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.

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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.

How to Specify a Custom Hanger

As an engineer, it makes things easy when the buildings being designed are rectangular. This tends to make the connections occur between nice perpendicular members, and standard connectors and joist hangers can be used.

But buildings are not always rectangular and connections are not always between perpendicular members. Non-perpendicular members can have a skewed connection, where the supported member is moved side to side from perpendicular; or a sloped connection, where the supported member slopes up or down from a standard horizontal orientation; or a combination of the two.

To help with these situations, Simpson Strong-Tie offers a couple of options. The option chosen may depend on the timeframe in which the hanger is needed, the load demands on the hanger or the cost of the hanger.

If the demand load is low and an immediate solution is desired, Simpson Strong-Tie offers several adjustable hangers that can be skewed, sloped or both in the field.

LSU adjustable joist hanger

LSU adjustable joist hanger

A common adjustable joist hanger is the LSU/LSSU series, which can be sloped up or down and skewed right or left up to 45 degrees.

Remember that these hangers must be installed to the carried member prior to installation of the supported joist.

Other series of hangers are only adjustable for skew or slope.  For example, the THASR/L series is designed to accommodate connections skewed from 22½ to 75 degrees. Conversely, the new LRU ridge hanger is designed to support rafters at ridge beams with roof slopes of 0:12 to 14:12. Finally, the SUR/SUL/HSUR/HSUL series is not adjustable, but is manufactured with a skew of 45 degrees either right or left in several sizes.

THASL hanger

THASL hanger

LRU ridge connector

LRU ridge connector

HSUR hanger

HSUR hanger

If none of these pre-manufactured solutions fits your specific need, there are still options. This entails a custom-manufactured hanger. Many, but not all, joist hangers can be custom-made for specific slopes, skews, combinations of slopes and skews, and even alternate widths and alternate top flange configurations.

If this type of hanger is needed, a good place to start is the Hanger Options Matrix at the back of the Simpson Strong-Tie® Wood Construction Connectors Catalog. It is also available at strongtie.com.  An excerpt is shown below. This chart identifies which hangers can be modified, how they can be modified and to what extent they can be modified. There are two tables – one for top flange hangers and one for face mount hangers.

The Hanger Options Matrix is available in Simpson Strong-Tie(R) Wood Construction Connectors Catalog or at strongtie.com

The Hanger Options Matrix is available in Simpson Strong-Tie(R) Wood Construction Connectors Catalog or at strongtie.com

Once the user has found a hanger that can be modified to fit the actual situation, the next step is to calculate any load reductions, if applicable. The column at the far right gives the Wood Construction Connectors Catalog page number that lists any load reductions for the various options. If multiple options with reductions are specified, only the most restrictive load reduction needs to be applied, not all the reductions.

As an example, let’s say we need to hang a heavily loaded double LVL hip member from the end of an LVL ridge beam. We would look at a GLTV top flange hanger, skewed 45 degrees to the right, sloped down 45 degrees, with its top flange offset to the left. We see from the table above that all these options are permitted. If we go to page 220 (or strongtie.com), we can see what the load reductions would be for these options. The reductions are as follows:

  1. Sloped and skewed configuration for the GLTV has a maximum down load of 5,500 pounds.
  2. Offset top flange for the GLTV requires a reduction factor of 0.50 of the table roof load.
  3. BUT, skewed and offset top flange hangers have a maximum allowable load of 3,500 pounds.
  4. Offset top flange results in zero uplift load.

So the allowable load of our skewed, sloped, offset top flange GLTV would be 3,500 pounds downward and 0 pounds uplift. In this case, it was clear what the reduction was for our combination of modifications. If it is not listed specifically and you have multiple modifications with multiple reduction factors, use only the factor that results in the biggest reduction, not all of the listed reduction factors.

The next thing to do is to call out the desired hanger properly so that Simpson Strong-Tie can manufacture it to your needs. This is typically done by taking the regular product name, adding an X, and then calling out the modifications individually at the end.

For our hanger, assuming the hip is 3-1/2″ by 11-7/8″, the standard hanger would be a GLTV3.511, and the modified hanger would be called out as a GLTV3.511X, Skew R 45, Slope D 45, TF offset L.

There is one final consideration when hangers are both sloped and skewed. In this case, the top of the supported member (joist) will not be horizontal when it is cut, one side will be higher than the other. The user must decide and specify where he or she wants the upper side of the joist to fall. There are three options: high-side flush, center flush or low-side flush. We see that often users will want to specify high-side flush so that the joist ends up flush with the top of the supporting member, but that would be up to the user. This specification is added to the end of the callout name listed above. These cases are illustrated below.

A related matter occurs when the top flange of a hanger is sloped up or down. In this case the user also has to specify whether the joist is to be low-side flush, center flush, or high-side flush. But, in this case, the side is in reference to the top flange, not the joist. Specifying low-side flush will result in the top of the joist being flush with the lower side of the sloped top flange, not the low side of the joist.

If all of this seems confusing and somewhat difficult, it can be. Fortunately, Simpson Strong-Tie has developed a new web application – the Joist Hanger Selector – which automates this entire process. This app is located on strongtie.com/software.

Once you agree to the terms and conditions, choose the type of hanger you want to specify, then select the types of members being connected. This is what it would look like for our example.

jhs-input

 

This is where the user specifies any modifications required. Required loads can also be entered at this point. This is what it would look like for our example.

jhs-input2

Then, just click “CALCULATE” and the possible options will be shown. And here we see our GLTV3.511X, SK R 45, SL DN 45, TF Offset L, with a load of 3,500 pounds, just as we thought! I love it when a plan comes together.

jhs-input3

Hopefully, this web app will help you specify custom hangers with ease. Are there any other applications we could develop that would make specifying connectors easier? Let us know.

Upcoming events

The 22nd International Specialty Conference on Cold-Formed Steel Structures is coming up Nov. 5-6 at the Hilton Ballpark Hotel in St. Louis, MO. It is sponsored by the Wei-Wen Yu Center for Cold-Formed Steel Structures at the Missouri University of Science and Technology.

A biannual event, this conference brings together leading scientists, researchers, educators and engineers in the field of research and design of cold-formed steel structures to discuss recent research findings and design considerations. This year’s conference features 12 technical sessions covering a wide variety of topics. For more details, visit the conference website.