Wet-setting anchor bolts/holdowns

Question:
I have heard that wet-setting anchor bolts and holdowns is not acceptable but it appears to be common practice throughout my jurisdiction. Can you provide some background information as to why it should not be allowed?

Answer:
It has been my experience that vertical reinforcement and other items that are to be embedded in the concrete are often "wet-set" or "wet-stabbed" in addition to anchor bolts and holdowns. This tends to occur more often in residential construction, rather than commercial, as special inspections are often required in commercial construction for these elements.

So why should these elements be tied in place prior to the concrete pour? The Structural Engineer's Association of Utah (SEAU) recently published a letter addressed to building officials addressing this issue. The following text is taken directlly from that letter and includes specific code references and SEAU's explanation as to why wet-setting should not be allowed.

IBC Section 1912 states that anchors shall be designed per Appendix D of ACI 318, where even the preliminary “Definitions” section calls out an “Anchor” as either being “cast into concrete” or “post-installed into hardened concrete”, and not listing “wet setting” as an option. Even more clear is the definition of “Cast-in Anchor” in the same section, where it states “installed before placing concrete” (italics added). IBC Table 1704.4 calls specifically for the periodic inspection of “reinforcing steel, including … placement”, but calls for continuous inspection for “bolts to be installed in concrete prior to and during placement”. IBC 1704.13 also states that unusual “Materials and systems required to be installed in accordance with additional manufacturer’s instructions that prescribe requirements not contained in this code” shall require special inspection. Section 109.3.1 calls out that “any required reinforcing steel is in place” prior to foundation inspections, and section 109.3.2 states that “other ancillary equipment items are in place … before any concrete is placed” below slabs. While none of this states “anchor bolts” or “holdown straps” tied into place, the intent seems obvious.


The IBC does have exceptions to the special inspection requirements in section 1704, primarily for “minor” work or for “Group R-3” residential construction. But even in the IRC, Section R109.1.1, it again requires that “any required reinforcing steel is in place and supported prior to the placing of concrete”. If the reinforcing is required to be in place prior to inspection, it only seems a natural extension that the IRC also intends for anchorages that rely upon the strength of this adjacent reinforcing to also be in place prior to inspection and placing of concrete.


As interpreted from the code, SEAU recommends that all embedded anchors and other hardware for IBC governed construction be firmly supported and tied into place prior to pouring of concrete, or that the placement of these anchors is continuously special inspected as they are being “wet set”. We also recommend this same interpretation be used for embedded light gage straps and other undefined anchors. Light gage holdown straps and other similar anchors are no longer considered “unusual”, but they certainly do carry with them “additional manufacturer’s instructions” for careful installation, and are normally a part of the seismic force resisting system. The action of tying all anchors into place before pouring, rather than allowing “wet setting” of anchors during pouring, helps to insure proper consolidation of concrete around the anchor and thus proper structural action of the anchor as it takes structural loads. Most Engineers, as well as most Building Officials, have seen the voids often left to one side or the other of a “wet set” bolt or dowel or strap – sometimes obviously reducing it’s structural capacity and increasing liability to the Engineer, Building Official, Owner and Contractor. When embedded dowels, bolts and straps are “wet set” we would recommend that a randomly selected portion of these embedded hardware are pull tested to full rated capacity prior to acceptance by the Engineer or Building Official.