Published on idealista: “Earthquakes: the importance of rehabilitating resistant houses”

The recent earthquakes in Turkey and Morocco that resulted in the loss of tens of thousands of lives once again reminded us of the impact of such natural disaster on human lives, and raised our awareness on the quality of buildings and how it should be controlled in security measures.

As a matter of fact, it has been well known by the Portuguese public that a large part of the nation’s land is in a so-called seismic-prone zone, where there exist high risks of having earthquakes. Indeed, the entire city of Lisbon and its surrounding areas are classified as high to medium seismic risk, where old buildings until the 1960s in historical areas are regarded as being especially vulnerable to high seismic risks.

A natural question to ask would be: How do we know if our homes are built with qualities that will withstand certain level of earthquakes? After all, we would expect that safety is one of the most important functions of a building.

However, to our surprise, the safety of a building’s structure has apparently been long neglected. As an example, in the evaluation of properties by the Portuguese Tax Authority, the value is based on a formula considering factors such as the size of interior and exterior areas, the direction towards the sun, the floor levels etc. The quality of the structure related to the seismic risk zone, is not included in the formula at all.

As a matter of fact, it is very difficult for a house owner in Portugal to tell the structural quality of his property. This element remains unreported throughout all official documents that are presented to the buyer in front of the notary for any public deeds.

In order to find out about the quality of the structure, given the current legal framework, the only approach is to study the structural project of the building, with the assistance of a professional technician, to find relevant information from the document such as structural reinforcements, special materials and technologies applied for seismic-strengthening etc.

Such information is not easy to find and interpret, and the Portuguese authority does not make it compulsory for builders to make such information transparent and easily accessible to the public.

It was only in 2019 that the Portuguese government has made it compulsory for rehabilitation projects to include a “structural analysis” of the existing building, on whether the structure of the building is solid, and if not, what kind of interventions are needed. Even so, such studies are usually made without considering seismic resistance.

Rather, there are factors preventing developers from investing in structural reinforcements, namely the nonnegligible costs of structural works, which could add 15% to 35% on the total construction costs, as well as the considerable amount of time, which can count as much as 40% of total construction period. Compared to the choices of flashy kitchens and toilets that can impress buyers at the first sight, the structural works, contributing substantially to the quality of a building, rarely ever get noticed.

The confusion of “rehabilitation” and “remodelling” brings further ambiguity to the topic, where the latter works undergoes with lack of technical monitoring nor supervision, leading to further seismic risks in old buildings.

However, all the rehabilitation projects by Level Constellation in various prime zones of Lisbon had been adopting seismic resistant structures, since 2014. Working with some of the top structural engineers of the country, including A2P by Engineer João and Vasco Appleton, Level Constellation aims at constructing modern premium condominiums that will stand against earthquakes. Some of these projects have already become case studies, being recognized for their excellence in the solutions, and have inevitably resulted in national awards and nominations.

One example is Ouro Grand (architect CAN RAN, structural engineer A2P) , located on Rua do Ouro, which is one of the first Pombaline buildings to be deeply rehabilitated for housing in the Baixa area of Lisbon. Given the complication from alluvial/silt soils and high groundwater levels, the structural project adopted a mixture of reinforcement techniques with metal reinforcements and concrete projection. A group of 25-meter deep micropiles were employed to support the building through the swamp underneath Baixa. In addition, the historical facades, floor slabs, columns and beams were maintained and reinforced to keep the original look of the building of 250 years history.  The project won the best Urban Residencial Rehabilitation Award in SIL 2018, as well as Honorary Mention in the Category of Intervention in Lisbon of Prémio Nacional de Reabilitaçâo Urbana 2018.

Two other great examples are Classica (architect Frederico Valsassina, structural engineer A2P) and Gloria (architect Fragmentos, structural engineer Projectual), with the first located next to Restauradores/Av. da Liberdade, and the other in the middle of Av. da República. The two projects are perfect showcases of achieving the necessary balance between safeguarding heritage of historical buildings and ensuring habitability conditions, including seismic structural reinforcement, through the harmonization of various structural materials, including the use and rehabilitation of wood, light steel structures and, as such, respect for sustainable materials.


9 November, 2023

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