A36 Steel
The general-purpose carbon steel grade behind plates, angles and channels.
Quick Answer
A36 steel is a carbon structural steel grade covered by ASTM A36, with a minimum yield strength of 36 ksi. It is widely used for plates, angles, channels and miscellaneous metals. Estimators price it by weight. For wide flange beams the preferred grade is now ASTM A992, so the two should not be confused on a takeoff.
The Full Picture
ASTM A36 is the long-standing general-purpose structural steel specification in the United States. Its minimum yield strength is 36 ksi, and it is the grade most people mean when they say "mild structural steel." Because it is easy to cut, drill and weld, it became the default for plates, angles, channels, bars and the miscellaneous steel that surrounds a building frame: base plates, gusset plates, stiffeners, lintels, embeds and bracing.
The estimating trap is the wide flange beam. Years ago, A36 was routinely specified for W-shapes. Today the preferred material for W-shapes is ASTM A992, which has a 50 ksi minimum yield and 65 ksi minimum tensile strength, and AISC guidance advises confirming that a W-shape is available in any grade other than A992 before it is specified. A takeoff that carries every shape as "A36" from habit can misprice the frame or conflict with the structural general notes. Angles, channels and plates still commonly follow A36 or a higher-strength plate grade, so read the material notes rather than assuming.
On the plans, the grade appears in the structural general notes, usually a materials list such as "wide flange shapes ASTM A992, plates, angles and channels ASTM A36," and sometimes again in the steel specification section under Division 05. Plate callouts on details give thickness, width and length, for example PL 1" x 14" x 14". The grade rarely changes the quantity; it changes the price per pound and the lead time, and a mismatch between the general notes and a detail is an RFI, not a guess.
Because A36 products are sold and fabricated by weight, the takeoff unit is the pound or the ton. Plate is converted from dimensions at roughly 40.8 pounds per square foot per inch of thickness (steel at about 490 pounds per cubic foot). Angles and channels are taken off in linear feet and multiplied by the weight per foot from the shape tables. Fabricated pieces such as base plates are often counted by each and carried with a weight so the fabrication labor can be tied to tons.
Real Examples
Common Misconceptions
People assume: All structural steel on a project is A36.
Actually: A36 is common for plates, angles, channels and miscellaneous steel, but W-shapes are normally specified as A992 now. Read the structural general notes and the steel spec for each shape family.
People assume: The grade changes how many tons you take off.
Actually: Grade changes price per pound, availability and sometimes the size the engineer selects, not the weight arithmetic. Weight comes from the shape or the plate dimensions, so the quantity is the same until the design itself changes.
People assume: A36 is automatically the right substitute for any steel callout.
Actually: A substitute needs the engineer's approval. A lower-strength grade can fail the design, and a higher-strength one can change connection or weld requirements.
Frequently Asked Questions
What is the difference between A36 and A992?
A36 has a 36 ksi minimum yield strength and is general-purpose. A992 has a 50 ksi minimum yield and 65 ksi minimum tensile strength and is the preferred grade for wide flange shapes. Both are carbon structural steels, but they are specified for different shape families.
How is A36 steel quantified in a takeoff?
By weight. Plate is computed from thickness, width and length at about 40.8 lb per SF per inch of thickness. Angles, channels and bars are measured in linear feet and multiplied by the weight per foot from the shape tables. Totals are carried in pounds or tons.
Where do I find the steel grade on the drawings?
Look in the structural general notes, the steel specification section in Division 05, and individual connection details. When a detail disagrees with the notes, treat it as a question to submit before bid.
Does A36 cost more than A992?
Prices move with the market and the shape, so compare current quotes from your fabricator or supplier instead of assuming. The takeoff job is to price each shape at the grade the documents call for.
Is A36 used for anchor rods?
Anchor rods are covered by their own specifications, and the grade is called out on the foundation or anchor rod plan. Do not assume they follow the plate grade; confirm against the drawings.