If It Ain’t Broke, Don’t Fix It: An established stone anchoring methodology
August 2020 – by Daniel Picco
If there’s one thing the Covid-19 pandemic has given us in our line of work—it’s time! We’ve saved hours of commuting by working from home, and with this, the opportunity to do some digging in the archives. What we found was a legacy copy of PICCO Engineering News, Issue 2, Volume 2 – Fall 2002. As a Junior Connection Specialist (and student soaking in all the knowledge I can from my father Mike Picco), I was eager to see what late 2002 had to offer in terms of individual handset stone anchor systems, and how they differ from today. Truth is, not that much.
Caption: Legacy copy of PICCO News, , distributed by mail (2002)
Nothing new under the sun; nothing old under the moon
Saying that little has changed in the world of facade anchoring from 2002 until now is nonsensical. With aluminum rail systems, back anchored thin veneer, 3D BIM, new standards and regulations surrounding Leadership in Energy and Environmental Design (LEED) to only list a few, I understand that yes, since 2002, things have substantially changed. We have adapted by engineering and designing complex facade anchoring methodologies worldwide. However, when it comes to individually supported steel anchors, the many practices from 18 years ago remain today, which speaks volumes to the efficiency and feasibility of the system. We’ve referenced examples from our 2002 newsletter to prove this point.
Selecting and designing a proper anchoring system is one of the most important factors in determining the success or failure of a stone cladding project. Architects, Contractors, Fabricators, and Designers often minimize the importance of anchor design and the anchoring system. Unfortunately, in many cases anchors are designed and detailed with selfish motives. If anchors are included as part of the stone supply contract, they may be designed with cost being the prime factor, where little attention is given to the field adjustment and installation labour. In other instances, the building design has not given consideration to the stone anchor requirements, often resulting in substantial costs associated with elaborate and expensive sub-assemblies and anchoring systems. Anchoring systems and design require that several factors be considered—strength, type and thickness of the selected stone, loading conditions, environmental exposure, type of back-up, type and grade of materials specified, anchor costs, ease of installation, all which ultimately affects labour cost, to mention a few.
Caption: Typical stone anchor assembly: two-piece dowel connection on concrete backup
Continuing to build on a solid foundation
Until 2002, most ASTM Standards focused on the stone properties. Now more emphasis is being placed on the anchors and both their engagement into the stone and attachment to the structure. ASTM Standards are a guide; however, they still require engineering and proper direction.
ASTM C1242-00, Standard Guide for Design, Selection, and Installation of Exterior Dimension Stone Anchors and Anchoring Systems and ASTM C1354-96, Standard Test Method for Strength of Individual Stone Anchorages in Dimension Stone are two standards that focus on the importance of anchor design and selection. However, Codes and Standards generally establish only minimum requirements and should never be substituted for an engineered stone cladding system.
“Most cladding failures can be attributed to problems with the anchors or the anchoring system rather than the weaknesses in the bending strength of the stone panels. Regrettably in almost all cases the failures are linked to improper design and detail as well as the designer’s lack of experience and knowledge of the integral relationship between the stone’s behaviour and its supporting system.”
Caption: Aga Khan Park: example of individually supported steel anchors
Keys to Success
When close attention is paid to detail, a good stone anchoring system will always prove successful in the field. Such items needing consideration are:
Anchor adjustment: wherever possible use a two-piece connection with adjustment in all three directions: in/out, up/down and side to side
Consistency: use as few connections as possible to get the job done
Access: ensure that the anchor is accessible for installation and adjustment:
— Wherever possible use only four anchors per stone, two top and two bottom
— Understand the stone and anchor installation sequence including stone handling and setting equipment
— Ensure all stone panels are individually supported, joint size is sufficient and provisions for differential movement has been allowed for
— Past experience—stone installer’s preference and familiarity with certain anchoring systems
— Cost—a good design does not have to be an expensive design
The proper design, detailing, specifying and inspection of a well-engineered stone anchoring system can be both challenging and rewarding not to mention the satisfaction achieved right through from the design team to the stone mason for a job done right.
These keys to success have helped us deliver the value engineering which our clients hold in high regard, for 28 years and counting...
For more information contact: firstname.lastname@example.org
Junior Connection Specialist at PICCO Engineering
Daniel has proudly been with PICCO Engineering since 2016. In addition to connection and anchorage design, Daniel works directly with clients ensuring all preferences, site conditions and best practices are met. His keen attention to detail provides our clients with the confidence and comfort to successfully deliver projects. Daniel holds a diploma in Architectural Technology from Sheridan College.
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