Wooden vaulted churches in the Basque country: measuring units and their relation to 16th century naval structures

Iglesias con bóvedas de madera en el País Vasco: unidades de medida y su relación con las estructuras navales del siglo XVI

Teresa Artola-Guijarro

Built Heritage Research Group (GPAC), University of the Basque Country (UPV/EHU) Vitoria-Gasteiz. Spain

teresartola@gmail.com, http://orcid.org/0009-0001-5970-9212

Alejandro Martínez de Arbulo

Kyoto Institute of Technology, Kyoto. Japan

https://orcid.org/0000-0002-0211-1164

ABSTRACT

In CIMAD 11, Pedro Hurtado-Valdez presented an interesting paper on the myths and facts of the construction of Castilian wooden vaults between the 17th and 18th centuries, attempting to refute the belief that the genesis of wooden vaults in Spain and Latin America had its antecedents in the construction of ships in the Basque regions, and in the naval experience of some writers of previous centuries.
A more in-depth study of the geometry of the structure of the wooden vaulted roofs of Basque churches of the 15th and 16th centuries, catalogued in Ars Lignea in 1996 by Alberto Santana and other authors, was an unfinished task that had hardly been addressed since that publication.
In this article, we want to present our conclusions on the veracity of this hypothesis by comparing the codo de ribera, a standard measurement used in the naval construction from 1590 onwards, with the dimensions of the pairs of arches that form the barrel vaults of four churches analysed by laser scanner in the Gorbea valleys: Santa María de Goikuria, San Bartolomé de Olarte, San Pedro de Zaloa and San Lorenzo de Otzerimendi.

Keywords: wooden vaults; wooden architecture; shipbuilding; codo de ribera; Basque country.

RESUMEN

En CIMAD 11, Pedro Hurtado-Valdez nos presentó una interesante ponencia acerca de los mitos y verdades de la construcción de bóvedas de madera castellanas entre los siglos XVII y XVIII, intentando desmontar la creencia de que la génesis de las bóvedas de madera en España y en Hispanoamérica tuvo sus antecedentes en la construcción de navíos en las regiones vascas, y en la experiencia naval de algunos tratadistas de los siglos precedentes. Un estudio más profundo acerca de la geometría de la estructura de las cubiertas de madera de las iglesias vascas de los siglos XV-XVI catalogadas en Ars Lignea en 1996 por Alberto Santana y otros autores, era una tarea pendiente que desde aquella publicación apenas se había abordado.
En este artículo queremos presentar nuestras conclusiones acerca de la veracidad de esta hipótesis mediante la comparación del codo de ribera, medida estándar utilizada en la construcción de las naves desde 1590 en adelante, y las dimensiones de los pares curvos que forman las bóvedas de cañón de cuatro iglesias analizadas a través del láser escáner ubicadas en los valles del Gorbea: Santa María de Goikuria, San Bartolomé de Olarte, San Pedro de Zaloa y San Lorenzo de Otzerimendi.

Palabras clave: bóvedas de madera; arquitectura de madera; construcción de navíos; codo de ribera; País Vasco.

Supplementary information ↓

Content

1. INTRODUCTION AND RESEARCH AIM

2. MATERIALS AND METHODS

3. SHIP’S CARPENTRY

3.1. Frame manufacture

3.2 Bending parts

3.3 Measurement units

4. ARCHITECTURAL CARPENTRY / STRUCTURAL WOODWORK

4.1 Carpenter guilds

4.2 Basque wooden barrel vault

4.3 Measurement units

4.4 Wooden joints

5. CONCLUSIONS

REFERENCES

1. INTRODUCTION AND RESEARCH AIM ↑

The Basque Country is a region in northern Spain and southern France with a distinct language, culture, and architectural style. Because of its historically dense forests, the region has a rich tradition of using wood in both building and naval construction.

The Basque wooden churches had massive stone walls, but their roof structures were always built with wood. Early examples, such as the 16th-century church of La Antigua de Zumarraga, originally had exposed wooden roofs with no ceilings. Later, vaulted ceilings were added for two main reasons: to improve the building’s appearance and prevent dust from falling, and to comply with the demands of visiting bishops’ overseers who required more dignified and solemn interiors [1][1] T. Artola-Guijarro y A. Martínez de Arbulo, “Churches with wooden vaults in the Basque Country: An analysis of design techniques and measurement units,” Int. J. Architectural Heritage, pp. 1–26, Nov. 2023. https://doi.org/10.1080/15583058.2023.2277320.

In wooden churches, the complexity of the structures that make up the vaults and their curved shape, which resembles the upturned hull of a wooden ship, suggest that there was an exchange of techniques between carpenters and shipbuilders, and this is still perpetuated by many historians who promote such myths among tourists and become part of popular belief.

Research into traditional Basque architecture has largely focused on residential buildings, particularly baserris (farmhouse), and numerous studies have been published on the subject since the late 19th century. The carpentry techniques used in these structures have also been analysed [2][10] M. Barkham, “Sixteenth century Spanish Basque ships and shipbuilding: The multipurpose nao”, Postmedieval Boat Ship Archaeol., Estocolmo, 1985..

By contrast, the study of wooden structures in religious buildings is a relatively recent phenomenon. The “Ars Lignea” volume [3][2] A. Baeschlin, La arquitectura del caserío vasco, 2a ed. Bilbao: Bibl. Vascongada Villar, 1968. provides a comprehensive survey of 61 churches in the Spanish Basque provinces, detailing their wooden roofs, ceilings, and choirs. However, the architectural drawings in this volume lack the precision required for an in-depth analysis of design methodology and measurement units. Although a study of six Gipuzkoan churches has recently been published [4][4] R. Ayerza, Iglesias de madera en Gipuzkoa. Bilbao: Univ. Del País Vasco, 2019., this work only analysed the buildings’ overall proportions and not the design of their vaults.

In 2011, at the 1st Ibero-Latin American Congress on Wood in Construction, Doctor of Architecture Pedro Hurtado-Valdez presented an interesting paper debunking the myth that the first wooden vaults were inspired by naval vessels [5][5] P. Hurtado-Valdez, “Bóvedas de madera y construcción naval: Mitos y verdades de la construcción de bóvedas de madera castellanas entre los siglos XVII y XVIII,” presented at CIMAD 11, Coimbra, Portugal, jun. 7–9, 2011.. Enrique Nuere had also focused on the differences in carpentry techniques previously, in 1996 [6][6] E. Nuere, La carpintería de armar española. Madrid: Munilla-Lería, 1996.. Despite both working with wood, shipwrights and carpenters employ distinct techniques due to the vastly different constraints of their trades. It was highly uncommon for a practitioner of one craft to be proficient in the other: a shipbuilder would not typically design a church roof, nor would a church carpenter construct a ship. While some individuals might have possessed exceptional cross-disciplinary skills or performed basic timber preparation for either trade, rigorous journeyman exams clearly defined the specialised knowledge acquired through extensive apprenticeships. This specialisation generally meant that apprentices learned their master’s trade exclusively. In his article [5][5] P. Hurtado-Valdez, “Bóvedas de madera y construcción naval: Mitos y verdades de la construcción de bóvedas de madera castellanas entre los siglos XVII y XVIII,” presented at CIMAD 11, Coimbra, Portugal, jun. 7–9, 2011., Hurtado-Valdez emphasises the positive aspects by drawing a comparison between the construction techniques used for the ship’s ribs and those used for wooden vaulted arches. However, this comparison is not supported by evidence beyond historical documents from that period. This article aims to provide further evidence to support that analysis, using data collected from four Basque churches with wooden barrel vaults, the oldest examples of their kind still standing.

2. MATERIALS AND METHODS ↑

Since 2020, the authors of this article have been studying four churches with wooden barrel vaults dating from around 1550, carrying out various analyses using laser scanning to obtain precise measurements and carry out a comparative study.

These churches are located near the Biscayan town of Orozko (see in Figure 1) and are as follows:

San Bartolomé de Olarte (1520-1560), San Pedro de Zaloa (1530-1660), San Lorenzo de Otzerimendi (1550) y Santa María de Goikuria (1770).

Figure 1: Location of the churches (source: Google Maps modified by the authors).

Based on this situation, this study has used the data previously collected at different stages [1][1] T. Artola-Guijarro y A. Martínez de Arbulo, “Churches with wooden vaults in the Basque Country: An analysis of design techniques and measurement units,” Int. J. Architectural Heritage, pp. 1–26, Nov. 2023. https://doi.org/10.1080/15583058.2023.2277320:

1. Collection of historical information from the Ecclesiastical Historical Archive of Bizkaia (AHEB-BEHA)
2. On-site data obtained by laser scanning (Leica RTC360), where it was particularly important to record the curved shape of the wooden frames.
3. Creation of 3D models and architectural drawings, which allowed us to obtain real measurements of the vaults, including their deformations.
4. Analysis of the geometry and units of measurement of the vault, which allowed us to make comparisons with ship hulls built at the same time using codo de ribera as main unit.

The article points out that the architectural and naval techniques are too complex to allow for interchanges. What is certain is that the details of the methodology used to design the wooden vaults are still unknown. In this paper we are going to dismantle the hypothesis that suggests that there was an exchange of techniques between ship carpenters and shipbuilders.

3. SHIP’S CARPENTRY ↑

3.1. Frame manufacture ↑

As mentioned in the introduction, the complexity of the vault structures and their curved shape, reminiscent of an inverted wooden ship’s hull, suggests an exchange of techniques between roof carpenters and shipbuilders. Thus, the wooden element in shipbuilding that is usually associated with arches for the construction of vaults, due to its curved shape, is the frame, Spanish cuaderna [5][5] P. Hurtado-Valdez, “Bóvedas de madera y construcción naval: Mitos y verdades de la construcción de bóvedas de madera castellanas entre los siglos XVII y XVIII,” presented at CIMAD 11, Coimbra, Portugal, jun. 7–9, 2011..

As Cruz Apestegui explains [7][7] C. Apestegui, Arquitectura de los navíos de la carrera de Indias. Madrid: Naval, 1992., the construction method of superimposed ligatures, also known as varenga-genol, whose origins date back to at least the 15th century, is the one used by shipbuilders for the manufacture of all high board vessels in the peninsular Atlantic. This method of construction was used until the 18th century. From 1751, the frame system began to resemble the vault construction system more closely.

The technique consisted of creating a basic structure on the keel of the ship, called a ‘fixture’, on which the ship was then sheathed. This system consisted of overlapping connections joined by dovetail joints, as illustrated in Figure 2.

These frames were placed transversely and consisted of thick curved timbers of varying dimensions, joined together with wooden dowels and dovetail joints. The later ligatures are not connected to each other, the inner and outer lining being the only fastening element between them [7][7] C. Apestegui, Arquitectura de los navíos de la carrera de Indias. Madrid: Naval, 1992..

Figure 2: Master Frame Section of a 16th-century Galleon Note. Adapted from Cuaderna Maestra [Master frame], by Albaola Itsas Kultur Faktoria, n.d. ( https://albaola.org/cuaderna-maestra/).

It is estimated that in the second half of the 16th century the annual production of the southern Basque region was 20 ships of 100 tonnes or more. The Basque region had all the necessary components for an active shipbuilding industry: hemp from the north, resin from the Landes in south-west France, wood from the Pyrenees and the Bayonne area, and iron from the mountains of the Biscay province [8][8] L. Odriozola Oyarbide, “La construcción naval en Gipuzkoa en el siglo XVI-XVIII,” Itsas Mem.: Rev. Estud. Marítimos País Vasco, no. 2, pp. 93–146, 1998..

The region also had an abundance of skilled workers who had formed guilds of carpenters, coopers, blacksmiths, coppersmiths, cobblers, rope makers, sail makers, gunsmiths and the like.

In the 1570s, however, Basque shipbuilding began to decline. One of the reasons was the depletion of timber reserves. As early as 1561, Sir Thomas Chamberlain wrote that the Basques had cut down the best trees without planting others [8][8] L. Odriozola Oyarbide, “La construcción naval en Gipuzkoa en el siglo XVI-XVIII,” Itsas Mem.: Rev. Estud. Marítimos País Vasco, no. 2, pp. 93–146, 1998.. The result was that there was little timber left for shipbuilding, hence the rise in prices, which had doubled in 30 years. There was also a shortage of wood for forges, where the smelting process to produce iron required huge amounts of fuel. Clearly, without a policy to promote the renewal of their resources, the Basque provinces would be unable to meet demand given the small size of their territory.

On the other hand, from the 16th century onwards, the internal organisation of shipbuilding in Spain was highly hierarchical [8][8] L. Odriozola Oyarbide, “La construcción naval en Gipuzkoa en el siglo XVI-XVIII,” Itsas Mem.: Rev. Estud. Marítimos País Vasco, no. 2, pp. 93–146, 1998.. The master craftsmen of the naval works were the shipwrights (for the structure), the carpenters (for the interior) and the caulkers (for the waterproofing). They were assisted by other craftsmen such as nail-makers, anchor-makers, coopers, riggers, ox carriers, sawyers, plank-makers, shipwrights and stonemasons.

Even the shipwrights were employed for two different jobs: some had to work in the shipyards, with their attendant subspecialisations, and others had to go out into the woods in search of the timber needed for the work.

A working environment with such peculiarities did not leave much room for the application of other fields of carpentry than those in which the carpenter had been trained, since shipbuilding had its own rules and construction systems to obtain the elements for the assembly of a ship.

The activities of the shipwrights ranged from the selection of trees in the forest, the sawing, the manufacture of the various parts, their assembly and the overall construction of the hull, as well as the caulking or waterproofing of the joints. [5][5] P. Hurtado-Valdez, “Bóvedas de madera y construcción naval: Mitos y verdades de la construcción de bóvedas de madera castellanas entre los siglos XVII y XVIII,” presented at CIMAD 11, Coimbra, Portugal, jun. 7–9, 2011..

3.2 Bending parts ↑

If the shipwrights and carpenters made up the bulk of the carpenters employed in shipbuilding, there was another group of wood specialists whose participation was also very active and decisive: the surveyors. They were responsible for selecting and directing the cutting of the wood to be used. It was an extremely difficult and delicate task because, on the one hand, they had to make use of the natural shapes of tree trunks and branches to make the main parts of the ships. The master selectors took advantage of the natural curvatures of cultivated oaks to obtain the necessary pieces (Figure 3). On the other hand, they had to take into account not only the orientation of the trees at the time of felling, but also all the various angles formed by the curves of these “delicate and easily bend trees”. For all this, these experts counted on the invaluable help of the sawyers and some ship carpenters [8][8] L. Odriozola Oyarbide, “La construcción naval en Gipuzkoa en el siglo XVI-XVIII,” Itsas Mem.: Rev. Estud. Marítimos País Vasco, no. 2, pp. 93–146, 1998..

There were other ways of bending the ribs, such as applying heat [9][9] M. Araya López, “Determinación de características de curvado de madera sólida...”, Tesis, Univ. Tecnol. Metrop., Chile, 2005., but it seems that the Basque builders, who had an abundance of wood at their disposal, did not have to resort to these alternatives.

Figure 3: Cultivated oak trees. All parts of the oak tree could be used to provide the different types of naval parts that make up a ship. (source José Lopez, Bertan, Gure Itsasontziak).

3.3 Measurement units ↑

Sixteenth-century Basque shipbuilding was renowned for its multipurpose ships, known as naos or galleons, which were designed for multiple purposes. These vessels could be used for whaling, cod fishing, transporting wool, trading with the Indies or serving as warships. Due to the prevalence of hostilities and piracy, Basque merchant ships were always armed. Although they were adapted for combat, the fundamental design of their hulls remained unchanged [10][10] M. Barkham, “Sixteenth century Spanish Basque ships and shipbuilding: The multipurpose nao”, Postmedieval Boat Ship Archaeol., Estocolmo, 1985..

Shipbuilders used the sexagesimal system and used whole fractions as divisions. The precision used was much lower than that used in normal analysis, and often a ship that was designed, laid out and started construction with certain dimensions had different measurements at the end of its construction, due to the fact that the shipyards were located on muddy ground that allowed the fixing points of the parts to move.

Regarding the definition of historical units, the codo de ribera was different in the south and north of Spain. According to Dueñas Fontán [12][12] M. de Dueñas Fontán, “Medidas de los navios de la jornada de Inglaterra,” in Curso de verano: La arquitectura y construcción nav. en España durante la época de los descubrimientos geográficos, El Escorial, España, Madrid: Cuadernos Monográficos del Instituto de Historia y Cultura Nav., 1996., a 32-finger (55.667 cm) codo de ribera was used in Andalusia, while a 33-finger (57.468 cm) codo de ribera was used in northern Spain. This was the measurement used in our geometric analysis.

An analysis of 25 construction contracts [10][10] M. Barkham, “Sixteenth century Spanish Basque ships and shipbuilding: The multipurpose nao”, Postmedieval Boat Ship Archaeol., Estocolmo, 1985. from 1545 to 1611 reveals remarkable consistency in the proportions of Basque ships. The dimensions and proportions of Basque vessels between 1545 and 1600 are detailed in Table 1. This analysis shows an average keel-to-beam ratio of 1.89. This ratio remained constant for approximately 66 years, indicating a lack of evolution in the basic shape of the hull.

Table 1. The dimensions and proportions of Basque ships built between 1545 and 1600 are shown here. All measurements are in codos de ribera, where one codo equals 57 centimetres (source: authors)

YEAR	PLACE	BEAM	DEPTH	BEAM TO DEPTH RATIO	LENGTH	LENGTH/BEAM
		MANGA	PUNTAL EN MANGA	MANGA/PUNTAL	ESLORA	ESLORA/MANGA
1600	Zumaya	15	11	1,36	47	3,13
1545	Fuenterrabia	14	10	1,40	43	3,07
1591	Zumaya	15	10	1,50	46	3,07
1590	Zumaya	15	12	1,25	47	3,13
1585	Lezo	16	11,5	1,39	--	--
1567	Usurbil	16,75	10,5	1,60	50	2,99
1585	Orio	16	11	1,45	51	3,19
1578	Motrico	17,66	11	1,61	--	--

The generic ratio ‘As, Dos, Tres’, in which the beam was 1, the keel was 2 and the length was 3, was an approximate formula for a nao, so slight variations were possible [11][11] C. Rahn Phillips, “The Evolution of Spanish Ship Design from the Fifteenth to the Eighteenth Century,” Amer. Neptune: Quart. J. Marit. Hist., vol. 52, no. 1, 1992..

In Barkham table the average ratios for a Basque ship of 200–800 tons were as follows: beam: 1; keel: 1.9; length: 3.1; and strut(depth) on beam: 0.69.

To lay out the master frame (the section of the ship where the maximum beam is located), the plan and depth were first defined. The plan was established as a fraction of both the beam and the depth. The plan is the lowest and widest part of the bottom of the ship’s hold, or the horizontal section formed by flat floor timbers on each side of the keel. The depth, on the other hand, was measured from the plan to the main deck.

The profile of the master frame, from the plan to the main deck, was drawn using an arc of a circle. Similarly, the length on deck was defined from the outset to determine the fore and aft overhangs. Finally, while the sternpost was traced with a straight line, the stem was shaped using an arc.

The profile of the master frame (midship section) was defined using arcs of a circle, following treatises such as the Instrucción Náutica of 1587 (Figure 4). Similarly, the length on deck was defined from the outset to determine the fore and aft overhangs. Finally, while the sternpost was traced with a straight line, the stem was shaped using an arc [6][6] E. Nuere, La carpintería de armar española. Madrid: Munilla-Lería, 1996..

Figure 4: 400 ton nao, measurements in “codos” (source Instrucción náutica 1587).

4. ARCHITECTURAL CARPENTRY / STRUCTURAL WOODWORK ↑

4.1 Carpenter guilds ↑

An important element in understanding the difficulty of allowing master carpenters to work in “architectural carpentry” as well as in “ship carpentry”, and vice versa, is the labour relations established in Spain and managed by the guilds [13][13] A. J. Albaronedo Freire, “Fuentes legales sobre construcción: Las Ordenanzas de Sevilla (1527),” in Actas del Tercer Congreso Nacional de Historia de la Construcción, vol. 1, Madrid, España: Inst. Juan Herrera, oct. 26–28, 2000, pp. 1–12..

It should be remembered that the supply of wood was not free, but controlled by a monopoly of the guild, which only allowed its sale to its members.

In the Iberian Peninsula, builders worked in an environment governed by guilds and activities characterised by professional zeal [5][5] P. Hurtado-Valdez, “Bóvedas de madera y construcción naval: Mitos y verdades de la construcción de bóvedas de madera castellanas entre los siglos XVII y XVIII,” presented at CIMAD 11, Coimbra, Portugal, jun. 7–9, 2011..

4.2 Basque wooden barrel vault ↑

The first type of wooden vault built in Spain was constructed using wooden ribs. In the Basque Country there are four churches with barrel vaults and they are characterised by being structures in which the transverse arches act as curved pairs supporting a row that acts as a longitudinal rib [5][5] P. Hurtado-Valdez, “Bóvedas de madera y construcción naval: Mitos y verdades de la construcción de bóvedas de madera castellanas entre los siglos XVII y XVIII,” presented at CIMAD 11, Coimbra, Portugal, jun. 7–9, 2011.. This structure is based on transverse arches supporting a longitudinal ridge, whose geometric complexity can be appreciated in the 3D model of Goikuria (Figure 5).

Figure 5. 3D cover of Santa María de Goikuria (source: Landa Ochandiano).

The vaults of Zaloa and Otzerimendi are the only surviving examples where the original 16th-century naves preserve their specific timber frames intact; both temples maintain their wooden structures unaltered (Figures 6 and 7, respectively). In San Bartolomé de Olarte (Figure 8), however, the original boarding that once filled the interstices between the arches has been removed. Meanwhile, the hermitage of Santa María de Goikuria presents a similar aesthetic—as seen in Figure 9—despite being an 18th-century replica of the Olarte model. Beyond these specific cases, the barrel vault solution was a relatively common feature in the presbyteries of numerous smaller 16th-century hermitages.

Figure 6. Inner nave of San Pedro de Zaloa (source: authors).

Figure 7. Inner nave of San Lorenzo de Otzerimendi (source: authors).

Figure 9. Inner nave of Santa María de Goikuria (source: authors).

There is no single paternity to the Basque wooden vault, but three different cultural vectors come together in the genesis of these vaults: firstly, the local tradition of building free-standing carpentry structures; secondly, the desire to imitate the designs of Castilian masonry vaults; and thirdly, a correct assimilation of the Flemish, Burgundian, and Norman practice of creating Gothic ceilings of apparent carpentry. This triple cultural inheritance would determine the formal typology of Basque wooden vaults, but the decisive factor in each case for the adoption of a wooden roof instead of a stone one was undoubtedly economic.

For reasons of economy, the churches of the Basque Country were covered with wooden vaults, adopting a Flemish practice and aspiring to a Castilian style. And probably for the same initial reason, ribbed or ligneous barrel vaults were adopted in some rural villages in the north-west of the peninsula, without there being any authorship or chronological relationship between the two regions beyond a mere typological affinity [6][6] E. Nuere, La carpintería de armar española. Madrid: Munilla-Lería, 1996..

4.3 Measurement units ↑

In our studies [1][1] T. Artola-Guijarro y A. Martínez de Arbulo, “Churches with wooden vaults in the Basque Country: An analysis of design techniques and measurement units,” Int. J. Architectural Heritage, pp. 1–26, Nov. 2023. https://doi.org/10.1080/15583058.2023.2277320, the geometrical analysis of the shape of the vaults has revealed a rich variety of construction techniques. This analysis reveals semicircular profiles in Otzerimendi and Zaloa (Figures 10 and 11), a pointed profile in Olarte (Figure 12), and a more complex oval curve in Goikuria (Figure 13).

While the vaults of San Lorenzo de Otzerimendi and San Pedro de Zaloa have an identical semicircular shape, the vault of San Bartolomé de Olarte has a pointed profile formed by two intersecting semicircular arches. The later vault of Santa María de Goikuria is the most geometrically complex: its profile is made up of three tangent arches that form a continuous oval curve. These changes can be interpreted as reflecting the evolution of architectural styles and tastes.

In order to know the units of measurement used in the design of these vaults, their main dimensions were converted into the units historically used by Basque carpenters: feet, cubits and codo de ribera. The first two were generally used by architectural carpenters, while the latter was used by naval carpenters. It was found that the main dimensions of the vaults in the four buildings could be expressed as combinations of whole numbers and simple fractions when converted into feet or cubits, making them the most likely units of construction. In particular, the foot was the unit that allowed the easiest expression of the main dimensions of the vaults. On the other hand, the dimensions of the vaults cannot simply be expressed in codos de ribera. This supports the hypothesis that architectural carpenters, rather than shipbuilding carpenters, designed and built these vaults [1][1] T. Artola-Guijarro y A. Martínez de Arbulo, “Churches with wooden vaults in the Basque Country: An analysis of design techniques and measurement units,” Int. J. Architectural Heritage, pp. 1–26, Nov. 2023. https://doi.org/10.1080/15583058.2023.2277320.

Figure 10. Geometric analysis of the vaults of San Lorenzo de Otzerimendi (source: the authors).

Figure 11. Geometric analysis of the vaults of San Pedro de Zaloa (source: the authors)

Figure 12. Geometric analysis of the vaults of San Bartolomé de Olarte (source: authors).

Figure 13. Geometric analysis of the vaults of Santa María de Goikuria (source: authors).

We can summarise these measurements of the vaults in Table 2 below, based on the same data we used to examine the proportions of the geometry in the design of a 16th-century ship.

Table 2: This table shows the dimensions and proportions of Basque wooden vaults built between 1550 and 1771. All measurements are in codos de ribera, where one codo equals 57 centimetres

YEAR	PLACE	NAVE WIDTH (W)	RIB VAULT HEIGHT (H2)	WIDTH TO HEIGHT RATIO (W/H2)	LENGTH	LENGTH/W
ca. 1550	Otzerimendi	10,39	5,51	1,89	12,67	1,22
1550-1560	Zaloa	10,41	5,46	1,90	16,36	1,57
1560-1570	Olarte	17,42	8,70	2,00	18,61	1,07
1771	Goikuria	11,73	4,63	2,53	15,68	1,34

4.4 Wooden joints ↑

The process of assembling two or more pieces of wood to form a whole from which the parts cannot be separated is called joinery.

The wooden ribs that make up the arch of our wooden vault are joined together using mechanical joints, which employ fittings, nails or screws. These joints work by transmitting forces through the wood, creating localised compression.

To span the widths of the temple, the arches are formed with overlapping pieces using half-lap splice joints (Figures 14 and 15). These joints were not typically used for ship frames, for which dovetail joints were preferred.

The following joints were found in our churches:

Half-lap splice joint: A lap joint is a type of joint in which the pieces overlap. In a half-lap joint, material is removed from both pieces so that the resulting joint is as thick as the thickest piece.

In most half-lap joints, the pieces are the same thickness, with half this thickness removed from each. The joint can be reinforced with dowels or mechanical fasteners to prevent twisting of the wood.

Figure 14. Arch assembly in San Bartolomé de Olarte with a half-lap splice joint (source authors).

Figure 15. Detail of arch assembly in Santa María de Goikuria (source authors).

Mortise and tenon: A mortise and tenon joint is a technique used to connect two pieces of wood. This technique has been used by woodworkers around the world for thousands of years to join pieces of wood at right angles, although it can be used at any angle.

These joints are simple, strong and stable, and can be used in many projects to create an attractive finish. They can be either glued or friction-fitted into place. However, this type of joint is difficult to make due to the precise measurements and tight cuts required. The tenon is formed at the end of one component — typically a ‘rail’ — and fits into a square or rectangular mortise cut into the corresponding component.

The keystones of the vaults are resolved using mortise and tenon joints, as observed in Goikuria and Zaloa (Figures 16 and 17).

Figure 16. Keystone assembly at Santa María de Goikuria (source 3D Landa Ochandiano).

Figure 17. Keystone central rib at San Pedro de Zaloa (source authors).

5. CONCLUSIONS ↑

When we compare the proportions of a typical section of our churches with those of a contemporary 16th-century galleon, it becomes clear that they do not match. The lack of correspondence between both structural systems is made evident when overlaying their profiles, where divergent design criteria can be observed (Figure 18).

The average width of churches is around 11 codos de ribera (this was never an exact measurement, as it was not used for the design), while the average width of ships is 15.

The length is also not comparable, at around 50 codos de ribera on average, compared to 15 codos de ribera for churches. The beam/depth ratio is 1.5 in ships and closer to 2 in churches, and the length/beam ratio is 3 in ships and 1.3 in churches.

Figure 18. Overlay of the cross-section of the Olarte barrel vault and the main frame of a 400-tonne ship. (Source authors).

With all that has been analysed above, we can conclude that the structural characteristics of the ships and the church roofs followed different criteria, as evidenced both in their construction, their geometry, and their assembly.

Nor does it seem possible that the carpenters who worked in the naval shipyards could have participated in the construction of the church roofs, as it has been demonstrated after the geometric comparison that the dimensions used by the two groups are not correlative.

The methodology developed in this research, which combines 3D scanning with geometric analysis, can be used in the future to study other historical buildings, including more complex wooden vaults in the Basque Country and elsewhere. The information on original construction techniques and measurements obtained through such studies will help us to better understand these historic buildings and plan future conservation interventions.

Future research will focus on the detailed cataloguing and geometrical analysis of the timber joinery. Furthermore, dendrochronological testing will be conducted on the primary structures to establish a precise dating, providing a complete technical and historical record of these 16th-century wooden vaults.

Supplementary information ↑

Funding sources

This work was supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI Grants-in-Aid for Scientific Research, Grant Numbers JP18K13917 and JP22K14412.

Supplementary material

Not applicable.

Data availability

Not applicable.

Acknowledgements

The data collection and surveys for this research were carried out in collaboration with Enklabe KST, Tknika and IG Karratu Arkitektura SLP.

The authors would like to express their deep gratitude to the parishes, communities and custodians of the churches studied, whose efforts have ensured the preservation of these buildings and without whose cooperation this research would not have been possible.

Authorship contribution statement

Teresa Artola-Guijarro: Conceptualization, Investigation, Data curation, Formal analysis, Visualization, Writing – original draft.

Alejandro Martínez de Arbulo: Conceptualization, Formal analysis, Funding acquisition, Investigation, Methodology, Writing – review and editing.

Competing interests

The authors of this article declare that they have no financial, professional or personal conflicts of interest that could have inappropriately influenced this work.

Statement on the use of Artificial Intelligence

Not applicable.

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