ADOPTING AN ALTERNATIVE CONSTRUCTION TECHNOLOGY IN CENTRAL AND SOUTH AMERICA By David Riley Retired Building Consultant.
In many parts of Central and South America, post contact, mortared cut stone was the historical building material of choice for hundreds of years until various other cementitious configurations took precedence.The exception was timberframe built over stone over concrete foundations as found in nations with less stone and/or abundant timber. Solid poured concrete is expensive and unnecessary to execute most structural programs in the southern hemisphere, especially where seismic resistance is nil to low, so a typical combination of lightly reinforced poured concrete pilasters enclosing mortared infill hollow-block became a common design meme for walls. Some floor assemblies also utilized unit masonry. This system has proven itself economically worldwide. In theory, its current variations can provide as much loading and seismic capacity as necessary, but can fail due to weak or nonexistent engineering, poor workmanship including admixture control and little buy-in from construction participants. ‘Death by concrete’ was a common phrase bandied about in the relief community after the Haiti earthquake. The problem with the current methodology is that for both the pilaster and the infill components of this program, quality control is difficult to execute. Central America, like Asia, is plagued by issues related to productivity, quality control, difficulty of real-time material testing, inspection verification etc. There is an alternative, one that is easily capitalized within existing material production infrastructure, engineered on a modular basis, more productive of time and capital savings and more amenable to easier inspection/documentation. Drystacked unit masonry allows rapid placement of the final form elements and simultaneous addition of the required amount of concrete and steel re-inforcement. Per unit of material and labour cost, the cement used in concrete adds much more structural value than cement used in mortar and the configurations in which the reinforcing is added are much more flexible for given structural programs. The dry stacked concept is used sporadically around the world, using many materials besides masonry, but is curiously absent in most of Central and South America, where it could easily cut building costs and provide much more consistent and less costly structures, thus freeing labour and capital for other allocations within projects. It’s also better suited to DIY building, a common occurrence in the southern hemisphere. Not only does drystacked masonry add more flexibility to both architectural and structural design, it also allows greater variation in the design and execution of reinforcement as well as less labour spent in the co-ordination of ancillary trades. The idea that drystacked masonry is better suited to
countries with high labour costs is completely mistaken and simply based on its greater market penetration there. A modular drystacked system can function to support almost any architectural or engineering program with anywhere from 3 to an infinite number of basic block shapes. It empowers the production of wall systems at one storey per day with less manpower. People ask, if drystacked masonry makes so much sense, why is it not in greater North American usage? Well it is. It’s just that the comparable North American adoption route now often involves expanded polystyrene, recycled wood fibre/ concrete or other material combinations because of the current program requirements for lower energy usage. The general principles and results, as they relate to material and labour savings, are similar. Capitalizing a project to convert an existing small or midsize block manufacturer to one producing such a modular line is not prohibitively expensive. The program would involve building an accessory production line and then building some demonstration buildings, stand-alone or preferably as part of an existing project. With proper marketing and education, this change to a more modular system has the capability to significantly “disrupt” both professional and DIY building practice. All over Central and South America, lack of productivity, quality control, desired adherence to international building standards and difficulties with material testing regimes and verifiable inspection systems are holding back the region in ways that have not been countenanced in the energy, telecommunications and aviation fields. This step forward is inevitable. Billions of dollars are sitting on the table for future entrepreneurs. Timing simply depends on who decides to capitalize it. ADDENDUM This article was written in 2011. Little has changed. Some people call this type of product, eco-block or lego-block. A complete line of this product can make this form of building as easy for the inexperienced as putting together IKEA “flat pack furniture”. People should Google ‘mortarless masonry wall systems’. What you will see is just a tiny hint of the potential for this idea. It is infinitely adaptable according to each region’s building needs, available raw materials and engineering imagination. In the Guyana context, it could be done with various cementitious and clay formulae, again depending on the overall building requirements.