Building Costs Per Square Metre in the Philippines & Disaster-Proof Building Methods

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Building Costs Per Square Metre in the Philippines and Disaster-Proof Building Methods

Contents:

  • PSA Residential Building Costs – Philippines

  • PSA Non-Residential Building Costs – Philippines

  • Building Costs in Philippines – International Construction Market Surveys

  • Regional Costs of Building in the Philippines – 17 Main Regions

  • Philippines Household Income vs Building Costs By Region

  • Building Methods used in the Philippines

Newly built 2 bedroom structural concrete house with living room completed on July 2020 (Price  ₱720,000) situated on Household 30, Midfarm Road, Purok 6 in Kulasihan, Lantapan, Mindanao, Philippines – Source Lamudi

Introduction

The building costs per square metre in the Philippines vary by region and province. As is the norm in the construction industry, the type of building, its use, size as well as the material specifications, skilled labour and location will influence the cost. The Philippines is located in the Asia Pacific region, a region known for its tumultuous weather and geographical conditions which calls for safe and disaster-proof building methods.

The Philippines has 81 administrative/political provinces which are divided into 17 cultural/geographical regions. The Philippines government statistics authority (PSA) publishes construction cost statistics of all 81 provinces in the country on an annual, quarterly and monthly basis. In this post, we shall analyze the residential and non-residential costs (industrial, commercial, institutional, agricultural) of building across the provinces and regions in the Philippines. The residential building costs include different types of residences such as single family homes, duplex/quadruplex houses, apartments and condominiums.

PSA Residential Building Costs – Philippines

National Average Costs for New Residences

A significant decline in costs was observed in all residential construction with the exception of single family homes. The national average cost of building a single family home was ₱9,949 per square metre in 2019 and ₱9,475 per square metre in 2018, which was a 5% increase from the previous year.  The square metre cost of building a quadruplex or duplex house decreased from ₱10,126 in 2018 to ₱9,553 in 2019. There was also a decrease in costs for two other types of residences, namely apartments (₱8743 to ₱8577) and condominiums (₱18,776 to ₱15,094). Other residences which don’t fall in the above named categories saw a decrease in building costs (₱9210 to ₱7583) for the successive years 2018 and 2019, respectively.

A look at the bar graph below shows that there is a small variance in cost between single family homes, duplex houses, quadruplex houses and apartments if ₱300 to ₱1300 per square metre is an extra amount you are willing to build a new house for. Otherwise, the superficial area rate for building an apartment is always lower than building a single family home, duplex or quadruplex. However, note that an apartment will accommodate more tenants or occupants per square metre than a single family home, duplex or quadruplex. Also, since an apartment is a huge block of compact individual family units, the final project cost will be exceedingly higher than a single family home, duplex or quadruplex.

Bar Graph_Residential Building Costs Per Square Metre in The Philippines 2019_2018

A condominium is the most expensive residential property to build in the Philippines, with its price per square metre at 1.5 to 2 times the cost of a single family home, and 1.75 to 2.1 times the cost of an apartment.

The line graph below shows that the construction cost per square metre for duplex houses, quadruplex houses, apartments, condominiums and other residential properties has been declining since 2018 in the Philippines. In 2019, condominiums had the highest cost decrease at -19.6%, followed by other uncategorized residential buildings at -17.7%. Duplexes and quadruplexes saw a -5.7% decrease in construction cost, with apartments having the smallest decrease in cost at -1.9%

Line Graph_Residential Building Costs Per Square Metre in The Philippines 2019_2018

The only type of residence which maintained an increase from year to year are single family homes, which registered a 5% cost increase in 2019. The year 2000 witnessed the outbreak of the global Covid-19 coronavirus pandemic which had a negative effect on many countries, disrupting the economy, normal business and life as we know it. The Covid-19 pandemic will certainly have an impact on local as well as global building trends. Building costs are more likely to decrease further as consumers lose their income and purchasing power due to lockdown regulations put in place by governments to prevent the spread of coronavirus.

Provincial/Regional Average Costs for New Residences

The table below shows the average building cost per square metre for residential buildings in each of the 81 provinces in the Philippines. The cost range is ₱5,000 to ₱15,000 per m2. The cheapest places to build a residence are Lanao Del Norte, Compostela Valley, Camigiun, Zamboanga Del Norte and North Cotabato at ₱5,000 per m2. These are followed by Sarangani and Maguindanao (excluding Cotabato City) at ₱6,000 per m2.

Bar Chart – Residential Building Costs Per Square Metre Philippines 81 Provinces and Regions

Nine provinces of the Philippines, namely Negros Oriental, Davao Del Norte, Dinagat Islands, Surigao Del Norte, Isabela City, Bukidnon, Aurora, Agusan Del Norte and Leyte are priced at ₱7,000 per m2 for new home construction.

The province of Guimaras, Misamis Occidental, Occidental Mindoro, Bulacan, Romblon, Apayao, Ifugao, Marindique, Agusan Del Sur, Third District and Bohol come in at an average price of ₱8,000 per m2 for a newly built residence.

Fifteen provinces, Davao Occidental, Misamis Oriental, Cavite, Northern Samar, Davao Oriental, Abra, South Cotabato, Cagayan, Zamboanga Sibugay, Lanao Del Sur, Oriental Mindoro, Southern Leyte, Ilocos Sur, Batangas, Tarlac and Biliran have a residential building cost rate of ₱9,000 per m2.

Seventeen provinces in the Philippines, Siquijor, Kalinga, La Union, Sultan Kudarat, Ilocos Norte, Zamboanga Del Sur, Cotabato City, Zambales, Sorsogon, Camarines Sur, Negros Occidental, Catanduanes, Nueva Ecija, Eastern Samar, Quirino, Nueva Vizcaya, Western Samar and Pangasinan have a building cost per square metre of ₱10,000.

If anything above the median value of ₱10,000 per m2 is considered expensive, then twenty provinces in the country fall under this category. It will cost you 11,000 pesos per m2 to build a new residence in the province of Capiz, Iloilo, Isabela, Rizal, Bataan, Antique, Cebu, Aklan and Pampanga.

Three provinces, First District, Quezon and Albay are priced at 12,000 pesos per m2 for new residential buildings.

Building a new home in Laguna, Camarines Norte, Benguet, Palawan and Second District will cost you 13,000 pesos per square metre. The most expensive place to build a new home is Batanes at 15,000 pesos per square metre, followed by Davao Del Sur, Masbate and Fourth District at ₱14,000 per m2.

The province of Cavite has the highest number of new residential construction projects at 2,603, followed by Negros Oriental, Davao Del Sur, Batangas, Bohol, Laguna and Cebu with a little over a thousand projects. There are also a substantial number of projects in 26 provinces ranging from 200 to 970 per province. Nineteen provinces have new projects in the range 100 to 200 per province. Twenty five provinces have between 10 and 100 newly built residences. Provinces with less than 10 new projects are Abra, Ifugao, Davao Occidental, Agusan Del Sur, Zambaoga Sibugay and Isabela City, with Isabela City having only one project throughout the year.

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PSA Non-Residential Building Costs – Philippines

National Average Costs for New Non-Residential Buildings

Unlike residential construction which realized a significant decline in overall costs, non-residential construction (commercial, industrial, institutional and agricultural buildings) exhibited a significant rise in costs with the exception of agricultural buildings which declined in costs. The table below shows the average building costs per square metre for non-residential buildings across all categories.

The national average cost of building a commercial property rose from ₱8,788 in 2018 to ₱10,626 per square metre in 2019, which is a percentage increase of 20.9% from the previous year. The square metre cost of building industrial properties rose from ₱6,530 per m2 in 2018 to ₱7,084 per m2 in 2019, which is a percentage increase of 8.5%. Institutional buildings, which happen to be most expensive property to build, had their building rate increasing from ₱13,970 in 2018 to ₱16,211 per m2 in 2019. Agricultural facilities are the only property which declined in building costs, with costs falling from ₱4,845 in 2018 to ₱4,421 per m2 in 2019, a decrease of -8.7%

A look at the bar graph below shows that there is a significant variance in cost between commercial, industrial, institutional and agricultural buildings, with a minimum and maximum cost range of ₱2,663 and ₱11,790 respectively, between the four types of properties. Institutional facilities are the most expensive property to build in the Philippines, followed by commercial facilities. Industrial and agricultural facilities are on the lower side of the cost, with agricultural buildings being the cheapest to build countrywide.

Bar Graph_Non-Residential Building Costs Per Square Metre in The Philippines_2019_2018

Institutional facilities are 3.7 times more expensive to build than agricultural buildings, 2.3 times more expensive than industrial buildings, and 1.5 times more expensive than commercial buildings.

Commercial buildings had the biggest increase in building rates, followed by institutional buildings, additions and industrial buildings.

Additions in the non-residential category realized an increase in construction costs, with the superficial floor area building rates rising from ₱9,359 to ₱10,795 per m2 in 2018 and 2019 respectively.

Line Graph_NonResidential Building Costs Per Square Metre in The Philippines 2019_2018

Provincial/Regional Average Costs for New Non-Residential Buildings

The table below shows the average building cost per square metre for non-residential buildings in each of the 81 provinces in the Philippines. The cost range is ₱5,000 to ₱28,000 per m2. The cheapest places to build a commercial, institutional, industrial or agricultural building are Abra and Bulacan at ₱5,000 per m2, followed by Camarines Norte, North Cotabato, Apayao and Lanao Del Norte at ₱6,000 per m2.

Bar Chart – Non-Residential Building Costs Per Square Metre Philippines Provinces and Regions

Six provinces of the Philippines, namely Leyte, Zamboaga Del Sur, Occidental Mindoro, Isabela, Dinagat Islands, Third District and Bohol are priced at ₱7,000 per m2 for new non-residential construction.

The province of Western Samar, Agusan Del Sur, Guimaras, Bukidnon, Zambales, Palawan, Surigao Del Norte, South Cotabato, Southern Leyte, La Union, Nueva Ecija and Oriental Mindoro come in at an average price of ₱8,000 per m2 for a newly built commercial, industrial or institutional facility.

Ten provinces, Cavite, Pampanga, Catanduanes, Masbate, Laguna, Sorsogon, Marinduque, Camarines Sur, Ilocos Norte and Nueva Vizcaya have a non-residential building cost rate of ₱9,000 per m2.

Eight provinces in the Philippines, Davao Del Sur, Rizal, Davao Del Norte, Bataan, Lanao Del Sur, Cagayan, Siquijor, Misamis Occidental and Misamis Oriental have a building cost per square metre of ₱10,000.

If anything above ₱10,000 per m2 is considered expensive, then thirty seven provinces in the country fall under this category. It will cost you 11,000 pesos per m2 to build a new shopping mall, factory, higher learning institution or commercial farm in the province of Batangas, Negros Occidental, Zamboanga Sibugay, Cebu and Albay.

Eleven provinces, Sultan Kudarat, Ilocos Sur, Benguet, Kalinga, Romblon, Capiz, Batanes, Agusan Del Norte, Antique, Isabela City, Northern Samar and Zamboanga Del Norte are priced at 12,000 pesos per m2 for new industrial/commercial buildings.

 

Building a new facility in Iloilo, Aurora, Negros Oriental, Tarlac, First District and Quezon will cost you 13,000 pesos per square metre. In the region of Pangasinan, Cotabato City, Second District and Fourth District, commercial and industrial developments cost around ₱14,000 pesos per square metre.

The most expensive place to build a new facility is Maguindanao (excluding Cotabato City) at 28,000 pesos per square metre, followed by Quirino at ₱21,000 per m2, Davao Oriental at ₱19,000 per m2 and Eastern Samar at ₱17,000 per m2.

Other expensive regions are Aklan, Sarangani and Ifugao at ₱16,000 per m2, Biliran, Camiguin and Davao Occidental at ₱15,000 per m2.

The province of Bulacan has the highest number of new commercial/industrial construction projects at 382, followed by Cebu at 373, and Davao Del Sur, Davao Del Norte, Pangasinan, Cavite and Batangas with a little over 200 projects.

Eighteen provinces have new projects in the range 100 to 200 per province. Forty one provinces have between 10 and 100 newly built facilities. Provinces with 10 or less than 10 new projects are Davao Occidental, Western Samar, Camarines Norte, Cotabato City, Lanao Del Norte, Ifugao, Batanes, Zamboanga Sibugay, Nueva Vizcaya, Agusan Del Sur, Maguindanao, Abra, Isabela City and Lanao Del Sur, with Isabela City and Lanao Del Sur having only one project throughout the year.

Building Costs in Philippines – International Construction Market Surveys

Arcadis Construction Cost Survey

Arcadis is a global consultancy firm founded in 1888 and based in Netherlands, specializing in the design of projects and solutions for architecture, engineering, urban/town planning, sustainable development, environmental engineering, transport, water and utilities. The international consultancy has more than 350 branches around the world, spread across 40 countries and 28,000 employees in 70+ countries, including Europe, Middle East, Asia Pacific, North and South America. Besides design and engineering, the company provides extensive services in quantity surveying, project management, cost management, contract management, procurement, asset management and BIM.

Arcadis handles high value projects for a wide variety of clients such as city/town councils, governments, parastatals, state-owned enterprises, corporations, commercial property developers, building contractors, banks, pension fund companies, asset managers, insurance companies, retailers,  manufacturers, utility companies, energy/power generation plants, mining companies, gas and oil extraction plants. Examples of projects where Arcadis has participated in include the Millau Viaduct (multi-span cable bridge), Echo Park in Los Angeles, Gerald Desmond Bridge in California, Nova Apartments/Shopping Complex UK, NorthConnex Tunnel Motorway Australia, Prince Sultan Medical Park Saudi Arabia, Porte de Gesvres Ring Road/Flyover France, Qatar FIFA World Cup Stadium, Jakarta International Velodrome, Manchester Victoria Station, Calais Port Expansion, Siam Paragon Shopping Mall Bangkok, Renovation of Bayernoil Refinery in Germany and Kuala Lumpur International Airport City.

A look at the Philippines building costs per square metre by Arcadis Inc show that they are extremely higher than PSA rates. For example, the cost of building average standard high-rise apartments is ₱39,790 to ₱46,650 per m2 excluding electrical and mechanical installation. High end high-rise apartments are even more expensive at ₱53,526 to ₱92,080 per m2. Average standard terraced houses are ₱36,813 to ₱43,581 per m2.

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PSA rates indicate a rate of (₱8743 to ₱8577 per m2) for apartments, (₱18,776 to ₱15,094 per m2) for condominiums, and ₱9,553 per m2 for quadruplex/duplex houses.

ARCADIS – Construction Costs Philippines Arcadis – Residential Commercial Industrial (1)

 

ARCADIS – Construction Costs Philippines Arcadis – Residential Commercial Industrial (2)

Why is there a discrepancy between Arcadis and PSA building rates? It’s not just Arcadis costs, but building cost data from other construction management consultancies such as Turner & Townsend, Davis Langdon and AECOM exhibit the same trend. Well, it’s not a complicated matter. Engineering/construction management consultancies build up rates from their own in-house cost data obtained from past and current projects. Building costs are based on tender prices, and since these consultancies specialize in high value projects, the rates are going to be skewed in that direction. On the other hand, PSA rates are based on building plans approved by local authorities and their valuations thereof will represent a wider sample of building costs in the Philippines.

ARCADIS Mechanical and Electrical Installation Costs Philippines (1)

ARCADIS Mechanical and Electrical Installation Costs Philippines  (2)

ARCADIS Bill of Quantities Construction Building Rates  in Manila, Hong Kong, Singapore, Kuala Lumpur and Bangkok (1)

ARCADIS Bill of Quantities Construction Building Rates  in Manila, Hong Kong, Singapore, Kuala Lumpur and Bangkok (2)

Regional Costs of Building in the Philippines – 17 Main Regions

Regional Average Costs for New Residences

The table below shows the average building cost per square metre for residential buildings in each of the 17 cultural/geographical provinces of the Philippines. The cost range is ₱7,000 to ₱13,000 per m2. The cheapest regions to build a residence are the National Capital Region (NCR) at ₱7,000 per m2, followed by Cordillera Administrative Region (CAR), Ilocos Region, Cagayan Valley and Central Luzon at ₱8,000 per m2.

Line Chart – Residential Building Costs Per Square Metre_Philippines 2019_17 Main Regions

Line Chart (Ascending Order) – Residential Building Costs Per Square Metre (Pesos) for 17 Main Regions in the Philippines

The region of Calabarzon comes in at 9,000 per m2. Seven provinces of the Philippines, namely MIMAROPA, Bicol, Western Visayas, Central Visayas, Eastern Visayas, Zamboanga Peninsula, Northern Mindanao are priced at ₱10,000 per m2 for new home construction.

The province of Davao Region and SOCCSKSARGEN come in at an average price of ₱11,000 per m2 for a newly built residence.

The most expensive region to build a home is the ARMM, with a residential building cost rate of ₱13,000 per m2, followed by Caraga at ₱12,000 per m2.

The Autonomous Region in Muslim Mindanao (ARMM) has the highest number of new residential construction projects at 2,187, followed by Caraga at 1,333. Davao and SOCCSKSARGEN have over 800 projects. Northern Mindanao has 756 projects. Between 400 and 600 projects are found in Central Visayas, Eastern Visayas and Zamboanga Peninsula. Calabarzon, MIMAROPA, Bicol and Western Visayas have between 200 and 300 projects. CAR, ILocos, Cagayan Valley and Central Luzon have between 100 and 200 housing projects. NCR has a substantially lower number of new constructions at 13.

Regional Average Costs for New Non-Residential Buildings

The table below shows the average building cost per square metre for non-residential buildings in each of the 17 cultural/geographical regions in the Philippines. The cost range is ₱7,000 to ₱16,000 per m2. The cheapest regions to build a commercial, institutional, industrial or agricultural building are Bicol at ₱7,000 per m2, followed by Eastern Visayas, Calabarzon and MIMAROPA at ₱8,000 per m2.

Line Chart – Non-Residential Building Costs Per Square Metre (Pesos) for 17 Main Regions in the Philippines

 

Line Chart (Ascending Order) – Non-Residential Building Costs Per Square Metre (Pesos) for 17 Main Regions in the Philippines Ascending

Four provinces of the Philippines, namely Zamboanga Pensinsula, Central Luzon, SOCCSKSARGEN and Central Visayas are priced at ₱10,000 per m2 for new non-residential construction.

The province of CAR comes in at an average price of ₱11,000 per m2 for a newly built commercial, industrial or institutional facility.

Davao Region, Western Visayas and Cagayan Valley have a non-residential building cost rate of ₱12,000 per m2.

The most expensive region to build a new facility is the NCR at 16,000 pesos per square metre, followed by Caraga at ₱14,000 per m2, ILocos and Northern Mindanao at ₱13,000 per m2.

The region of Central Luzon has the highest number of new commercial/industrial construction projects at 271, followed by CALABARZON at 257 and Central Visayas at 255. SOCCSKSARGEN, Northern Mindanao, Eastern Visayas, ILocos, Western Visayas and Davao Region have between 100 and 200 projects each. Cagayan Valley, MIMAROPA and NCR have between 40 and 85 projects. Bicol, Caraga, Zamboanga Peninsula and CAR have between 15 and 35 projects each, with CAR having the lowest number of new constructions at 18.

 

 

Philippines Household Income vs Building Costs By Region

When looking at residential building costs in a specific region, one has to know the affordability of building a house based on average local income or wages. If you are living and working in that region, would you afford to build a house based on your monthly household income?

The average national household income in the Philippines was 313,000 pesos per year in 2018 (converted to US$6231.27 in 2018 or US$14,813.34 on 19 September 2020). It will take at least 1,597 months (133 years) to save this amount of money for a ₱500,000 house, which is an insurmountable cash purchase feat for someone earning a local wage.

PSA Average Income by Region_Philippines 2018 – Income Expressed in Thousand Pesos on Graph

 

PSA Average Income by Region_Philippines 2018 Ascending Order – Income Expressed in Thousand Pesos on Graph

Someone earning ₱313,000 a year will be in a suitable financial position to buy or build a new decent home valued at 450,000 to 500,000 pesos within four years, if they are saving half of their earnings.

Single Storey Rowhouse Units – 1 Bedroom House  Units on Lot in San Pedro_Sto_Tomas Batangas City, Philippines  – Price 504,000 Pesos , Built in 2016

RFO Townhouse 2 Bedroom Double Storey Rowhouse Units – Price 450000 Pesos by Pasinaya Homes Philippines, Built in 2018 (1)

RFO Townhouse 2 Bedroom Double Storey Rowhouse Units – Price 450000 Pesos by Pasinaya Homes Philippines, Built in 2018 (2)

RFO Townhouse 2 Bedroom Double Storey Rowhouse Units – Price 450000 Pesos by Pasinaya Homes Philippines, Built in 2018 (3)

RFO Townhouse 2 Bedroom Double Storey Rowhouse Units – Price 450000 Pesos by Pasinaya Homes Philippines, Built in 2018 (4)

According to TradingEconomics, the average nominal wages in the Philippines have been increasing year by year since 2010. In 2018, the average nominal wage was ₱13,487.30 per month.

According to NWPC (National Wages and Productivity Commission), a body of the Philippines Department of Labour and Employment, the minimum monthly wage based on NWPC daily minimum wage rates is shown in the table below for all 17 cultural/geographical regions in the Philippines:

Table – NWPC Minimum Wages and Rates Philippines 2020

Lower Minimum Wage

The lower minimum wage range is ₱8,460 to ₱15,000 per month across all regions. Region 1 (ILocos) has the lowest minimum wage at ₱8,460 per month and NCR has the highest minimum wage at ₱15,000 per month. The average minimum wage is ₱9,836 per month.

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Upper Minimum Wage

The upper minimum wage range is ₱9,300 to ₱16,110 per month across all regions. Region 5 (Bicol) has the lowest minimum wage at ₱9,300 per month and NCR has the highest minimum wage at ₱16,110 per month. The average minimum wage is ₱10,992 per month.

The question one has to ask is, is there a correlation between the regional household income and building costs per square metre in the Philippines? Line graphs plotted for these two metrics can help you notice the relationship between them in a specific region. As you can see in the line charts below, there is no correlation between the household income and residential building costs in the Philippines. The red and blue curves are quite different and irregular, i.e. there is no similarity between them, which tells us that building costs are not proportional to average regional income. In countries such as the UK where building costs are more or less proportional to average local income, the building cost curve and income curve are more or less similar.

The best way to determine the affordability of building a new residence in a selected region of the Philippines is using a cost factor found by dividing cost with income (Cost/Income). In this case, the higher the building cost factor, the more expensive it is to build a home in that region with respect to local income. The cost factor line graph is shown below:

Line Chart – Regional Income vs Building Cost_Philippines

Line Chart – Regional Residential Building Cost vs Income for 17 Main Regions of the Philippines

 

Line Chart – Regional Residential Building Cost vs Income for 17 Main Regions of the Philippines Ascending

As you can see, the cost factors for each region were displayed in ascending order starting with the lowest and ending with the highest. In this case, CALABARZON is the most affordable region to build a new dwelling if you are living and working there, followed by NCR, Central Luzon, Caraga, SOCCSKARGEN, Northern Mindanao and Central Visayas.

Zamboanga Peninsula, ILocos and CAR are somewhere in the middle, with medium building costs. The most expensive region to build a new dwelling if you are living and working there is ARMM, followed by Bicol and Davao region.

 

Building Methods used in the Philippines

The Philippines is a group of islands and archipelagos in the Asia Pacific ocean, so essentially it is a waterlocked country, highly vulnerable and exposed to not only tropical cyclones (aka typhoons or hurricanes), tsunamis (storm surge), floods, flash flooding, landslides and water logging, but also the region lies in an earthquake and volcanic zone. A look at geographic facts and history shows that The Philippines has suffered 24 volcanoes and 10 deadly earthquakes in the past, with about 140 earthquakes of magnitude 3.4 or higher on the Richter scale taking place each month. About 7,000 to 10,000 earthquakes are recorded each year, with 95% of them being weak seismic vibrations below magnitude 3.0

Each year, the Philippines is hit by about 20 typhoons, with 5 super typhoons causing severe destruction to property and buildings, as well as resulting in loss of life. According to ADRC, volcanic eruptions, super typhoons and earthquakes have caused extensive damage and destruction to buildings in the past, displacing millions of people, injuring thousands and taking hundreds of casualties. In 1991, the Mount Pinatubo volcano destroyed 40,000 dwellings and damaged 70,000 houses. In 2013, Super Typhoon Haiyan razed down over a million houses and caused damage to property and infrastructure worth 19.6 billion pesos. In 1990, a major earthquake measuring 7.6 on the Richter scale destroyed 100,000 houses in Central Luzon.

As you can see, the Philippines is vulnerable to all kinds of natural disasters which are concentrated in a tumultuous geographic area known as the Pacific Ring of Fire, known for its highly unstable geology and weather conditions. The question is what is the best building method or construction technology for a building located in the Pacific Ring of Fire?

Lightweight building materials or cladding such as timber, aluminium, PVC, EPS, XPS and PU sandwich panel walls are considered safe for building a house in an earthquake zone because they are less or non-fatal when the building shakes and collapses. However, lightweight/flexible materials and structures cannot withstand a typhoon, as they are easily blown away and flattened by powerful winds and gusts travelling at up to 380km/hr. A typhoon can uproot trees, telecom/electricity line poles and flatten structures. It will throw around cars, huge boulders and debris, damage houses and kill people. In this regard, a concrete/masonry building is best suited for a typhoon because it can withstand the strong winds and gusts, but this type of building is dangerous and hazardous when hit by an earthquake, as the walls made of heavy materials will collapse and kill occupants.

In an area which is vulnerable to earthquakes and typhoons, a suitable design which can withstand the impacts of these hazards is recommended. The building should not be blown away or flattened by typhoons, and it should not collapse during an earthquake, endangering the lives of occupants.

Reinforced Concrete Structural Frame

Structural engineers recommend a structurally stable concrete/masonry building reinforced with ring beams and columns to counter the effects of a typhoon and earthquake. In this case, the structural frame or skeleton is made of reinforced concrete beams and columns connected together to make a strongly bonded entity which will subside, settle or topple over as single unit without breaking apart into pieces. During construction, the concrete block/brick walls are tied to RC columns with hooked steel ties to prevent them from falling off the structural frame during an earthquake. Reinforced concrete columns are placed at corners, door openings, wall intersections, as well as at strategic intermediate positions suitably spaced on long span elevations of the house. This sturdy structure has ring beams at plinth level as well as at eaves height above windows and doors. To meet safety requirements, the gable of a concrete/masonry house shouldn’t be built from bricks, concrete blocks, stone or other heavy material which can be fatal on falling over. Lightweight materials such as timber, PVC or sandwich panels should be used for the gable walls instead. Even better, if safe alternative materials are not available, your architectural building design shouldn’t include gables on its elevations. Otherwise, hipped roofs and flat roofs are recommended for concrete/masonry buildings in an earthquake zone.

Single-storey houses are safer than multi-storey dwellings in a typhoon or earthquake. A multi-storey residential building can also be safer if attention is paid to its structural engineering design, ground conditions, soil mechanics and quality of workmanship. If any of these features are neglected or poorly done, the building will be hazardous to its occupants during a natural disaster. The picture below (Fig.1) shows a partially-finished house that was toppled over by an earthquake. The structural frame of the house had been completed at this stage and it was built to high structural engineering standards and workmanship. The superstructure structural design, material specification and quality of workmanship was excellent, but the foundations were not strong enough for the ground conditions. The question is who or what is to blame for the collapse of this house? Should we blame the location of the site, earthquake or poor foundation specification? Was a geotechnical site investigation done during the preliminary stage to determine the ground conditions? A detailed geotechnical site investigation and suitable foundation could have prevented this tragedy. However, even though this house was tipped over by an earthquake, the best thing is that it didn’t break into pieces of rubble which could have endangered the occupants. It remained intact as a single unit.

Fig 1 – Concrete House with Good Structural Frame But Poor Foundations Toppled Over by an Earthquake in the Philippines

Other considerations for building a disaster-proof house is its plan shape and symmetry, and the number of wall openings it has. Square and circular house plans are able to withstand both lateral and shear cyclonic wind forces, while narrow and elongated plans offer poor resistance. Square and circular structures can also withstand seismic vibrations much better than narrow elongated structures. If possible, your external building corners should be rounded or chamfered to smoothly deflect wind forces. Lastly, it is recommended to reduce the number of openings as well as their size on your external walls. Large openings take in huge wind inflows, increasing internal pressure (uplift) which can push up and blow away the roof.

Landslides

Houses should be built far from cliffs and top edges of hills to prevent collapse in the event of a landslide. Houses built in valleys, on hill slopes, under cliffs and hill edges are also subject to collapse and being buried by debris during a landslide. Check the building codes in your area to find the minimum distance that you can build away from cliffs and hill edges.

Water Logging

Do not build a house in a waterlogged or swampy area unless you can afford to drill deep pile foundations to reach firm ground or rock strata. In most cases, the average homeowner cannot afford to drill pile foundations since they are costly, so in this case you have look for a suitable location which is free from water logging and wet ground. Houses built in low-lying areas, basins and valleys along rivers and shorelines are also vulnerable to water-logging caused by high water table and flooding due to tsunamis and heavy rainfall.


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