The latest social housing for IBAVI in Palma de Mallorca by H Arquitectes is proof that existing buildings are a valuable material resource It is not possible to buy a plastic straw on the island of Mallorca. The same goes for disposable plastic plates, cups and cutlery; six‑packs of beer are held in cardboard holders rather than plastic rings. Since March 2021, it has been illegal to distribute single‑use plastic products in the Balearic Islands, in a bid to reduce the enormous amount of household waste generated each year: over 800,000 tonnes in 2022, 60 per cent greater per inhabitant than elsewhere in Spain due to huge influxes of tourists – in the summer, the population of Mallorca doubles.  Though efforts have been made to reduce plastic waste, the same drastic action has not been applied to building materials. Over 600,000 tonnes of construction and demolition (C&D) waste were processed in Mallorca in 2023, a number rapidly increasing year on year. Since 2006, all C&D waste (that is not illegally flytipped) is processed by the private company MAC Insular under a public contract. Over 95 per cent of the material they receive, they claim, is reused, recycled or undergoes ‘material recovery’, meaning it is crushed into a range of aggregates that are sold for a profit and used, for example, as backfill for roads. They claim that 3 per cent of the waste they receive is ‘energetically recovered’ (incinerated) and 1.4 per cent goes to landfill – amounting to over 8,000 tonnes.  When the Instituto Balear de la Vivienda (IBAVI, the Balearic Social Housing Institute) identified a plot in the Camp d’En Serralta neighbourhood of Palma, Mallorca’s capital, for housing for people over the age of 65, the disused school building on the site was considered a resource, rather than something to be thoughtlessly discarded. Adaptive reuse was considered by IBAVI but ultimately dismissed; unoccupied for many years, the building was found to be structurally unsound. As a result, the ‘mining’ of the building for material was stipulated in the competition held in 2021.  The project had two parts: a demolition project undertaken by a local architect, and a construction project that was won by Barcelona‑based practice H Arquitectes. Central to the proposed strategy was the recycling of the wall material – assumed to be concrete – as giant aggregate in new concrete blocks, using lime rather than cement, and cast in individual block moulds that could be reused. H Arquitectes had employed a similar tactic in two houses near Girona – in Ullastret in 2017 and Pals in 2023 – where stones from existing structures on the site were used as ‘cyclopean’ aggregate. The competition prescribed a fast construction period, so the architects proposed that the blocks could be fabricated on site while the building was being demolished.  Once demolition started, they discovered that this banal‑looking building was not concrete but loadbearing sandstone – known as marès – underneath the white render. Built in the first half of the 20th century as part of the masterplan for the city devised by engineer Bernardo Calvet in 1901, many of the outwardly unremarkable buildings in the neighbourhood are made in this way. Once deconstructed, the stone was broken into large chunks to be used as super‑sized aggregate – there was not enough material to be used in its original loadbearing state. But rather than cast into block moulds, which would have meant the marès chunks remained hidden, the architects tested a different method; large square slabs, 4m by 4m, were cast and then cut into blocks, revealing the stone chunks like almonds in nougat. The architects created an inventory of more than 50 block sizes and cutting templates for each cast slab, resulting in some 4,300 blocks. Once dry, the slabs were cut using the same machinery as is used elsewhere on the island for cutting marès blocks – familiar technology to local workers – and were laid using a traditional mortar‑laying technique and wood spacing pegs, without any steel reinforcement. Most of the blocks had to be craned into place – the largest blocks weigh up to 900kg.  In addition to chunks of recycled marès, each block contains marès gravel and sand from a quarry on the island, as well as cement, which makes up about 5 per cent of the mix, and 1 per cent lime. Lime without cement was used for the first batches but the mix was found to be structurally insufficient to comply with legal requirements; lime takes much longer to cure and reach an adequate strength – time they did not have. It was also cheaper, saving money that had to be found as the contractor charged more for the change to the block production method. ‘Lime concrete is more healthy,’ acknowledges H Arquitectes co‑founder Xavier Ros. ‘It’s more respectful of the environment.’ But for this project, ‘it was the way to find the solution’. The first limecrete blocks were used for the top floor, creating a visible tide mark on the western elevation.  The walls run from the street to the internal courtyard, with the stepped section of the thick structural walls visible on each elevation. The walls decrease in depth by 100mm floor by floor – the thickest on the ground floor are 640mm deep, thinning to 340mm on the top floor – as the forces they carry decrease. The CLT floors sit on the ledges left by each receding wall, and the spaces between the walls at each end are infilled with timber‑framed windows, supplemented by insulated panels of larch cladding on the street side. While the structure is alluringly simple and legible, the decreasing depth of each wall also means that each floor is different, precluding the efficiency (and reduced opportunity for mistakes) that repeated windows and facade elements would have allowed.  The living spaces of the 25 units are dictated by the structure: small dual‑aspect flats of around 30m2 occupy the space between parallel walls, with one room opening onto the deck overlooking the courtyard, one overlooking the street, and a kitchen and shower room at the centre. This small floor area is supplemented by a shared laundry, two common rooms (for playing cards, for example) and a communal roof terrace, as well as the garden in the courtyard. There are two units, on the chamfered corner of the block, with a second bedroom for a live‑in carer if necessary. The three flats on the top floor are the crown – though similar in floor area to the other flats, they are less deep, flooded with light, and have access to large terraces. In each, the concrete blocks, timber ceilings and concrete floors are left exposed, and will remain so; residents are not allowed to redecorate or make any permanent changes to the interiors.  On the lower ground level – the level of the original playground – a fifth floor is tucked between the existing concrete retaining walls holding up the street, and a sunken courtyard. These flats are different in character to the others; they are single aspect and have solid grey concrete ceilings and walls (the recycled marès blocks could not be used for structural reasons). Their tough and industrial aesthetic may be desirable among architects and other young creatives, but there are concerns they may prove challenging for some of their elderly residents. Many of the IBAVI social housing projects have striven for passive heating and cooling; Peris+Toral Arquitectes’ social housing project in Eivissa contained no air conditioning or mechanical heating. Here, there is no air conditioning – the massive walls will provide thermal mass to protect against the summer heat, like the stone walls of a cathedral – but there are traditional radiators for heating during winter. Though the decks around the courtyard are south‑facing, they are shaded year‑round by the surrounding tall buildings. Most apartments (except the corner and lower ground units, which are single aspect) are cross‑ventilated, and chimneys that crenellate the roof extract air from kitchens and bathrooms.  The finished building boasts low embodied carbon emissions of 417kg of CO2 per square metre (by comparison, Peris+Toral’s project, made of compressed earth blocks, was 423kg of CO2 per square metre). Over 95 per cent of the existing building material was repurposed in the project, amounting to just over 1,000 tonnes; the building’s concrete and ceramic material was used as fill for the foundations. The roof tiles were reused in another IBAVI social housing project in the nearby village of Santa Eugènia, and only around 55 tonnes were taken elsewhere to be recycled. This project is likely to be the first example of urban mining in Mallorca. ‘It’s not easy to work like this on the island,’ Ros admits. As such, it is not a perfect project; the use of cement was regrettable but understandable. Though not cheap by local standards at €1,600 per square metre (including demolition costs), the project has proven that recycled material can be used successfully in a social housing project in Mallorca. A project of loadbearing stone – as IBAVI itself has designed on the outskirts of Palma (AR April 2022) – may have been even less carbon‑intensive, but it would not have set this admirable precedent.  With the swing to the right of the Balearic government in 2023, IBAVI’s social housing commissions have taken a turn away from the impressive ecological paradigm it had set since 2017. As the last projects from this period come to fruition, this important work must be propagated and take root elsewhere, in less hostile climes.  2025-05-07 Eleanor Beaumont Share AR May 2025CircularityBuy Now