Prefabricated Rebar Cages for Footings and Piers

A rebar cage for a footing or pier is the bottom mat, vertical bars or dowels and ties for one element, assembled into a single unit before the concrete goes in. Building cages at grade, rather than tying every bar in the excavation, is usually faster and easier to inspect, especially when the same footing repeats across a job. The bars themselves are cut and bent in the shop to the footing schedule, tagged by footing, and assembled either at the shop, in a yard or on site beside the hole.

Procut cuts, bends, tags and bundles the bars for footings, piers and columns to your bar lists. If you want cages preassembled rather than delivered as tagged parts, ask us about your job when you request a quote.

What goes into a footing cage

The bar arrangement always comes from the structural drawings (or, for a house, the approved design). Not every footing needs reinforcement at all; our guide to whether footings need rebar under the Ontario Building Code covers that question. Where they do, a typical reinforced footing has some or all of these parts:

• Bottom mat. Bars in both directions near the bottom of the footing. Under RSIC (Reinforcing Steel Institute of Canada) standard practice, if the drawings do not show bar lengths, footing bars are detailed straight and extend to within 75 mm of each face.
• Top mat. Some heavily loaded or large footings also have a top layer.
• Dowels or starter bars. Bars bent with a foot at the bottom that sit on the mat and stick up to lap with the column, pier or wall steel above. Unless noted otherwise, RSIC practice makes footing dowels the same size and spacing as the vertical bars they connect to.
• Ties around the dowels. A few ties in the footing depth hold the dowels in position and square to each other.
• Chairs or supports. These hold the mat at the right height for the cover shown on the drawings.

For sizes, spacing and quantities in footings, see rebar for footings in Ontario.

Pier and column cages

Piers (including the round sonotube piers used under decks, porches and posts) and concrete columns are built from vertical bars wrapped in ties or a spiral:

• Vertical bars run the height of the pier and lap with the dowels from the footing.
• Ties wrap the verticals at the spacing on the drawings. RSIC practice starts the lowest tie no more than half a spacing above the top of the footing, and adds extra ties where vertical bars are offset bent.
• Spirals replace individual ties in many round columns. By RSIC practice a spiral's outside diameter is 80 mm less than the column's unless specified, finished with an extra one and a half turns at the top and bottom, and kept at the correct pitch with vertical spacers.

Our article on custom stirrups and ties covers tie shapes, hooks and sizing.

One scope point to settle early: for caissons and cast-in-place piles, RSIC notes that the reinforcing is usually supplied and installed by the caisson or piling subcontractor. Check who carries those cages before you assume they are in the rebar package.

Prefabricated cages or tie in place?

Both methods are common. The right choice depends on the size of the element, how many repeat, and the site.

Prefabricating cages at grade works well when:

• Many footings or piers repeat the same arrangement
• The excavation is deep or tight, so less time in the hole is safer
• You want an inspector or engineer to check cages before they go in
• The schedule needs placing done quickly between excavation and pour

Tying in place makes more sense when:

• Cages would be too heavy or floppy to lift without distorting
• The element is one-off or oddly shaped
• Bars must interlock with existing steel or adjacent elements
• Transport size or site access rules out moving finished cages

A common middle path is a kit of parts: every footing's bars cut, bent and tagged together, assembled on a flat surface beside the excavation, then lowered in. You get most of the speed of prefabrication without trucking bulky cages.

Tying, stiffness and lifting

A cage that is going to be lifted is a different animal from a mat tied in place.

• Tie more intersections. RSIC practice treats tying every fourth or fifth intersection as normal for placed steel. A cage that will be lifted needs more ties to hold its shape, especially at corners. Tie wire is normally 16 gauge black annealed unless the job specifies otherwise.
• Do not weld for convenience. Tack welding rebar cages to stiffen them changes the steel. Welding of reinforcing bars must be authorized by the engineer and done to CSA W186 with qualified procedures and welders.
• Plan the lift. Use proper slings or a spreader bar, pick from several points, and never drag a cage. RSIC guidance calls for approved slings and equipment for hoisting assembled reinforcement.
• Check before the drop. Confirm dowel projection, position and cover blocks before the cage goes in. Once it is in a narrow hole, adjustments get hard.

Lifting heavy assemblies is a safety-critical task. Follow your site's lift plan and your local safety authority's requirements.

Common mistakes with footing and pier cages

Most cage problems show up when the next pour starts, which is the worst time to find them:

• Dowels in the wrong place. Dowels have to line up with the column, pier or wall above, not just sit somewhere on the mat. Set them from grid lines, and brace them so they do not get knocked during the pour.
• Cages sitting on the soil. A mat laid directly on the ground has no bottom cover. Use chairs or concrete blocks sized for the cover on the drawings.
• Wrong pier height. Pier verticals cut to the drawing height will not work if the footing ended up lower than planned. Confirm elevations before the pier steel is fabricated.
• Missing top ties. The ties near the top of a pier are the easiest to forget and the first ones an inspector checks.
• Look-alike cages swapped. When two footing types differ by one bar size, label each finished cage with its mark and keep the tags on until it is in the hole.

What to send to order footing and pier steel

To quote and fabricate footing and pier reinforcement accurately, send:

1. Structural drawings with the footing and pier schedule, including typical details for dowels and ties
2. Footing and pier marks and counts, such as how many F1, F2 and P1
3. Pier heights, from top of footing to the top of the pier, or the founding and top elevations
4. Cover requirements, which drive mat and tie sizes
5. Whether you want parts tagged per footing for assembly at grade
6. Delivery sequence, so footing steel arrives before pier and wall steel

If founding elevations are not known yet, say so. RSIC practice notes that field fabrication is sometimes needed when founding elevations are unknown, and it is better to hold back a few vertical bars than to fabricate them to a guess.

Get a quote for footing and pier reinforcement

We prepare take-offs and quotes free of charge from your drawings, then detail, cut, bend, tag and deliver the steel for your footings and piers, with phased deliveries across the GTA and Ontario. We also install rebar; tell us whether you need supply only or supply and placing.

Send your footing schedule or see our services for detailing, fabrication, delivery and installation.