Structural Steel Tie-Ins

Written for Canada. Plans are metric, but many crews and suppliers work in feet and inches, so this site gives both: millimetres and metres, with feet and inches beside them. Codes are the National Building Code of Canada 2020 (NBC 2020) Part 9 as your province adopts it. A number marked Confirm has not been checked against every province, so check it with your own authority before you act on it.

Reviewed by a working tradesman with 17+ years in the field.

Some links on this site are affiliate links. If you buy through them we may earn a commission at no extra cost to you. Affiliate disclosure

Anchors, embeds and dowels that connect concrete to steel columns, beams and plates, and how to keep them exactly where the drawings put them.

The big idea

Tie-ins connect concrete to steel columns, beams, plates and frames, and pass the loads between them. Most are set during the concrete work and cannot be changed afterward, so a bolt that is 10 mm (3/8 in) out can mean a delay of days and a visit from the engineer. Accuracy matters more here than almost anywhere else on the job.

Steel connections to concrete are engineered. Steel design follows CSA S16, and welding must be done by a firm and welders certified to CSA W47.1 and W59. Anchor and embed details come from the structural drawings.

Types of tie-ins

• Anchor bolts and rods: cast in concrete to hold columns and base plates.
• Base plates: steel plates bolted to the concrete, usually set on grout.
• Embed plates: plates cast into walls or slabs, with studs or bars, for welding steel on later.
• Dowels: bars that connect concrete to concrete or to a steel element.
• Shear studs: studs welded to beams for composite slabs.
• Column ties: steel cages or anchors that connect concrete to columns.

Anchor bolt installation

Anchor bolts must land exactly where the drawings put them. A few millimetres can stop the steel from fitting.

1. Use a template. Made for the job, to hold the bolts at the right spacing.
2. Fix the template. To the forms or the rebar, so it cannot move.
3. Check spacing, projection and orientation. Against the drawings.
4. Check the layout. Against gridlines or survey points before the pour.
5. Protect the threads. Keep them clean and covered so concrete cannot foul them.
6. Check again during the pour. Bolts can shift when concrete hits them.

Check the group with diagonals

A rectangular bolt group works like a small building. Example: four bolts at 200 mm × 300 mm (8 in × 12 in). The diagonal is √(200² + 300²) = 360.6 mm (14 7/16 in), and both diagonals must read the same. If they do not, the group is out of square, so find the bolt that moved.

Projection

The bolt must stand high enough to pass through everything it holds, and show thread beyond the nut. Example with made-up numbers: grout 25 mm + plate 20 mm + washer 4 mm + nut 25 mm = 74 mm (2 15/16 in), plus the thread the drawing requires past the nut. The drawing gives the real number.

Embed plates

• Set at the face or depth shown on the drawings.
• Fix them firmly so they cannot move or tip.
• Keep the welding face clean and free of concrete.
• Check location against the structural drawings and the surveyor's marks.
• Studs or bars welded to the back of the plate transfer the load into the concrete.

Column tie-ins and shear connectors

• Place the rebar cage around the column base as drawn.
• Tie dowels from the footing to the column encasement.
• Keep the required cover around the steel.
• Plumb and brace the column before forming around it.
• Shear studs are welded to the beam by a certified welder before the deck or form goes on. Keep them clean and at the spacing drawn, and keep the required slab thickness over them.

Rebar and steel together

• Do not let rebar touch steel unless the design says so. They are different metals with different roles.
• Keep cover between the rebar and the steel surface.
• Use hooks or bends where the drawings call for them.

Forming and pouring around steel

• Cut forms tight around columns and plates, and seal gaps so grout and concrete cannot leak.
• Brace more heavily, because steel creates uneven pressure.
• Check plumb and alignment before the pour.
• Watch bolts and plates for movement during the pour, and check the projection height.
• Vibrate carefully near embeds so they do not shift.
• Make sure concrete fully surrounds the anchors and embeds.

Common mistakes

• Bolts out of line or out of plumb
• Embed plates set too deep or too high
• Bolts shifting during the pour
• Not enough bracing
• Rebar touching steel
• Wrong projection height
• Trying to fix a bad bolt in the field without approval