Stair headroom

What is stair headroom and where is it measured?

Stair headroom (Slovak podchodná výška schodiska) is the clear vertical distance above a staircase flight that a person needs to pass without striking the head. The university textbook Konštrukcie pozemných stavieb: Schody measures it on a vertical line. The line runs from the front edge of a step up to the lowest obstruction above it. That obstruction is usually the underside of the ceiling slab or a beam at the upper landing. The dimension decides whether a person can use the flight without a knock. It is a safety measure first and a comfort measure second.

Headroom is not the same as the height of the room. A room can have a generous ceiling and still give poor headroom. This happens when the flight runs under a beam, a bulkhead or a duct. Make the check along the flight itself, not from the room height on the floor plan.

What is the minimum headroom over a stair in a family house?

For a family house the decree 532/2002 gives one number directly. Section 45(3) says the main stair and the corridor have a clear headroom of at least 2,100 mm. The same paragraph asks for a clear width of at least 900 mm on the main stair and 750 mm on an auxiliary stair. The decree does not say where on the flight the 2,100 mm is measured.

The decree is not the only rule. Section 27(2) leaves the smallest headroom, the flight width and the landing sizes to the Slovak technical standard. That standard is STN 73 4130. That standard is a paid text and was not read for this entry, so this entry quotes no value as coming from it. Decree 532/2002 stays in force until the new building act 25/2025 gets its implementing regulations. The latest date is 31 March 2027 (section 84(23)(b) of the act). Check the rules in force on the date of your project.

How does stair headroom set the opening in the ceiling slab?

The stair opening in the upper floor slab has to be large enough that the required headroom is met at every point along the flight. The opening is not just the footprint of the flight. Its far edge sits where the upper end of the flight passes the underside of the slab. Size the stair from the top down. Fix the upper floor level first, then find where the flight meets the slab.

In practice the section is drawn first. A flight at a given slope rises toward the opening. The opening has to start far enough back that the clear space above the flight stays at or above the minimum. Trimmers and headers that frame the hole take up width, so the net clear opening is smaller than the drawn outline. By the textbook formula a steeper flight needs more vertical clearance. That moves the opening as well as changing its size.

How does the flight angle change the required headroom?

The textbook (Žilinský and Gieciová, Slovak University of Technology in Bratislava, 2018) gives the minimum headroom as hp = 1500 + 750 / cos γ. The result is in millimetres and γ is the slope of the flight. It gives the perpendicular passage dimension as hd = 750 + 1500 times cos γ, measured at right angles to the flight. These formulas come from a textbook, not from the decree. Use them as a check on a design. They do not replace the staircase pitch rules or the 2,100 mm of the decree.

The same textbook classifies stairs by slope, and the riser height grows with the slope. Gentle flights have shallow risers, while steep flights have deeper risers.

The values below are calculated from the textbook formulas and rounded to the nearest millimetre. Headroom grows as the flight steepens, while the perpendicular passage shrinks.

The textbook says hd must not fall below 1900 mm in residential and office buildings. For attic stairs the value is only a recommendation. On these figures a flight at about 40 degrees reaches that limit. The decree caps a main flight at 35 degrees. Only a stair inside a dwelling under 3,000 mm or a basement stair may go to 41 degrees (section 27(4)). The steep end of the table matters mainly for those exceptions. The textbook formula gives more than 2,100 mm at every slope. The decree figure and the textbook figure are not the same test. The architect checks which one applies against the standard.

How is stair headroom different from passage height?

Stair headroom and passage height are often confused because both are measured against the same flight. They answer different questions. Headroom is the vertical clearance above the front edge of a step, and it protects the head. Passage height runs perpendicular to the flight and protects the space a person walks through on the slope. The flight angle drives both, so a design that passes one check can still fail the other.

What usually cuts stair headroom in family houses?

Most shortfalls come from changes made after the structure is fixed. Common causes are a suspended ceiling lowered beneath a flight and a beam or duct above the upper steps. Another is an opening sized in plan without a section check. A loft conversion can run into the same problem. The roof line often comes down closer to the stair than the floor plan suggests.

Fixing a shortfall later is expensive. Moving a slab opening or changing a flight usually means reworking the structure. Fix the clear space while the section is still a drawing.

How should stair headroom be checked in a Slovak design?

Check it in four steps. First, take the flight slope from the section. Second, measure the clear space vertically from the front edge of the steps to every obstruction. Include beams, ducts and any suspended ceiling. Third, compare the result with the 2,100 mm of decree section 45(3) for a family house. Fourth, check the figures against the current text of STN 73 4130. The Normoff catalogue lists it as valid, with the issue date 16 November 1985. The architect does this before the stair is drawn into the slab.