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The construction raises a metallic structure attached to the facade and expands the apartments without the residents having to leave. The solution became a trend in São Paulo, but in practice, it only works financially in large high-standard properties and depends on technical and legal regulations.
Old buildings that never had a balcony can now gain a new one, built from the outside in, through a retrofit technique that has been attracting attention in São Paulo. The method raises a metallic structure attached to the building’s facade and creates a new space in each apartment, expanding the usable area without demolishing what already exists. The promise is to significantly increase the property’s value, although the solution still faces high construction costs and the need for approval from the condominium owners.
The intervention gained visibility after videos of buildings being expanded in mid-air went viral on social media in 2026. In the images, steel structures appear on the outside of already inhabited buildings, as if a new metallic building were being fitted into the old one. Behind the trend is mainly the São Paulo company BR Retrofit, created in 2012 by Alberto Alves, who was looking for a balcony with a barbecue in his own apartment and couldn’t find anyone to do the complete service.
How the balcony is built without emptying the building
The entire metallic structure is assembled on the facade, and the construction progresses from bottom to top without families needing to vacate the apartments.
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According to the responsible company, the assembly is quick and can rise between 15 and 20 floors in about a month, although the complete schedule, including foundations, approvals, and finishes, can take up to a year.
The most impressive detail is that the wall separating the living room from the new space is only opened at the end of the work, so as not to disturb those living there.
Even the breaking of the wall to integrate the living room with the balcony is done from the outside, so that the original window remains intact while the external structure is not ready.
In practice, the resident watches the expansion happen from the other side of the glass and only starts using the balcony when everything is completed.
How much it costs and how much it adds value
The cost and value increase figures help to understand why the technique generates so much interest, but also why it is not suitable for everyone.
According to information presented about one of these projects, the price of the expansion is estimated to range from 10,000 to 14,000 reais per square meter built, a value that varies according to the need for new pillars, the type of structure, and the building’s conditions.
It is a high investment, which needs to be added up and shared among the residents.
On the other hand, the selling argument is that the expanded square meter becomes worth the same as the rest of the apartment at the time of resale.
In valued regions of São Paulo, where the square meter can exceed 20,000 reais, expanding a balcony would mean adding a space that is worth much more than it cost to build.
It is worth treating this appreciation as an estimate, since the real gain depends on the market, location, and the deduction of the construction cost, and it is not an automatic profit.
Why the solution is restricted to high-end properties
Although videos suggest that any apartment can gain a balcony, the technical reality is much more restrictive.
Specialized reports show that the solution is feasible mainly in high-end properties, in spacious apartments in upscale neighborhoods, and is far from meeting the needs of small properties.
The balconies executed by this type of company usually range from 35 to 90 square meters, a size that alone already exceeds the area of many compact launches sold today in the city.
The explanation lies in the complexity and cost of the structure needed to support the expansion.
Balconies with more than 2.5 to 2.8 meters in depth require the installation of pillars that go down to the basement, which means creating new foundations for the building, using cranes and pre-fabricated metal structures.
This set increases the cost of the project and makes it unfeasible for buildings whose apartments do not support, in value and design, an investment of this magnitude.
The rules that decide if the building can or cannot
Before dreaming of the balcony, the condominium needs to face a series of technical and legal requirements.
There is no specific legislation for balcony retrofitting, but the construction must respect the minimum setbacks of the land provided by municipal law.
If the building is very close to the neighbor, it is not possible to extend the cantilever slab without violating these setbacks, which makes the expansion unfeasible.
There is also the so-called rule that limits the non-computable area per floor, according to architects interviewed by the press.
The approval of the residents is usually the biggest obstacle, alongside the bureaucracy of the city hall.
The construction changes the entire facade and depends on the agreement of the condominium owners in an assembly, a process that, in reported cases, took about four years to complete.
Added to this is the increase in property tax, as the tax is recalculated based on the new square meter value of the apartment, and the need to incorporate the extra area into the property’s registration, transforming the physical expansion into a registered asset gain.
The balcony built from the outside in is an example of how retrofitting can transform old buildings without anyone needing to move.
The technique is creative, enhances the property, and responds to a real demand from those who love the neighborhood where they live but miss an outdoor space.
Even so, it is important to see its limits, that is, the high cost, technical restrictions, and dependence on collective approval make it, for now, a niche solution, aimed at high-end apartments.
And you, would you like to see your building gain a balcony like this, built from the outside without needing to leave home? Comment if you think it’s worth the investment, if your condominium would agree to such a project, and if you believe the technique will become popular for smaller apartments in the future. The conversation is open to those interested in real estate, renovations, and the real estate market, with respect for different opinions.
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