What to check before buying a flat: a checklist
Before signing there are three things to review: the paperwork (land-registry extract, debts, building inspection), the condition of the home, and what appears on no document and can't be seen on a viewing: the sun, the light, the noise, the heat, the connection and the neighbourhood. This checklist puts all three in order, says how to check each point yourself and which ones a report like Asoleo's covers.
Reviewed on 26 October 2026. Documents and deadlines vary by region: this is a general guide, not legal advice.
What no document shows, and a report can measure
These are the eleven points a report on a specific flat can give you from official data, before the viewing or between two viewings.
Sun and orientation
On your own. Check which way each window faces and view the flat at two different times: a viewing only shows one hour of one day. Before you go, see the winter sun on the street for free in Sunlight by neighbourhood in Barcelona, Madrid and Valencia (indicative for the last two).
In the Asoleo report. The hours of direct sun a year on each window, when it comes in and leaves and how much arrives on 21 December, counting the buildings and trees in front. With LiDAR where there is some; indicative, from the Cadastre's buildings, in the rest of Spain.
Natural light
On your own. Notice how much sky you see from the window, not just whether the sun comes in: a wide courtyard or street gives light without direct sun.
In the Asoleo report. For each window, how much sky it sees and what blocks it. It tells natural light apart from direct sun.
Summer heat
On your own. Ask about orientation and floor, and whether there are awnings or shutters: a west-facing window on the top floor tends to heat up more.
In the Asoleo report. The solar energy reaching the glass of each window on an average day in July and in January, and how many hours of direct sun coincide with a street above 28 °C. It is exposure to the sun, not the temperature inside the flat.
Noise
On your own. Visit at night and at rush hour, with the windows open and closed, and ask the neighbours about bars, building work and traffic.
In the Asoleo report. The day and night level of each façade from the official noise map and its year, against the WHO's 45 dB at night; where there is no map, an estimate by category. It is outdoor noise, not what you hear inside.
Building and energy certificate
On your own. Ask for the energy certificate, which is compulsory when selling or renting, and the year the building was built.
In the Asoleo report. The year built, the homes and commercial units according to the Cadastre and the rating of the certificates registered in the building (Catalonia, the Valencian Community and Madrid), and the flat's own if there is one.
Fibre and mobile coverage
On your own. Ask which operator has fibre and test your phone inside the flat.
In the Asoleo report. Which operators bring fibre to the building and at what speed, and which have 4G and 5G in the street, from the Ministry for Digital Transformation. Fibre in the building is not the same as a socket in the flat.
Tourist flats
On your own. Read the community statutes and ask the neighbours whether there are tourist apartments.
In the Asoleo report. The registered tourist homes in the building and within 100 m, and whether the flat itself is registered, where the register is public (Catalonia, Andalusia and the Canary Islands).
Air and low-emission zone
On your own. Check the council's website: what traffic restrictions apply and from when.
In the Asoleo report. NO₂, PM2.5 and PM10 for the area against the WHO and EU limits, and whether the building is inside a low-emission zone and what it restricts, in cities with data.
Walking distances
On your own. Walk to the metro, supermarket, health centre and school at the time of day you would.
In the Asoleo report. The walking minutes to the nearest metro, train and bus (with their lines), supermarket, health centre, school and park, from OpenStreetMap data.
Flooding, radon and planning
On your own. Ask the council about planning restrictions and look at the official flood-zone maps.
In the Asoleo report. Whether the building is in an official 10-, 100- or 500-year flood zone, the radon in the area, the land class and the planning in force (with the detailed classification in Catalonia, Madrid and the Valencian Community).
Reference price
On your own. Compare with similar listings in the area and with typical rents.
In the Asoleo report. The area's average rent and its range (Ministry of Housing), the municipality's average appraisal if it has over 25,000 inhabitants and whether it is a tight residential market zone. It is not a valuation of the flat.
What a report doesn't replace: ask for it separately
These are documents and checks that come from the seller, the registry or a surveyor. Asoleo doesn't include them.
Land-registry extract (nota simple)
It says who the owner is, the registered surface area and whether there are charges, such as mortgages or seizures. You can request it online from the Spanish Registrars' association.
Debts to the community and special levies
Ask for the certificate of debts to the owners' community, the latest minutes and whether any works or levies are planned.
Building inspection (ITE) and condition
The building's technical inspection is compulsory depending on its age and the region. If it is unfavourable, there may be works for the owners to pay for.
Condition of the home
Damp, electrical and water systems, windows and insulation: a surveyor sees these on an inspection; a report built on public data doesn't.
Certificate of habitability and licences
It isn't required in the same way in every region: ask whether you need it in yours and whether renovations had a licence.
Costs of the purchase
Besides the price, taxes (which depend on the region and on whether the home is new or second-hand), notary, registry and agent's fees.
For a specific purchase, have a lawyer or an agent review the documents.
Limits of a report like Asoleo's
- It measures the outside of each window and façade from public data: it doesn't see awnings, shutters, small building works or the condition of the flat inside.
- The sun is calculated from a 3D model of the surroundings. With LiDAR the margin is about 5 to 20 min a day depending on resolution; from the Cadastre's buildings, indicative, 20 to 40.
- It is not a valuation or a certificate, and each chapter gives its source and date, or says there is no data.
Frequently asked questions
What should I check before buying a flat?
Three groups of things: the paperwork (land-registry extract, debts to the community, the building's technical inspection), the condition of the home (damp, installations) and what appears on no document and can't be seen on a viewing: the sun, the light, the noise, summer heat, the connection and the neighbourhood. The checklist on this page puts them in order and says which ones an Asoleo report covers.
How can I tell if a flat is bright?
Natural light and direct sun are not the same: a window onto a wide street or courtyard gets light from the sky even if the sun never reaches it. For the sun, view the flat at two different times and note which way the windows face and what is in front. Asoleo calculates the hours of direct sun on each window across the year and how much sky it sees.
How can I check the noise in a flat?
Visit at night and at rush hour, with the windows open and closed, and ask the neighbours. Before that, look at your city's official noise map: Asoleo reads it for each façade and gives the day and night level with the year of the data; where there is no map, an estimate by category with an error of about 5 dB.
Is the report useful if I'm renting?
Yes. Sun, light, noise, heat and surroundings matter just as much when renting, and the report takes a couple of minutes, between one viewing and the next. You don't need the purchase documents (land-registry extract, community debts).
How much does it cost, and does it work outside Barcelona?
€19 where there's LiDAR (Catalonia, Navarre and the Basque Country) and €12 in the rest of Spain, VAT included, no account. Outside the LiDAR areas the report has the same content except for the accuracy of the sun, which is indicative, and the sun on balconies, terraces and roofs.