CLR means clear — either a clear, unobstructed dimension between finished faces, or clear cover from a concrete face to the nearest reinforcing steel.
CLR does two different jobs on a drawing set, and both are numbers people build to. Work out which you are reading.
Meaning 1: a clear dimension
It is measured between the faces of the two things named, with nothing permitted to intrude, and it is almost always a minimum rather than a target. 1000 CLR between a bench and a wall means you must finish up with at least 1000 of usable gap.
Here is where clear dimensions bite. A clear dimension is measured to the finished surface unless the note says otherwise. A structural dimension is measured to the structural face. Linings, battens, render, screed, tiling and tolerance all live between the two. Lift shafts, stair widths, accessible circulation and plant zones are all specified clear, and all get built short by somebody who set out to the stud line and then lined it.
If a lift supplier or a joinery shop asks for a clear dimension, they mean after finishes, at the worst point in the opening.
Meaning 2: clear cover to reinforcement
On reinforced concrete drawings, CLR is the distance from the concrete face to the outside of the nearest steel. Nearest is the operative word. In a beam or column that is usually the fitment – the ligature, stirrup or tie – not the main bar, so 40 CLR TO LIGS and 40 CLR TO MAIN BARS put the main steel in different places, changing bar chair heights and effective depth. Slabs have no fitments, so cover is measured to the nearest bar in the mat.
Cover is a durability and fire requirement, not a site preference. The value depends on the exposure classification together with the concrete strength grade and curing method, and it can be driven by fire resistance instead. It is set by AS 3600 in Australia, ACI 318 in the US, and Eurocode 2 with its UK National Annex and BS 8500 in the UK. The governing figures are in the concrete notes. Read them there, not from memory.
How it appears on a drawing
As a clear dimension, with both faces named:
1500 CLR BETWEEN FACE OF WALL AND EDGE OF BENCH
In a door schedule, where clear opening is the compliance number:
D04 - 920 LEAF - 850 CLR OPENING MIN
As cover on a reinforcement note, US style:
#5 @ 8" O.C. B/W, 2" CLR
The Australian slab equivalent, which spells cover out:
N16 @ 200 CRS EW BOTTOM, 40 COVER
And on a beam, where cover is measured to the fitments:
3-N20 BOTTOM, N12 LIGS @ 200 CRS, 40 COVER TO LIGS
Terms it gets confused with
- CL or C/L – centre line. A hazard where an office legend also abbreviates clear to CL.
- CLG – ceiling.
- COVER – clear cover written out. AU and UK drawings prefer this.
- NOM – nominal, a naming size rather than a measured one.
- RO (rough opening, US) and structural opening – the hole before finishes.
- CRS and O.C. – centre to centre spacing, not clear between.
AU and UK versus US practice
Region changes the likely reading. On US structural drawings, CLR specifically means clear cover – 2" CLR beside a bar call-out is cover. On Australian, New Zealand and UK drawings, cover is usually written COVER or C=, or called nominal cover under Eurocode terms, so CLR there is more often a clear dimension. The sheet’s legend still wins: offices working to US templates will not follow the regional pattern.
Where to check on your own drawing set
- The abbreviations legend, and whether the office distinguishes CLR from CL.
- The concrete notes, for the cover schedule by element, exposure and grade.
- The architectural notes, for whether dimensions are to structure or finished faces.
- The door schedule, for clear opening widths. In Australia, doorways on a continuous accessible path of travel require a minimum 850 mm clear opening under AS 1428.1, which commonly needs a 920 mm leaf. US ADA standards require a 32 in minimum clear width at a doorway. Confirm both against the edition your project is called up to.
For the neighbouring tags, our A-Z list of engineering drawing abbreviations has them in one place.
Other meanings of CLR
CLR is a household cleaning product (Calcium Lime Rust), the Common Language Runtime in Microsoft .NET, and “cleared” in aviation radio shorthand. In medicine it is used for clearance. None of these overlap with drawing use, but they crowd the search results.