Column

A column is a vertical structural member that carries loads from beams, floor slabs and the roof down to the foundation, mostly by compression. In a house it stands where a solid wall would be awkward. Examples are the corner of an open living room, a glazed facade, a garage opening, or the end of a beam. Columns are the vertical part of a frame structure. They also appear as porch supports, carport posts and inner supports for heavy beams.

What is a column in a building?

A column is a compression member. The beams and slabs above deliver their load to its top, and the column passes that load down to the foundation. In a flat slab on columns, punching around the column often decides the slab thickness (JRC Eurocode 2 worked examples, section 1.5.1.1). The engineer therefore checks the column head as well as the shaft.

How does a column carry load?

A column works mainly in compression, but a real column is not perfectly straight or perfectly centred under its load. Eurocode 2 therefore adds an imperfection eccentricity to the first-order load eccentricities. The column then also carries some bending (JRC worked examples, section 3.2.2.4).

The slenderness of a column decides how much this bending grows. Eurocode 2 defines slenderness as the effective height l0 divided by the radius of gyration i. The radius i belongs to the uncracked section. The effective height depends on how stiffly the beams hold the column ends. For a rectangular section the worked examples give the shortcut slenderness = 3.46 · l0 / h. Here h is the section depth in the direction under study. So the section depth works against slenderness: a deeper section gives a lower slenderness for the same height.

Second-order effects are the extra bending that appears when the column deflects under load. Eurocode 2 lets the designer ignore them in two cases. The first is when they are smaller than 10 % of the first-order effects. The second is when the slenderness is below a limit value λlim. If the slenderness is above that limit, the second-order effects must be included in the design. These checks belong to the structural engineer.

Which materials are columns made from?

Reinforced concrete, steel and timber cover most residential columns. The choice depends on the structural system, the loads above, the fire requirements and how visible the column will be. The table gives what the sources say about each material.

Material	Typical use in a house	What the sources say	Watch-outs
Reinforced concrete	Columns in a frame, carports, basements	Eurocode 2 sets a minimum concrete cover over the reinforcement for each exposure class. EN 1992-1-2 covers fire design	The cover must be kept intact so the steel stays protected
Steel	Slim columns in open rooms, glazed facades, garage bays (see steel frame construction)	Exposed steel weakens at high temperatures, so protection materials insulate it for the required fire resistance period	Corrosion needs moisture and oxygen. In a dry, heated interior the corrosion risk is insignificant
Timber	Posts in timber-frame houses, pergolas, porch supports, or glued laminated timber posts	Fungal decay needs a timber moisture content of about 20 % to 60 %	Keep timber away from moisture, including at the base of the post

Each material has its own Eurocode part. EN 1992 covers concrete, EN 1993 steel, EN 1995 timber including glued laminated timber, and EN 1996 masonry. EN 1991 covers the actions on structures. The Slovak standards office ÚNMS states that from April 2010 the Eurocodes are the only standards for designing building structures in Slovakia. National annexes set selected parameters for each country.

How is a column different from a load-bearing wall?

Both carry vertical load, and the difference is in how each element collects the load. The table compares them.

Element	How it carries load	Effect on the layout
Column	Collects the load of beams and slabs at one point and passes it down to the foundation	Gives open bays, but each column needs a designed connection above and below
Load-bearing wall	Carries the weight of the floors and roof above it along its full length	Openings in it need a designed lintel or beam

In a frame house the columns and slabs form the structure and the walls can be non-structural. In a masonry house the walls carry the load, and columns appear only where a designer wants an open bay. Find out which system a house uses before any renovation, because only an engineer can tell after inspection whether a wall or column carries load.

Who designs a column and which rules apply?

Under Building Act 25/2025 § 9 ods. 8, the designer of the static part of the project documentation answers for the design of the load-bearing structures. This includes the static assessment of their mechanical resistance and stability. The static part also includes a verifiable static calculation. Act 138/1992 § 5 ods. 4 lists the design of load-bearing structures among the services of an authorised engineer for building statics (inžinier pre statiku stavieb). The architect coordinates the column positions with the layout, and the engineer sizes the columns to the Eurocode part that matches the material.

What should a homeowner check before changing a column?

Any change to a column starts with an assessment by a structural engineer, not with demolition. The engineer works out what the column carries and what can replace it, and writes that in the static calculation. The homeowner can prepare with these points:

• Identify what the column supports: roof, upper floors, a beam or a balcony.
• Look at the base for moisture. Timber decays where its moisture content stays high, and steel corrodes where moisture and oxygen are both present.
• Note cracks, a tilt or a bow in the column and report them to the engineer.
• Ask which temporary supports the works need and how the new load path will be formed.

On the permit side, Building Act 25/2025 § 18 ods. 2 requires a decision on building intent for a change of a completed building, unless the act says otherwise. Under § 18 ods. 3 písm. h), an alteration needs notification when the works may endanger mechanical resistance and stability. The page on building alteration notification explains this filing,. Involve the designer and the building authority early.

Why does column placement matter in early design?

Column positions decide the spans of the beams and slabs that the engineer must then design. The JRC worked examples state that deflection limits govern slab thickness and that punching often governs it for flat slabs (section 1.5.1.1). A column placed to suit the furniture plan alone can force a longer beam span or a thicker slab elsewhere. For this reason the structural engineer should join the layout discussion before the plan is final.