Who pays to replace a shared riser or drain stack?
The shared riser is paid for by the comunidad de propietarios according to each owner's share (coeficiente). It is a common element, and under the Ley de Propiedad Horizontal, works needed to keep the building safe and in repair are mandatory and need no prior vote. Your part is the pipework and branches inside the flat. The exception: if the leak came from your own alteration, you pay.
The owners' meeting does not debate whether the work is needed but how: timing, contractor, budget and cost split. If you live abroad, ask the administrador early what has already been approved and what sits on the list of future levies.
Where does your flat end and the shared property begin?
A practical rule: whatever serves several flats is common; whatever serves only yours is private. The vertical drain stack, the water and gas risers, the main supply line and the meter boards on the staircase are common. The branch from the riser to your tap, toilet and meter is yours. The exact line is written in the building statutes and in the nota simple, and in old buildings it rarely matches intuition.
The classic dispute sits at the joint: the junction, plug or branch tied into the common stack. Whoever altered it answers for how it was done. That is why you should photograph everything before the walls close and keep the files. They will matter if, three years on, a stain appears on the ceiling below.
What is wrong with cast-iron stacks in old buildings?
A cast-iron stack from the early 1900s can last decades, but its weak points are well known: rust inside and out, cracked sockets, dried-out seals and noise. In practice the first signs are a smell in the bathroom, a damp patch beside the stack and vibration when flats above flush. If the building has already had leaks, a camera inspection of the pipe is worth it.
In a luxury renovation noise is treated separately: even a new PVC stack rattles, so you want acoustic pipe with a heavy layer and rubber-lined clamps. A single flat cannot swap its section alone. The work runs the full height of the building, cuts water to neighbours and needs a shared schedule. That is why the plan is agreed with the comunidad from the start.
Are there still lead pipes in Barcelona?
Yes. In some buildings from before the 1960s, lead branches or sections remain, most often at the entry point or in kitchen feeds. They are easy to spot: lead is soft, dull grey, scratches with a coin and is not magnetic. A water test from the tap after a night of no use tells you the rest.
A renovated flat should not keep any lead: it comes out from the entry point to the taps. But you cannot touch the common riser without a comunidad decision, so at the start of the project ask the administrador a direct question about the riser and supply materials. If lead is found in your section, now, with the walls open, is the cheapest time to replace it.
Will the building's electrical supply handle the new load?
Not always. A premium renovation often asks for 9.2 kW or more: induction hobs, ovens, air conditioning, underfloor heating, EV charging. The main supply line and entry point of an old building were sized for the 3 to 5 kW per flat of the past, and under simultaneous peaks they heat up and the main switches trip.
The sequence is this: first ask the distributor (in Barcelona, e-distribución) what capacity is available on your line, then have the electrician calculate the real demand, and only then sign the increased-power contract. If the line cannot cope, the comunidad decides: reinforcing the shared line is paid for by the building. The usual steps are 5.75 and 9.2 kW, but the project has the final word.
Can a bathroom be moved far from the stack?
It can be done, but every metre of pipe costs money and fall. A waste pipe needs a slope of about 1 to 2 cm per metre, and if the bathroom moves 4 or 5 metres from the stack, the floor has to rise or the pipe hides in the ceiling of the flat below, which cannot happen without that neighbour's consent. Old timber-joist floors do not welcome extra screed weight either.
The ways out: a raised floor in the bathroom, a macerator for small fixtures (noisy, rarely right for a luxury job) or moving only the shower and basin and keeping the toilet near the stack. This is decided at the layout stage, before walls are marked out. Once the tiles are down, such surprises cost several times more.
Where to start and how BCN YARD can help
Start with three documents: the ITE report, the minutes of recent owners' meetings and the riser diagram, if there is one. Then a technician inspects the shafts and checks what has already been renewed. The result defines what you do inside the flat, what you ask of the comunidad and in what order.
BCN YARD runs these projects in Russian and Spanish with one person responsible for the site: a visit and measurements, a look at the risers and boards, then a phased estimate. If you need backing with the comunidad, we can prepare a technical note that works well at the meeting.
Frequently asked questions
Who is liable if a riser leaks into a neighbour's flat?
If the defect is in the common riser, the comunidad and its building insurance answer for it. If the leak comes from your branch, your tap or your alteration, the owner is liable and the home insurance steps in. That is why you should keep drawings, photos of concealed work and the pressure-test record.
Do I need comunidad approval to replace pipes inside my flat?
For pipes inside the flat that do not touch common elements, no owners' vote is needed, but you should notify the administrador and the president if the work is noisy or needs the building's water shut off. Tying into a common riser, drilling a slab or working in a shaft does need authorisation.
Can a whole-building riser be replaced without every neighbour agreeing?
Yes. Works to keep the building safe and in repair are mandatory by law and do not need unanimity. The contractor and budget are voted at the meeting under the Ley de Propiedad Horizontal, and cost is split by coeficiente. Unanimity would only be needed for changes affecting the statutes or the facade.