When you buy off-plan from a builder or developer, or you build a new property by your own , the builder or developer, together with the architect, must guarantee you that the essential and most important parts of the construction will be secure at least for ten years, in order to follow the Spanish Law.
In order to confirm this responsibility, the Spanish regulations forces to the developers of new buildings to insurance the most important parts of the construction, as the foundations, internal structure, bines, etc. Other defects affecting the habitability of the property are covered for 3 years. Other minor defects are covered for 1 year. In the last two cases insurance cover is not required, but obviously if a builder can offer this as an additional guarantee, it will be better.
Also, this is an additional guarantee for the construction, because the same insurance company will force the builder to pass determinate quality inspections, to check the quality of the materials and the works made in the property, in order to give the proper policy.
The Ten Years Insurance (or “Seguro Decenal”) is compulsory when the promoter is a company with the activity to build houses for sale.
But, it is voluntary when the promoter is a particular (the owner of the plot). This is called in Spain “Autopromotor”, translated as “Self-Promoter” or “Self-Developer”. This is the case in which a particular buys a land in Spain with the intention to build a house for him as main, or second residence, but he has not the activity of buying for sale. In these cases, the Spanish law give the option to these particulars not to apply for this insurance, because the Spanish Government understand that, if a particular is building something to live inside, he will take the necessary care to build in safe and in a secure condition. So the particular can choose whether to save costs avoiding to pay this insurance; or in instance, to contract this insurance to have a better protection against big construction problems and defects.
But, if you, as self-promoter chose not to apply for this insurance, when you sell the house in the future to other buyers, the Spanish Laws forces you to inform them that the construction is not covered with this guarantee and they must accept this condition from the sale. From the point of view of an eventual buyer, it will be always a better option to buy a property with this insurance. So, they must be duly informed, and they must confirm, that the property is not with any insurance in this way.