Short answer: there is no standard size, and the number everyone repeats — 200 × 200, the "8 by 8" — is not permitted for a column in a special moment frame. NSCP 2015 Section 418.7.2.1 sets a minimum shortest dimension of 300 mm. More surprising: the load almost never decides the answer. On a typical house bay the axial demand sits around 40% of capacity even on the undersized section. Three other things decide it, and the tool below shows you which one bites first.
Search for a house column size and you get scanned student assignments and forum replies quoting 200 × 200 with four 12 mm bars. That combination is not invented — it is what thousands of Philippine houses were built with, and most are still standing. What it is not is a design, and in Seismic Zone 4 the difference shows up once, at the worst possible moment.
Start with the thing everyone assumes is decisive, so we can set it aside honestly.
Take an interior column on a 4 × 4 metre bay in a two-storey house. It carries one suspended floor and a light roof. Using the same NSCP values published in our dead and live loads reference — reinforced concrete at 23.6 kN/m³, residential live load 1.9 kPa from Table 205-1, plus AEDO planning allowances for finishes, ceiling and partitions — the suspended floor comes to about 5.5 kPa dead and 1.9 kPa live, and the roof adds roughly 0.35 kPa dead and 1.0 kPa live.
That is about 146 kN of service load arriving at the base of the column, and a factored demand near 193 kN. A 200 × 200 column with four 12 mm bars has a pure axial capacity of roughly 460 kN. The demand is about 42% of it.
So on axial load alone, the undersized column passes comfortably — and that is precisely the trap. Pure axial capacity is a number you can only spend once. Real columns in a frame carry bending at the same time, and the interaction between the two is what a design actually checks.
Turns a bay spacing into the real service and factored loads on one interior column, then tests a proposed section against the three NSCP rules that govern residential columns. It hands you the load in kilonewtons at the end, ready for the footing calculator. This is a screening tool, not a structural design.
If the load does not govern, something else must. For a Philippine house it is these three, in roughly this order of severity.
Rule 1 — 300 mm Minimum, and It Is Not Negotiable
NSCP 2015 Section 418.7.2.1 requires a column of a special moment frame to satisfy both of the following: the shortest cross-sectional dimension, measured on a straight line through the geometric centroid, shall be at least 300 mm; and the ratio of the shortest cross-sectional dimension to the perpendicular dimension shall be at least 0.4.
Two consequences follow. A 200 × 200 column is out. And a "slim" column — say 150 × 500, chosen so it disappears into a wall — fails the second test at a ratio of 0.30, even though its area is generous. This is a dimensional rule, so reinforcement cannot buy your way out of it. The section either has the dimensions or it does not.
Rule 2 — Between 1% and 6% Steel (8% Outside a Special Moment Frame)
NSCP 2015 Section 410.6.1.1 requires the area of longitudinal reinforcement in a non-prestressed column to be at least 0.01Ag and not more than 0.08Ag. For a column of a special moment frame — the Zone 4 default in the tool above — Section 418.7.4.1 tightens this to at least 0.01Ag and not more than 0.06Ag.
The lower limit is about behaviour over time — creep and shrinkage transfer load from the concrete into the steel, and a column with too little steel has nowhere to put it. The upper limit is about buildability: steel that congested cannot be concreted properly, and at a lap splice the local bar area doubles. A 300 × 300 column needs at least 900 mm² of longitudinal steel, which eight 12 mm bars (905 mm²) or six 16 mm bars (1,206 mm²) will provide. Four 16 mm bars give only 804 mm² and fall short.
Rule 3 — Strong Column, Weak Beam
NSCP 2015 Section 418.7.3.2 requires that at each joint, the sum of the nominal flexural strengths of the columns be at least six fifths of the sum of the nominal flexural strengths of the beams framing into it. The only alternative the Code offers, Section 418.7.3.3, is to ignore that column's strength and stiffness in the lateral system and design it under Section 418.14 — which does not make a weak column acceptable.
The intent is plain once stated. In a severe earthquake something has to yield, and the code decides in advance what. A beam that hinges sags and damages one bay. A column that hinges takes the storey and everything above it. This is the rule that most often pushes a residential column past the 300 mm minimum — a deep beam demands a stronger column, so the framing scheme and the column size are one decision, not two. It is also why a column schedule cannot be copied between houses: it depends on the beams framing into it.
The same principle drives most of what we describe in why buildings fail.
Run the tool a few times and the pattern shows up quickly. These are the variables that matter, ranked by how hard they push.
| Variable | Effect on column size | Why |
|---|---|---|
| Bay spacing | Strongest | Load scales with area. Going from 3 × 3 to 5 × 5 m nearly triples the tributary area on the column |
| Roof type | Strong | A concrete roof deck replaces about 0.35 kPa of GI roof with roughly 3.5 kPa — on the top storey that is the whole load case |
| Beam depth | Strong, indirectly | Deeper beams are stronger beams, and Section 418.7.3.2 then demands stronger columns at the joint |
| Number of storeys | Moderate | Adds axial load, but axial rarely governs; it matters more through seismic mass |
| Concrete strength | Weak | Moving 20.7 to 27.6 MPa buys capacity you were not short of |
| Soil bearing capacity | None on the column | It decides the footing entirely, and the column not at all |
That last row is worth sitting with. Column size and footing size are set by two different things. The column answers to the frame and the code minimums. The footing answers to the ground. Our footing size calculator takes the loads this page produces and sizes the pad against NSCP Table 304-1 — and the bearing value it uses should come from a soil boring test, not an assumption.
Owners resist this change on cost, so it is worth pricing honestly.
A 300 × 300 column has 2.25 times the concrete volume of a 200 × 200 one. Over a two-storey house with, say, twelve columns at 6 metres of total height, that is roughly 3.6 m³ of extra concrete plus the additional steel and formwork. Against a house costing several million pesos, it is a small fraction of one percent of the build — well inside the contingency in our cost per sqm guide.
The cost of the other decision is not measured in pesos. If you are weighing this on an existing house rather than a new one, our second-floor screening check covers what happens when the columns were already built to the smaller size, and our seismic retrofit cost guide prices the fix.
Structural plans and the computations behind them must be signed and sealed by a PRC-licensed civil engineer to support a building permit application under PD 1096. A column schedule with no computations behind it is the single most common reason a residential structural set is returned by the plan-checker.
What that set costs is set out in our guide to what house plans actually cost, and the filing fees themselves come from our permit fee calculator.
Clause references are quoted from NSCP 2015, Chapter 4 — Structural Concrete: Section 418.7.2.1 for the 300 mm minimum dimension and the 0.4 aspect ratio, Section 418.7.3.2 for the six-fifths strong-column rule, Section 410.6.1.1 for the 1% to 8% longitudinal reinforcement limits, and Section 418.7.4.1 for the 1% to 6% limits on special moment frame columns. Loads follow NSCP 2015 where the Code gives a value — reinforced concrete unit weight 23.6 kN/m³ (Table 204-1), residential live load 1.9 kPa and exterior balconies 2.9 kPa (Table 205-1), flat roof live load 1.0 kPa (Table 205-3). The floor finish (1.05 kPa), ceiling (0.50 kPa) and partition (1.00 kPa) dead loads, the roof dead loads (light GI 0.35 kPa, tile roof 0.90 kPa, concrete roof deck 3.50 kPa), the 1.9 kPa live load used for a concrete roof deck, and the 2.4 kPa office-use option are AEDO planning allowances, not NSCP table values; Table 204-2 lists, for example, ceramic or quarry tile on a 25 mm mortar bed at 1.10 kPa. The load values match published in our dead and live loads reference. Axial capacity uses the tied-column expression with φ = 0.65. Everything on this page is a screening aid; none of it substitutes for a sealed design.
An engineer designs the reinforced concrete columns of a 2-storey house in STAAD. From the AEDO YouTube channel, uploaded 2021-02-07.
What is the standard column size for a 2-storey house in the Philippines?
There is no standard size, and the figure most often repeated online is one the code will not accept. NSCP 2015 Section 418.7.2.1 requires that a column forming part of a special moment frame have a shortest cross-sectional dimension of at least 300 millimetres, and a ratio of shortest to perpendicular dimension of at least 0.4. A 200 by 200 millimetre column, the size commonly described as the standard 8 by 8, does not meet the first requirement. For a two-storey house designed as a special moment frame, 300 by 300 is the practical floor, and the real size follows from bay spacing, the seismic design of the frame and the soil beneath it.
Does the load decide the column size?
Almost never, in a house. A typical interior column in a two-storey residence on a 4 by 4 metre bay carries a factored axial load somewhere near 190 kilonewtons, while even a 200 by 200 column with four 12 millimetre bars has a pure axial capacity of roughly 460 kilonewtons. The axial demand is therefore about forty percent of capacity, which looks comfortable and is misleading. What actually governs residential column size is the combination of code minimum dimensions, the bending that arrives with earthquake and wind, and the detailing that has to physically fit inside the section.
How much steel goes in a house column?
NSCP 2015 Section 410.6.1.1 requires the area of longitudinal reinforcement in a non-prestressed column to be at least 0.01 of the gross area and not more than 0.08 of it. For a column of a special moment frame, Section 418.7.4.1 tightens the upper limit to 0.06 of the gross area. So a 300 by 300 column, with a gross area of 90,000 square millimetres, needs at least 900 square millimetres of longitudinal steel, which eight 12 millimetre bars (905 square millimetres) or six 16 millimetre bars (1,206 square millimetres) will satisfy. Four 16 millimetre bars give only 804 square millimetres and fall short. The upper limit exists because congested steel cannot be concreted properly. Bar count and arrangement also have to suit the tie spacing and the beam bars passing through the joint, which is why the schedule comes from a design rather than a rule of thumb.
What is the strong column weak beam rule?
NSCP 2015 Section 418.7.3.2 requires that at a joint, the sum of the nominal flexural strengths of the columns be at least six fifths of the sum of the nominal flexural strengths of the beams framing into it (the alternative in Section 418.7.3.3 is to ignore that column's strength and stiffness in the lateral system). The intent is to make beams hinge before columns do in a severe earthquake. A beam that hinges sags and damages one bay. A column that hinges can take the storey and everything above it. This is the rule that most often pushes a residential column above the code minimum dimension, and it cannot be satisfied by inspection or by copying a schedule from another house.
Can I use the same column size on both floors?
Usually yes, and it is often the sensible choice. The upper column carries far less axial load, but reducing its size creates a change of section at the floor level, complicates the formwork and the bar splices, and can produce an unwanted stiffness change in the frame. Keeping one size through both storeys and varying only the reinforcement is common practice in Philippine houses. The saving from stepping a residential column down is small, and it buys a detailing problem at exactly the location where the frame is most vulnerable.
How do I size the footing under the column?
From the service load at the base of the column and the allowable bearing pressure of the soil, not from the number of storeys. The tool on this page gives you the service dead and live load in kilonewtons, which is exactly what our NSCP footing size calculator takes as input. It sizes the footing against NSCP 2015 Table 304-1 allowable foundation pressure by soil class, and applies the depth increase rule. The bearing value itself should come from a soil boring test rather than an assumption, because an assumed bearing capacity is the most common reason a house settles unevenly.
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.
Structural analysis to NSCP 2015 — seismic and wind, frame design, foundation design, full detailing — delivered as drawings signed and sealed by a PRC-licensed civil engineer, anywhere in the Philippines.
