In order to deal with the subject of this entry, it is necessary to distinguish between two periods: the first, between 1949 and 1965, when practically all the housing promoted by RENFE was built, and the second, between 1965 and 1989, when the main promoter group was made up of the cooperatives formed by railway workers. This distinction derives from the technical regulatory context, which prescribed construction solutions and materials in the housing project, and also with regard to the availability of materials to carry out the construction.
In this sense, for the dwellings of the first period, two technical regulations were in force: at first, the Order of 29 February 1944 (BOE, no. 61, 1 March 1944) was approved, which determined the minimum hygienic conditions that dwellings had to meet, drawn up at the proposal of the Local Health Commission and which basically consisted of a compendium of 14 precepts which did not deal with the issue of foundations and structures, However, it did require, for dwellings on ground floors, or in those that were allowed below street level, to guarantee waterproofing or insulation against damp, which in some cases would result in sanitary floor slabs. It also prescribed the waterproofing of walls and floors, but, in the projects consulted in this first period where the structural system mainly used is load-bearing walls, apart from the brevity of the project documentation, there are no project prescriptions in this sense for dwellings located on the ground floor, which was the most common situation in this first period.
The second mandatory regulation for the dwellings under study was the Order of 12 July 1955 approving the text of the technical ordinances and construction standards for “low-income housing”. In these regulations, just as the prescriptions for dwellings in the first group are limited to the fact that the building must comply with existing municipal ordinances, for those in the second group, to which all the dwellings under study belong, the following are established: minimum project contents, details of the urbanisation projects in accordance with existing planning, suitability of the land and its valuation (Martínez-Corral & Cuéllar, 2020).
With regard to the suitability of the land, the sixth ordinance establishes ten prescriptions for land that is unsuitable for building, largely due to the lack of possibility of laying foundations because of the presence of fill, archaeological zones, dune areas or similar, or because the cost of laying foundations on it was excessive, very hard or soft land that required piling or similar solutions (Illustration 1). The paradox of the matter is that no geotechnical study of any kind was prescribed, nor did the reports state the technical reasons for the choice of ground or the reason for the maximum ground stress determined for the calculation of the structure beyond generic descriptions of the qualities of the ground.
Illustration 1. Foundation pits in the housing development built by RENFE in Algodor (1955).
In the fifth part of the document, which deals with construction standards, the brief first ordinance is extremely ambiguous about how foundations should be laid (Illustration 2): on the one hand, it states that the width of the foundation must be the width tolerated by the supporting soil, without regulating how to determine the resistance of the soil or providing solutions in the event of uneven soil throughout the support plane (e.g. tying of foundations); on the other hand, it allows any solution a priori, although the cheapest economic solution takes precedence. Once again, it is not the technical constraints that take priority, but the economic ones.
Illustration 2. Example of foundations in the housing development built by RENFE in Paseo de las Delicias in Madrid (1954).
With regard to walls, the only structural system contemplated in the aforementioned Order, it is somewhat more extensive, although equally ambiguous. It establishes, on the one hand, that the width of the walls must come from the calculation that guarantees stability and insulation, although again without specifying conditions or calculation methods. On the other hand, it admits material variety, although with certain limitations depending on the case. The use of tapial, an ancient technique that takes its name from the formwork consisting of tamping damp earth, is allowed, but with conditions and exclusively in those areas where its use was typical without specifying them, although it is certain that it was a technique profusely used in Spain in both monumental and popular architecture (Font & Hidalgo, 2011). The conditions for its execution were that it had to be brickwork and ensure insulation against damp by means of masonry plinths and perimeter pavements, and to reinforce corners and weak points by means of masonry or concrete reinforcement. The same conditions apply to adobe construction. The construction of block walls is also permitted, but in this case, given the lack of ordinances on the subject, the INV had to be consulted beforehand on the possibility of their use.
In the case of masonry, it requires the lining of the interior and the use of hydraulic mortar for grouting. It should be noted that this is a period when multi-layer walls did not exist. Hence the requirements for the coating of the interior face, as well as the numerous pathologies in terms of insulation, due to thermal bridges or others. Mass and reinforced concrete load-bearing walls are also authorised, as are framed walls, although with either masonry or lightweight slabs authorised by the INV: those with reeds, mud, peat or similar materials required prior approval in each case from the aforementioned institute.
The standard opts for brick without requiring any conditions regarding its use. This is in line with the projects analysed, where, up to now, no use has been made of rammed earth or adobe and, on a few occasions, masonry has been used, especially on the ground floor, with the most common use of brick as a structural material in this first period (Illustration 3).
Illustration 3. Construction section of the housing development built by RENFE in the railway district of Las Matas, Madrid (1963).
The absence of prefabrication in housing construction and the abuse of brick was a common criticism in scientific articles of the time. A decade into the study period, the comparative tables that the engineer Presa Santos (1972) drew up between various European countries on either side of the Iron Curtain with respect to the level of prefabrication in housing construction achieved on the basis of UN data are noteworthy. The difference is abysmal: in no Western European country was prefabrication used in housing construction except in specific examples, while in Eastern Europe or the USSR prefabrication was commonplace. Paradoxically, construction systems were much more developed in Western Europe (Presa Santos, 1972).
Font, F., & Hidalgo, P. (2011). La tapia en España. Técnicas actuales y ejemplos. Informes de la Construcción, 63(523), 21-34. https://doi.org/10.3989/ic.10.015
Martínez-Corral, A., & Cuéllar, D. (2020). Las soluciones constructivas en la vivienda durante el franquismo: El caso de la vivienda ferroviaria. Informes de la Construcción, Vol. 72, 558, e341, abril-junio 2020. https://doi.org/10.3989/ic.71047
Presa Santos, J. L. (1972). La prefabricación de la construcción. Revista de obras públicas, 119, 307-310.