15.2 Construction Joint Schedules & Structural Pour Break Details
Key Takeaways
For nonprestressed floor and roof systems, ACI 318-19 Section 26.5.6.2(b) places construction joints in the middle third of slab, beam or girder spans unless the licensed design professional approves otherwise.
Measure a girder joint’s required two-beam-width offset from the intersecting beam face. Submit an unshown or different location or detail for design review.
Check the approved surface preparation and reinforcement. Remove laitance, prewet immediately before new placement and remove standing water.
Under ACI 318-19 Section 26.5.7.2(a), wait until the vertical supporting concrete is no longer plastic before placing the supported beam, girder or slab.
Use the approved waterstop profile and section to locate the seal and confirm it stays in position during consolidation.
15.2 Construction Joint Schedules & Structural Pour Break Details
Use the placement plan, construction joint schedule and structural sections together. A construction joint divides successive placements at an interface that can be detailed and prepared for the required structural and exposure conditions. When deliveries or formwork sequencing change, a proposed stop still needs to be reconciled with the approved construction documents.
1. Read the joint symbol and section
| Detail | What the drawing establishes | What to verify in the field |
|---|---|---|
| Construction joint | Where successive placements meet and how reinforcement or other load-transfer features cross the interface | Bulkhead location, specified surface preparation and approved bar, dowel, key or waterstop detail |
| Contraction joint | Where a weakened plane controls the location of shrinkage cracking | Joint line, cut or groove geometry and load-transfer devices if shown |
| Isolation joint | Separation that allows adjacent elements to move independently | Full separation and filler or other detail shown, with bonded reinforcement interrupted |
The same joint can serve more than one function where the design combines them. Read the section even when the plan has a familiar abbreviation. A planned stop with continuous bars and a roughened face may have a different detail from the stop at a slab edge that is also intended to permit movement. An unexpected delay between layers can produce a cold joint. An unshown location or different detail must be submitted to the licensed design professional for review under ACI 318-19 Section 26.5.6.2(a).
2. Apply span and offset rules to the correct reference lines
For nonprestressed concrete in floor and roof systems, Section 26.5.6.2(b) places construction joints in the middle third of the spans of slabs, beams and girders unless the licensed design professional approves otherwise. Prestressed concrete is outside this middle-third rule. Section 26.5.6.2(c) separately requires a girder construction joint to be at least two intersecting-beam widths from the beam face unless the licensed design professional approves otherwise.
Span rules and structural details work together. The center of a span can still contain a framing intersection, opening or other feature that affects the approved joint location. Where a plan uses column gridlines, read the detail and convert coordinates to the span reference used for the check. A beam’s centerline and its face also give different distances. For wall and column joints, use the approved locations. Where ACI 301-20 Section 2.2.2.5(a) applies without a project change, its defaults place these joints at the underside of slabs, beams or girders and at tops of footings or slabs.
Worked example: Girder G10 and Beam B15
Girder G10 is a nonprestressed floor girder with a 30-ft clear span. In this example, all distances are measured from the left support face. Beam B15 frames into G10 with its centerline at 15 ft and a width of 18 in. The contractor proposes a bulkhead 14 ft from the same support face. Assume no approved alternative to the code locations.
- The middle third extends from ft through ft. The proposed location at 14 ft passes that check.
- Beam B15 is 1.50 ft wide. Its faces are at ft and ft. Twice the width is 3 ft. A joint to its left must be at or before ft. One to its right must be at or beyond ft.
- The proposed location is 0.25 ft, or 3 in., from the nearer beam face. It misses the required 3-ft offset. The ranges that meet both geometric checks are 10–11.25 ft and 18.75–20 ft, including their endpoints. The inspector records the discrepancy and the dimensions. A proposed location in either range still goes through applicable design review and approval before being used.
3. Match the interface to the specified load-transfer detail
Check the bars, splice locations, dowels or keys that the drawing shows. A bar that passes continuously through a bulkhead and a bar that ends there with a designed lap or coupler involve different checks. Read the bar marks and continuity details on both sides. Verify that the bulkhead accommodates the specified bars and waterstop, can remain on line during the first placement and fits around penetrations without allowing excessive mortar loss. Record any moved or terminated steel before it is concealed.
ACI 318-19 Section 26.5.6.2(d) through (f) requires cleaning and laitance removal, intentional roughening where specified, and prewetting immediately before placement with standing water removed. When the design relies on the roughened hardened-concrete condition of Table 22.9.4.2, check the specified full amplitude of approximately 1/4 inch and the clean contact surface. The table distinguishes that condition from a clean, nonroughened interface. The reinforcement and limits in the shear-friction design still matter. If the bulkhead strips to reveal a smooth face at a location detailed as roughened, document the condition and verify the approved preparation before the next placement.
4. Follow the sequence and waterstop detail
Before placing a beam, girder or slab on cast-in-place vertical supports, check the condition of the supporting concrete. ACI 318-19 Section 26.5.7.2(a) requires it to be no longer plastic. Follow any approved sequencing requirements in addition to that condition. For example, a two-hour interval on the contractor’s schedule does not resolve an observation that the supporting concrete is still plastic.
Where the wall section shows a centerbulb PVC waterstop centered on the joint, confirm the bulb aligns with the joint plane and the anchoring flanges extend into the respective placements. Check its supports, the bulkhead fit and accessible clearances for concrete placement. After stripping, verify that the exposed flange remains in position and is clean and undamaged before it is concealed by the second placement. A hydrophilic strip applied to hardened concrete is a different installation. Use the specified product, its required cover and the approved substrate preparation. In both cases, inspect for displacement and lack of consolidation around the seal.
The inspection record should identify the joint mark, placement stages, required and measured offsets, bar and waterstop details, condition of the interface and any discrepancies. Use the approved detail or the documented disposition to verify correction.
Under ACI 318-19, where is a construction joint located in a nonprestressed floor beam if the licensed design professional has approved no alternative?
At the face of a support
At the quarter point of the span
At any location selected by the concrete contractor
Within the middle third of the span
Girder G10’s intersection with Beam B15 has its nearer beam face at 14.25 ft. B15 is 18 inches wide. A joint is proposed at 14 ft from the same datum. How does this proposal compare with the ACI 318-19 girder offset rule if no alternate location has been approved?
It meets the rule because the joint is in the middle third.
It misses the rule because the 3-inch measured offset is less than 36 inches.
It meets the rule because the beam centerline is 12 inches away.
It misses the rule because the joint must be at least one full span from the beam.
A foundation-wall section shows a centerbulb PVC waterstop centered on the joint plane. Which installed condition matches the detail?
The bulb aligns with the joint plane and the flanges extend into the two placements.
The bulb is cast wholly into the first placement and both flanges stay on that side.
Both flanges are folded against the exposed concrete face.
The bulb is punctured so that it can be wired to the center reinforcement.
A contractor plans to place a supported slab two hours after the vertical cast-in-place supports were placed. What condition does ACI 318-19 Section 26.5.7.2(a) require before the slab placement?
The supports must have been placed for at least 30 minutes regardless of their condition.
The supporting concrete must no longer be plastic.
The supports must reach the full specified compressive strength.
The slab can be placed while the supports are plastic if the slab uses self-consolidating concrete.
Sections you finish are checked off in the contents.