Lima residents must inspect and repair vulnerable roofs following recent rainfall that highlighted major structural risks across the capital, a construction specialist has warned.
The warning follows an advisory from the National Meteorology and Hydrology Service of Peru, known as Senamhi, regarding potential heavy downpours in Lima linked to the El Nino weather phenomenon.
Jose Iman Silipu, a civil engineer and lecturer at the National Training Service for the Construction Industry, Sencico, told the state news agency Andina that poor drainage, flat surfaces, and unsealed fissures leave many homes at serious risk of leaks and structural collapse.
The Peruvian capital sits in an arid coastal desert that receives minimal rainfall throughout the year, with weather typically limited to fine winter mist. Because intense storms are rare, many residential properties, especially self-built houses in developing districts, feature flat roofs constructed without slope, waterproof sealants, or dedicated drainage systems.
Climatologists warn that coastal El Nino conditions, which warm equatorial Pacific sea surface temperatures, can rapidly alter those patterns and dump unseasonal torrential rain on infrastructure ill-equipped to handle it.
Structural hazards in residential roofing
Iman Silipu explained that the lack of roof inclination is one of the primary causes of household water damage, because it prevents rainwater from draining away and forces it to pool overhead.
On properties covered with corrugated calamine metal sheets, accumulated water creates concentrated dead weight that can bend structural supports and cause roofs to collapse inward. The specialist noted that calamine sheets installed completely flat are particularly dangerous during heavy downpours.
Concrete slab roofs present different structural dangers when water stands for extended periods. Standing moisture seeps into micro-cracks on the surface, eventually reaching the internal steel reinforcement bars. Once dampness reaches the metal, corrosion sets in, rusting the steel and progressively weakening the overall strength of the entire building.
Older homes built with traditional adobe, a sun-dried mud brick widely used along the Peruvian coast, face severe decay during rainfall. Iman Silipu warned that persistent water softens and erodes mud roof layers while deteriorating the wooden load-bearing beams that support them.
Inspection and drainage guidelines
To reduce the danger of property damage, Iman Silipu outlined several practical measures that residents should carry out before heavier rains arrive.
Homeowners must first inspect the slope and overall condition of their roof structure. Every roof surface requires an adequate gradient so that rainwater flows immediately toward runoff points rather than gathering in stagnant puddles. Anyone with horizontally installed calamine sheeting must check whether it can bear water weight, while occupants of older adobe buildings should inspect timber beams for dampness, rot, or bending.
For reinforced concrete roofs, property owners need to search the entire surface for visible cracks and fissures. Identifying and sealing these openings early prevents moisture from migrating inward to the reinforcing rebar.
The engineer also recommended fitting gutters or half-pipe channels along roof perimeters to collect falling water. These collection channels must connect to vertical downpipes that guide runoff safely to the street or into open ground away from building foundations. In buildings with existing roof sumps or floor drains, owners should consider installing extra conduits to expand evacuation capacity during heavy rain.
Plumbing precautions and waterproofing limits
Iman Silipu cautioned residents against diverting collected rainwater into domestic sewer drains. Storm runoff routinely carries sand, dust, and debris that can block indoor piping and trigger blockages across the public sanitation network.
Waterproofing additives and protective coatings can defend concrete slabs against dampness, but the specialist stressed that they must be prepared and applied strictly according to manufacturer instructions. These chemical barriers lose effectiveness over time and cannot substitute for an active drainage network. Homeowners must use them alongside gutters and pipes that clear water off the roof.
Finally, the engineer advised residents who detect major structural damage or have doubts about the strength of their home to request a professional technical inspection before attempting repairs.
