Renovate an old villa or demolish and rebuild?
Renovate if the structure is sound, the house already occupies more floor area than today's plan would allow, and it has character. Demolish when the structure is damp-damaged, the layout cannot be fixed and the rules allow at least the same area. The decision rests on three documents rather than taste: a structural survey, a planning report and two budgets.
Planning is often decisive. A house from 1975 may have been built under rules that gave more buildable area than today's. Demolition wipes out that advantage: the new building fits only within the current ratio. That is why the planning report from the ayuntamiento is requested before demolition is even discussed.
A second factor on the coast: if the plot falls inside the influence zone of the Ley de Costas, demolishing and rebuilding the same volume can be harder than renovating, and approvals take longer.
What do 1970s houses usually hide?
Almost always the same things, and we know it from site experience. Hollow-brick walls with an uninsulated air gap, hence thermal bridges at slabs and columns. A flat roof with an asphalt membrane that has leaked for years and soaked the slab. Aluminium windows with no thermal break and single glazing.
The services are worse than they look. Electrics without earthing and, in some houses, aluminium wiring; steel water pipes narrowed by scale; cast-iron or fibre-cement drains cracked with age. If the house is not connected to the sewer there is a septic tank, often home-built, which must be replaced or connected to the network.
A separate find is asbestos-cement on roofs and in water tanks. Spain banned asbestos in 2002, so anything built earlier has to be checked. Only a company entered in the RERA register can remove it, under a work plan; it cannot be dismantled by the owner.
Damp in the ground floor and basement of hillside houses: waterproofing is missing or rotten. It is found before the budget, not after the wall is opened.
Does the roof have to be replaced completely?
Most often yes, and here is why. The roof of an old house is a stack of layers that have aged together: where there is a leak, the insulation, the slab and the timber have almost always got wet as well. Patching one zone opens a path for water into the next.
On a flat roof everything is replaced down to the slab: screed to falls, vapour barrier, 10–15 cm of insulation (by calculation), membrane and a protective layer or gravel. On a pitched tile roof the battens and rafters, the underlay and the tiles are checked. Beams hit by woodworm or termites are treated or replaced. Catalonia is known for subterranean termites, and their traces are looked for before any finishing.
A partial repair makes sense if the structure is dry and the leak is local: one outlet, one parapet. The decision is made after a survey that opens up the layers, not from a photograph. The roof line in a villa budget is larger than it looks, because parapets, downpipes and the preparation for solar panels come with it.
What almost always changes: windows, envelope and services
The list changes from house to house, but three items repeat. Windows: old aluminium with single glass is replaced by thermally broken profiles with double or triple glazing and solar control; on west and south elevations, protection from overheating matters more than protection from cold.
The thermal envelope. Insulating outside with an ETICS system (external insulation with a thin render) removes thermal bridges and keeps the interior volume, but it changes the look and needs approval if the facade sits in a protected area. Insulating inside is cheaper and easier on site, but the thermal bridges remain and, with damp in the wall, condensation becomes a risk.
The services are redone entirely: electrics, water supply, drainage, climate. Aerothermal heating instead of a gas boiler, underfloor heating or fan coils, ventilation with heat recovery, water treatment. If the house is lived in during summer, it makes sense to fit smart control and leak sensors from the start rather than after the first flood.
How do you find out whether previous owners' extensions are legal?
Compare four sources: the building licence and the certificate of completion (certificado final de obra) in the town hall archive, the nota simple from the Registro de la Propiedad, the Catastro data, and the real measurements of the house. If the areas do not match, something was added without being regularised.
In practice, in houses from the 70s and 80s you find garages turned into rooms, verandas glazed in, an attic built over the garage, and a pool or pergola outside the permitted building zone. Some additions can be legalised and some cannot, and the limitation period depends on the type of infringement and regional rules. A planning lawyer decides this, not the seller or the site foreman.
If you are buying, the check happens before the deal. If the house is already yours, it happens before design: the budget and the works permit rest on the legal floor area. Sometimes it is better to demolish the unlawful part than to regularise it, and that decision is made before work begins. More on the procedure in our article on legalising old works.
What to do with the old pool and the garden?
A pool from the 70s or 80s almost always has no overflow edge, a tiled shell, a plant room that has leaked for years and a pump in a damp pit. It is surveyed: is the shell watertight, what supports it, where does the water go. If the shell is sound, it is restored with new lining and waterproofing and fitted with modern filtration and heating. If cracks run through the structure, building a new pool is cheaper.
Turning an old pool into an overflow pool is difficult: it needs different edge levels, an overflow channel and a balance tank. So if you want a pool with an infinity edge, both paths are priced when you choose between renovating and demolishing the shell.
The garden of such a villa is usually overgrown: pines right against the walls, roots under the foundations, evergreen thickets that block machinery access. An arborist assesses the trees and the roots under the pool and walls are checked before work starts. The irrigation is redone as drip and the water restrictions of drought years are taken into account.
How to decide and where to start
The order is this. First a visit and measurements to understand the real condition. Then a structural survey, a geotechnical check if the house is on a slope, and a report from the ayuntamiento with the permitted parameters. Then two budgets: renovation, and demolition with new build, compared on time, price and final floor area.
The comparison counts everything honestly: removal of rubble and asbestos, temporary housing, taxes, time until you can move in. On a deep villa renovation the price gap with demolition sometimes shrinks to almost nothing, and then the character of the house or a floor area you could not get again wins.
BCN YARD renovates flats and houses turnkey and builds houses. We run the site in Russian and Spanish, with our own crew and trusted subcontractors, one person responsible, and payment under the contract in stages. The exact price comes in the estimate after the visit and measurements; we answer enquiries within an hour.
Frequently asked questions
How long does a villa from the 70s-80s take to renovate?
It depends on how deep the work goes and on approvals, so a reliable answer comes only with the estimate after a survey. The licence takes a couple of months in some towns and longer in others. Allow time for hidden finds when walls and roofs are opened: asbestos, rotten beams, damp.
Can you live in the house during the renovation?
With a full replacement of roof, windows and services, you cannot live in the house: there is no water or power, and dust and noise run all day. A phased approach is possible if there is a separate wing or guest house, but it lengthens the work and raises the cost. It is usually simpler to rent somewhere for the duration.
Do you have to keep the facade of an old villa when renovating?
Only if the house is listed in the municipal catalogue of protected buildings or stands in a protected area. An ordinary villa from the 70s or 80s is usually not, but facade insulation and new openings still go through the licence. The catalogue check is done at the ayuntamiento before design.