joist hanger Archives -

How to Pick a Connector Series: Selecting a Joist Hanger

A quick glance through the Simpson Strong-Tie® Wood Construction Connectors catalog shows that we manufacture at least 29 different models of face-mount wood-to-wood joist hangers, three separate models of face-mount wood-to-masonry hangers, 42 different models of top-flange wood-to-wood joist hangers, four different models of top-flange wood-to-masonry hangers and 15 models of specialty joist hangers. And that’s not even counting heavy truss girder hangers or multiple- member hangers. So it’s no wonder that sometimes it’s difficult to pick exactly the right hanger for your particular application.

There are many things to consider when picking a joist hanger. The first may be what your load requirements are, including their direction. That will sometimes determine the second consideration. Do you want to use a top-flange or a face-mount joist hanger? Top-flange hangers typically have higher down loads with fewer fasteners, but must be installed when there is access to the top of the supporting member and often before the joist is in place. On the other hand, face-mount hangers can be installed after the joist is in place, and can have higher uplift loads, but will use more fasteners.

Speaking of fasteners, any fastener preference can determine your selection of a hanger. Joist hangers can be installed with common nails, screws (SD for lighter hangers and SDS for heavier hangers), or even bolts, for heavy glulam hangers. See here for information on the various fasteners that can be used with our connectors. The Simpson Strong-Tie Wood Construction Connectors catalog does not list allowable loads for joist hangers installed with SD screws, but you can find them here; just click on the link of the product to find its allowable load. Also, if the joist hanger will be installed with pneumatic fasteners, we have a Technical Bulletin on the possible load reductions that will result.

Another thing to consider at the beginning is what types and sizes of members are being connected together. Is your connection all solid-sawn dimension lumber, engineered wood or structural composite lumber, glulam beams, or trusses? All these types of wood products require different hangers.

Furthermore, joist hangers will have different capacities based on the species of wood to which they are being attached. For example, the truss hangers in the table below have allowable loads listed for Douglas Fir-Larch, Southern Pine and Spruce-Pine-Fir/Hem Fir. Most standard solid-sawn joist hangers, on the other hand, will only have two load ratings, DF/SP and SPF.

Top-flange hangers are sensitive both to the species of wood and to the type of engineered wood to which they are attached. Because of that sensitivity, they have to be tested to each different type of engineered wood that could be used as a header and may have different published allowable loads for each type as shown here.

Is the joist framing into the side or top of a concrete/masonry wall? Then a special joist hanger is required. Is the joist connecting to a nailer on top of a steel beam or concrete/masonry wall? Nailers require top-flange hangers and can result in loss of allowable load if you have to use shorter nails, so you need to check that carefully. There are special tables published for nailer loads for top-flange hangers.

Another consideration is the orientation of the members. In a perfect world, all connections will be between perfectly perpendicular members. But in the real world, joists may be rotated side to side (skewed), or up or down (sloped), or some combination of the two. There are a couple of options in those cases. Hangers such as the SUR/SUL series are available pre-skewed at 45 degrees. Adjustable hangers such as the LSU/LSSU series can be adjusted within limits to certain slopes, skews and slope/skew combinations. Simpson Strong-Tie also has the capability to custom-manufacture quite a few types of hangers to any slope or skew within certain limits, based on the hanger. All of these options, including any load reductions required, are listed in the Hanger Options section of the catalog or website. The table there gives the various options available for each product and clicking on an individual hanger in the website table will send you to a page with the specific reductions for each option.

Another important consideration is the installed cost of the joist hanger. Simpson Strong-Tie publishes what we call an Installed Cost Index, where the total installed cost of a hanger, including fasteners and labor, can be compared for related hangers. For example, there are six joist hangers listed in the Solid Sawn section for a 2×6 joist. They are listed in order of increasing Installed Cost Index. To choose one, simply find the one with the lowest installed cost that meets your load requirements.

Obviously, this is a lot to think about when trying to choose a simple joist hanger. In order to make choosing a connector as easy as possible for our customers, Simpson Strong-Tie offers two different software tools to help. The first is our old standby, the downloadable Connector Selector. This is a versatile program that will help the user pick a joist hanger, truss hanger, multi-truss hanger, column base, column cap, holdown, mudsill anchor, hurricane tie, multi-ply lumber fastener, embedded anchor bolt or hinge connector. It can be downloaded from here. You can see from this example that the Connector Selector gives several options for nailing of joist hangers that may not be directly listed in the catalog.

For a quick aid in choosing a connector, Simpson Strong-Tie recently developed our Joist Hanger Selector Web App. This is found directly on the strongtie.com website. While not necessarily as versatile as the Connector Selector, it has a much easier-to-use graphic interface where the user can choose any option they wish. Just simply choose the desired hanger type, the header member, the joist member, the fastener type, any hanger options and input any design load requirements, then hit calculate, and your choices show up immediately.

Here is the output shown for the same inputs as the Connector Selector above. The app will initially show only the most common models that provide a solution, but the user can click SHOW ALL MODELS for a more complete list of solutions. The user can also click on the “+” next to the model name to get additional fastener options.

A final consideration in choosing a joist hanger is the finish desired. Simpson Strong-Tie manufactures joist hangers in several different finishes: Standard G90 zinc coating, ZMax® G185 zinc coating, HDG hot-dipped galvanization after fabrication, Type 316L stainless steel and powder-coat painted. The environment where the joist hanger will be installed and the material it will be in contact with (treated wood or other corrosive materials) will both influence which finish should be chosen. Guidance for selecting finishes is found in our literature and on our website. Also remember that the finish of the fastener used needs to match the finish of the connector.

We hope you find these tools helpful the next time you need to choose a joist hanger. Are there any other tools you need to help you specify Simpson Strong-Tie connectors or anchors? Tell us below.

Testing Fasteners for Deck Ledger Connections

This week’s blog post was written by Aram Khachadourian, R&D Engineer for Fastening Systems. Since joining Simpson Strong-Tie 14 years ago, he has designed and tested holdowns, hangers, truss connectors and anchor bolts. He has drafted numerous acceptance criteria as well as quality standards. His current focus is the development, testing and code approval of structural fasteners. Prior to his work at Simpson Strong-Tie, he spent his time designing steel buildings including strip malls, wineries and airplane hangars. Aram graduated from the University of California at Davis with a Civil Engineering degree, and is a registered professional engineer in California.

As we approach the beginning of spring, homeowners across the country are starting to turn their thoughts to the backyard and making plans to add a new deck for summer enjoyment.

As a contractor, designer, or homeowner, you want to know that this new deck will have the structural integrity to stand firm for many years and remain safe for everybody who will use it. While there are many aspects to building a safe, strong deck, today we are focusing on the attachment of the deck ledger to the structure.

Prior to 2009, numerous catastrophic deck failures attributed to improper deck ledger attachments demonstrated the need for building code guidance. A calculated solution was overly conservative because the sheathing layer, typically present between the deck ledger and the structure’s band joist, was considered to be a gap in the connection. A prescriptive approach to deck ledger attachments was finally introduced in the 2009 International Residential Code (IRC). Table R502.2.2.1 provided fastener spacings for ½”-diameter lag screws and bolts. These values were based on testing conducted by researchers at Virginia Tech and Washington State University.

The tests included a variety of band joist types, with pressure-treated Hem-Fir as the deck ledger material. The deck ledger was tested at high moisture content to represent a wet, worst-case field condition. The test assembly had a load bar spanning two joists that were attached to the deck ledger with joist hangers. The ledger was attached through the sheathing to the rim board. Only the rim board was supported by the test frame. The average ultimate load was divided by a factor-of-safety of 3 and then further divided by the load duration coefficient of 1.6 to achieve an allowable load. These values were then applied to a deck live load of 40 psf plus a deck dead load of 10 psf to derive allowable fastener on-center spacings for various joist spans.

When Simpson Strong-Tie began to rate fasteners for ledger connections, we used a similar method of testing and analysis. However, we incorporated a few changes. One of the changes we implemented was a symmetric test set-up. The original test assembly had a ledger on one end of the joists and a support member as the boundary condition on the other. We put a ledger at each end of the joists so stiffness differences in the supports would not affect the test results. We also chose a larger factor-of-safety of 3.2 (instead of 3.0) to maintain consistency with calculation of fastener allowable loads in other applications. In order to provide our customers with a broader range of construction options, we tested many typical rim board and ledger materials, and we ran tests with single and double ledgers. You can see an example of a typical test set up here:

A typical testing set up — Testing deck ledger connections.

We have tested many Simpson Strong-Tie® Strong-Drive® fasteners for ledger applications including the SDWS Timber screw (SDWS22DB), SDWH Timber-Hex SS screw (SDWH-SS), SDWH Timber-Hex screw (SDWH19DB), and SDS Heavy-Duty Connector screw (SDS). We also have information regarding ledgers attached to studs and ledgers fastened over gypsum board. You can find all of this information in our latest fastener catalog.

One final construction tip – deck ledgers can fail due to cross-grain tension. This occurs when the joist hangers are attached to the deck ledger near the bottom of the ledger, but the fasteners holding the ledger to the building are near the top of the ledger. To prevent cross-grain tension failure, place the joist hangers so at least half of the ledger fasteners are below the joist hanger line.

Take a look through the various ledger options in our fastener catalog, and if we don’t address your condition, let us know. As always, call us in the Engineering Department if you have questions.

Please share your feedback in the comments area below.

Introducing the Joist Hanger Selector Web App

Designing buildings and dealing with construction has always been a satisfying career for me. It is challenging to design a complete structural system, coordinate with the other consultants and create a clear set of construction documents for the contractor. Throughout my career, I’ve occasionally had a few panicked “Uh oh!” moments. I hope I’m not alone in admitting those happen. These typically occur far away from work when something prompts me to think about a project. I might see concrete being placed, then question whether I remembered to change the reinforcing callout on a mat slab I had just designed. I can’t stop thinking about it until I get back in the office to check.

I had an “Uh oh!” moment a few days after I started work at Simpson Strong-Tie. We have a training plan I call Catalog 101 where new engineers meet with each engineer who is an expert for a given product line. After I had met with our experts on holdowns, concrete anchors and engineered wood products, it was on to top-flange hangers (and my “Uh oh!” moment).

After learning a lot of things I didn’t know about hangers, we moved on to available options for some of our top-flange hangers – sloped, skewed, sloped and skewed, sloped top-flange, and offset top-flange. I learned that some hanger options get full load, some have small reductions and others large reductions. For example, the GLT with an offset top-flange gets 50% of the table load.

GLT/HGLT hanger options section of Wood Construction Connectors Catalog, C-2013

“Uh oh!”

I had recently designed a project and specified a bunch of GLT hangers with offset top-flanges. I hadn’t noticed there was a reduction for this modification; I just thought it was really cool that Simpson Strong-Tie had a hanger that worked at the end of a beam. Minor panic set in until I could check my calculations. Fortunately, the beams at the framing conditions that required offset hangers had half the load of the typical beams, so the hanger was okay even with the load reduction.

Hanger Option Matrix from Wood Construction Connectors Catalog, C-2013

The Wood Construction Connectors Catalog has a Hanger Options Matrix that makes it relatively simple to see which options – sloped, skewed, concealed, welded – are available for each hanger. The pages following the options matrix have more detailed information about size restrictions and load reductions associated with each option. It can be somewhat tedious to sift through all of the options and apply the reduction factors, so I always recommend using the Simpson Strong-Tie Connector Selector® software to do the work for you.

Connector Selector software allows you to input you geometry and loads and returns a list of connectors that meet those requirements, including any reductions due to modifications. Connector Selector is a desktop application, which needs to be downloaded and installed on your PC. Engineers have indicated they like the functionality of Connector Selector, but wished the input was more intuitive and preferred it as a web application.

I’m happy to say we listen, and the new Simpson Strong-Tie Joist Hanger Selector web app is available now. The easy-to-use interface enables users to quickly select the connection details and print out results. You can access the app from any web browser without having to download or install special software. The allowable loads are automatically calculated to reflect reductions associated with modifications – no more “Uh oh!” moments for me (at least with hangers).

Joist Hanger Selector App — The joist hanger selector app makes it easy to pick the right hanger.

Give the new Joist Hanger Selector web app a try and let us know what you think. We always appreciate your feedback!