Metal Building Tips
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More on Open Wall Conditions – Endwalls
In an earlier published “Tip”, we discussed how best to handle wall conditions that are open for something other than traditional girts and metal wall panels. That would include Masonry, Tilt-up Concrete, and vertical Stud walls supporting EIFS or brick. Now I would like to address a special subset of Value Engineering for Open Wall Conditions.
Specifically, let’s talk about open endwalls. They could be open for any of the materials mentioned above or they could be open for “Wind”, or open for “Other”, e.g. tie-in to an existing building. If the endwall is open for material By Others, you would almost certainly require a support beam (spandrel) at the top of the wall to laterally support the wall system. That spandrel is generally a structural channel bolted to the bottom flange of the purlin at or near the rake. If the endwall is open for Wind or for Other, a spandrel generally would not be required. In either instance, no lateral wall support is required from the endwall columns. That means the endwall columns are carrying vertical loads only, but they are also laterally unsupported their entire length.
Here’s where we can introduce a bit of Value Engineering. Tall columns that are laterally unbraced become very heavy very fast. An option to providing a bearing frame (with the required “X” bracing) would be to specify a non-expandable modular main end frame. Instead of wind columns spaced at 20’ o.c., you would be looking at pipe columns at 30’ or 40’ or even 50’ o.c, The optimum module spacing depends primarily on building width and, to a lesser degree, building height. Following are suggested module spacings for selected building widths:
Building Width Modules
80’ 2@40’
100’ 3@33’-4”
120’ 3@40’
150’ 4@37’-6” or 3@50’
200’ 6@33’-4” of 5@40’ or 4@50’
If your building is tall, or if you have only a few bays, you can expect to save as much as 4% of the building cost. But even if you only need a 14’ tall building that is 500’ long, you may still realize cost savings that may give you the edge against your competition.
Just as “there is more than one way to skin a cat”, there is more than one way to price a building. Astek II is capable of pricing a wide array of options and conditions. Hopefully, this will become one more tool in your Builder’s tool box to build on your success.
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Loads Primer
Most everyone understands that all buildings must be designed for Code mandated loads including Snow Load, Wind Load and Seismic Loads. The magnitude of any one of those loads depends on other site – specific and building – specific factors that may be less understood. Following are basic definitions of some of these: Roof Exposure, Building Enclosure, Wind Exposure Category, and Occupancy Category.
Roof Exposure
Fully Exposed: Roofs exposed on all sides with no shelter afforded by terrain, higher structures, or trees.
Partially Exposed: Roofs that contain parapets or RTU’s or do not comply with “Fully Exposed.”
Sheltered: Roofs that are located tight in among conifers.
Building Enclosure
Open: All walls at least 80% open
Partially Enclosed: Picture a parachute. A building where wind can enter but not escape.
Enclosed: All other buildings
Wind Exposure Category
“B” Urban and Suburban areas, wooded areas, or other terrain with numerous closely spaced obstructions having the size of single-family dwellings or larger. Exposure B shall be assumed unless the site meets the definition of another type exposure.
“C” Open terrain with scattered obstructions, having heights generally less than 30’ extending more than 1500’ from the building site in any quadrant.
“D” Flat, unobstructed areas exposed to wind flowing over open water (excluding shorelines in hurricane-prone regions) for a distance of at least 1 mile
Occupancy Category
I Low Hazard, Agricultural, Minor Storage
II Normal
III High Occupancy, Public Utilities, Jails
IV Essential Facilities, Fire and Police Stations, National Defense Buildings
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In the past couple of years, many of you have pursued Bid work, primarily because the current market for our traditional Design-Build business has dramatically declined. One thing in particular I have noticed in reviewing countless Bid drawings, is that Collateral loads, or Dead loads are often inflated or overstated. It is not uncommon to see a “Dead” load of 20 psf. The intent may be to also cover the weight of the structure, but then, it is generally someone’s conservative guess.
One of the downsides of Bid work is that efforts to clarify information such as this can often be futile. If you are fortunate, perhaps you will have the opportunity to “educate” the responsible party. Or perhaps you may be able to submit an alternate bid based on Collateral loads defined by you in accordance with your understanding of the project requirements. In any event, I have compiled a list of weights for common building materials. These are very generic in nature and care should be taken in their use.
Roof
Asphalt shingles………. 3 psf
¾” plywood…………… 3 psf
22 ga. 1.5 B deck……… 2 psf
Polyisocyanurate Insulation Board (per inch of thickness)…. 0.25 psf (e.g. Thermax)
60 mil EPDM roof membrane………………………………... 0.50 psf
(22 ga 1.5 B + 3” Polyiso + EPDM………………………….. 3.25 psf)
Ceiling
Acoustical Ceiling………….. 1 psf
Mechanical Duct Allowance.. 4 psf
Gypsum Board, ½”................. 2 psf
Sprinklers, wet……………… 3 psf
Sprinklers, dry……………… 1.5 psf
Walls
4” Brick……………………………………..…… 39 psf
4” Brick + ½” plywood + metal studs…………... 45 psf
8” Hollow Concrete Block w/ grout @ 24” o.c…. 54 psf
Floors
Concrete, per inch of thickness… 13 psf
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What are the benefits of Metal Roofing?
- Standing Seam Roofs: Metal provides a wide variety of standard and custom colors, many of which excel in solar reflectivity values for cool roof ratings. These products allow the insulation to sit into a space between the panel and the frame, increasing the effective R-Value and improving the system performance while providing a high degree of weather-tightness to guard against leakage. When investing in a standing seam roof, it is important to partner with a manufacturer that is backed by engineering support to ensure that the roof is right for the building. Other talking points to share with building owners are:
- According to the American Iron and Steel Institute, metal roofs that are properly installed last between 40 and 60 years and require significantly less maintenance than other materials.
- If your customer is expanding their facilities and has roof problems resulting in leaks, high maintenance costs, low energy efficiency, or they need to meet new wind uplift requirements, retrofitting a roof with metal may be the best answer.
- Metal roofs can be totally recycled and can usually be installed right over an existing roof, keeping materials out of landfills and saving natural resources. According to a 2007 Corps of Engineers study covering the last 40 years, 7-10% of landfill space is occupied by obsolete roofing material.
- This structural addition will extend the lifecycle of your building and, when combined with a color that is selected with energy efficiency in mind, should improve energy efficiency.
- Cool Roof Colors: (Links to Color Charts) When utilized with an appropriate roofing slope, the specific color palette can reduce energy consumption and help prevent the occurrence of heat islands where they are a problem.
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How do I get my customer to think outside of the box?
Have you ever watched the face of your potential customer change from a smile to a grimace at the mere mention of a metal building as a possibility for their new project? As soon as you mentioned the word “metal”, you singlehandedly caused their vision of a beautiful building to plummet to a plain box with simple colored metal panels for the walls and roof. Oftentimes, this is because the end user is not well versed on the versatility of metal building construction.
As you well know, metal buildings have evolved dramatically over the years. Instead of a standard box with metal panels, metal buildings are now disguised with more traditional construction materials such as wood, brick, stone, concrete and glass which are harmoniously combined with the steel structure, thus, creating an endless possibility of design options for the end user. Whether the owner desires to have a breathtaking attention grabber or a chameleon in their community, a hybrid metal building system will meet his every need.
So how do you meet the objections to a metal building system when meeting with your customer?
Regardless of the application, A&S Building Systems believes that metal buildings provide the greatest design flexibility allowing you to create an impressive looking structure without having to sacrifice the functionality, energy efficiency, or economic benefits afforded to you through the use of a custom designed metal building system. To create this sense of freedom, there are four key benefits that the end user should know.
- The sky is the limit. If you can imagine it, a metal building system could make it possible. Think of your metal building system as just the infrastructure. There are infinite possibilities as how to best customize your project. However, it is important to involve the manufacturer early in the process so that they can help you with every aspect of your project. (Links to Galleries)
- Metal building systems provide unparalleled long-term functionality when compared to traditional types of construction. They are designed to be fire resistant, capable of withstanding the harshest of elements, and are less affected by insect infestation. If you live in an area afflicted by heavy snows, earthquakes, or hurricanes, a metal building will ensure that your investments are protected. This is important to owners, particularly those making long-term investments.
- Metal building systems offer cost savings not provided by traditional construction such as speed of construction, lower in place costs, lower building maintenance costs, and lower heating and cooling costs. In these competitive times, owners are interested in solutions that provide immediate cost benefits as well as long-term savings. Work with your manufacturer to help understand how their system meets these needs
- Metal buildings systems are inherently designed to promote building green. The most recent developments in the metal building industry are focused on energy efficiency and sustainability. Furthermore, they will reduce your operating costs and enhance the value of your assets and overall profits, including the building itself.
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What is Green?
In recent years, A&S, along with the rest of the construction industry, has experienced a greater demand for environmentally-friendly, or green, construction solutions. A green building has characteristics that reduce its environmental impact during its life cycle—from construction all the way through to the end of the building’s useful life. These green building characteristics are measured against three criteria:
• The environmental impact the building will have now and in the future when considering such factors as energy use, efficient use of space, recyclability, and the materials used for construction, all in an effort to conserve natural resources.
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Various government and private, non-profit agencies recognize green construction efforts through certification programs. The ENERGY STAR program, through the US Department of Energy and the Environmental Protection Agency, and LEED (Leadership in Energy and Environmental Design) Green Building Program of the US Green Building Council (USGBC) are two of the construction industry’s most sought after certifications.
ENERGY STAR is committed to protecting the environment by certifying and promoting the use of energy-efficient products. Customers using these products help reduce energy consumption, protect the environment and likely save money as a result. A&S is an ENERGY STAR partner through our extensive line of cool roof panels offered by MBCI® and ABC®.
USGBC’s LEED program is designed for building owners and operators. To receive certification through the USGBC’s LEED program, designers, builders and building owners incorporate energy saving strategies throughout the complete cycle of a building, from best construction practices to occupation and the end of the building’s useful life. Strategies include choosing environmentally sensitive design, roofing, insulation, delivery methods and other criteria, which earn points toward certification.
The US Green Building Council cites these advantages for building green:
| • Decrease in a building’s cost to operate, including energy savings • Increase in a building’s value, improving ROI • Improved occupant comfort • Increase in a building’s occupancy capacity • Increase in potential rent • Reduction in urban heat island effect and smog • Mitigation of global warming |
A&S is a leader in innovation and the delivery of products that meet our customers’ current needs and anticipated growth in years to come. A&S produces products that, when used as part of well-designed building project, measure well against the environmental, economic and health criteria considered for these certifications. One example is A&S’s insulated panel systems offered by IPS® and MBCI® , which provide many green benefits, including superior insulation values that reduce the energy needed for heating or cooling the facility.
In addition to construction products, A&S’s hub-and-spoke distribution system is another advantage we offer. Our facilities are networked, allowing us to determine the closest manufacturing plants with the capabilities to meet the specifications of a given order. Our national coverage enables us to deliver to many jobsites within a 500 mile radius, greatly reducing emissions from and fuel used for shipping.
A&S is committed to supplying our customers’ products that support green building programs. We will continue to invest in research, development and testing, which will allow us to provide innovative green solutions for our customers and the end users we all serve.
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How can I ensure my roof is properly installed?
Weathertightness Warranties: A&S believes if the building owner has to file a claim against a roof manufacturer’s Weathertightness Warranty, then someone has not done their job correctly. A&S’s goal is to be an active partner to ensure:
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- • the roof is properly detailed before installation begins
- • the roof is properly installed before the warranty is issued
- • the building owner is satisfied with his A&S roof
Although A&S has its own version of the industry standard type of Weathertightness Warranties, we offer our Single Source™ Weathertightness Warranty Program to accomplish the goal of being an active partner to the building owner. This program puts the complete burden for proper installation of the Roof System* squarely on the shoulders of A&S from the date of substantial completion. In the remote chance that a claim is ever filed against a Single Source™Warranty, the building owner makes one call… to A&S.
All Single Source™Warranties require that an A&S certified installer, with a photo ID, be present on the jobsite at all times. In addition, a minimum of three inspections will be required during the course of roof installation. These inspections will be conducted by competent inspectors, selected by A&S, that are knowledgeable about the erection and installation of A&S’s roof systems. A&S offers three levels of Single Source™Warranties depending on the level of protection the building owner requires.
*Roof system is defined as the A&S furnished roof panels, flashing, and related items used to fasten the roof panels and flashing (including roof jack and curb attachments pre-approved in writing by A&S) to the roof structure.
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What are the Benefits of Insulated Metal Panels?
Insulated metal panels (IMPs) provide flexibility for building owners and architects and offer an architecturally attractive and elegant appearance for buildings. They are ideal for a wide range of building projects, including green building construction, and contribute to LEED certification.
IMP Benefits and Incentives
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Interior Main Frame Columns
To Fix or Not To Fix...
In general, the most economical member for an interior column will be a round pipe. When a particular frame design is impacted by drift criteria, at some point it makes sense to use a built-up interior column and fix the top. This column will be more expensive than the pipe but it can serve to restrict frame drift, thus resulting in a less expensive frame overall.
Generally, tall buildings in high wind areas or with restrictive drift criteria can benefit by using fixed-top interior columns. For taller buildings with small modules, it may also be more economical to use larger modules, thus eliminating an interior column or two.
Fixed Base interior columns may also be employed to reduce frame drift and achieve better pricing in some of these instances, but this should always be communicated to all parties involved in a project since foundation costs will most likely increase.
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Bracing
Astek II will allow you to brace only one bay in a building if you choose even if the building is 900’ long. However, one of the primary rules-of-thumb for bracing is to brace at least one bay for every 5 bays in a building. As with many other building parameters, you can experiment with some buildings to achieve an optimal design. As a case in point, I chose a random Astek file with building dimensions of 100’ X 250’ X 24’, 10 bays at 25’. I priced the building with 1, 2, 3, 4, and 5 bays of bracing. The Sell prices are as follows:
| 1 Bay | $98,733 | * Not an acceptable choice since a min. of 2 braced bays required. |
| 2 Bays | $97,901 | |
| 3 Bays | $97,419 | |
| 4 Bays | $96,786 | |
| 5 Bays | $97,337 |
If you would have asked me how many bays to brace for this particular building, I probably would have told you 3. However, you can see that the optimum solution was 4 braced bays. The savings over 3 bays was $633, almost 1% of the total price, enough to lose a job in some cases.
Moral of the story: AstekII will only price what you tell it to price. Only from experimenting with those parameters; over which you have some measure of control, can you calculate the most competitive price.
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Open Wall Conditions
It wasn’t too long ago that the majority of metal buildings were built with a metal skin wall system. It is now more common, certainly in commercial and institutional applications, to see something other than metal walls on a metal building. Two of the most commonly employed wall materials are EIFS and masonry or a combination of both. There are a couple of issues that you should be aware of as you endeavor to value engineer your project.
First, if your wall material is comprised of concrete or masonry, you should strongly consider allowing column flange braces to the wall system. These are the same flange braces you are accustomed to seeing for girts. When you select “Columns to be Braced by Masonry / Tilt-Up” in the “Options” screen for “Open Areas”, the Engineer will optimize the placement of flange braces to brace the column and minimize costs. This practice generally cannot be employed with a metal stud wall since the studs usually lack the required lateral stiffness.
Secondly, masonry and EIFS wall systems will ordinarily employ a spandrel beam (or beams) instead of multiple rows of zee girts. If the wall system is partial height, it may be possible to use a channel fastened to and located directly on top of the wall. In this instance, the channel beam is considered fully braced.
For a full open wall, the spandrel beam is generally located as high as possible and placed directly behind the wall system. You will be prompted for “Connection Spacing of Wall Attachment to Beams” in the “Beam” screen in “Open Areas”. We also suggest you check the “Use Flange Bracing” box. Here, again, the Engineer will optimize the placement of flange braces to minimize costs. For optimum pricing, the spandrel beam will be braced generally at 1/3 or ¼ points.
One additional comment relating to masonry and EIFS wall systems: For very tall walls, perhaps greater than 16’ or so, it may be necessary to add an additional spandrel beam, depending on the vertical spanning capacity of the studs or masonry. You should consult the Project Engineer of Record to determine if intermediate wall support is required.
Of course, should you have any questions regarding value engineering for your particular project, we encourage you to contact your A&S District Manager.
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Snow Load / Roof Slope Interaction
Now that most of us have gotten comfortable using the latest Astek II software, you probably know that it is very accurate and complete for a wide array of buildings. As such, it is a true design and pricing tool. Many of you have discovered you can change parameters such as roof slope, bay spacing, module spacing, and bracing to arrive at an optimum building solution.
Roof system designs are largely governed by snow loading and the manner in which that snow is applied per Code requirements. Following are some general guidelines to assist you in determining the optimum roof slope.
- For wide clearspan buildings, consider increasing the roof slope to 2:12, or even larger.
- Consider using lower slopes for modular buildings.
- Unbalanced Snow Loads are not required for roof slopes less than ½:12. Consider using 7/16:12 roof slope, especially if Ground Snow is greater than 20 psf.
The minimum slope for PBR is ½:12 and for Stand Seam roofs, the minimum slope is ¼:12. And, too, roof slope is often dictated by aesthetic considerations. But, beyond that, we encourage you to experiment with different roof slopes to arrive at an optimum building solution.
Of course, should you have any questions regarding value engineering for your particular project, we encourage you to contact your A&S District Manager.
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Metal Building Tips
More on Open Wall Conditions – Endwalls
In an earlier published “Tip”, we discussed how best to handle wall conditions that are open for something other than traditional girts and metal wall panels.
Read more...