Design to the structural code
The National Structural Code of the Philippines (NSCP 2015) sets the wind loads a building must resist. They depend on where the building is, since design wind speeds differ across the country, and on how exposed the site is. Coastal sites and open hilltops see higher wind loads. A licensed structural engineer calculates them for your lot.
Roof shape and overhangs
- Hip roofs, which slope down on all four sides, generally perform better in strong winds than gable roofs with tall, flat end walls.
- A moderate roof pitch is better than a very flat or very steep one.
- Keep eaves and overhangs short and well tied. Long, unsupported overhangs catch the wind and can pull the roof off.
Our La Union bungalow uses a pyramidal hip roof designed for wind-load resistance. It's the defining feature of the house.
Tie the roof down
The weakest point is usually where the roof meets the walls. Research after Typhoon Yolanda found that roof panels are often the first thing lost. To prevent it:
- Tie the roof framing to the wall beams with steel straps or connectors, not just nails or mortar.
- Fasten roofing sheets with the right fasteners, spaced closer at the edges and corners, where wind uplift is strongest.
- Use roofing and framing of adequate thickness for the design wind load.
A continuous load path
Wind forces have to travel from the roof through the walls and columns down to the foundations. Every link needs to be connected: roof to beams, beams to columns, walls to the frame and columns to footings. Reinforced concrete frames and properly reinforced hollow-block walls do this well when they're detailed and built correctly.
Doors and windows
Openings are weak points. If a window or door breaks during a typhoon, wind rushes in, pressure inside the house rises, and the roof can be pushed off from below. Strong frames, impact-resistant glass or storm shutters protect the openings, and with them the roof.
Water, flooding and the coast
- Set the finished floor above known flood levels for the site, and plan where water will drain.
- Use gutters and downspouts sized for heavy rain.
- Near the coast, as in much of La Union and Ilocos Sur, use corrosion-resistant fasteners, connectors and finishes. Salt air corrodes ordinary steel.
Before each typhoon season
- Check the roof fasteners and replace any rusted or loose ones.
- Clear gutters and drains.
- Trim trees and branches close to the house.
- Secure or store anything loose outdoors.
Common Questions
What is the best roof for typhoons?
A well-tied hip roof with a moderate pitch and short overhangs generally performs best. How the roof is connected to the walls matters as much as its shape.
Are concrete houses typhoon-proof?
Concrete walls resist wind well, but many concrete houses still lose their roofs. The roof framing and its connections to the walls are what usually fail, so they need as much attention as the walls.
Can an existing house be made more typhoon-resistant?
Often, yes. Adding roof straps, upgrading fasteners and protecting windows can make a real difference. An engineer should check the existing structure first, and we can design the renovation.
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