Greetings,
Most cantons in Switzerland - with the exception of "GUSTAVO" cantons - operate cantonal buildings insurance (homeowners insurance) schemes (you can find out more in this guide to buildings insurance in Switzerland). In these cantons, homeowners are required to take out this basic, compulsory building insurance from the cantonal insurance scheme.
However, not all hazards are covered by basic buildings insurance. For example, while flood damage is covered, water damage due to broken pipes or leaks normally is not covered.
Hazards which are covered by your cantonal buildings insurance cannot usually be covered on a first loss basis.
If you have optional, supplementary buildings insurance or if you live in a canton which does not have compulsory buildings insurance, then first loss insurance may be an option. There are private Swiss insurance companies which provide first loss policies as an option for buildings insurance.
Best regards from Moneyguru
More on this topic:
First loss policies explained
Buildings insurance in Switzerland