Building Heritage In The Alto Douro Wine Region, Portugal – Tabique Wall Nails Characterization

Jorge PINTO,João Carlos LANZINHA,Rui CARDOSO

doi:10.21307/acee-2016-007

Abstract

Abstract The Alto Douro Wine Region, a region located in the northeast of Portugal, presents an abundant building heritage which consists of tabique constructions, a vernacular construction technology. This technology uses raw materials such as stone, an earth-based material and wood, besides metal nail sensure the timber connections and the required structural safety. Previous research works have shown that most of the existing tabique buildings, in this region, present signs of marked deterioration and some of them are clearly near collapse. This reality is justified, among others, by the non-engineered character of this construction technology and subsequent loss through time of the associated empirical technical knowledge, consequently, conservation and repairing works are urgently needed. These aspects, added to the dearth of knowledge related to this building heritage have motivated this research work which is focused on studying the nails traditionally applied in those tabique buildings. In this article, and for the first time, a nail geometrical and material characterization is presented and discussed. The results highlight a wide nail dimensional variety, being iron the main chemical element identified. Beyond that, this study demonstrates that those nails should no longer be maintained in service and that new nails should be applied in future conservation and strengthening works. Finally, some guidelines regarding tabique rehabilitation and nail rusting prevention are mentioned.

Highlights

Vernacular constructions are widely present in the built environment of many regions worldwide [1]
The nails visual inspection indicates that a corrosion process has already started along the entire nail surface of all the nails collected. This nail rusting is, we believe, in part due to atmosphere corrosion, a consequence of the loss of the tabique wall original and filling protective coating, one of the main reasons of the actual tabique building decay [8, 9], to wood corrosion induced in iron by highly corrosive woods, as chestnut, and due to high moisture content transfer between the environment and the filling earth-based material, due to seasonal changes
This paper aims at characterizing geometrically and materially steel nails since they play an important role in the timber structure of a tabique building element, at our knowledge, the connection between timber structural elements as pavements, tabique walls or beams is exclusively executed with those metal connectors

Summary

Introduction

Vernacular constructions are widely present in the built environment of many regions worldwide [1]. This reality is explained by the massive desertification of the northeast of Portugal, a result of littoral urbanization, one of the most important menaces to this built heritage, and by the non-engineered character of this technology [11] whose design and construction techniques ce are based on builder’s know-how resulting from past experience and tradition and whose empirical technical knowledge associated is being lost through time This construction technology, modest and without any heritage protection whatsoever, incorporates sustainable design principles, transmits important skills and knowledge from the past to the present, is a useful and handy reference manual for engineers and other experts and is located in a classified UNESCO‘s World Heritage Site, representing a unique building heritage which should be cherished, preserved and brought to the generations in suitable conditions, contributing to preserve the historical and cultural identity of this region. They are found to connect tabique wall components (e.g. boards, laths and rails, Fig. 4a and 4b) and tabique walls and floors/roofs systems and they are applied as connectors of traditional exterior revetments (e.g. schist slates and metal corrugated sheets) of a tabique wall, Fig. 4c

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Conclusion