A base plate template is a drilled plywood or steel plate that copies a column's base plate hole pattern and holds the anchor bolts in position while the concrete is poured. It works with the base plate layout (the anchor bolt plan) from the steel shop drawings, which locates every column, bolt pattern and elevation off the building gridlines. Get the layout and templates right and the columns drop straight onto the bolts. Get them wrong and the steel waits on site while someone works out a fix.
Base plate layout: what the anchor bolt plan shows
On a steel job, the base plate layout is usually issued as an anchor bolt plan (also called a setting plan or anchor rod plan) with the steel erection drawings. It is often one of the first drawings released, because the concrete is poured long before any steel arrives. A complete plan shows:
- Gridlines and column marks for every column, matching the erection drawings
- Bolt pattern for each base plate type, dimensioned from the gridlines, not just from the column centre
- Offsets where a column is not centred on the gridline intersection, such as edge and corner columns
- Bolt size, length, grade and projection above the top of concrete, plus the nut and washer arrangement
- Elevations: top of concrete or pier, and underside of base plate or top of steel, so the grout space is clear
- Orientation of each column (which way the flanges or long side of the plate face), with a north arrow
- Template marks where several base plate types share a pattern, so one template design serves many columns
- Notes on bolt material and finish, setting tolerances and who supplies the templates
Base plate details are shown separately: plate size and thickness, hole size and location, the weld from column to plate, and any shear lug or stiffeners. For how the plate itself is sized, see column base plate design to CSA S16, and for rod size, hole size and edge distance, see anchor bolts for base plates.
What a base plate template is
A template is a flat sheet, usually plywood or thin steel plate, drilled with the anchor bolt pattern of the base plate it represents. It is marked with:
- The column mark or template type
- Centrelines in both directions, so it can be lined up with gridlines on the forms or survey stakes
- An orientation mark (an arrow or "N") so the template can't be set rotated
- The bolt projection or top of concrete reference, where the template sets the bolt height
The anchor bolts pass through the template holes and are held by nuts above and below it, which fixes both their spacing and how far they project above the concrete. The template is fastened to the forms or to a frame above the footing so it can't move during the pour.
Templates are made from the same base plate drawing the fabricator uses, so the bolt pattern matches the plate holes. Templates on plywood are cheap and easy to make on site; steel templates hold their shape and can be reused on repetitive jobs. Who makes them varies by project, so check the contract.
How anchor bolts are set with a template
This is general practice, not a procedure for any specific job. The site's layout, the engineer's details and the anchor bolt plan govern.
- Lay out the gridlines on the forms or on offset stakes from the survey control, not from the edge of the formwork.
- Assemble the bolts in the template, with nuts on both sides set to the projection on the plan.
- Set the template on the gridlines with its centrelines matched and the orientation mark the right way.
- Plumb the bolts. A bolt that leans can be in the right place at the template and the wrong place at the plate, and it can stop the plate from going on.
- Secure everything. Tie the bolts to the reinforcing cage and brace the template to the forms so vibration and concrete placement can't move it. Make sure the bolts and the rebar don't clash, which is easier to solve at the detailing stage than on the day of the pour.
- Protect the threads with tape or sleeves so concrete doesn't foul them.
- Check after the pour while the concrete is still workable, and again once it has set.
- Remove the template and keep the bolts protected until erection.
For heavier columns, the anchor bolts are sometimes cast in pipe sleeves so they can be moved slightly to suit the plate, then the sleeves are grouted. Whether that is allowed is the engineer's call.
Survey before the steel comes
The single most useful step is an as-built survey of the anchor bolts and bearing elevations after the concrete is placed, sent to the fabricator and erector before the steel ships. A survey catches:
- Bolt groups that are rotated or shifted off the gridline
- Bolts that are leaning, bent or too short above the concrete
- Top of concrete elevations that leave too little or too much grout space
- Missing bolts or bolt groups
Base plate holes are made larger than the bolts so the column can be set despite small placement errors, with heavy plate washers over the holes. But there is a limit to what an oversized hole can absorb. The tolerances that apply, and how the layers of tolerance stack up, are covered in steel fabrication tolerances under CSA S16.
When bolts are out beyond the tolerance, the fix depends on how far out they are and what the column carries. Options include slotting or enlarging holes, a new base plate with a different pattern, or abandoning the bolts and installing post-installed anchors. Each needs the engineer's approval. Don't bend, heat or cut anchor bolts to make a column fit without that approval.
How the layout ties into shop drawings
The anchor bolt plan, the base plate details and the column piece drawings all come from the same model or drawing set, so they agree with each other. Changes made in one place have to flow to the others:
- A column moved on the architectural drawings must change the anchor bolt plan before the concrete is poured, not after.
- A plate size change may change the bolt pattern and the template.
- A revised top of concrete changes the bolt projection and the grout space.
Issue the anchor bolt plan early, mark every revision clearly, and make sure the concrete crew is setting bolts from the latest one. For what happens after the bolts are set, see setting steel columns on footings and pedestals and grouting base plates.
Base plates and layouts from Procut
We prepare shop drawings in house, including base plate details and layouts tied to the column drawings, and we fabricate base plates, columns, HSS posts and connection plates to your details with CWB certified welding. Engineering services are available for projects that need them. Ask us about anchor bolts and templates when you send your drawings, and we'll tell you what we can include.
Send your structural drawings for a free take-off and quote, or see our services for shop drawings, fabrication and delivery across the GTA and Ontario.
Frequently asked questions
What is a base plate template?
A base plate template is a flat piece of plywood or thin steel plate drilled with the same hole pattern as a column's base plate. It holds the anchor bolts in the right position, spacing and projection while the concrete is placed, then comes off once the concrete has set.
What does a base plate layout drawing show?
It shows each column location by gridline and mark, the anchor bolt pattern and its offsets from the gridlines, bolt size and projection above the concrete, top of concrete and top of steel or underside of base plate elevations, the grout space, and the orientation of the column. On steel jobs this is usually called the anchor bolt plan or setting plan.
Who sets anchor bolts for steel columns?
Usually the concrete contractor or general contractor sets them, using the anchor bolt plan from the steel shop drawings. The steel fabricator or erector rarely sets them. The contract should say who supplies the bolts and templates, who sets them and who surveys them.
What happens if anchor bolts are in the wrong place?
Small errors are taken up by the oversized holes in the base plate and plate washers. Larger errors need a fix approved by the engineer, such as a modified base plate, new post-installed anchors or a different connection. Surveying bolts before the steel is fabricated or shipped catches problems while they are cheap to fix.
