TOS means top of steel: the level of the top of a steel member, normally the top of a beam's top flange, used to set out the frame. What TOS means TOS means top of steel - the level of the top of a steel member. For a beam that is the top of the top flange. For a column it is normally the top of the cap plate, though some offices quote the top of the shaft instead, so it … [Read more...] about What Does TOS Mean on a Drawing? Top of Steel
What Does TOC Mean on a Drawing? Top of Concrete
TOC means top of concrete: the level of the finished concrete surface before any screed, topping or floor covering is added. What TOC means TOC means top of concrete - the level of the concrete surface at that point, as the concreter will leave it, before any screed, topping, tiles or floor covering go on. It exists as a separate callout because concrete is rarely the … [Read more...] about What Does TOC Mean on a Drawing? Top of Concrete
What Does AHD Mean on a Drawing? Height Datum
AHD means Australian Height Datum - the national vertical datum Australian drawings measure their RLs from, with zero at approximate mean sea level. What AHD means AHD is the Australian Height Datum - the national reference surface that Australian drawings measure heights from. When a drawing says RL 42.600 AHD, it means 42.600 m above that surface. AHD was adopted in … [Read more...] about What Does AHD Mean on a Drawing? Height Datum
What Does RL Mean on a Drawing? Reduced Level
RL means reduced level: the height of a point measured from the vertical datum the drawing nominates as zero, written in metres as RL 24.350. What RL means RL stands for reduced level. It is the height of a point measured vertically from whatever surface the drawing nominates as zero. The word "reduced" is a leftover from levelling fieldwork. A surveyor books staff … [Read more...] about What Does RL Mean on a Drawing? Reduced Level
What Does O/A Mean on a Drawing? (Overall)
O/A means overall — the dimension spans the full extent of the item, outside face to outside face, including frames, end plates, linings and projections. O/A is a hand-lettering habit that survived the move to CAD, and it is still all over Australian and UK drawings. It looks trivial until you realise it is one of three numbers describing the same object. What O/A … [Read more...] about What Does O/A Mean on a Drawing? (Overall)
What Does CLR Mean on a Drawing? (Clear)
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 … [Read more...] about What Does CLR Mean on a Drawing? (Clear)