1The aim of this paper is to analyse the North-Western corridor of the Madrid metropolitan region in order to contribute to the contemporary debate on cities and peripheries. While most of current literature tends to focus on post-suburbanisation and polycentrism, it might be useful to reconsider suburbanisation as an ongoing phenomenon in the north-western area of the Madrid region. This area is academically interesting in two respects: on the one hand because of the existence of a second-home tradition as a precursor to the contemporary suburbanisation process; on the other, for the spatial arrangement of residential developments around relatively compact pre-existing rural villages diverging from the classical stereotype of sprawling peripheries. The presence of new or re-converted permanent residential areas represents the last phase of a process going from the settlement of second homes close to pre-existing rural villages to the transformation of these second homes into principal residences. This process entailed a reconfiguration of housing types and living spaces, offering an opportunity to reflect, from a historical perspective, on the role of developers in housing production and temporal evolution of urban morphology.

Methodology

2In order to explore this phenomenon three approaches were adopted: a theoretical approach, in order to set the research against the background of the current debate on the contemporary metropolis and its implications for the Madrid development; a historical approach, which was necessary to define the origin of the single-family housing development and suburbanisation process in the Madrid region and its North-Western corridor; and a quantitative approach, needed to define the boundaries of the study area and gather statistical data about local case studies.

3The aforementioned approaches were combined or used separately in each step of the research process. After defining the theoretical framework, the authors identified a group of municipalities as the study area of their research using the following criteria: territorial continuity, relative proximity to the A-6 motorway (maximum 20 km distance buffer, considering that accessibility is a major factor affecting permanent use of residences), location within the Central Sierra NUTS4 zone (a sub-region of the Madrid region whose boundaries are officially established by the Madrid Institute of Statistics), and similarity of historical backgrounds. These criteria excluded the areas of San Lorenzo de El Escorial (and consequently of other municipalities for the spatial continuity principle), South of the study area, for its history and uniqueness as heritage site, and two municipalities North of the study area, which were closer to the A-1 Madrid-Burgos motorway and relatively far from the A-6 infrastructural corridor.

4Once the study area was determined, the next step was highlighting the origins of the suburbanisation process in this area. This meant demonstrating how single-family second homes anticipated the diffusion of permanent-use single-family housing as a product of metropolitan deconcentration occurring in the Madrid region. This process required a profound analysis of the historical evolution of local urban patterns considering their morphology as a tangible result of each historical period, together with a study of stakeholder relationships in housing delivery. This part of the research combines an historical approach with an appropriate use of quantitative data in order to analyse the transition between second homes and principal residences, which defined the starting point of suburbanisation, implying with this term a permanent use of residences in the study area. The authors used and elaborated statistical information from the National Spanish Census, the Madrid Regional Institute of Statistics and the Alpedrete municipal government and the Rural Register of Property while the base layers for maps were provided the Madrid Institute of Statistics and the National Register of Property. The last part of the paper focuses on a more detailed case study at the sub-municipal scale, which is representative of the aforementioned historical background of the entire study area and all the transformations involving use of residences, urban morphology and housing delivery.

Current debates about the metropolis and peripheries and their impact on the Madrid metropolitan region

5The current trends characterising the configuration of metropolitan areas and regions are expressed in a complex dichotomy between the central city and the outskirts: the central core of the city maintains a certain role fostered by gentrification processes and a neoliberal urbanism promoting renewal, or corporate projects supported both by public institutions and private stakeholders (Brenner and Theodore 2008); suburbs and rural-urban fringes are characterised by more dispersed patterns and in certain cases by the development of metropolitan sub-centres configuring a regional polycentric model (Giampino 2010; Hall and Pain 2006). A wealth of expressions have been used to describe the contemporary metropolis, such as post-metropolis (Soja 2000), post-suburbia (Borsdorf 2004), city explosion (Font 2004), city-region or urban region (Terán 1992; López de Lucio 1999; Valenzuela 2009), focusing on different nuances of the phenomenon.

6The importance of metropolitan peripheries has been highlighted in the existing literature, utilising terms such as urban sprawl, dispersed or diffused city. These erroneously refer to very different contexts, but have in common the general pattern of deconcentrating populations and activities. The description of peripheries is often directed to comparisons between European and North American patterns, in spite of the existence of evident differences (Giampino 2010). Nevertheless, globalisation and economies of scale have been responsible for the emergence of ‘urbanalisation’, a term coined by Muñoz (2005: 113) to describe how the contemporary city is evolving towards a “standardised and common type of landscape” in which “fragments of a city are now reproduced, replicated, cloned in another”.

7Given this context, the Madrid metropolitan region exemplifies the physiotype of the contemporary European Mediterranean city, partially diverging from the traditional image of compactness. While it was originally an archetype of monocentrism in the 1960s, the Madrid metropolitan region underwent a process of deconcentration and was gradually converted into a hybrid between polycentrism and dispersal configuring an area which extends beyond the regional administrative boundaries (Roca et al. 2011; Feria 2008). This paper focuses more on the dispersed aspect of the Madrid metropolitan region than on the simultaneous polycentrism. The increase in distances between dwelling place and workplace and the rise in housing prices in the centre of Madrid fostered a centrifugal movement of population and a conversion of suburban second homes into principal residences, mostly inhabited by middle-class white collar workers. Single-family housing, as the most popular second home type in the Madrid area, is at the heart of this process, whose impact is particularly evident in the North-Western zone of the metropolitan region.

Second homes and single-family housing in the Madrid region: key points and historical background

8The origin of suburban single-family housing in the Madrid metropolitan region dates back to the second half of the 19th century and was clearly connected with second homes built before the Spanish Civil War in holiday centres of the North-Western Madrilenian Sierra. They were unplanned developments devoted to the bourgeois class, easily accessible by train and situated around pre-existing villages such as Los Molinos, Collado Mediano, Alpedrete or Cercedilla, designated as “the capital of summer holidays” (Valenzuela 1977: 335). The process of suburbanisation, involving a permanent use of residence, initially developed beginning in the 1960s in other municipalities such as Pozuelo de Alarcón or Las Rozas de Madrid.

9During this decade, in addition to the “holiday detached housing developments”, still present in the Sierra, a series of permanent-use “detached housing developments for decongestion” was created to improve quality of life for the upper classes seeking an escape from the chaos of capital city (Instituto de Estudios Turísticos 1969: 14). The so-called ‘chlorophyll ideology’ entailed a commercialisation of landscape in the name of a “nostalgia of a lost paradise, a mix of bucolic and vegetal” (Gaviria 1969: 59). The detached second homes built in the 1960s and 1970s were mainly constructed in areas close to bordering provinces, where permissive planning regulations (Valenzuela 2003: 118) together with a general lack of oversight allowed construction on rural land. These provinces, such as Toledo or Ávila, have increased their importance in recent years, absorbing part of the second-home demand generated by the Madrid population (López 2004:291).

10At the beginning of the 1980s, the main reason for acquiring a single-family house in the Madrid Region was still related to holidays, although the number of houses acquired as principal residences increased in the second half of the 1970s (Gago 1981: 15, 179-180 and 265). From the 1980s and 1990s, developers have aimed to maximise their profit through a densification of settlements and reduction of expenses, focusing on affordability (Del Canto 1987: 396) and mostly constructing semi-detached and terraced houses.

11In the last decade the transition or co-existence between second homes and principal residences has been evident, emerging clearly in the North-Western corridor of the metropolitan region, where different processes are still in progress: from the consolidation of old residential settlements close to semi-urban centres to the transformation from holiday homes to principal residences, together with the adaptation of pre-existing rural activities (Valenzuela 2001: 7).

Ongoing transformations and residential development in the North-Western corridor of the Madrid metropolitan region: historical and empirical analysis

12The study area of this research is composed of a group of municipalities (Moralzarzal, El Boalo, Becerril de la Sierra, Collado Mediano, Alpedrete, Manzanares el Real, Cercedilla, Navacerrada, Guadarrama, Los Molinos), the so-called North-Western corridor, situated close to an historical railway route and the highway connecting Madrid with Galicia. All of these settlements have a relatively compact structure, stemming from their medieval configuration as rural villages devoted to agriculture and husbandry. The gradually encroaching Madrid metropolitan development has overlaid this original rural structure inserting new elements according to the type of linkage established with these towns in different historical periods. Until the 19th century the connection with capital city was mainly based on the trade of local rural products. From this period the creation of a railway line and the existence of extensive landed properties devoted to leisure activities and hunting, utilised by gentry and heirs of aristocratic families, started to modify the original configuration of those rural settlements.

13The importance of the proprietors of those large pieces of landed properties increased particularly during the 1960s, when they promoted a series of upper-income detached housing developments taking advantage of permissive provincial regulations and in the absence of municipal planning. The first examples of detached housing in the Madrilenian North-Western Sierra were actually second homes, built between the end of 19th and beginning of 20th century around the old villages. These middle-class neighbourhoods, designated as colonias, were created by municipal governments or local proprietors subdividing land into plots and anticipating the aforementioned development of upper-class residential neighbourhoods, named urbanizaciones and often developed by the land owners themselves. The preferred location for these luxury homes were areas with highly appreciated environmental values such as pre-existing holm-oak woods, producing a phenomenon of “naturbanisation” (Prados 2009).

14Beginning from the 1990s, second homes were spread among all social classes, overcoming the traditional elitist character of this house type and displaying a certain connection with the housing market boom, added investment value to the typical leisure function of these properties. At the same time, the aforementioned increase in housing prices in Madrid produced a re-use of old second homes transformed into principal residences, and new homes were constructed expressly to be used as primary residences. The transformation process from second homes to principal residences can be easily displayed by using quantitative data. One approach is a comparison, already mentioned by Valenzuela (2003: 130), between second homes and principal residences in the area during the period 1981-2001 using Census data. In a town like Alpedrete, the ratio second homes-principal residences decreased from 3.11 to 1.02 in twenty years, attaining a situation of balance between the two typologies. There are other municipalities of the area, such as El Boalo (from 4.01 to 1.89) and Moralzarzal (from 3.95 to 1.0), in which second homes are still prevailing in 2001 over principal residences and some others, such as Collado Mediano (0.84 in 2001) where second homes were already numerically inferior to primary residences in 2001.

15Another important piece of statistical information is provided by 2001 Spanish Census data regarding second-home visitors and resident population (Table 1), compared by using a percentage value designated as rate of linkage (Rate of linkage = [(residents+visitors)/residents]x100). A rate which is lower than 200% indicates a predominance of residents over the number of visitors linked to second homes, occurring where the transition between second homes and principal residences had a stronger impact (Moralzarzal, Alpedrete, Collado Mediano).

Table 1. Residents and second-home visitors (2001) per municipality

Municipality	Residents	Second-home visitors	Rate of linkage, %
Navacerrada	1,953	3,136	260.6
Becerril de la Sierra	3,733	4,656	224.7
Boalo (El)	3,704	4,247	214.7
Guadarrama	10,546	10,686	201.3
Cercedilla	5,535	5,269	195.2
Manzanares el Real	4,547	4,119	190.6
Molinos (Los)	3,752	2,958	178.8
Moralzarzal	6,739	4,655	169.1
Collado Mediano	4,695	3,215	168.5
Alpedrete	8,514	5,440	163.9

Source: Author, based on data from the National Spanish Census

16Analysing the percentage of second homes relative to the total of dwellings per municipality (Table 2), available between 1991 and 2001, it is possible to detect a generalised decrease, particularly evident in Guadarrama (-30.3), Collado Mediano (-24.6) and Alpedrete (-24.4). In contrast, Becerril de la Sierra, which is also the second municipality in the rate-of-linkage ranking displayed in Table 1, increased its number of second homes by 3.3 percentage points.

Table 2. Second homes/Total dwellings (%) per municipality

Municipality	1991, %	1996, %	2001, %	Variation 1991-2001, pp
Guadarrama	73.32	67.02	43.04	-30.28
Collado Mediano	65.08	60.41	40.43	-24.65
Alpedrete	70.48	48.80	46.05	-24.43
Boalo (El)	77.82	58.97	58.27	-19.55
Moralzarzal	68.48	58.16	49.96	-18.52
Manzanares el Real	76.06	65.68	58.43	-17.63
Navacerrada	74.40	67.78	62.25	-12.15
Cercedilla	63.85	64.81	53.04	-10.81
Molinos (Los)	58.63	52.31	52.18	-6.45
Becerril de la Sierra	70.03	66.15	73.33	+3.30

Source: authors, based on data from the Madrid Institute of Statistics

17More recent information regarding last decade is only available at sub-municipal scale. For this reason, we selected as a representative case study a group of neighbourhoods belonging to the municipality of Alpedrete, considering this town as a meaningful example of the type of transformations occurring in the North-Western corridor of the Madrid metropolitan region. This town is significant because of the presence of all the different types of housing developments (Table 3) from the neighbourhoods originally devoted to second homes to the more recent permanent-use houses.

Table 3. Selected housing developments in Alpedrete

Type	Name	Date of origin	Area (m2)	Developer	Main house type	Original use
Colonia	El Carmen	1929	181,300	Municipal government	Custom-built detached	Second homes
Colonia	Colonia de la Lanchuela	1929	70,631	Municipal government	Custom-built detached	Second homes
Urbanización	Los Berrocales	1969	900,000	Private developer	Custom-built detached	Second homes
Urbanización	Mataespesa	1967	430,200	Private developer	Custom-built detached	Second homes
Urbanización	Valdencina	Approx. 1970	135,000	Private developer	Custom-built detached	Second homes
Urbanización (new generation)	Londres	2002	145,600	Private developer	Mass-produced semi-detached	Main residence

Source: authors, based on data by Valenzuela (1977), Ayuntamiento de Alpedrete (1994) and Madrid Institute of Statistics.

18The aforementioned colonias are represented by Colonia del Carmen and Colonia de la Lanchuela, created by the municipal government in 1929 as an expansion of the urban grid. The urbanizaciones Los Berrocales, Mataespesa and Valdencina were constructed between 1967 and 1970 by private developers and conceived as automobile-oriented plutocratic enclaves with a sinuous street design, partially based on collectors and cul-de-sacs. Both categories were former second-home developments later converted into permanent residences. Results in Table 4 demonstrate that the ratio between number of residents (implying with this term a permanent use of houses) and the number of existing houses (gradually built on vacant plots of land) increased considerably through the years. Considering the fact that those neighbourhoods maintained their original forms through the years, we can conclude that the existing second homes have been gradually converted into primary residences and the recently built brand-new houses have probably been constructed for permanent use.

Table 4. Ratio residents/existing houses in former second-home neighbourhoods

Neighbourhood	1986	1996	2009	Increase 1986-2009, %
Los Berrocales	0.42	1.00	2.10	402.1
Mataespesa	0.78	1.44	1.82	132.0
Valdencina	0.20	2.15	3.66	1,768.8
El Carmen	0.94	2.13	3.37	257.5
La Lanchuela	0.97	0.91	2.66	175.2

Source: Madrid Regional Institute of Statistics and Spanish Register of Property.
Analysis by the authors

19The housing development named Londres represents the new generation of urbanizaciones of the last three decades, devoted to principal residences. It is characterised by a densification of plots over a planned grid and mass-produced semi-detached housing, according to the current real-estate market requirements. In this sense, it diverges from the previously mentioned examples, characterised by custom-built detached houses and a different street design (figure 4). Figure 5 constitutes a photographic summary of the three mentioned types of housing development, the colonia, the first-generation urbanización and the new-generation urbanización.

Conclusions

20This article examines the evolution of suburban functions of a region in the North-West corridor of metropolitan Madrid through the analysis of an area which is representative of an ongoing process of residential deconcentration. This area is unique and notable as it demonstrates the different phases involved in the suburbanisation of spaces previously dominated by secondary vacation and leisure properties. The description of such suburban landscape was developed by means of a morphological analysis displaying different housing patterns according to their period of origin. A common characteristic of these housing developments is that they are settled around existing old rural villages maintaining a certain degree of compactness at municipal scale, partially diverging from the archetypal definition of sprawl. Moreover, recent housing developments tend to become denser and, despite being a product of metropolitan deconcentration, in their local context they might be defined as a form of urban extension to pre-existing settlements, being this relative compactness at municipal scale a typical characteristic of the Madrid residential suburban and peri-urban development. Besides its morphological significance, the case study of the North-Western corridor of the Madrid metropolitan region offered a new perspective on the contemporary role of single-family housing, representing an opportunity to permanently reuse pre-existing second homes in an area which reached its suburban status only recently after being a holiday destination for several years. It also demonstrated that suburbanisation, involving a permanent use of brand-new houses, is a phenomenon which is still in progress in some locations, while others have already achieved a post-suburban phase.