Last updated: October 2, 2026
Structural integrity is a requirement. A tie force is not.
That is the whole problem. Canada’s code asks for a structure that absorbs local failure without widespread collapse. It does not hand you a kilonewton-per-metre to put on a drawing. The number most Alberta precast jobs end up using is borrowed from the American code, through the precaster’s own design practice. Nobody writes that down in the specification. It shows up as a connection detail, and it shows up late.
This page is the tie side of robustness. Load paths, diaphragm action and connection hierarchy are covered in our precast concrete design overview. This page carries the integrity requirement itself and the paperwork it lands on.
What structural integrity means in the code
Integrity is defined as a performance, not a detail.
The national Structural Commentaries define structural integrity as “the ability of the structure to absorb local failure without widespread collapse.” Nothing in that sentence names a member, a bar size or a connection. It names an outcome.
Two consequences follow immediately.
- A connection can satisfy every strength check in the design and still fail the integrity intent, because strength is checked member by member and integrity is checked building-wide.
- Integrity applies during construction, not only at handover. The Commentary is explicit that partially completed structural systems need enough strength, ductility and lateral stability of their own to resist progressive collapse. A precast frame is a partially completed system every single day until the last connection is grouted.
The code points integrity back at the standards — with three exceptions
The code notes take a clear position: Part 4 and the referenced CSA design standards generally provide a satisfactory level of structural integrity. Then they name the cases where that is not enough.
| Case named in the code notes | Why precast lands in it |
|---|---|
| Building systems with components of different materials whose interconnection is not covered by the existing CSA standards | A precast panel bolted to a steel frame, or a hollow core slab bearing on masonry, is exactly this. The panel has a standard. The frame has a standard. The connection between them has an engineer. |
| Buildings outside the scope of the existing CSA design standards | Modular stacking, dry-assembled systems, unusual spans and transfer conditions. |
| Buildings exposed to severe accidental loads such as vehicle impact or explosion | Parkades, loading docks, truck bays, utility and industrial structures. |
Read the first row again. The code is telling you that the interface is where integrity gets decided, and that the interface is the part no single standard owns. On a precast job that interface is the embed, the plate, the weld and the grout. It is the precaster’s drawing and somebody’s seal.
The six ways integrity gets achieved
The Commentary lists the recognised measures. Precast engages all of them, but not equally.
| Measure in the Commentary | What it looks like on a precast job |
|---|---|
| Control of accidental events, including protective devices | Bollards, barriers, impact-protected columns at drive lanes. |
| Local resistance of key members | A heavier column or corbel at a transfer, designed to survive the event. |
| Design of tie forces — vertical, horizontal and peripheral | Integrity ties. The indirect route, and the one that ends up in the connection schedule. |
| Alternate paths of support | The key member is assumed failed, and the damaged building is checked to carry dead load plus a portion of the live load. |
| Control of widespread collapse through structural separation | Movement joints, separate towers, firewalls that do not drag the next bay down. |
| Treating the system as a whole, effectively tied together | The Commentary’s own summary position: a building should not be sensitive to local accidental failure. |
The Commentary also sets a threshold for when a key component deserves special treatment: a probability of accidental damage of approximately 10⁻⁴ per year or more. That is a design judgement, and it is made by the engineer of record, not by the precaster. But it changes what the precaster has to supply, so it has to be made before shop drawings start.
Tie design is listed as an indirect means. That word matters commercially. Indirect means nobody has to run a collapse analysis — provided the minimum tie criteria are met. Skip the ties and the alternate-path analysis becomes the fallback, and that analysis is not a shop drawing revision. It is a redesign.
The tie numbers come from the American code
Here is the part that catches estimators.
The Canadian concrete design standard governs precast design and sends fabrication and erection to the Canadian precast standard. What it does not publish is a table of prescriptive integrity tie forces for precast. The American code does, and Canadian precast practice uses those values when the Canadian documents are silent. Two independent sources — the PCA/StructurePoint integrity guide and PCI’s Standard Design Practice — agree on the substance.
| Requirement | Value or rule | Source |
|---|---|---|
| Members tied together | Members of a structure shall be effectively tied together. Tension ties are required in the transverse, longitudinal and vertical directions, for precast buildings of all heights. | PCA / StructurePoint |
| Friction | “Connections that rely solely on friction due to gravity forces are not permitted.” | PCA / StructurePoint |
| Vertical integrity ties, precast wall panels | At least two vertical integrity ties per connection, each with a nominal tensile strength of at least 10,000 lb. | ACI 318-19 §16.2.4.3(b) |
| Base of a precast column, pedestal or wall | The connection to the foundation must satisfy the integrity tie provisions. | ACI 318-19 §16.3.6.1 |
| Precast bearing wall structures, three or more storeys | Additional integrity requirements apply above that height. | PCA / StructurePoint |
| Ties to the lateral system | Transverse and longitudinal ties must connect individual precast members to the lateral-load-resisting system. | PCA / StructurePoint |
| Base with no tension | Where the design produces no tension at the base, ties may be anchored into an appropriately reinforced slab on grade. | PCI Standard Design Practice |
One note on editions. The older PCI practice document cites these provisions under a 16.5 numbering; the current American code carries them under 16.2.4 and 16.3.6. Same requirement, renumbered. If a specification cites a clause number without an edition year, ask which edition it means before anyone details to it.
The “friction is not permitted” line is the one that kills field improvisation. A panel sitting on a ledge, held by its own weight, is not tied. It is parked.
What belongs on the drawings, and what it costs to decide late
| Decision | Which drawing it lands on | Consequence if it comes late |
|---|---|---|
| Whether the structure is treated as three or more storeys for integrity | Design brief, before the connection concept | Panel connection concept changes; embeds move |
| Integrity tie type and count at each panel-to-panel connection | Erection drawings and connection details | New embeds. Embeds are cast in. Cast-in means a new pour. |
| Base connection detail and whether the slab on grade is the anchorage | Foundation drawings and precast erection drawings | Anchor bolt layout changes after the footing is poured |
| Who seals the connection design | Submittal cover sheet | Shop drawings stall in review |
| Tie continuity across a movement joint | Erection drawings | Field-welded fixes that compromise the joint |
| Protection at impact locations | Site and structural drawings | Bollards added after topping is placed |
The pattern is the same every time. An integrity tie is an embedded item. Embedded items are decided before the piece is cast, not before the piece is set. The gap between those two moments is the lead time, and that is where the cost sits. Our quality control process catches a missing embed in the plant. It cannot catch a tie that was never specified.
Where robustness is actually lost
Five field conditions, all common.
- Ties omitted at the last panel in a run. The run closes, the geometry is tight, and the final connection becomes a shim stack. The tie was in the detail and not in the wall.
- A tie welded to the wrong plate. The plate is there for alignment, not tension. It is thinner, and it is anchored for shear.
- Grout placed after loading. A grouted connection is not a tie until it has cured. Loading the floor first means the tie exists on paper only.
- Ties cut for a penetration. A later trade needs a hole. The tie is in the way. Nobody on site knows it is an integrity tie, because the drawing calls it a tie.
- Temporary bracing released early. Until the ties are complete, bracing is the integrity system. Releasing it on schedule rather than on completion is the single most common erection-stage robustness failure. Our panel installation sequence sets the order.
All five are inspection items, not design items. Put integrity ties on the erection hold-point list and sign them off connection by connection. A tie that was installed and then cut reads the same on a completed-percentage report as a tie that is still working.
Four questions to send the precaster before bid close
Short list. Each answer changes a price.
| Question | Why it changes the number |
|---|---|
| Is this a bearing wall structure, and how many storeys for integrity purposes? | Sets whether the additional provisions apply, which sets the embed count per panel. |
| Who seals the integrity connection design? | Decides whether the connection engineering is in the precast price or the consultant’s fee. |
| Are any panels part of a firewall, and which firewall approach is used? | Changes the panel itself, not just the hardware. |
| Does the slab on grade carry the base anchorage? | Moves reinforcement from flatwork scope into structural scope. |
Ask all four at once. Asking them one at a time across three weeks is how a submittal cycle becomes two.
A worked read of one tie line
A specification says: precast wall panels, four storeys, bearing wall structure, integrity ties per code.
Read it in this order.
- Height trigger. Four storeys is above the three-storey threshold. The additional bearing wall integrity provisions apply. The project is not in the minimum case.
- Panel-to-panel. At least two vertical integrity ties per connection, each with a nominal tensile strength of at least 10,000 lb. Two ties, not one oversized tie. The count is part of the requirement.
- Base. The connection to the foundation has to satisfy the same provisions. If the design shows no tension at the base, the slab on grade can be the anchorage — but then the slab reinforcement becomes a structural submittal item, not a flatwork item.
- Lateral system. Transverse and longitudinal ties have to reach the lateral-load-resisting system. Draw the path. If it stops at a panel, it is not a tie.
- Friction. Check every connection for a detail that works only because the piece is heavy. Replace it.
Five readings. Four of them change an embed. That is why this belongs in the pre-bid conversation and not in the first submittal cycle.
Precast firewalls are their own robustness case
The national Commentary treats firewalls separately, with three recognised approaches: a double firewall, a cantilever firewall standing independently, and a tied firewall whose lateral forces are resisted by the framework on the other side. It also recognises weak-link connections, which let the supported construction collapse without severely damaging the firewall itself.
A precast firewall can be any of the three. The choice changes the panel, the connection and the reinforcement, and a tied firewall is designed for a factored horizontal force derived from the weight of the collapsing structure plus a share of the snow load, with an allowance for strength loss at high temperature. Pick the approach before the panels are detailed. A cantilever firewall and a tied firewall are not the same product with different hardware.
Where this page stops
This page is integrity ties and robustness only. It does not cover seismic force modification factors, importance factors or storey sway limits. It does not cover fire-resistance ratings or acoustic separation ratings. It does not cover bearing length, bearing pads, joint grout proportions, erection tolerances, or how units are supported while stored on site. Those are separate specifications with separate numbers, and each has its own page.
FAQ
Does the Canadian code give a tie force for precast? No. It states the integrity objective and sends design to the concrete design standard. The prescriptive numbers used in practice come from the American code and from PCI’s design practice.
How many integrity ties does a precast wall panel connection need? At least two vertical integrity ties, each with a nominal tensile strength of at least 10,000 lb, under ACI 318-19 §16.2.4.3(b).
Can a connection rely on the weight of the piece? No. Connections that rely solely on friction from gravity forces are not permitted.
Does the three-storey threshold apply to any precast building? It applies to precast bearing wall structures. Additional integrity requirements apply at three or more storeys.
Who designs the integrity ties? The engineer of record sets the requirement and the design forces. The connection design is usually sealed as part of the precast submittal. Confirm the split in writing before shop drawings start.
When does this have to be decided? Before casting. Integrity ties are embedded items, so a late decision is a new pour, not a revision.
Get the detail before you bid it
We supply structural precast for commercial, industrial, parking and municipal work across Alberta, and we have detailed integrity connections for decades of projects. Send us the structural drawings and the specification section. You get back the connection concept, the embed schedule, a current lead time, and quantity pricing on the panel count you are actually buying.
Start with our precast solutions by sector, or review how beams and columns carry load into the same connections.
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