By David Biggs
This month’s questions come from a reader, a mason contractor about architectural design practice, and an engineer. What questions do you have? Send them to email@example.com, attention Technical Talk.
Q. A reader writes“In the June 2019 article, you discussed seismic anchors that include wire reinforcement in the bed joints that are mechanically connected to the anchors. One statement you made was that “However, there are no requirements to mechanically attach the wire reinforcement to the anchors”. This seems to be at odds with ASCE 7-16, Section 126.96.36.199 for SDC C and above.
A. Thanks for the comment! Some additional explanation is required.
First, the project discussed in the previous article was based on 2015 IBC which references ASCE 7-10, not ASCE 7-16. In addition it was in Seismic Design Category (SDC) B, not SDC C and above. The statement you mention was specific to that project. However, your question raises a point that could use some further discussion on a broader basis.
ASCE 7-16 and TMS 402 (masonry standard) are both referenced standards in 2018 IBC.
Graphically we get:
IBC Section 188.8.131.52 also modifies TMS 402. The modification for anchored veneer includes:
“14.4.6 Modifications to Chapter 12 of TMS 402
184.108.40.206 Corrugated Sheet Metal Anchors. Add Section 220.127.116.11.1.1 to TMS 402 as follows:
18.104.22.168.1.1 Provide continuous single wire joint reinforcement of wire size W1.7 (MW11) at a maximum spacing of 18 in. (457 mm) on center vertically. Mechanically attach anchors to the joint reinforcement with clips or hooks. Corrugated sheet metal anchors shall not be used.”
Within TMS 402-16, Section 22.214.171.124.1 applies to anchored veneers in SDC C and above.
So, if the project discussed had been built under 2018 IBC, not 2015 IBC, it still would not require mechanical attachment to wire reinforcement because the project is in SDC B.
Now let’s go back to the original project criteria with the 2015 IBC. It included two referenced standards ASCE 7-10 and the masonry standard ACI 530-13/ASCE 5-13/TMS 402-13. Yet, within ASCE 7-10, it reference masonry standard ACI 530-02/ASCE 5-02/TMS 402-02.
Here we have a dilemma due to a lack of consistency. Two masonry standards are referenced, not just one. The dilemma is the two standards have different criteria regarding this issue.
ACI 530-02/ASCE 5-02/TMS 402-02, Section 126.96.36.199.3.3 stated “Mechanically attach anchors to the joint reinforcement required in Section 188.8.131.52.2.4 with clips or hooks”. This section applies to SDC E and F. The joint reinforcement requirement mentioned applies to SDC D and above.
In ACI 530-13/ASCE 5-13/TMS 402-13, anchored veneers are addressed in Chapter 12. There is no requirement for mechanically attaching wire reinforcement to the veneer anchors. In previous editions of the masonry standard, these were required in SDC E and F, but were removed in the 2013 edition based upon testing that indicates they were “not necessary or useful” (as stated in TMS 402-13 Commentary, Section 184.108.40.206.3).
Finally, ASCE 7-10 modifies ACI 530-02/ASCE 5-02/TMS 402-02. The language is essentially what we saw in ASCE 7-16.
“14.4.6 Modifications to Chapter 6 of TMS 402/ACI530/ASCE 5
220.127.116.11 Corrugated Sheet Metal Anchors
Add Section 18.104.22.168.1 to TMS 402/ACI 530/ASCE 5 as follows:
22.214.171.124.1 Provide continuous single wire joint reinforcement of wire size W1.7 (MW11) at a maximum spacing of 18 in. (457 mm) on center vertically. Mechanically attach anchors to the joint reinforcement with clips or hooks. Corrugated sheet metal anchors shall not be used”.
Within ACI 530-02/ASCE 5-02/TMS 402-02, Section 126.96.36.199.1 applies to SDC C and above.
ASCE 7-10 has some errors:
- It wants to add 188.8.131.52.1, but that Section already exists.
- They want us to attach the wire reinforcement to the veneer anchors starting with SDC C. But, the prescriptive requirement to use wire reinforcement in the veneer does not apply until Section 184.108.40.206.2.4 which is for SDC D and above.
So as designers, we have some decisions to make when using ASCE 7-10. Do we use joint reinforcement in veneers at SDC C and above so we can attach the veneer to the anchors? Or, do we ignore the modifications listed for ACI 530-02/ASCE 5-02/TMS 402-02 because that edition was never referenced in the 2015 IBC?
As originally discussed for the original project, the end result is that being in SDC B, it is not necessary to mechanically attach anchors to the joint reinforcement. Nor is it necessary to use joint reinforcement in the veneer purely for seismic requirements. We did determine in the original article that joint reinforcement in the veneer was necessary due to the use of stack bonding, not seismicity.
However, remember that the IBC through ASCE 7 overrides the masonry standard and mandates mechanically connected wire reinforcement in veneer for SDC C and above.
Sorry for the long-winded response. If you are still with me you get a gold star!
Q. The next question comes from a mason contractor. “One of our upcoming projects has relieving angles and lintelsover openings. The drawings show the lintels being 15” high. The drawings don’t call out or show any ties at these locations. We asked an RFI as to how to handle the situation because ties are usually within 8” of openings.
The reply back from the architect was that there needs to be a tie installed into the angle iron. We put together a change order to add the ties. They came back with that we are suppose to know the code and should have figured them there. I have never come across a detail like this and I am at a loss on why are we (the Mason Contractors) are suppose to engineer a detail that should already be designed. We bid the drawings; we’re not engineers. Would love some feedback on this.”
A partial view of the detail is shown in the following figure:
Figure – Partial project detail
(Courtesy of Cantarella & Son, Inc., Pittsfield, MA.)
A. You raise some interesting points that require several responses.
- The first is with regard to knowing the code. The code is for the designers; the specifications are for the contractors. My opinion is that designers can’t delegate code requirements to contractors and the RFI response is incorrect if it indicated that contractors should know the code and should include code required design information in their bids and submittals. I am in favor of contractors becoming aware of code issues to be more informed to ask questions. It appears you did just that. However, the designers should resolve the design issues, not the contractor. Since your contract requires you to follow the specifications, let’s look at the project’s masonry specifications which you supplied separately. They state “Space anchors as indicated, but no more than 16 inches o.c. vertically and 16 inches o.c. horizontally with not less than one anchor for each 2.67 sq.ft. of wall area.” Based upon area requirements provided, 2.67 sq.ft. is equal to 384 sq. inches which would allow anchors to be spaced within 16 inches over an opening (16 inches x (8 inches + 16 inches) = 384 sq. inches. See the graphic below.
So, the project specifications would allow placing the first anchor 16 inches above the opening. If 8 inches is the design requirement for the maximum spacing over an opening, it should be so detailed or specified in the contract documents.
2. The second issue again goes back to the project detail and the specifications. The detail shows a 15–inch high bent plate hung from a steel channel. The specifications state “Fasten screw attached anchors through sheathing to wall framing and to concrete backup with metal fasteners of the type indicated”.
In the specifications, there are four types of anchors provided. My review indicates none of the four will work for the project detail; there is insufficient cavity space for the specified anchors.
The specifications are written for the typical details of anchoring to cold-formed metal studs or concrete. The project detail shown is a specific condition that was repeated at several locations on the building, but which was not detailed or specified sufficiently. The RFI response should have provided a proper tie as well as fasteners into the steel plate.
3. Although this was not part of the question, the depth of the bent plate should be discussed since the 15–inch length raises questions. If the hanger channels are supporting the lintel, why does the plate have to be so long? Is it there for structural purposes or simply as a flashing back-up? The length of the plate adds significant complications for the construction of the veneer as noted by the anchor question.
- Contractors are expected to follow the project design details and specifications, not design the details. Design reviews should address completeness and constructability.
- Contractors that question design details prior to construction bring added value to the project by attempting to resolve issues before they get into the field.
- Project specifications need to be coordinated with project details.
Q. An engineer writes that they have to designsupport for a newopening in an existing masonry wall. How is that done? Does it matter if the wall is brick or CMU?
A. Thanks for the question. There are several considerations including how to support the opening while the permanent reframing is installed. There are options dependent upon the size of the opening and the loading on the wall. The methodologies generally apply to both brick and CMU. Let’s discuss a few relative to the following figure.
Figure – Elevation
- The first step in planning any new opening in an existing masonry wall is to determine the expected loading over the opening, the resultant jamb loads, and out-of-plane loads. While this discussion is primarily for supporting vertical loads over the proposed opening, the jambs and segments of wall that remain above and below the new opening must also be checked for axial and out-of-plane loads.
The analyses and design will be based upon the choices made in the planning step. Let’s look at some options.
2. Supporting the wall while the opening is cut in:
3. For light loads, steel angles can be used for both the temporary support and the permanent framing. Install one angle by removing the mortar in the bed joint. Extend the angle into the masonry jamb to achieve adequate bearing once the masonry is removed. Once installed, repeat with the second angle. Once stable, remove the masonry below. See the following figure.
Figure – For light loads
b. For larger loads, angles might not be sufficient. In this case, channels with a welded steel plate could be used. This solution is limited to walls where the framing can be placed on the exterior of the wall where it will be covered by finishes or even left exposed. Fireproofing may be required as well.
The channels can be attached to the wall with bolts to provide bracing. Extend the channel and plate into the jamb to achieve adequate bearing once the masonry is removed. Once installed, repeat with the second channel. If the masonry jambs are overloaded by the new framing, channels can be added at the jambs as well. Once the opening is stable, remove the masonry below.
Figure – For heavier loads
c. For large loads, where the framing can’t be left exposed on the face of the wall, the framing often includes wide-flanges or channels in the plane of the wall. One or more members can be used dependent upon the wall thickness. The challenge here is that the masonry has to be removed before the framing is installed. That requires a separate temporary support system. Options include:
- Angles or channels (as previously discussed) used above the opening.
- Shoring and needle beams. This involves needling the wall with short beams through pocket wall openings to create support above the proposed opening (see next figure where an existing opening is to be enlarged).
The following figure shows portions of a shop drawing prepared for a small needling/shoring project. With little effort, this can be expanded for a much larger opening with more needles.
Figure – Partial shop drawing for needling
(Courtesy: Safe Unlimited Masonry, Mississauga, ON, Canada)
After the temporary support is installed, the masonry below can be fully removed, the new steel framing beam support installed, and masonry infilled between the new beam and the existing masonry. Finally, the needles are removed and the pocket openings infilled. Again, fireproofing of the steel may be required. The following figure shows the opening completed with the original header beam removed.
- External shoring can also be used as an option. Using shoring in combination with the angle and channel options avoids the needle pockets and rebuilding the masonry below the needles. The next figure shows this graphically.
- Intermittent piers can be left in place and used along with shores to facilitate installing shorter beam segments. 1.= install portion of beam; 2.=install shoring post and remove portion of masonry. 3.=install next beam segment, splice to first, and repeat 2. Continue until full opening is completed.
There can be variations on this scheme based upon field conditions.
- There is no one method that always works when planning the design of a new masonry opening. Engineers need to select one and provide details accordingly.
- The actual installation of framing for a new masonry opening is considered “means and methods” by the contractor. Engineers should cooperate with the contractor to evaluate alternate methods and determine whether a design modification is necessary.
- Besides supporting the vertical load above a new opening, engineers much check the existing masonry for out-of-plane effects and reinforce as needed.
Thank you again for following this column. Remember, by bonding we get stronger! Keep the questions coming! Send them and your comments to firstname.lastname@example.org, attention Technical Talk.
David is a PE and SE with Biggs Consulting Engineering, Saratoga Springs, NY, USA (www.biggsconsulting.net). He specializes in masonry design, historic preservation, forensic evaluations, and masonry product development.