Check which type of flooding the map shows
One map may show areas that could flood from a river or seasonal stream. Another may study flooding from the sea. These are different situations: consulting one does not mean the other has also been checked.
Before concentrating on colours, find the publisher, what the map represents and its date. Read the legend explaining symbols and colours too. This helps you understand which question the map answers and what remains unknown.
- Check whether the map covers rivers and streams or coastal flooding.
- Check the publisher and stated date.
- Look up the legend before interpreting an unexplained colour.
Look at the garage, entrance and access routes too
Do not look only at the point marking the address. Part of the garden, garage access or approach road may be inside a marked zone even when the entrance is outside. Examine the whole plot and how you reach the home.
If you are buying an upper-floor flat, also consider the building's shared spaces. Even if water did not reach your home, it could affect a basement, access or shared installations. The map guides these questions; it does not determine what would happen on each floor.
- Locate the building entrance and garage ramp.
- Check courtyards, basements and spaces below street level.
- Ask about the routes you would need to use during heavy rain.
An unmarked home is not guaranteed never to flood
Being outside a marked flood zone does not guarantee that water can never enter. The map may not cover every area or type of flooding. A study may be missing for this location, or the information may not have been accessible.
The distinction matters: ‘not shown on this map’ is not the same as ‘no risk’. If information is unavailable, the question remains open. Ask about previous water ingress in the home, garage or building and request documents that could clarify it.
- If the home is unmarked, first check that the map studies this area.
- Keep missing information on your checklist.
- Ask the seller and owners' association about known water ingress.
Use the map to ask specific questions
If the map marks part of the plot or leaves a question, save a screenshot with the date and map name. You can then show exactly what you saw and ask how it relates to the home you want to buy.
Ask the seller about previous events, repairs or measures installed to prevent water ingress. If the answer could change your purchase decision or renovation plans, consult the municipality or a professional able to inspect the home and documents.
- Save the map together with its colour legend.
- If flooding has occurred, ask when, how far the water reached and what followed.
- Seek advice on important uncertainties before deciding.
Frequently asked questions
If my home is not shown in red, is it safe?
Colour alone cannot establish that. Check what each shade means and which area has been studied. A home not being marked on that map does not exclude other water problems or replace questions about past events.
Should I be concerned about a third-floor flat?
Height matters, but you also use the entrance, garage and building installations. Check those spaces and ask what happened during previous heavy rainfall.
Where to consult this information
These official pages help you learn more and prepare your questions.