12.1 As-Built Surface Tolerances & Architectural Concrete Finishes (ACI 117)

12.1 As-Built Surface Tolerances & Architectural Concrete Finishes

Start with the surface designation and specified method of evaluation. A wall can meet a thickness or plumbness tolerance while exceeding the allowable local offset at a panel joint. A floor can meet an overall profile requirement while missing a minimum local value in one area. Identify the measurement and the comparison criterion before recording a discrepancy.

1. Check the specified formed finish

Where ACI 301-20 Section 5.3.3.1 applies without a different requirement, SF-1 is the default for the formed surfaces described as buried or covered by other building systems. Other formed surfaces default to SF-2. Read the specific contract designation and applicable Section 5.3.3.2 requirements.

Check separately the size limits for voids and projections in the selected finish. Architectural work can include an accepted mockup, a form liner pattern, a rubbed finish or an exposed aggregate treatment. Compare actual color, texture, surface irregularities and specified tie-hole treatment with the applicable requirements. For tie holes to be patched, use the approved material and the ACI 301-20 Section 5.3.7.2 procedure as applicable. It specifies cleaning and dampening before use of the site-mixed portland-cement repair mortar referenced in Section 5.3.7.4. Approved alternative materials follow their instructions. Where ferrous ties and SF-2 or SF-3 are specified, verify the project breakback or the 3/4-inch ACI 301-20 default.

2. Distinguish abrupt and gradual surface irregularities

ACI 117-10 Section 4.8.3 sets limits for both abrupt and gradual formed-surface irregularities. Measure an abrupt step within 1 inch of the irregularity. For a gradual departure, use the gap under a 5-ft straightedge between contact points.

For example, an approved Class B wall has a 5/16-inch abrupt offset at a panel seam. Its limit is 1/4 inch. The measured step exceeds that limit by 1/16 inch. Record the face, seam and measuring location. Use the approved disposition for correction and verify the result separately from the wall’s global alignment.

3. Check floor profile test scope and timing

ACI 117-10 Sections 4.8.4 through 4.8.6 distinguish specified methods for random-traffic floor surface tolerances. ASTM E1155 is a statistical profile method. In the inch-pound application, $F_F$ characterizes short-distance changes in slope over 2 ft and $F_L$ uses elevation differences between points 10 ft apart. Higher values indicate better performance on that measure. If the specification instead uses the manual straightedge method in Section 4.8.6, allow a freestanding 10-ft straightedge to rest naturally on the slab and measure the largest gap between its support points. In the flat category, at least 90% of the samples must have gaps no greater than 1/4 inch, and all must be 3/8 inch or less. Thus, even if 95% of the sample results are 1/4 inch or less, one 7/16-inch gap exceeds the separate all-samples limit. ASTM E1155 results are unsuitable for enforcing fixed-path vehicle floor tolerances, which require the applicable specified method for the wheel paths.

Under Section 4.8.4.4, measure and report the test surface within 72 hours after finishing and before supporting shores are removed. Check any other applicable project timing provisions. For example, ACI 301-20 Section 5.3.4.3 requires specified floor-surface measurements within 72 hours after finishing and before stressing tendons or removing supporting formwork or shoring. ACI 117-10 Section 4.8.5.4 limits the specified overall and minimum local levelness criteria to level slabs-on-ground and level suspended slabs shored when tested. Record the actual support condition, timing and test method.

ACI 117-10 Section 4.8.5 distinguishes specified overall values for the specified overall area from minimum local values. The default minimum local values are three-fifths of their respective overall values unless otherwise noted. For example, specified overall values of $F_F=35$ and $F_L=25$ give default local minima of 21 and 15. If a correctly tested applicable local area has $F_F=20$, it misses that local minimum even if the overall flatness result reaches 35.