Do the Bells of BIM Toll for Thee?
With the advent of the abacus, man has created tools to assist with performing advanced functions, a physical instrument to support his multidimensional mind.
Today, we have computers with thirdparty CAD structural design programs, accounting programs with timesheet modules and telephones that include a camera, scheduler/calendar, e-mail, text messaging, MP3 players, walkie-talkies and video streaming. We are an advanced society with many tools (and toys).
Over the years, I have managed construction documents produced by ink on Mylar, pencil on vellum, in CAD and soon under building information modeling (BIM).
A couple of decades ago, we used light tables and pin bars to coordinate multidiscipline plans, overlaying each discipline's plans and identifying the regions of potential conflicts, meeting regularly to discuss the project nuances. Now we upload DWFs and PDFs to FTP sites for final oversight/coordination prior to plan approval.
Even today, the best means to identify construction document conflicts (in my opinion) is to overlay the plans - get all the disciplines (including the trades) into one room and overlay the plans and discuss the possible options/solutions. Communication is the key to project success, and physically comparing notes, exchanging ideas and face-to-face collaboration is best - it has worked well for the past several millennia.
What is BIM? As the acronym suggests, BIM is a tool for communicating information; another physical instrument to ensure we communicate with our fellow design team members in a new dialect within CAD.
Is it another substantial investment of resources (6k per seat and one year's training before producing definitive results) and another layer of isolation between the disciplines/trades?
Is BIM an exceptional resource that transforms complex projects and integrates them into a digestible project through multilevel/dimensional communication?
Do the bells of BIM toll for thee? They toll for the transition of the design industry - now contemplate that!
January 2009 Builder Architect Edition Issue
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It's All in the Presentation
Over the past years, we have encountered several religious denominations engaged in rehabilitation of their structures. Many denominations, under the direction of influential leaders, outgrow their sanctuaries and need to either enlarge or raze the existing buildings, or relocate to accommodate their growth and their expanding community outreach services. When it becomes evident that one of these changes must take place, a select architectural group (those who are able to maneuver about the church building committees) presents the church building committees' dreams to the congregation. The congregation approaches the proposal with zest and a true belief that the dream will manifest itself as they imagine.
My thoughts were immediately directed towards building rehabilitation, which we have encountered with several religious structures over the past years.
Enter stage left the engineering consultant, who immediately bursts the bubbles of the entire well-meaning choir group, not to mention the Sunday school teachers, deacons and assistant pastor, by pronouncing the project economically infeasible. What do you expect? Engineers have been trained (most likely from childhood) to be pessimistic about everything. They are paid to identify any pitfalls that can make the project unsuccessful (and you wondered why all the girls in college flocked to the business and architectural majors rather than the engineers; being a pessimist really didn't help the social life!).
However, engineers are also problem solvers. That is the other side of the coin; we have a solution for everything, even if you don't want it.
So, before the architect can start packing his bag, expecting to be fired at any minute, the engineer with a serious brow says, "However, we could do this and this … but, it is your decision! Let's take a look at this and this … I will get back to you in a couple days." Eventually, the client makes the decision to go for rehabilitation or even razing the building to manifest the church building committees' dreams, and everyone's hope is restored.
So, did you ever wonder why the engineers always get the prom queen eventually? It's how you present the options; it's all about the presentation … it's all about the presentation.
August 2008 Builder Architect Edition Issue
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Library of Details - A Powerful Tool
As a result of the accumulated technical knowledge and experience that an architectural or engineering or company attains over the years, a Library of Details is no doubt a key technical resource that has to be created. Obvious questions that may cross your mind would include: What exactly is a Library of Details? How do I, as the client, benefit if the technical resources (i.e., architects and engineers) I hire have a Library of Details?
A Library of Details is a technical resource that the architect/engineer can use to extract the most common and typical details applicable in repetitive and common conditions. These details are a useful resource when establishing a package of typical details mostly known as standard details. The standard details package becomes essential in the preliminary phase of the project planning process. It acts as a starting point in the design process.
Having a Library of Details considerably improves efficiency by cutting the time spent to recreate the same repetitive details, and it promotes high quality control through constant review and refinement of details, both of which help to yield the best design solution.
In order for the Library of Details to be an efficient and reliable resource, it is vital for the library to be organized in a way that is easy to use according to specific needs and technical requirements of the project. The Library of Details catalogued by product type, assembly location or materials used ensures quick search results and an efficient way to save the details based on the specific types and conditions that are being used in the design process.
Time saved to produce details al- ready created for another project, which may have similar conditions means there is less possibility for errors to occur as the details are constantly updated. Thus, less management time is needed as the detail sheets are assembled according to the type of construction and any other technical criteria.
It is very important to understand that creating a Library of Details is a consistent process of developing, revising and updating these details to depict current code information, most efficient building-assembly solutions and the most current building products available. The revising and updating process enriches the entire Library of Details system, providing an opportunity to incorporate new systems and procedures applicable to specific design criteria. When the detail is revised, it allows for better construction solutions, which can save the client potential construction labor and material costs.
Within an organization, the Library of Details can also work as a potential resource for training of new design staff. A Library of Details allows the design professional the ability to utilize concepts and design solutions already implemented on previous successful projects that have already proven to be the most effective. The engineer would be able to save much design time by extracting from the core of the detail the basic concept/idea and using that as a starting point to assemble the required and desired detail applicable for a specific project.
As part of the project planning process, the standard Library of Details is a rich and useful resource, which can instantly guide the first steps of the preliminary design. It is also a reliable tool in providing virtual feedback to assure that the proposed system in place is feasible and economically viable.
In terms of sustainability and a green solution, all efforts in planning ahead, standardizing to avoid conflicts in the execution of the design process and using the appropriate materials in an appropriate manner are a crucial contribution that the use of standard procedures such as standard details can bring to a project.
Creating a Library of Details is just the beginning. The key distinction for having a successful Library of Details is for it to be regularly updated. Frankly, we view our library as on ongoing work in progress. As long as our industry has code changes, products are developed, efficiencies are created and so on, the library needs to evolve with those changes.
Creating and maintaining a useful Library of Details requires an investment of time. However, the benefits of having such an important tool are far reaching for the design professionals, the construction team, the client and the environment.
July 2008 Builder Architect Edition Issue
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Solar Panels /Tiles
Innovation and Structural Considerations
With the increasing implementation of green-building practices, concepts from the past have been resurrected and are being presented as advancements within the residential construction industry.
ADVANCE FRAMING/ OPTIMUM VALUE ENGINEERING
In our recent column, we discussed "Advanced Framing/Optimum Value Engineering," and presented an overview of advanced framing, which was developed in the 1970s by NAHB and HUD and referred to a variety of techniques designed to reduce the amount of lumber used (reducing structural redundancies) and waste generated in the construction of wood-framed houses. In addition, it also improved energy efficiency and acoustical performance.
SOLAR PANELS
In addition to the above efficiencies achieved through advanced framing for residential construction, the evolution of solar panels has progressed immensely since the 1970s with the implementation of a combination of revolutionary materials to drive efficiencies from below 10% to the high teens. For example, an individual 32"x62" SunPower 215 solar panel produces 215 watts at 17.3% efficiency. SunPower gains greater efficiencies from their panels partially because the electrical contacts are placed on the back of the solar cells, which also results in a better-looking panel compared to the conventional silvery-blue solar panels with which most of us are familiar.
Current solar panel systems have been refined to "stand off" current roofing material with sufficient attachment to withstand wind uplift loads, as well as to provide adequate ventilation below the panel for maintenance purposes.
Since solar panels are typically installed postconstruction, the additional 2.4 lbs./ square foot beyond the existing roofing material weight may warrant evaluation of the current roof structure (stick framed or trusses) for its ability to vertically support the added assembly. Also, the added panel weight may increase the seismic lateral loads at the roof level sufficiently enough to exceed the existing shearwall panel capacities and/or wind loads (solar panels will act as hydrofoils upon pitch roofs), creating uplift connection and framing concerns. Thus, within high wind or seismic regions, having a structural review and implementing recommendations by an engineer may be prudent.
SOLAR TILES
Recent advancements in technology over the past decade have brought about the introduction/improvement of solar roof tiles, which have been integrated into new residential home construction utilizing flat or S-Tile concrete roofing material.
Solar tiles have been recently accepted by home buyers without reservations and have even provided bragging rights for homeowners to their friends and colleagues. But who wouldn't be bragging about being ecologically friendly as their SunTile roof converts up to 22% of available sunlight into electricity!
Since the solar tile material (5 lbs./ square foot) is installed during new construction, the originally prescribed concrete tile roofing material (7.5 to 9 lbs./square foot) is substituted with the solar tile (SunPower SunTile) without any structural ramifications.
COMMERCIAL APPLICATIONS
Solar panels are rapidly appearing within new retail construction as well as existing retail buildings, which are being structurally evaluated/rehabilitated to accept rooftop-mounted solar panel arrays and associated equipment, such as control panels/converters.
The electricity produced utilizing the rooftop-mounted solar arrays are easily powering the interior store lights for thousands of Big Box stores (like Macys, Lowe's, Target, Wal-Mart). Can you imagine the number of solar panels you can get on a 50,000-square-foot box store?
SUMMARY
Solar energy is present every day (OK, unless you are in Alaska … which experiences variances of almost 24-hour daylight to 24-hour night).
We have millions (more like hundreds of millions) of square feet of retail rooftops and billions of square feet of residential rooftops in the U.S., which all see the light of the sun. Our task is to effectively capture this energy resource consistently with solar tiles and rooftop-mounted solar panels while folding it into current designs (architectural and structural) that enables the installation of "optional (solar) equipment."
June 2008 Builder Architect Edition Issue
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Show Me Some L OVE Advanced Framing/Optimum Value Engineering (OVE)
Paris A. Tabor P.E.
The topic of green building is everywhere. Mostly, architects have led the discussion with some inviting the project team to collaborate with them.
Structural engineers can also lead the green conversation, contributing significantly to their projects. This month's article introduces advanced framing, a method to promote green building.
Advanced framing (developed in the 1970s by NAHB and HUD), sometimes called optimum value framing (OVE), refers to a variety of techniques designed to cut back on the amount of lumber used by reducing structural redundancies and waste generated in the construction of a wood-framed house as well as improving energy efficiency and acoustical performance.
Combining the following principles into the building design would be a big step towards achieving an efficient assembly and ultimately achieving OVE:
- 24'' o/c framing: Beginning with the principle of "direct alignment" or "in-line framing," the roof trusses (including girder trusses) will have to align with the second floor wall studs, which will align with the first floor wall studs.
- Exterior walls: 2x4 versus 2x6: Using 2x6 in lieu of 2x4 assembly will permit higher R-value insulation to be installed within the wall cavity.
- Modular layout: Architectural design (i.e., face of sheathing dimensions) as well as establishing roof overhang depth along the roof pitch/plane based upon a 24'' module.
- Window/door header jack studs/trimmers/cripples eliminated: Use fasteners (nails or hangers) in lieu of door/window trimmer at openings. In addition, eliminate cripple stud trimmers at windowsill.
- Window/door openings layout: Position window/door openings to align with 24'' modules, i.e., door/window king stud align with 24'' stud layout. In addition, utilize window manufacturers that have 22.5'', 46.5'', 70.5'', etc., rough-opening requirements.
- Single wall top plate - exterior and bearing walls: Based upon the "direct alignment" principle, top plates will not experience mid-span loading, thereby reducing assembly requirements (all top chord breaks will require metal strap installation).
- Single wall top plate - interior nonbearing walls: Any nonbearing partitions can be built with a single top plate.
- Correct-size headers: Sizing all roof load-bearing headers for actual anticipated load and eliminate all headers at interior nonbearing walls and use 2x stick-framed headers.
- Floor rim joist header: In lieu of door/window header installation to support the assembly above, utilize the continuous floor rim joist capacity. At higher loading conditions, it will require double rim joist - floor joist hangers may be required over "header" length.
- Framing practices: Use ladder blocking or 2x6 backing nailer in lieu of "Ts," "open corner" framing, drywall clips at interior corners and top plate (eliminating backing). Utilize "blueboard" at the exterior nonshear wall lengths rather than OSB/plywood sheathing when doing "full-building wraps."
With the above practices in place, you should achieve many advantages, including:
Energy Efficiency
With the wider stud spacing, heat loss (conductivity or thermal bridging) through the studs is reduced, and a greater percentage of insulation can be installed within the wall cavity.
With floor rim headers, wall insulation may be placed directly over door/window headers thereby increasing the overall wall assembly R-value.
Potential annual heating and cooling cost savings of up to 5%.
2x4 versus 2x6
Using 2x6 in lieu of 2x4 wall assembly will permit higher R-value insulation to be installed within the wall cavity.
2x6 and 24'' o/c versus 2x4 and 16'' will equate to similar lumber unit project requirements.
Lumber Material and Waste Reduction
Average material cost savings of $1,000 for a 2,400-square-foot house.
Labor Cost Savings
Fewer studs to carry, fewer to install, fewer to cut, fewer to nail and less waste to manage/haul away.
Anticipated labor cost savings of between 3% to 5%.
Optimum value framing (OVE) requires advanced planning and detailing to anticipate all aspects of the construction assembly; consequently, framers unfamiliar with the techniques may need additional training or consultation to become accustomed to a different way to lay out and construct advance framing projects.
Some industry professionals have adopted OVE in a piecemeal manner rather than incorporating all of it at once, as they were more comfortable doing so. Some builders have implemented this piece by piece over many homes, with plans to incorporate more, rather than piling on all the changes in at one time.
Whether you decide to implement part or all of it at once, it is a step forward in the right ... green ... direction.
May 2008 Builder Architect Edition Issue
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California Historical Building Code
Title 24 Part 8
By Perry A. Tabor, P.E.
The California Historical Building Code (CHBC) provides specific regulations (alternative building codes) for the preservation, restoration, rehabilitation, relocation or reconstruction of qualified historic buildings or properties so as to preserve their original or restored architectural elements and features. At the same time, it provides for the safety of occupants and for the reasonable accommodation of people with disabilities.
While these alternative solutions are intended to protect historic buildings from the adverse impact of certain requirements of the regular building code, they also translate into cost-effective incentives as described by the California Office of Historic Preservation.
A "qualified historical building" is defined as any building, group of buildings, district, site or object, which is listed by any level of government as having historic importance. This also includes those resources listed in the State of California's evaluated inventory, and given any level of significance other than "not eligible." Also included are ships and railroad rolling stock of historical significance.
The CHBC recognizes and endorses the need - on a case-by-case basis - to find and adopt reasonable alternative situations where strict compliance with established statutes or regulations would jeopardize the historic building's appearance or rehabilitation economic viability (i.e., full upgrade of building).
The "triggers" for full upgrading to current standards, with respect to length of vacancy, change of occupancy, or percentage of value of the work proposed, and which exist in other codes, are not recognized by the CHBC, which concentrates instead on the preservation-sensitive resolution of genuine safety considerations.
Structural/seismic upgrading issues are governed by the CHBC, permitting design based on real values (performance) of archaic materials and solutions based on engineering principles and professional judgment (providing a framework within which unique solutions may be custom tailored to the specific problems related to each unique historic resource), rather than solutions limited to code-based (pre- scriptive) formulas. This flexibility usually translates into a higher degree of retention of the historic fabric.
You may very well benefit if your building qualifies as a "historical building."
Here are some places to research whether your property "qualifies":
- The Office of Historic Preservation: computer lists of the National Register and California Register
- Local planning office: usually the best place to find local lists
- Local heritage or history commissions
- Local neighborhood or preservation organizations: these groups may have access to official lists but can't create official lists
- Local, state and federal agencies that promulgate projects: CalTrans, Department of Water Resources, Department of General Services/ Real Estate Services Division, local water agencies and local public works departments
April 2008 Builder Architect Edition Issue
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Are You at Risk When the Next Earthquake Hits?
The New Building Code May Affect Your Answer!
By Perry A. Tabor, P.E.
In California, a building's structural ability to resist seismic activity is a key factor in its continued viability. Assuming that we have another seismic event similar to Loma Prieta - which many experts predict is inevitable - all buildings that suffer "earthquake" damage starting January 1, 2008, would require full engineering studies, including repair documentation in order to comply with the 2007 California Building Code (CBC).
The California Building Standards Commission has adopted the 2007 CBC (Title 24, Part 2), effective January 2008, which includes Chapter 34: Existing Structures, as well as the California Historic Building Code (Title 24, Part 8) and the Existing Building Code (Title 24, Part 10).
Under Chapter 34, all building structural repairs/additions (including seismic damage repairs) will require a complete structural engineering feasibility study of the entire building, both damaged and non-damaged. In addition to the required full documenta- tion and construction design documents, it is also required that the building be structurally upgraded to the 2007 CBC [qualified historic buildings are mandated to meet 75% times the seismic forces prescribed by the 1995 edition of the CBC].
Imagine the bureaucratic aftermath that may result from a 15-second seismic event? It may very well translate to a multitude of commercial/residential building owners awaiting engineering reconnaissance, analysis, design and governing agencies plan approval prior to making the necessary repairs. Meanwhile, businesses will be adversely impacted daily while remaining inoperable, and primary residences will remain uninhabitable with yellow or red tags hanging from their doors. There simply are not enough qualified engineers to meet this spontaneous need that a single seismic event can suddenly impose upon building owners.
Of course, building owners can take the chance that their buildings would not be impacted by a seismic event during their ownership and that they won't be subject to such challenging conditions. Alternatively, there are some reasonable steps that can be taken before the next seismic event occurs. Proactive measures to help mitigate the risk include:
Structural Risk Assessment: Structural site reconnaissance and report identifying the building assembly's structural "weakest links": whether deficient members, incomplete lateral system, insufficient foundation and/or inadequate connections.
Benefit Cost Analysis: Based upon the structural risk assessment, establish probable cost for repairs, economic construction repairs resulting impact upon the current operation, current building value, maintenance cost/extending building cycle, etc. versus probable seismic event occurrence and associated inoperation/repairs during the building's life cycle.
Thus, determine whether to proceed with structural rehabilitation as part of building retention or relinquish the building to reduce liability.
Buildings that were constructed or rehabilitated (entire building) more than 10 years ago will most likely benefit from having a structural risk assessment/benefit cost analysis. Establishing a current building assessment will certainly assist building owners to make the most informed, timely and intelligent decision whether to retain and repair their properties or to relinquish and reinvest.
When (not if) the next Loma Prieta occurs, will you be standing in line with the rest of the masses to hire an engineer to begin the process or have you been proactive by taking appropriate steps to reduce your liability under the current 2007 CBC?
January 2008 Builder Architect Edition Issue
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Are You Ready for the New Building Code?
California Makes Way for the International Building Code
By Perry A. Tabor, P.E.
As Builder/Architect's structural engineering expert columnist, we continue to feature our monthly "Structural Design Corner," bringing you interesting and useful information, including viable design innovations and alternatives.
This month we are discussing impending significant building code change. While there is a great deal of information on this topic to cover, our objective is to provide you with a general overview and encourage you to start now, if you haven't already, to familiarize yourself with the changes that will take effect on January 1, 2008.
The International Building Code (IBC)/California Building Code (CBC) will soon be upon us in all its glory. We escaped the 2003 decision by the California Building Standards Commission to adopt the National Fire Protection Association's model code NFPA 5000 when Gov. Schwarzenegger's administration rendered a decree that the adoption of the NFPA 5000 by Gov. Davis' administration was nonbinding. We are now being asked to come to the table on January 1, 2008, with the 2006 IBC and 2007 CBC under our arms.
Since we've had an eight-year hiatus from the three-year cycle of code updates, we as a building design community are having difficulty getting out of the big chair. We were quite comfortable in the big chair; the 1997 UBC fits like an old pair of slippers, and frankly, our bones are stiff from not moving around. Well, it is time to get up, down a cup of coffee, get outside (of your comfort zone) and exercise (work the mind).
Design professionals (yeah, you!), on January 1, the governing agency has an obligation to enforce the 2007 CBC, and if they don't, they face the potential of being liable for malice. So they will be coming to the table in a big way. Of course you can still submit your project under the 1997 UBC (if you didn't bother updating your design and specifications to the earlier enacted 2000 CBC), and in turn, get a laundry list of plan check comments, delay project approval, face losing a client and damaging your professional reputation. But I'd suggest avoiding that option.
Instead, if you haven't already, now is the time to begin implementing the code changes into your schematic designs (e.g., side yard setback) or start producing construction documents under the 2007 CBC.
Ensure that your library has the 2007 CBC and then invest the time to read the CBC at least a couple times. You will be amazed at code changes. This column is not big enough to list all of the changes in the code (both structural and non-structural) from the 1997 UBC. Just within the "Structural World," we are seeing changes in load combinations (the need to consider temperature and rain), seismic vertical effects, revamped wind design methodology, amplified collector loads, etc.
Because the 2007 CBC seismic criteria have moved from "Life Safety" to "Collapse Prevention" design criteria, we have, under the 2007 CBC, yielded a 10% to 40% reduction in seismic lateral loads depending upon the project location. However, one upside of the recent new design criteria is that the code updates and building rehabilitations are yielding substantial economiesfor "seismic prone" projects with the design-level criteria reduction.
Unfortunately, there is no simple way to become current with the 2007 CBC (there are differences between the IBC and CBC). Simply put your nose to the grindstone, study and put your knowledge to work. Also, you may benefit from taking an overview course, such as those provided by CALBO, SEAOC, AIA and ICC.
We hope that this article moves you into taking immediate action. We want to make sure that no one is asleep at the wheel and that our design industry is prepared for the unavoidable code transition.
November 2007 Builder Architect Edition Issue
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The Distinction Between Special Inspections and Site Observations
By Perry A. Tabor, P.E
Although the common industry term "special inspection" is sometimes interchanged with "periodic site observation," the distinction between a special inspection (which is required for most construction projects) and other types of site inspections or observations is important to describe.
SPECIAL INSPECTIONS
A special inspection is the monitoring of the materials and workmanship that are critical to the integrity of the building structure to assure that the approved plans and specifications are being followed in the actual construction, and that relevant codes and referenced standards are being observed. The special inspection process is in addition to the regular "inspections/observations" that may be conducted by the city building inspector, site engineer and architect as part of the periodic structural observations. The special inspector shall furnish continuous inspections at all times or as the construction requires their presence.
International Building Code (IBC), Section 1704.1 states: Where application is made for construction as described in this section, the owner or the registered design professional in responsible charge acting as the owner's agent, shall employ one or more special inspectors to provide inspections during construction on the types of work listed under section 1704. NOTE: Some seismic design categories and wind exposure categories may additionally require the special inspector to prepare a quality assurance plan. See sections 1705 and 1706 for requirements.
The building official must approve every special inspector. All inspectors are required to provide proof that they meet the minimum qualifications.
The IBC Chapter 17 can be broken down primarily into two parts: the building permit requirement and the report requirement.
Building Permit Requirement
- The permit applicant shall submit a statement of special inspections prepared by the registered design professional in responsible charge as a condition for permit issuance. This statement shall include a complete list of materials and work requiring special inspections by this section and the inspections to be performed.
Report Requirement
- Special inspectors must keep records of inspections and furnish inspection reports to the registered design professional in responsible charge. The reports must indicate that the work inspected was done in conformance with the approved construction documents. Discrepancies must be brought to the attention of the contractor and non-corrected discrepancies must be brought to the attention of the registered design professional in responsible charge. A final report of inspections documenting required special inspections and correction of any discrepancies noted must be submitted to the registered design professional in responsible charge at the completion of the project. The design professional shall forward a copy of the final report to the building official for their records.
The registered design professional in responsible charge can be either the architect or the structural engineer. Since the structural engineer is typically a consultant to the architect, the architect should decide who will take what responsibility and specifically state so in any contract with the consultant. The contract between the owner and the architect should also state whether the owner or the architect is hiring the special inspectors. The owner ultimately is the one who is responsible for the cost of special inspections, but normally the contractor is responsible for the cost of any re-inspections or retesting. This should be stated clearly in the specifications.
The architect or engineer of record should outline in their project documents which minimum special inspections are required as well as ensure that their relevant section of the Certificate of Substantial Completion form has been revised to reflect these required inspections. The architect or engineer of record, as well as the contractor, special inspector and owner will also be required to sign the Special Inspection Acknowledgement form provided by the Governing Agency Building Department.
The architect or engineer of record is reminded that this form is a legal document, that changes to the wording of this certification is not usually permitted and the assurances are professional certifications of fact that should not be taken lightly.
September 2007 Builder Architect Edition Issue
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To Be or Not To Be - Light-Gauge Steel - That Is the Question
By Perry A. Tabor, P.E.
Our recent articles featured the integration of certain innovations, manufacturers' components and engineered panels. This month's article features another innovation: light-gauge steel (LGS), also known as cold-formed steel (CFS).
To best serve your industry, your clients and your community, it is incumbent upon you to familiarize yourself and your colleagues with various available building materials, construction methods and design approaches before you actually commence your design.
Being innovative, creative and efficient with your design can result in saving significant resources, as well as construction costs while still achieving a structurally sound project. Conversely, innovation under certain project conditions may not bring the results you expect to achieve.
One relatively recent innovation, over this past decade, has been the use of LGS in residential construction.
Often, we are asked, "Should I build in LGS or wood?" We believe that the answer lies in the project details. Here are just a few questions you may want to consider when evaluating whether to use LGS or wood for your residential project.
- Repetition: Are the floor plans being repeated over several floors (as with apartments and townhouses), or are there over 150 units comprised of five floor plans (as with production housing)?
- Project Scale: Is the project over 100,000 square feet total?
- Complexity: Are there any substantial plan articulations involved?
- Labor Force: Are there qualified trades to erect and to perform mechanical-electrical-plumbing trade services? Do the MPE trades recognize the economies available (e.g., pre-punched studs and floor joists)?
- Fire-Rating: Does code restrict the use of combustible assembly (e.g., wood framing with plywood assembly) in favor of non-combustible assembly (e.g., LGS assembly) with composite concrete deck?
- Economies: What is the current and forecasted price of lumber versus LGS materials? (Wood and LGS oscillate as competitive materials.)
- Site Constraints: Would prefabricated building assembly address site constraint conditions (e.g., lacking construction material staging area)?
- Maximized Floor Area: Is the wall assembly envelope required to remain consistent over several floors? (LGS can achieve substantial increased strength without increasing the material thickness before requiring increasing wall thickness.)
- Quality Control: Entire building assembly can be computer modeled prior to precision machine-cutting and labeling components within a production facility. Also, the material is resistant to shrinkage, twisting, cupping, splitting, warping, rotting and insect infiltration as is common with wood assembly.
Once you have addressed these preliminary questions, you should be able to make a more informed decision as to whether LGS or wood is the right choice for your project.
Our firm, TEAC Structural Engineering, has proactively supported and encouraged the advancement of LGS residential projects through industry education and advocacy, as well as by embracing its use in a large percentage of our production and attached housing, and with a small percentage of our custom homes. In so doing, we have become a respected leading authority in LGS projects.
Hopefully, you found our brief introduction to LGS to be informative. If you would like to see this topic covered in greater detail, please let us know. Otherwise, we look forward to covering other innovations and topics of interest in future articles.
September 2007 Builder Architect Edition Issue
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Are All the Good Lots Going, Going, Gone?
Making Way for WAFFLEMAT Foundations
With most "good lots" gone, residential home builders are regularly faced with a major challenge: expanding construction activities into areas previously considered less desirable (e.g., hillsides, shallow water tables, highly expansive or collapsible soil).
Traditionally, one of the following three foundation approaches have been incorporated by home builders in these situations:
- Post-tension (P/T) with slabs on grade
- Drilled pier and grade beam with raised floor assembly
- Driven pile with both slab and raised floor when over bay mud
Unfortunately, each of these approaches brings a series of individual and combined limitations, including increased material costs, extended building cycle and the need to mitigate present/future risk and warranty issues.
As a result, builders have started to integrate alternative foundation types.
The WAFFLEMAT foundation system application for expansive soils has gained great interest for many home builders as an alternative, particularly to the P/T slab-on-grade used in a "marginal soil" environment.
The WAFFLEMAT system has voids underneath (formed with the 8.5" high WAFFLEBOX), allowing the expansive soil to move, as opposed to the P/T slab that rests entirely on the grade and responds in turn to soil expansion. Even if water was to seep underneath, the voids provide space for the soil to expand and contract, thus avoiding the uplift stress that, in excess, may cause the P/T slab to fail (crack).
On the Bay Meadows project, our office turned to the WAFFLEMAT foundation system when P/T slab-on-grade was analytically proven to be incapable of providing satisfactory edge-and-center deflection requirements, as well as exceeding the geotechnical engineer's allowable bearing pressures.
WAFFLEBOXES are made from 100% recycled reprocessed polypropylene (plastic), a "green" product.
Nominee for '07 Air Quality Management Award in Greenhouse Gas Emissions Reduction category, due to 20% mitigation of concrete use (eliminating 5 to 9 tons of CO 2 emissions) per residential foundation.
WAFFLEMAT has been implemented in 7 million square feet of residential units or approximately 4,000 homes in Northern California, which equates to 20 to 36 tons of CO 2 emissions eliminated over the past 10 years.
The polypropylene material used is tough and impact resistant, ensuring that the WAFFLEBOXES will hold up well in the construction environment, including being strong enough to support the weight of the concrete workers during the installation and the pouring process. It is a highly stable and chemically nonreactive resin that, when covered with concrete, will last decades before any degradation. It is impervious to water as well as water vapor, thus providing an effective moisture barrier.
A fairly good rule of thumb for calculating the number of WAFFLEBOXES required for a given floor is to divide the total square footage of the foundation by 4 to 4.5. For example, for a 2,000 square footprint, the approximate range of required WAFFLEBOXES would be 444 to 500 boxes.
The amount of time required to install WAFFLEBOXES is determined by several factors; however, on average 75 WAFFLEBOXES are typically installed per hour.
For over 10 years, WAFFLEBOXES have been manufactured by Kennerley-Spratling, Inc., in San Leandro, CA, ksplastics.com
July 2007 Builder Architect Edition Issue
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Construction Innovations: Engineered Panels in Residential Construction
By Perry A. Tabor, P.E.
As Builder/Architect's structural engineering expert columnist, we continue to feature our monthly "Structural Design Corner," bringing you interesting and useful information, including viable design innovations and alternatives.
Last month, we discussed the integration of one such innovation: manufactured components. This month's article features another innovation: engineered panels. Engineered shear panels have been well received by the industry and have permitted the expansion of architectural freedom in an ever-increasing stringent construction environment.
Over the recent decades, residential customer demands upon architecture has commanded increased window and door sizes in an effort to tie the home interior with the outdoor environment.
In addition, floor plans have seen increased square footage, integration of open floor plans (e.g., great rooms: combination family room, kitchen and dinette), higher plate heights and an increased percentage of two-story units, while parcel square footage has decreased and typical roofing material has changed from asphalt composition or wood shake to heavier concrete tile.
In addition to these significant changes, the seismic code requirements have increased two- to threefold and lumber strength values have decreased during the past couple of decades.
As a result, housing units have become more vertical with reduced lower level interior walls, concrete slabs have been piled on the roof and the walls have more openings than a block of Swiss cheese! All the while, structural demands are increased and material strengths are decreasing.
"We are no longer in Kansas, Toto (1,500 square feet, four-bedroom rancher)" ... welcome to California (3,500 square feet, four-bedroom, three-story townhouse with tuck-under garage overlooking the Calaveras fault).
Fortunately, we've had material innova- tions to assist in addressing these significant changes, such as one introduced by Gary Hardy with the Hardy Frame (wood framing contractor who developed a light-gauge steel engineered shear panel for residential application), which was followed closely with the release of Z-Frame, Simpson StrongWall (light-gauge steel hardware manufacturer who developed a wood-composite engineered shear panel), TJ Panel and, most recently, the Simpson Steel StrongWall to address structural challenges noted above.
Essentially, the above mentioned engineered shear panels will substitute for field-installed plywood shearwalls and associated hardware by providing higher strength capacity with easier installation, as well as provide solutions to narrower wall lengths, taller plate heights and higher lateral shear demands.
There are three very important things to remember when installing engineered panels: get the anchor and holdown bolts installed correctly; get the bolts right; and finally pay attention when installing the bolts.
At foundation construction:
- Ensure the forms are level and true, so that the panel stands plumb when bolted into position.
- Use the manufacturer's bolt template/guide, since the panel bolt hole can not be widened or re-drilled.
- Ensure the bolts are installed plumb, that the bolt diameter matches the panel specified and that length of concrete embedment is achieved (protecting [sleeve or taping] the exposed bolt threads is recommended).
After the bolt installation has been completed, the remaining construction is so simple that even Billy Bob and Joe Bob can easily take over, under the diligent supervision of Spot.
If you would like to see this topic covered in greater detail, please just let us know. Otherwise, we look forward to covering other innovations and topics of interest in future articles.
May 2007 Builder Architect Edition Issue
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Construction Innovations
Manufactured Components in Residential Construction
By Perry A. Tabor, P.E.
Last month we introduced ourselves as Builder/Architect's structural engineering expert columnist, featuring our monthly "Structural Design Corner."
In our first article, we suggested fully engaging structural engineers throughout various project phases and encouraging them to present viable design innovations and alternatives.
This month, we are discussing the integration of one such innovation: manufactured components.
FLOOR/ROOF SYSTEMS
The use of pre-manufactured roof and floor truss assembly, within production residential construction, has been around for decades.
Roof wood truss assembly, for residential construction, became mainstream in the mid-'70s, following the valiant efforts of Gang-Nail and other innovative manufacturers that had the fortitude to "stay the course."
Floor trusses in residential construction began to establish a foothold in the mid-'80s, with the introduction of open-web trusses, but had their market share tempered by the introduction of "I-joist" around the same time.
Both truss products were introduced and became widely accepted within the residential industry to address one or more of the following:
- Skilled labor requirement reductions
- Time of construction shortened
- Quality of construction/performance level improved
- Simplification of construction
PANELIZED WALLS
Like the pre-manufactured roof and floor truss assembly, panelized wall assembly is not a new concept, but its success has been challenged. This was mostly due to manufacturers' initial struggles in developing processes to take projects from modeling into full construction.
My first knowledge of panelized residential construction came through stories of projects in Kansas City in 1976, when one of my framing crewmen (Toby, a transplant from KC) told of panelized roofs, walls and floor on a raised foundation. He claimed that they could frame an entire house in one day! Until then, we thought we were smok'n, as we had a three-man crew taking less than two weeks to post and beam the underfloor, lay 2x T&G floor deck, framing walls with windows and exterior T1-11 siding installed, roll roof truss with fascia boards and gable rafters, plywood sheath roof and frame kitchen soffits for a single-story 1,500-square-foot house with a two-car garage.
THE BASICS ON PANELIZED SYSTEMS
A panelized system consists of prefabricated panels that are fabricated within a highly automated factory, with "the (manufacturer's) floor" equipment and fabrication process, driven by a computerized building model.
In other words, the structural system is modeled down to the window cripples, screw/nail count and curtain rod back blocks. Every piece in the entire building is assigned an identification code (subdivision ID, lot number, plan number, elevation ID, building line and wall panel number) and the computer establishes the most efficient means to cut the materials before the computer data is actually released to "the floor."
Once the data is released to "the floor," precise pieces are assembled into wall framing panels, then progress to having structural shear, holdowns, hardware, etc., applied, all the while being flipped over by hydraulic arms and traveling along rollers towards the loading dock to be palletized/packaged for delivery via flat bed and to be erected, in simple terms, "by the numbers."
Prefabricated panelized systems require additional planning to ensure the panels are manufactured to specifications. However, they are generally easy to install and can provide significant labor and construction time savings.
Because the panels are manufactured in a factory environment, there is an assurance of quality and consistency. However, flexibility can be limited (e.g., concrete foundations must be placed accurately) and any on-site design changes (e.g., model walk changes) can be costly and difficult.
Although the initial cost of prefabricated panels may be higher than that of conventional framing materials, the labor savings is often significant enough to offset the initial cost difference. Additional benefits that the panelized system provides include structural capacity resistance to damage from earthquakes, wind, moisture changes (kiln-dried lumber) and insect infestation.
PANELIZERS/TRUSS MANUFACTURERS
Today, there are several combined wall panelizers and truss manufacturers that can readily supply the Bay Area. In particular, there are four noteworthy firms that produce roof trusses, floor trusses/joist, as well as wall panels.
Notable firms within the wood assembly arena include Forma Home Systems (formahomes.com ) and Compu-Tech Lumber Company (computechlumber.com ). Both firms are led by production housing veterans, having decades of home construction experience.
Two leading firms within the CFS (cold formed steel) panelization industry are FrameMax (framemax.com ) and NEXFRAME, LP (nucor.com), a joint venture established by the subsidiaries of Nucor Corp. and Lennar Corporation.
We hope that our introduction to manufactured components was informative and we look forward to covering other innovations in future articles.
April 2007 Builder Architect Edition Issue
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Structural Engineers Can Do More Than Just 'Calc'
By Perry A. Tabor, P.E.
For over 20 years, we have been actively collaborating with building industry colleagues, acquiring valuable information that we look forward to sharing in this column. Our goal is to help introduce information in our monthly articles that can have a direct and positive impact on your future projects.
We are proud to serve as the structural engineering experts for Builder/Architect, featuring our monthly "Structural Design Corner."
The topics we will bring to you will include design concepts, innovations and trends, as well as practical considerations that can bring value to a wide variety of projects. More specifically, we will highlight the importance of having your structural engineer serve as a collaborative partner, actively participating from early conceptual design into design development and construction documents, and continuing through construction administration.
Architects are unquestionably the most visible design professionals associated with any building project. Who and what a structural engineer does is much less visible to the public, and his/her name is very rarely remembered. The satisfaction of efficiently transforming a concept into a tangible object that serves and shelters its occupants is the engineer's reward.
Builders and architects have welcomed a change from the old industry standard in which the structural engineer only became involved in a project after the architect has completed the fully dimensioned drawings with building elevations and sections, having limited input during the design phase and almost no involvement once actual construction began.
Today, structural engineers continue to be more fully involved as an integral part of the project team. There are certain stages of involvement that are particularly important to consider:
CONCEPTUAL DESIGN PHASE
Collaboration meeting(s) between the architect, owner/developer, structural engineer, geotechnical and other engineering professionals during the conceptual design can translate into substantial construction savings. This is the stage when the structural engineer can help by proactively discussing the most viable foundation and building assembly, as well as by identifying other challenges.
DESIGN DEVELOPMENT PHASE
Continued periodic collaboration between the owner/developer, design team and the general contractor can further refine construction savings. Together they can help to identify opportunities for practical plan modifications, as well as identify potential challenges such as grading, sound, etc. For example, in a recent project design meeting, the team agreed to move a window by just a couple of inches, which reduced member sizes as well as eliminated the need for a proprietary shear wall and additional structural hardware.
On small projects, a schematic design meeting may be more appropriate than the conceptual and design development phase involvement.
CONSTRUCTION DOCUMENT PHASE
As the design is evolving, periodic meetings should be held at milestone stages with the critical team members. Architects have an invaluable opportunity to enlist the participation of the structural engineer, truss manufacturer, framing contractor, HVAC engineer/contractor and sound consultant during superstructure discussions. It is also important to enlist the participation of the geotechnical, structural engineer, concrete contractor and civil engineer during foundation discussions.
Their joint collaboration (value engineering) can help to identify appropriate cost-saving assemblies prior to finalizing the building design, as well as create an opportunity to introduce alternative assembly or design considerations much earlier than by value-engineering during the construction process.
On small projects, a preconstruction meeting during which the project team briefly can interface may be more appropriate than the above-listed construction documentation phase outlined meetings.
CONSTRUCTION OBSERVATION PHASE
Periodic site observations by the structural engineer during various structural stages of construction is critical and will vary by project type, size and complexity. At a minimum, site observations should be conducted at foundation reinforcement, rough framing and interior/exterior/roof shear, as well as after the HVAC/plumbing/electrical installation.
The engineer can often assist to identify non-compliance structural assembly and offer immediate solutions/directions to rectify the assembly, avoiding potential construction delays and reducing their clients' potential liability.
In addition to fully engaging structural engineers throughout the above-described phases, it is also important that the structural engineer be encouraged to present viable design innovations and alternatives. Structural engineers can be forward-thinking in implementing new concepts and communicating new methodologies. Becoming familiar with and evaluating alternative materials can often lead to introducing design options that promote greater flexibility, easier installation, reduced delays and lower construction costs overall.
We plan to discuss the integration of such innovations and alternatives in our next monthly article.
We've highlighted certain design and construction stages in which to involve your structural engineer. Do you currently engage your engineer as a collaborative partner to the fullest extent? If not, we encourage you to join the increasing number of building participants who wholeheartedly embrace this valuable concept of increased involvement. By doing so, you can yield cost savings and greater efficiency, while producing structurally sound homes and buildings.
March 2007 Builder Architect Edition Issue