-for-like on living surface and land surface.
Discount for defects (EPC, roof, non-compliant drainage, RGA exposure). Add for rare assets (view, perfect south exposure, total quiet, outbuildings). You'll land on a realistic range before making an offer.
The 12 most common mistakes
The disasters we see most often in BienCheck reports on houses.
- 1
Skipping the loft
If you don't inspect the framework, you're buying blind. Insist, even if the agent grumbles.
- 2
Skipping the cellar
Damp, cracks, standing water. That's where you see the real state of the house.
- 3
Trusting the seller on the roof
Ask for the redo date and the invoice. No invoice, no warranty.
- 4
Ignoring clay shrinkage
Strong clay zone is a real risk and insurance premiums climb. Check Géorisques.
- 5
Skipping septic
No SPANC report, or a non-compliant one, that's €6,000 to €15,000 to plan.
- 6
Underestimating the EPC
A poorly insulated F or G means €3,000 to €5,000 a year heating and €25,000 to €70,000 of works to bring up to scratch.
- 7
Not reading the local plan
A buildable zone 50 m away can become an estate in 5 years. The town hall knows before you do.
- 8
Missing an easement
Right of way, view, utility, that changes your rights. The title deed lists them.
- 9
Confusing living surface and total surface
Garage, cellar, unconverted loft don't count as living. Check what you're actually buying.
- 10
Forgetting outbuildings
Pool, garden room, shed, solar panels. All have upkeep costs and sometimes tax.
- 11
Not testing the water
If the house is on a well, get the water tested. A non-potable well is a daily problem.
- 12
Rushing the compromis
A vague or missing mortgage clause and you lose your deposit if refused. Never sign without careful reading.
Hidden costs to plan for
The real spend on a house over 10 years, beyond the asking price. Orders of magnitude for an average house in metropolitan France.
| Item | Range | Watch out for |
|---|---|---|
| Notary fees | 7 to 8 % of price (existing) | 2 to 3 % on new builds. |
| Council tax (taxe foncière) | €800 to €3,500 a year | Often higher than for a flat, includes waste collection. |
| Roof redo | €12,000 to €35,000 | Every 30 to 50 years depending on material. Ask the date. |
| Drainage compliance | €6,000 to €15,000 | If SPANC non-compliant. One year deadline after sale. |
| Energy works (F → D) | €25,000 to €70,000 | Grants possible via MaPrimeRénov', eco-loan, CEE. |
| Boiler, chimney, septic maintenance | €300 to €800 a year | Mandatory for insurance. |
| Home insurance | €350 to €900 a year | More if pool, outbuilding, risk zone. |
| Entry works | €5,000 to €50,000 | Kitchen, paint, floors, windows. Get quotes. |
| Garden and outdoor upkeep | €300 to €2,000 a year | Mowing, pruning, gravel, gate paint. |
How BienCheck helps
For a house, BienCheck crosses your inputs with public data to surface every blind spot.
Free analysis right away
Score out of 100, strengths, alerts, price coherence with your local market.
Full Premium report
Deep read, negotiation margin, real cost over 10 years, PDF export.
See a sampleNatural and industrial risks
Flood, clay shrinkage, seismic, radon, ICPE industrial sites at the exact address.
See risksDetailed EPC analysis
Projected heating cost, renovation scenarios, Climate Law alerts.
Understand the EPC
House buyer FAQ
New build or existing house?+
New: pay more per m² but skip 5 to 10 years of works and benefit from an A or B EPC. Existing: negotiate and customise, as long as you budget works properly.
How do you check the roof without climbing it?+
Ask the redo date, the invoice and the warranty. Inspect the loft from inside and use a drone photo if you can. Or pay a roofer €200 to €400 for a diagnostic.
Is individual drainage expensive?+
Full compliance runs €6,000 to €15,000. Annual upkeep is €100 to €200 for emptying every 4 years or so.
Can you buy in a flood zone?+
Yes, but read the PPRI. Blue zone is buildable with constraints, Red is very restrictive and the insurance premium climbs.
What if the house is rated F or G?+
Negotiate hard (10 to 18 % margin possible) or plan €30,000 to €70,000 of works. Calculate MaPrimeRénov' grants before fixing your max price.
How do you know if it's in a clay zone?+
Géorisques.gouv.fr shows the precise map. If the zone is strong, check for cracks and the claims history.
What easements can affect a house?+
Neighbour right of way, view, planting, public utility, high-voltage line. All in the title deed and on the cadastre.
Refuse a house with cracks?+
Not systematically. Small horizontal cracks are benign settlement. Through vertical or stair-pattern cracks: get surveyed before signing.
What does a house really cost to run?+
Add the mortgage + council tax + insurance + heating + smoothed upkeep. A 120 m² house at €350,000 typically runs €1,900 to €2,400 a month all in.
Does a pool add or remove value?+
Adds value in the south and tourist zones. Sometimes removes it elsewhere (upkeep, energy, buyer fear). Check your local market.
What deposit for a house?+
Like a flat, 10 % minimum, 15 to 20 % ideally. With a house, add a works reserve of 3 to 5 % of the purchase price.
What to look at in the local plan?+
Buildable zone, max footprint, allowed height, set-back distances, future development zones around.
What if the septic isn't compliant?+
You have 12 months after sale to bring it up. Get a SPANC quote before signing to budget.
How do you test a well?+
Send a sample to an accredited lab. Count €80 to €200 for a full analysis.
Can a cellar be converted?+
Yes if it meets ceiling height, ventilation and the local plan. Check before buying based on that.
Can you resell a renovated house for more?+
Yes, especially if works hit EPC, kitchen, bathroom and roof. Expect 60 to 80 % recovery on well-targeted works.
Glossary
- PLU
- Local urban plan, municipal document setting building rules plot by plot.
- PPRI
- Flood risk prevention plan, splitting the commune into zones with rules.
- RGA
- Clay shrinkage-swelling: ground movement under foundations in clay zones during droughts.
- SPANC
- Public service controlling individual drainage installs.
- Easement
- Right a neighbour or the public exercises on your land (way, view, utility).
- Cadastre
- Public register of plots, giving boundaries, sizes and owners.
- Planning certificate
- Document listing urban rules applicable to a given plot.
- Building footprint
- Ground area occupied by the building, in m² or % of land.
- Footprint coefficient
- Maximum building ratio at ground level, set by the local plan.
- Living surface
- Closed and covered rooms with at least 1.80 m ceiling height, excluding walls and partitions.
- EPC
- Energy performance certificate, A to G rating.
- Framework
- Wood or metal structure supporting the roof.
- Ridge
- Top horizontal line of the roof.
- External wall insulation
- Highly effective energy retrofit technique.
- Mechanical ventilation
- Essential to extract humidity in a well-insulated house.
- MaPrimeRénov'
- State grant for energy renovation works.
- Eco-loan
- Zero-rate loan to fund energy renovation works.
- CEE
- Energy savings certificates, grants from energy providers.
- Géorisques
- Public portal cross-referencing natural and technological risks at an address.
- Compromis
- Pre-contract binding buyer and seller.
- Suspensive clause
- Condition that must be met for the sale to complete.
- Decennial guarantee
- Mandatory 10-year warranty covering damage to the structure.
Going further
A few BienCheck resources that complement this guide.
- The BienCheck Premium reportWhat a full report looks like for a house.
- Understanding the EPCRatings, costs, Climate Law, works to plan.
- Natural risksClay shrinkage, flood, seismic, radon, industrial.
- Buying an apartmentThe pillar guide for apartments.
- Buying building landTo build your house rather than buy existing.
- Negotiating a propertyEvery buyer-side negotiation lever.
- Clay shrinkageUnderstand RGA, by BRGM.
- DVF sourcesReal sales signed in France, free and public.
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