If you are buying your Spanish property with a Spanish mortgage you will need to have a valuation (mortgage survey) done on the property before the bank will issue you with a binding offer.
The lender is taking a guarantee over your property and so has a vested interest in the property and therefore needs to ensure that for example the square meterage is properly registered at the land registry, the correct licenses are in place and that the value of the property is in line with the purchase price.
These surveys are paid for by the borrower and you can either request the lender to arrange the survey or you can do an independent survey on the property. As long as the valuer (tasador) is acting for one of the regulated valuation companies (Sociedad de tasaciones) which are registered with the Bank of Spain, then the valuation will be acceptable to the Spanish banks for mortgage purposes. The valuer will visit the property, take photos and measurements but they will not do a structural survey. A Spanish valuation for mortgage purposes is more of a ‘box ticking’ exercise rather than a more in depth building survey. The valuers have to apply a rigid set of formulae in order to value the property, the neighbourhood and surrounding property values and its location. These details get input into their scoring system and the result which comes out is the stated value. They are obliged to operate this way by detailed laws and regulations which ensure standardisation as all properties are treated in the same way, but it can result in figures being removed from the reality of the market. In other words, this system may not be a true reflection of market value.