Hidden defects: what a pre-purchase technical report checks

A pre-purchase inspection by an architect or aparejador is a distinct professional procedure with a defined scope. It covers the visible structural condition—cracks, deflection and moisture traces suggesting movement in foundations or load-bearing elements—the apparent age and condition of general services such as electricity, plumbing and heating, the roof and façade, and older materials requiring special handling, including asbestos-cement components. It also compares the actual layout with official records to identify undeclared previous works. Each of these findings can independently change the renovation estimate; the inspection is much more than a general impression that 'the flat is in good condition'.

Why a layout discrepancy is not a minor issue

A difference between the actual and registered layout is not cosmetic. It indicates works that were not formally documented and may therefore fail the standards that should have applied, from wall load-bearing capacity to ventilation and electrical loads. This directly connects to the risk of unauthorised works when buying. The technical inspection identifies that risk physically, rather than only in documents: a specialist can see a removed partition or relocated bathroom even when the paperwork says nothing about it.

A technical report does not replace legal checks

An often-confused point is that a technical inspection does not replace legal due diligence—nota simple, encumbrances and cédula de habitabilidad checks—or the building's ITE history. These are parallel procedures with different purposes. Legal checks establish whether title is clear and what obligations exist; technical checks establish the property's physical condition and what lies behind the finishes. Both should proceed together, not sequentially or interchangeably. Clear title does not guarantee sound wiring, and good physical condition does not guarantee an absence of debts or encumbrances.

Why this must happen before arras

Commission an independent technical inspection before signing arras, rather than afterwards. At this stage, the report can identify defects capable of shifting the renovation budget by tens of thousands of euros. Once the deposit agreement is signed, room to renegotiate price and terms narrows sharply: discoveries then undermine the deal rather than help reshape it. In DNPI's due diligence, a technical inspection is a mandatory pre-purchase decision step alongside legal checks; see the due diligence checklist. The inspection's cost is negligible beside the cost of misjudging condition. Saving on it to accelerate a deal is particularly unwise where renovation makes up a substantial share of the project budget.