Every year, Philippine structures face the full force of supertyphoons — some of the most destructive storms on earth. Roof failures, wall collapses, and structural damage during typhoons are often not caused by weak concrete or poor workmanship.
They are caused by underestimated wind loads.
Proper NSCP 2015 wind load computation is not just a code compliance requirement — it is the first line of defense protecting lives, long-term investments, and the communities built around these structures.
This guide walks through the complete wind load computation procedure per NSCP 2015 Section 207A and 207B — from determining basic wind speed to computing final design wind pressure on building components.
This guide is based on NSCP 2015 (7th Edition), Section 207A and 207B — the main chapters governing wind loads on buildings and other structures in the Philippines. This guide is part of AEDO's NSCP 2015 Complete Guide →
The basic wind speed V is the 3-second gust speed at 10 m above ground in Exposure Category C (Section 207A.2). It is read from a contour map, and the map depends on the building's occupancy category (Section 207A.5.1):
| Occupancy Category (Table 208-1) | Wind speed map | Mean recurrence interval |
|---|---|---|
| I — Essential facilities | Fig. 207A.5-1C | 1,700 years |
| II — Hazardous facilities | Fig. 207A.5-1B | 700 years |
| III — Special · IV — Standard · V — Miscellaneous | Fig. 207A.5-1A | 300 years |
On the Category II map (Fig. 207A.5-1B) contours run from about 240 kph (e.g. Panay) to about 320 kph (northeast Luzon, Samar). Linear interpolation between contours is permitted, and islands and coastal areas outside the last contour use the last contour value (map notes 2 and 3).
Always read the exact V for your site from the correct figure. Section 207A.5.2 requires mountainous terrain, gorges, and special wind regions to be examined for unusual wind conditions.
Need wind load calculations for your project? A licensed AEDO engineer can compute NSCP 2015 Section 207 wind loads for your site — and deliver permit-ready structural drawings.
The highest contours on the NSCP 2015 maps run along the eastern seaboard — northeast Luzon and Samar reach about 320 kph on the Category II map. Many residential projects are still designed using outdated or unconservative wind speed assumptions, leaving them vulnerable during typhoon landfalls. Read the contour at your actual site, interpolate between contours where needed, and never carry over a wind speed from a project elsewhere.
Do not mix strength-level and allowable-stress wind loads. NSCP 2015 basic wind speeds are strength-level (wind load factor 1.0, Sec. 203.3); ASD combinations use 0.6W (Sec. 203.4). If you are designing with ASD load combinations, apply the 0.6W factor — failing to do so leads to severely over-designed or incorrectly calibrated wind load results.
NSCP 2015 places every structure in one of five occupancy categories listed in Table 103-1 (named in Table 208-1):
Check where your residential or commercial building falls in the Table 103-1 listing before picking a map.
For wind, the occupancy category does not set an importance factor. It selects the wind speed map in Step 1: Fig. 207A.5-1C for Category I, 1B for Category II, and 1A for Categories III, IV and V. The 207A.5 commentary explains that these separate strength-design maps, used with a wind load factor of 1.0, replace the single map with importance factors used in earlier editions.
Think of the occupancy category as how much society depends on this building staying safe. In NSCP numbering, Category I is the most critical (essential facilities), so it uses the map with the longest return period (1,700 years) and the highest wind speeds. Standard buildings use the 300-year map.
The exposure category defines the roughness of the terrain surrounding the structure, per NSCP 207A.7. It is one of the most consequential inputs in the entire wind load calculation — and one of the most commonly misapplied.
A two-storey house is being designed near an open coastal area in Samar, directly facing the Pacific Ocean with no significant obstructions upwind. Which exposure category applies?
Many engineers default to Exposure C when Exposure D clearly applies — especially for beachfront or bayside residential projects. Per Table 207B.3-1, Exposure C gives Kz values about 12–18% lower than Exposure D up to 30 m (for example 0.90 vs 1.08 at 6 m), narrowing to about 6% at 150 m, so the computed wind pressures are understated by that much. For structures near the coast or open water, always evaluate Exposure D and determine if it applies before defaulting to C.
Velocity pressure at height z is the core quantity from which all wind pressures are derived. It accounts for wind speed, terrain exposure, topography, and directionality:
qz = 0.613 × Kz × Kzt × Kd × V²
Kz = velocity pressure exposure coefficient · Kzt = topographic factor · Kd = wind directionality factor · V = basic wind speed in m/s
| Factor | Description | Typical Value |
|---|---|---|
| Kz | Velocity pressure exposure coefficient | 0.57 – 1.89 (Table 207B.3-1, varies by height up to 150 m and exposure category) |
| Kzt | Topographic factor | 1.0 unless the five conditions of Section 207A.8.1 are met; then Eq. 207A.8-1 |
| Kd | Wind directionality factor | 0.85 for buildings (Table 207A.6-1) |
Velocity pressure is essentially how hard the wind is pushing per square meter of surface area at a given height. A taller building catches faster wind higher up — that is why Kz increases with height. A structure on a hilltop or ridge catches even faster wind — that is what Kzt accounts for. The final number (in Pa or kPa) is multiplied by shape factors to get the actual force on walls and roofs.
For a two-storey building at 6 m height in Exposure C on flat terrain, with V = 250 kph (69.4 m/s) — an example value only; read the actual V for your site from the map for your occupancy category: Kz = 0.90 (Table 207B.3-1), so qz = 0.613 × 0.90 × 1.0 × 0.85 × 69.4² ≈ 2.26 kPa, or about 230 kgf per square meter of velocity pressure before pressure coefficients are applied — enough to peel improperly fastened roofing sheets or overload under-designed roof-to-wall connections during a strong typhoon.
For the Main Wind Force Resisting System (MWFRS), design wind pressure for enclosed and partially enclosed rigid buildings is computed per NSCP 2015 Section 207B.4.1 (directional procedure, buildings of all heights):
p = q × G × Cp − qi × (GCpi)
q = qz for windward walls, qh for leeward walls, side walls and roofs · qi = qh · G = gust-effect factor (0.85 permitted for rigid buildings, Section 207A.9) · Cp = external pressure coefficient (Figs. 207B.4-1 to 207B.4-3) · GCpi = internal pressure coefficient (Table 207A.11-1)
Low-rise buildings may instead use the envelope procedure of NSCP 2015 Section 207C for the MWFRS. For Components and Cladding (C&C) — individual roof panels, windows, wall cladding, and connections — use NSCP 2015 Section 207E (envelope procedure in Parts 1–2, directional procedure in Parts 3–5, appurtenances in Part 6), or the wind tunnel procedure of Section 207F. C&C pressures are often higher than MWFRS values and govern connection and fastener design.
Design wind pressure is the net outward or inward force per square meter that a structural element must resist. The external pressure (wind pushing on the outside surface) minus internal pressure (wind entering through openings and pushing outward from inside) gives the governing net pressure. For roofs, this is typically a large uplift (negative) force — which is what rips roofing off during typhoons. Designing roof connections for that uplift is part of every structural design we seal.
For projects located in coastal, bayside, or typhoon-prone regions of the Philippines, wind load analysis should always be verified by a licensed engineer familiar with NSCP 2015 Section 207. Using Exposure C where Exposure D applies alone understates Kz, and therefore velocity pressure, by about 12–18% for buildings up to 30 m, narrowing to about 6% at 150 m (Table 207B.3-1) — a margin that becomes catastrophic during a Category 4 or 5 typhoon.
In practice, wind load errors are among the most consequential mistakes in Philippine structural design. These are the most frequently encountered:
NSCP 2015 basic wind speeds are strength-level (wind load factor 1.0, Sec. 203.3); ASD combinations use 0.6W (Sec. 203.4). Mixing the two without conversion results in either unsafe (underdesigned) or uneconomical (overdesigned) members.
Enclosed, partially enclosed, and open buildings have different GCpi values. A residence with large openings or broken windows during a typhoon becomes a partially enclosed structure, dramatically increasing internal pressure and roof uplift. Many residential designs assume full enclosure, which may not hold during storm conditions.
Defaulting to Exposure C instead of the correct Exposure D for coastal and waterfront sites is possibly the single most common wind design error in the Philippines. This consistently produces unconservative results for beachfront, bayside, and island-based construction projects.
Hillside and ridgeline projects accelerate wind speeds beyond flat-terrain values. NSCP 2015 Section 207A.8.1 requires the speed-up (Kzt > 1.0 per Eq. 207A.8-1 and Fig. 207A.8-1) when all five conditions are met: an isolated, unobstructed hill, ridge or escarpment; protruding above upwind terrain by a factor of two or more; the structure in the upper half of the hill or near the crest; H/Lh ≥ 0.2; and H ≥ 4.5 m for Exposure C and D or 18 m for Exposure B. Many designs in elevated terrain use Kzt = 1.0, significantly underestimating the true wind pressure.
The BuildX NSCP Kit app automates Section 207A/207B wind load computations — basic wind speed inputs, exposure category selection, Kz tables, topographic factors, velocity pressure, and design wind pressure for both MWFRS and C&C. Runs on any device.
Statutes, codes, official tools and references used or referred to in this article, linked to their source. Links open in a new tab.
Prices, cost bands and rate figures in this article are AEDO Construction's own market and practice figures for Philippine work unless a source is named beside them. Code and statute references above link to the primary text.
Incorrect wind load assumptions don't just fail code review — they create real structural risk. Under-designed wind systems lead to:
AEDO Construction provides NSCP 2015-compliant structural wind analysis and full structural engineering services for residential and commercial projects nationwide — structural plans, BOQ, and design-build construction in Negros Oriental.
The Philippines sits in one of the most typhoon-active corridors on earth. Accurate NSCP 2015 wind load design is not a box to check on the drawing set — it is a direct commitment to structural safety for every person who will live, work, or seek shelter inside that building.
Getting it right means safer structures, better long-term performance, and buildings that hold when it matters most.
If you need assistance with structural analysis or design for your project, AEDO Construction is ready to help.
Wind loads in the Philippines are governed by NSCP 2015 Section 207, organised as Section 207A (general requirements), 207B (directional procedure for the MWFRS of buildings of all heights), 207C (envelope procedure for low-rise buildings), 207D (building appurtenances and other structures), 207E (components and cladding), and 207F (wind tunnel procedure). These sections cover basic wind speed determination, exposure categories, velocity pressure computation, and design wind pressure for both MWFRS and Components and Cladding.
There is no single national value. NSCP 2015 Section 207A.5.1 gives three contour maps by occupancy category: Fig. 207A.5-1C for Category I (Essential, 1,700-year MRI), Fig. 207A.5-1B for Category II (Hazardous, 700-year MRI), and Fig. 207A.5-1A for Categories III, IV and V (300-year MRI). On the Category II map contours run from about 240 kph (e.g. Panay) to about 320 kph (northeast Luzon, Samar). Read the exact value for your site from the correct figure, interpolating between contours where needed.
Exposure B applies to urban and suburban terrain with closely spaced buildings or wooded areas — the most common category in Philippine cities. Exposure C is the code reference condition: open terrain with scattered obstructions. Exposure D applies where open water or flat unobstructed terrain extends more than 1,500 m (or 20× building height) upwind, or the site is within 180 m (or 20h) of such an area (Sec. 207A.7.3) — many exposed coastline and bayside lots qualify. Exposure D produces the highest wind pressures and is frequently misclassified as Exposure C in practice.
Roof uplift failures are primarily caused by two factors: underestimated wind exposure conditions (wrong exposure category, especially near coastlines) and incorrect internal pressure assumptions. When a building envelope is breached by a typhoon — a broken window, failed door, or open garage — it becomes a partially enclosed structure. Internal pressure then acts outward on the roof from below simultaneously with the large external uplift suction on top. The combination of forces can easily exceed the capacity of under-designed roof-to-wall connections and fasteners.
Yes, for any building that needs a building permit, houses included. PD 1096 Section 301 requires a permit for any new building, and the Revised IRR (Section 302(3)) requires the civil and structural documents to be prepared, signed and sealed by a licensed civil engineer, with no storey threshold. Wind design is part of that structural design. Regardless of legal requirement, given the Philippines' typhoon exposure, NSCP-compliant wind load analysis performed or verified by a licensed engineer is strongly recommended for any permanent structure, especially in coastal or high-wind areas.
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