Can flooding bring a condo down?
The cloudy days and thunderstorms are getting more frequent, almost daily even. June is just a few days away, and so is the rainy season, when water from the skies (rain) and from below (floods) will test the very integrity of human structures.
Attention must be paid to condominiums, especially those built on areas that experience chronic flooding. Will such frequency of floods compromise the structural integrity of a condominium? And if it does, how would unit owners know if the structure has been compromised?
In a previous interview with Inquirer Property, civil engineer Benito M. Pacheco, national president of the Philippine Institute of Civil Engineers Inc., said the Philippines “still sorely lacks a systematic post-flood rehabilitation plan,” but he added that Filipinos were becoming more aware and proactive. “Even common homeowners I know put some thought and budget to reducing the potential effects of floods.”
Manny Crisostomo, former national president of the Subdivision and Housing Developers Association, said the Tropical Storm “Ondoy” experience has altered the way subdivisions have been planned and developed. “Before Ondoy, engineering plans for subdivisions were done mainly just to comply with existing land development and regulatory standards, (but) now most subdivision developers look into 50- to 100-year flooding histories of the areas they plan to develop.
“For existing subdivisions, mitigating measures like clearing and widening of drainage lines and adjoining waterways are being done on a regular basis, especially during the onset of the rainy season,” he said.
Inquirer Property asked a civil engineer, and this is what he revealed.
Alexis A. Acacio, director of the UP Institute of Civil Engineering, explained that constant submergence to water can loosen the ground that is supporting the foundations, therefore inducing settlement.
Weakened ground
“When soil is saturated with water, its strength substantially reduces. This is the same reason that we have landslides during the rainy season—a reduction in the carrying capacity of the ground. The ground can weaken when submerged and therefore settle,” Acacio warned.
Acacio added that if settlement of the foundation occurs, you may notice several things: cracks on the walls; doors that are difficult to open; and floor tiles cracking. He said, however, some cracks can be superficial and can mainly be due to the drying of the cement plaster.
“It is difficult to distinguish a structural crack from a superficial crack. When in doubt, ask your building or structural engineer,” Acacio quipped.
Should unit owners of upper (middle) floors be smug during the rainy season, knowing that they wouldn’t have to deal with the floods at ground level and leaking rooftops at the topmost floor?
“You may not be affected directly by the flood if you are on the upper floors, but there are things you should look at. If the foundation is affected, then its effect is translated to all floors,” Acacio explained.
Acacio added: “Also, submerged electrical lines at the lower floors can affect the electrical system of the entire building. If the drainage lines at the lower floor gets clogged due to the silt and mud induced by flooding, then the drainage system of the upper floors will likewise be affected.”
When asked if water seeping into cement structures without an effective waterproofing system can weaken the steel framework of the building, Acacio said there would be a possibility of steel corrosion. Once steel corrodes, structural integrity is adversely affected.
So, how quickly can steel corrode? Acacio replied that the rate of corrosion depends on the environment.
“If the structure is near the sea, then corrosion can be faster. As soon as corrosion starts, the steel’s strength is immediately affected. There are ways to check the integrity of the structure. A common one is to take core specimens of the concrete then test it,” he said.
Acacio added that X-ray methods are now available to check the integrity of the steel without “invasive” procedures.
“But take note that the X-ray method can only check the location of steel bars and reveal heavy corrosion. It cannot detect minimal corrosion,” Acacio stressed.
If you are considering buying a condominium unit during the rainy season, these are things you have to look out for:
1.) Buyers, according to Acacio, should check accessibility (roads), the frequency and level of flooding in and around the area, roof leaks, grounded electricity, porous walls and warping cabinets. He added that visiting a property during the rainy season can give you information that you may never be able to discover during the dry season.
2.) Access roads—in continuous heavy rain, you may be able to discover if the access routes to the site is passable or not. Access roads are as important as the site itself. If, for example, you are buying a house on an elevated site well out of reach of floods, but the access roads leading to it are always flooded even with just a heavy but short downpour, then the property may be compromised as well.
3.) Signs of flooding—even when it’s not raining, a buyer can find out if the area is prone to flooding. The most basic approach is to ask the residents themselves. If you can see sandbags and unusually elevated homes in the area, then it may be also be a sign that the subdivision easily gets flooded.
4.) Grounded electrical lines—a poorly maintained (and dangerous) electrical system sometimes shows its symptoms during the rainy season.
5.) Porous walls—walls and even firewalls are continuously exposed to rainfall. If these are not properly made or waterproofed, leak and moisture set in the house. You can only observe this when it’s raining.
6.) Overflowing rivers—if you are buying a property that is adjacent or near a river, then you must check if the river overflows when there is a heavy rainfall. You may ask residents, but better yet go there yourself.
