On September 19, 2017, during the earthquake in Mexico City, meticulously designed brick walls sustained almost no damage, while serious damage was concentrated in irregularly constructed or poorly detailed buildings. In the 2007 Pisco (Ica) earthquake, liquefaction of coastal soils exacerbated damage in heavy-duty housing, while lightweight enhanced quincha structures built according to technical guidelines performed better. These lessons underscore the importance of appropriate design, placement, and reinforcement decisions for earthquake-resistant housing.
1. Limited wall construction design and details
Constrained walls (concrete beams and brick or block walls enclosed by beams) remain the most economical and effective alternative for 1-3 story residential buildings in Latin America’s seismic zones, provided they are designed according to capacity and with well-connected diaphragms. The system provides flexibility and stability by integrating the ceiling/floor slabs with the walls and confining the walls with beams and rigid columns. Indeed, after the 2017 earthquake in Mexico City, it was observed that many confined-wall residential buildings sustained only minor damage: “most houses and buildings… have this structural system, and this does not mean that the system is weak; on the contrary, it is a very resistant system against seismic forces.”. The collapses identified were due more to unconfined walls or irregularities (e.g., a soft ground floor) than to the confinement system.
Local standards (NTC-Sismo CDMX 2017/2024 and RNE E.030/E.070, Peru) emphasize this approach: capacity-based design, regular layout (avoiding aggressive L or T layouts), diaphragms and integrated chains, and resistance hierarchy, where the confinement reinforcement is more flexible than the wall. In practice, a common design checklist is applied in Mexico/Peru:
- Regular and symmetrical layout; sturdy walls aligned on the plan. Avoid aggressive L/T or soft layouts (e.g., open garages).
- Castle (corners and critical points) and continuous connection beams (floors) and lintels.
- Separate openings at the corners; longitudinal reinforcements above/below (“chain”). Lintel properly fixed to the walls.
- Rigid diaphragms (reinforced concrete slabs or structural ceilings) with good connections to walls and temporary anchors.
- Reinforcement sized according to capacity: reinforced concrete must provide greater ductility than the wall (resistance hierarchy).
When all these details are taken care of, the behavior is very positive. In contrast, in 2017, the main causes of malfunctions were deficiencies in the castles, bases, or diaphragms.
2. Lightweight soil systems: improved quincha
Enhanced quincha combines a wood + reed/bamboo skeleton filled with mud with appropriate reinforcements to create walls that are very low in mass and have good seismic flexibility. Quincha, which has much less inertia than solid adobe walls, reduces seismic demands and exhibits a more gradual damage pattern (cracks form in the cladding rather than sudden collapse). It is a traditional system in Peru: “a seismic-resistant frame made of wood panels covered with reeds and mud”. Furthermore, thanks to its lightness, it has historically been used in high-rise buildings or roofs (e.g., colonial cathedrals) without causing instability issues.
Following the 2007 Pisco earthquake, enhanced quincha proved its applicability in the reconstruction of rural housing: when technical guidelines were followed (RC foundations, upper/lower bracing, cross-bracing in panels, moisture/termite protection, corner bracing, roof fastening, etc.), quincha houses performed quite well. Lightweight modules, a foundation ring and X-shaped connections in weak planes; upper wooden beams that secure the closure; drainage and wide eaves to protect against water. Although less rigid than clay, this degree of flexibility allows energy to be distributed without collapse. The Getty Conservation Institute documents that “the lightness of the quincha panel and its behavior during earthquakes… [enables its use] in complex roof construction”. In summary, when attention is paid to details (minimum concrete cores, mesh and plaster in cladding, wall-roof connections), improved quincha can be scaled as an earthquake-resistant housing solution.
Important details of the system (taken from the PREDES/SENCICO manuals):
- Lightweight modules mounted on the ground (RC or processed wood base) are fixed to the ground. X-shaped cross supports are added inside the panels for lateral stability.
- Continuous crown beams bolted to the posts (“timber chaining”). Rigid connection to the ceiling diaphragms (beams/cross beams).
- Protection against water and termites: waterproof skirting boards, plaster (barbotine) for exterior and interior spaces, pronounced eaves.
- Strong plaster (various layers) connecting the internal and external skeletons forms a thin boundary layer.
3. Reinforcement of existing clay bricks without removal
To improve existing adobe/self-built housing, low-cost materials that have proven effective both in the laboratory (PUCP) and in the field (Arequipa 2001, coastal regions of Peru)yetli stratejiler bulunmaktadır. Başlıca üç teknik şunlardır:
- Electrically welded wire mesh + plaster. The metal wire mesh is nailed or attached to both sides of the wall (using transition connectors), thus creating restrictive “false beams” and “false columns.” Cement mortar is then applied to both sides. This external reinforcement increases flexibility without displacing the residents by restraining the old adobe.
- Polypropylene geogrid (synthetic mesh). It works similarly: Plastic strips or meshes stretched horizontally/vertically are bonded with plaster to prevent wall cracking. It is chemically inert and corrosion-resistant.
- Synthetic rope nets (“drizas”). These consist of fiber ropes (e.g., polyester) that wrap around walls vertically and horizontally, forming a net. Each rope is secured and tensioned; this prevents the wall from collapsing during a major earthquake and significantly increases its durability. Developed in Peru, this system offers advantages such as inexpensive materials and easy installation, and has been approved in Chile and Peru.
All these solutions require continuity in terms of fastening at the corners, crowns (top and bottom), and ceiling tiles. The steps in the application are as follows: diagnose cracks and moisture; install wood/RC crowns screwed to the top of the wall and tightly secure the roof; secure the grid (metal, geo-grid, or rope) to all four sides of the wall with pass-through connectors; apply thick plaster to both surfaces; finally, secure the diaphragms (reinforce the ceiling beams, replace heavy tiles with lightweight coverings if possible). Tests conducted with these reinforcements have shown significant seismic improvements.
4. Location, shape, and diaphragms: Mexico City and the coast of Peru
Soil is very important. In CDMX, the soft lake beds in the Valley of Mexico amplify the shaking (especially over long periods) and prolong its duration, naturally increasing damage to structures that move slowly. Along the Peruvian coast (Ica/Pisco), loose sands and saturated areas liquefied during the 2007 earthquake, causing subsidence and cracks in foundations. Therefore, universal principles are recommended for basic residential design (applicable in Mexico and Peru):
- Avoid irregular planimetric shapes and soft ground effects. Do not design open garages or interrupted walls on the ground floor.
- Maintain the alignment of the walls between levels and the continuity of the chains/chain links at floor level.
- Continuous foundations (continuous beam foundations), paying attention to the soil-structure transition in soft layers.
- Lightweight roofs (metal panels, lightweight tiles) and rigid diaphragms that transmit concentrated forces to walls with limited strength. Optimal connection between the ceiling, wall, and crown must be ensured.
These points form the “80/20” rule of safety: A dwelling with a reasonably square plan, walls aligned properly and connected to each other by continuous crowns/diaphragms, and well-supported on the ground is highly likely to function properly during seismic movements. The CDMX (NTC-Sismo) and Peru (RNE) standards incorporate these principles: they prohibit weak ground floors, require tie beams and anchors, and regulate foundations for soft soils. In summary, the ground “dictates”: ensuring uniformity in ground floors and strength in roofs is crucial both in the Valley of Mexico and in Peru’s coastal plains.
5. Insulation and seismic control in residential buildings
Seismic isolation (e.g., using elastic supports or distributors) is included in standards (RNE E.031 in Peru; CDMX contains similar rules) and undoubtedly improves response. However, due to initial and maintenance costs, it is generally used in critical buildings (hospitals, schools, or luxury buildings). In social housing, the greatest “return” is achieved by strengthening the traditional structure: properly confining walls, integrated diaphragms, and solid anchors are often more cost-effective than isolation systems. In practice, accessible “80/20” solutions are encouraged:
- A rigid chain-link perimeter fence (RC or wood) at the top of the walls.
- Equipped connection elements (pins, plates) and roof beams between the ceiling and walls.
- Local reinforcements (metal, polymer, or rope meshes) in critical areas of existing buildings.
These supplements, when combined with prudent design, significantly reduce seismic demand. Nevertheless, pilot programs and guidelines exist in Peru and Mexico to evaluate low-cost isolators in residential buildings, but their widespread adoption (due to their high cost) remains limited. In general, seismic control in residential buildings today focuses more on strengthening existing structures than on isolation (though both approaches can be combined).
