Masonry Joint Reinforcement

Question: I was recently on a project where the plans only called for horizontal joint reinforcement and did not specify any additional horizontal rebar to be placed in grouted bond beams as is typical in our area. I have not seen this before... Is this allowed by the code?

Answer:
The short answer is yes, it is allowed by code.  With that in mind I have only seen one project in a high-seismic region such as ours use joint reinforcement in place of bond beam construction and it did not comply with the code.  So where does it say in the code that it is allowed and what should you look for?

IBC 2106.1 refers to Section 1.14.2.2 of ACI 530 for general reinforcing requirements for masonry shearwalls and further refers to Section 1.14.3 for Seismic Design Category (SDC) 'A', Section 1.14.4 for SDC 'B', Section 1.14.5 for SDC 'C', Section 1.14.6 for SDC 'D', and Section 1.14.7 for SDC 'E or F'.  So what do these sections in ACI 530 state?

Section 1.14.2.2 of ACI 530 essentially states that horizontal reinforcement can be provided by either joint reinforcement at 16"o.c. or reinforced bond beams at 10'-0"o.c. This horizontal reinforcement must also be provided above  and below all openings, at structurally connected roof and floor levels, and within 16-inches of the top of walls.  If joint reinforcement is used it shall consist of at least at least two wires of W1.7 (9 gage).  Ladder-type reinforcement as shown in Figure 1 below is most common.

Again, this section lists the general reinforcing requirements, but for this example I will assume the project falls within SDC 'D'.  Per IBC 2106.1 it must therefore comply with the additional requirements of Section 1.14.6 of ACI 530.  This section limits the spacing of horizontal reinforcement in masonry that is laid in a running bond pattern to 48"o.c., which is significantly tighter than the 10'-0" specified in Section 1.14.2.2.  The maximum spacing is reduced to 24"o.c. for masonry laid in a stack bond pattern.

While most projects you review will meet the requirement, Section 1.14.6.3 also lists a minimum ratio of steel to masonry area of 0.0007.  In the project I reviewed this is the item that did not meet code.  On the project in question 9-gage ladder-type reinforcement was used at 8"o.c. in an 8" CMU wall.  The joint reinforcement placed at 8"o.c. provided a steel area of 0.051in² per foot of wall.  The cross sectional area per foot of 8” CMU walls is 91.5in² (7.625”x12”).  Dividing the area of steel by the area of masonry gives a ratio of 0.00056, which is 20% less than the code-prescribed ratio of 0.0007.  There are ways that joint reinforcement can be used in high-seismic regions and still meet the code requirements.  In the example I used the engineer could have specified truss-type joint reinforcement (see Figure 2) or a thicker gage of ladder-type reinforcement. I hope that this helps.

Figure 1.  Ladder-type

Figure 2.  Truss-type

Helical Piers

Question:
How are other jurisdictions addressing helical piers? Would you require ‘Special Inspection’? What inspections would you have your department do? If you did not find the work until after it was done, what would you do to qualify the work? Would you require engineering? If so, what kind?

Answer:
I have reviewed projects involving helical piers on numerous occasions. The structural engineer typically notes on the plans where helical piers are required and the load they will need to support, but the helical pier design is often noted as a deferred submittal item. As you know, IBC 106.3.4.2 states that deferred submittals may only be allowed if approved by the building official. I have taken the stance that all foundation elements (i.e. helical piers, micropiles, Geopiers, shoring, etc.) are not allowed as deferred submittal items. I have found that most deferred submittals are often never submitted to the building official and that items are installed without the city’s review and approval. In reviewing helical pier submittals I have often found numerous items that need to be addressed so that reinforces my resolve to not allow the design as a deferred submittal.

So as a building official what should you require prior to approving projects including helical piers? Below is my own personal checklist of items that I require before issuing my approval on a project. I have included code references to support these requirements.

1. The project structural plans must note where the helical piers are to be located, the load they are required to support, and any applicable safety factors that should be used in the helical pier design. 
2. A soils report must be included with the helical pier submittal and must include the additional items listed in IBC 1808.2.2.
3. Helical piers are “specialty” piles and as such must meet the requirements of IBC 1808.2.3. To meet this section of the code I have required one of the following:
• Test data:  This data must show the allowable capacities of the systems proposed based upon testing. An ICC-ES report would be ideal, but the reports included on the ICC-ES website do not match the products that are currently produced by the leading manufacturers.  
• Load test: If applicable test data is not available (which is most likely the case) a load test should be provided in accordance with IBC 1808.2.8.3 to ensure that the pier capacity meets the required demand as specified on the project structural sheets. Many times multiple tests are required as some projects lists piers with different loading requirements. It should also be noted that the soils report may require load tests even if test data is available for the proposed piers.
4. Plans must be provided which note the material and construction requirements, the pier layout, and showing a detail of how the pies are to be attached to the foundations.
5. The submittal should be stamped by a licensed professional engineer in the state the project is located.

In regards to special inspection… Special inspection should always be provided on all deep foundation elements. Special inspections for helical piers should follow the applicable requirements of IBC Tables 1704.8 and 1704.9. In addition to these items, I have required special inspections to follow the guidelines noted in ER-5110. This is the ICC-ES report for A.B. Chance piers, and while it is outdated it is still useful for understanding the installation requirements of helical piers and any special inspection requirements specific to these systems. I should also note that the special inspections should be continuous during the pier installations.

Masonry Veneer Height Limitations

Question:
The UBC used to state what the height limitations were for brick veneer, yet it appears that the IBC does not provide a height limitation. Is there a restriction on the allowable height for masonry veneer?


Answer:
Yes, the code still specifies a height limitation for masonry veneer, however the IBC no longer lists this information in the code itself, rather it references ACI 530 for veneer requirements. I will try to break-down some of the masonry veneer limitations, including height, for both the 2006 IRC and the 2006 IBC.

2006 IRC:
In residential construction it is important to note that IRC R301.2.2.2.1 limits the dead load for exterior walls to 15psf, which would restrict the use of several types of masonry veneers although an exception is provided stating that veneers are allowed if they comply with IRC R702.1 and IRC R703.  IRC R301.2.2.3.1 also refers to these sections for masonry veneers located within Seismic Design Category 'C or above'.
IRC R702.1 is in reference to masonry veneers that are attached at the interior of the building and simply references the requirements of IRC R703.7.4 for anchorage requirements.

In regards to height limitations... IRC Table R703.7(1) provides the height limitations for residences located within Seismic Design Category 'C or below'.  It basically allows veneers up to a height of 30-feet above a non-combustible foundation with an additional 8-feet allowed at gable end walls. IRC Table R703.7(2) provides the requirements for residences located within Seismic Design Categories 'D0, D1, & D2'. In most cases the height of the veneer located within these higher Seismic Design Categories is limited to 20-feet above a non-combustible foundation with an additional 8-feet at gable end walls.

All masonry veneer must be supported by non-combustible lintels over window and door openings. IRC Table R703.7.3 provides acceptable lintel members and their spans. Veneer must also be anchored with corrosion-resistant ties in accordance with IRC R703.7.4. Please review IRC Figure R703.7 for required details of exterior masonry veneer such as a 1-inch air space, flashings, and a water-resistive barrier.

2006 IBC:
IBC 1405 lists many of the requirements for masonry veneer, including adhered veneer, stone, slab-type and terra-cotta. The IBC lists the requriements for each of these different systems but also refers to Sections 6.1 and 6.2 of ACI 530-05 for limitations.  So what does ACI 530 say?

Section 6.2.2.3.1.2 of ACI 530 limits the height of masonry veneer backed by wood framing or metal stud construction to 30-feet with an additional 8-feet at gable ends. This is irregardless of Seismic Design Category. So while the IRC limits veneer height to 20-feet in Seismic Design Category 'D', the IBC allows veneer backed by light framing materials to a height of 30-feet.

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.

Re-roofs: Structural considerations

It is my understanding that several jurisdictions do not require any significant information to be provided along with a re-roofing application.  There are a few structural issues that should be addressed before a re-roofing permit is granted.  Those issues include:

1. How many layers of existing roofing materials are there?

2. Will more than 4psf of additional dead load be added to the roof? (i.e. asphalt shingles to clay tiles)

3. Was the building built prior to 1975 and include unreinforced masonry bearing walls, parapets, or chimneys?

While item #1 is non-structural, the building code allows for only two layers of roofing materials. If the answer to question 2 is “yes” than an engineer should be involved.  If the answer to #3 is “yes” then engineered design for anchorage and bracing of the noted elements is required. The Structural Engineer's Association of Utah (SEAU) has created a handout for jurisdictions to use so that these items can be caught prior to issuing a re-roofing permit. The handout includes specific IBC, IEBC, and Utah State Amendment references.  The State of Utah currently exempts single-family residences from this requirement, although it should be noted that the IEBC includes no such exemption.  Please contact us if you would like a copy of the re-roofing questionaire.

New Deck Requirements

Question:
I have heard that there are new requirements for decks to have holdowns... Is that true?

Answer:
The answer to that question is both "yes" and "no". There are two common areas where you should be requiring holdowns at decks where you may not have been looking before. It is not a new requirement, but new information has been provided on how to enforce an old requirement.

The first location you should see a holdown device is at the connection of the deck to the house (if attached). Both IRC 502.2.2 and IBC 1604.8.3 require decks that are attached to a house to provide a positive attachment designed for both vertical and lateral loads. The code also states specifically that this attachment cannot consist of toenails or nails subject to withdrawal. While most think that face-nailing or screwing to a ledger meets both the gravity and lateral connection requirements noted, they are mistaken. The 2009 IRC now provides prescriptive ledger attachments to meet the gravity requirements as well as prescriptive lateral connection requirements. The lateral connections are provided by use of holdown deviices at two locations across the deck-to-home connection. These attachments tie into the actual floor framing rather than the ledger and rim board (see Figure 1). If permit applicants do not choose to use the prescriptive connection requirements, they must provide a design that takes into account the lateral connection of the deck to the primary structure. If the deck is free-standing, it should have its own lateral-force-resisting-system.

The second location to consider is at the guardrail post to deck connection. Recently Structure magazine addressed the connection of guardrail posts to residential deck structures. Both IRC Table R301.5 and IBC 1607.7.1 require that deck handrails be designed for a 200# concentrated load applied in any direction along the top of the rail. The article discusses studies that were performed to see what constituted a code-conforming connection of the guardrail posts to the deck. I was very surprised at the findings. Not only did assemblies using 1/2-inch lag screws not meet the code requirements, but some beefy-looking connections using 1/2-inch thru-bolts did not meet the force requirements. The article provides two details that do meet the code-prescribed force levels. Detail #1 (see Figure 2) is for posts attached inside the band joist. Detail #2 (see Figure 3) is for posts attached outside the band joist. These details require a holdown at each post (Simpson HD2A was used in testing). It is also important to note that the centerline of the holdown must be within two inches from the top of the joists. If you would like to read the entire article please go to the following link: http://www.structuremag.org/article.aspx?articleID=303

Figure 1.  Deck lateral connection

Figure 2.  Post inside band joist

Figure 3.  Post outside band joist

Eave blocking

Question:
I have heard that full-depth eave blocking is required by the building code, but contractors always argue that they have never been required to do this. Can you provide me some code references to support this requirement?

Answer:
This explanation is going to be a bit wordy, but it should give you plenty of ammunition to enforce full-depth blocking at the eaves.

First we need to understand that the roof and each floor level is considered a diaphragm. Diaphragms are essentially a beam. They lie horizontally and their main purpose is to collect the lateral earthquake/wind forces for the building. Those forces then need to be transferred down to the vertical elements (i.e. shearwalls) just as a beam is supported by columns.

Appropriate connections need to be made in order for these forces to be transferred adequately from the floor or roof into the shearwalls. Both the IBC and IRC require full-depth blocking to be provided between joists, rafters and trusses to aide in this force transfer from the diaphragm to the shearwalls, although it is not clearly stated.

We can quickly see this from the definition of an unblocked diaphragm in IBC 2302.1. While an unblocked diaphragm does not require blocking at panel edges throughout the diaphragm, it does require edge nailing (and therefore blocking) at the supporting members of the diaphragm. These supporting members are the shearwalls or collectors that transfer the forces to shearwalls (i.e. a drag beam or girder truss).

IBC Table 2304.9.1 and IRC Table R602.3(1) are the typical fastening schedules provided in the code. Each of these tables explicitly states how full-depth blocks are to be attached to the framing members at both the floor and roof levels.

IBC 2308.3.2 states that braced wall panels are to be connected to joists, rafters or full-depth blocking. Without the full-depth blocking at these braced panels (or shearwalls) an adequate force transfer cannot be accomplished. The exception provided in this section goes on to state that roof trusses must also have blocking provided at the ends unless another approved method is provided. The engineer may try to use another method to transfer the forces from the diaphragm into the shearwall, however blocking is the easiest and most common method.

IBC 2308.8.2 goes on to state that all joists shall be supported laterally at their ends and at all supports by full-depth blocking. IRC R602.10.8 has a similar requirement.

The following argument is commonly made: "I can't meet my venting requirements if I provide full-depth blocking between every truss". This is a pretty weak argument. As is shown in Figure 1, the full-depth blocking can be upturned periodically, birds mouths can be used, or the edges of the blocks can be notched to provide some venting. If this does not meet the venting requirements additional turtle vents or ridge venting should be added, but the eave blokcing requirement shuld still be met. Do not allow the blocking to be ommitted to meet the venting requirements.

I hope this helps you. I think there is plenty of ammunition here to show that it is required by the code.

Figure 1.  Typical Eave Blocking Detail