← Back to journal

What to consider before renovating an old house

You have the property. You have decided you want to renovate it. The temptation now is to dive straight in with quotes from contractors, or worse, with a contractor to whom you vaguely describe what you want. Before any of that, there is a diagnostic phase that is as important as the project itself: understanding the real state of the building you are about to intervene in. The surprises that emerge in a poorly studied renovation are the ones that blow budgets and timelines.

First: the structural diagnosis

Any renovation of a property more than forty years old should begin with a structural assessment by a qualified professional. The aim is not necessarily to produce a formal report — though sometimes that is required — but to know what you are working with before committing money to a layout project.

The most common problems we encounter in Málaga buildings from the 1950s to the 1980s are: hollow brick walls (tabicón) that have been incorrectly used as load-bearing elements and cannot receive additional loads; timber joist floors with woodworm, rot or accumulated overload damage; roof slabs with exhausted waterproofing that has allowed water ingress for years; and shallow foundations that have undergone differential settlement in soils with expansive clays.

None of these problems is necessarily insurmountable, but all have a repair cost that must be budgeted before designing anything else. A damaged timber floor that needs replacing with a concrete one can cost between €150 and €300/m² for the structure alone, excluding finishes or demolition works.

Services: in buildings before 1980, assume everything changes

In homes built before 1980, the electrical installation does not comply with the current Low Voltage Electrotechnical Regulations: aluminium rather than copper wiring in many cases, no earth connection, sections insufficient for current demand, electrical panels with no RCD or individual circuit breakers. A comprehensive renovation that retains the existing electrical installation is a safety risk.

The plumbing in buildings of that era is usually lead or galvanised steel. Lead has been banned for drinking water use since 2003; galvanised steel corrodes internally, accumulating deposits that reduce flow and contaminate water. Replacement with copper or cross-linked polyethylene (PEX) pipe is mandatory in any serious renovation.

The correct sequence for interventions in a comprehensive renovation is immovable: first demolition of what is being removed; then any structural works; then waterproofing of the roof and wet areas; then new services (electrical, plumbing, drainage, HVAC); then new partitions; and only then the finishes. Reversing this order — for example, fitting tiles before resolving the services — multiplies costs when the inevitable corrections require undoing finished work.

Damp: the enemy you cannot see

There are three types of damp, each with a different cause and a different solution. Confusing them is one of the most expensive mistakes in a renovation:

• Rising damp: groundwater rises through load-bearing walls by capillary action. It appears as staining at the base of walls, usually up to one metre high, with salt efflorescence. The correct solution is a damp-proof course: injection of hydrophobic resins at the base of the wall or, in serious cases, perimeter drainage.
• Condensation damp: internal water vapour condenses on cold surfaces (thermal bridges, glass, uninsulated external walls). The solution is improved thermal insulation and ventilation — not waterproofing agents.
• Penetrating damp: water entering from outside through cracks, defective joints, damaged roofs or unwaterproofed terraces. The solution is repairing the entry point — not treating the inside face of the wall.

Covering any of these three problems with waterproofing paint on the interior face of the wall solves nothing: the water will continue to enter and the coating will eventually detach. A correct diagnosis before acting saves, on average, between double and triple the cost of an incorrect intervention.

Current regulations come into play

Many owners are surprised to discover that applying for a major works licence to renovate an old building triggers the obligation to comply with the Technical Building Code (CTE) for the elements being worked on. Depending on the scale of the renovation, this may involve: improving the thermal insulation of the envelope to the minimum values of DB-HE, ensuring accessibility at building entrances and communal circulation areas if communal zones are affected, or reviewing the electrical installation in accordance with the REBT. None of this is an insurmountable obstacle, but it must be budgeted from the outset.

The real potential of old buildings in Málaga

Buildings from the 1950s to 1970s in Málaga city centre — and in the historic cores of the Costa del Sol — have real advantages that justify rehabilitation: clear heights of 3 metres or more that modern buildings rarely achieve, high-thermal-mass load-bearing walls, central locations with pedestrian accessibility, and a constructive solidity — solid brick, well-proportioned concrete structures — that the industrial construction of the 1990s lacks.

Their limitations are equally real: poor natural light in interior flats, long corridors and compartmentalised layouts suited to uses that have changed, absence of acoustic insulation between homes and floors, and the unavoidable need to renew all services.

The key is having a complete project before requesting quotes. A layout plan and a detailed descriptive report allow contractor quotes to be compared objectively. Without a project, each contractor prices what they understand — and what they understand is usually different from what the client wants.