FAQs

We receive dozens of calls each day from all over the country regarding TrimJoist® products. The questions below are a small sampling of those most frequently asked. If you need further explanation on any of these topics or if we don’t address your particular question here, please call us at 800-844-8281.

Why should I even consider an engineered joist when traditional solid joists are cheaper?

Solid 2x joists are cheaper on a per-unit basis. However, studies have shown that by the time culls, waste, and labor are considered, a more superior TrimJoist® floor system could have been installed. In addition, since TrimJoist® products use two-by-four raw materials, the environmental impact is much smaller than the loss of large old-growth trees that are required for traditional joists. Approximately 35 percent of each TrimJoist® product is recycled material.

What makes a TrimJoist® product different from other types of engineered joists on the market?

The TrimJoist® is a unique marriage of an open-web truss to a solid-web “I” section. This patented combination gives the TrimJoist® unparalleled versatility and utility on the job site. The TrimEnd™ “I” sections allow for a custom fit, while the open-web nature of the product allows for complete access to that valuable floor cavity space for ductwork, plumbing, and electrical needs.

Why do TrimJoist® products come in different depths?

The strength of any joist or beam is directly related to its depth. This relationship is exponential in nature. Thus, a 16-inch-deep joist is about 34 percent stronger than a 14-inch-deep joist and about 120 percent stronger than a 12-inch-deep joist. By comparison, a 14-inch-deep joist is about 64 percent stronger than a 12-inch-deep joist of equal span. While these percentages are only approximations, they give some idea of how increasing the joist depth improves performance as well as utility.

If the 18-inch joists are strongest, why not always use them instead of the 12-inch, 14-inch, or 16-inch joist?

Sometimes there are architectural constraints that can only be met by smaller depth joists. Also, since a joist is often spanning only 16 feet or less, the additional strength of the deeper joists can become overkill. However, for spans greater than 18 feet, the superior strength of the deeper joists becomes very noticeable.

What are the maximum spans for a given depth?

Presently, TrimJoist® products are manufactured in 24-inch incremental lengths beginning at 4 feet and working up to a maximum stock length that is depth-dependent. These maximums are as follows:

         Depth      Max Length
         -----      ----------
         12"        24 feet
         14"        26 feet
         16"        28 feet
         18"        30 feet

Thus it is possible to span 28 feet (allowing for end supports) with a 16-inch-deep TrimJoist®. This works great in basement-type construction by eliminating those unsightly pipe columns, extra beams, and footings.

At what on-center spacing are TrimJoist® products typically used?

Depending on the loading conditions (consult a TrimJoist® span chart or our engineering department), TrimJoists® products may be placed at any spacing from 12 to 24 inches. It is customary to place traditional joists at 16 inches on-center. However, since TrimJoist® products have a 3.5-inch-wide flange, many contractors choose a 19.2-inch spacing to maximize the price/performance ratio of the product. Most contractor-grade tape measures now have a marker every 19.2 inches for just this very purpose. This spacing will also work out correctly for your plywood subfloor. By using a 19.2-inch spacing, the flanges of the TrimJoist® are still only 15.7 inches apart. This makes the plywood subfloor behave like traditional joists at 16-inch centers.

Will I have squeaks with a TrimJoist® floor system?

Any floor system can have squeaks, even those made from steel and concrete. The trick here is to eliminate those factors that can cause squeaks. These factors are typically poor nailing, subfloor joints that are too tight, excess dead wood, and poor bridging. The TrimJoist® has many features to help avoid these problems.

Problem: Subfloor cannot expand and contract.
All wood fiber subfloor materials need to be installed with sufficient room to expand and contract as the ambient temperature and humidity changes. TrimJoist® provides a wide surface so that framing tolerances may be eased enough to eliminate this problem.

Problem: Poor application of underlayment.
Many contractors use a composite underlayment board in areas that require carpeting. This underlayment is non-structural, but provides a very smooth surface. More often than not, the underlayment is attached only by nails. Over time, these nails begin to rub against the underlayment, causing squeaks. We suggest that the underlayment be attached with both screws and glue with the same care as was taken with the subfloor.

Problem: Subfloor not adequately attached to joist system.
Conventional 2x joists or narrow-flange, I-beam type wood products do not provide sufficient surface for good nailing technique. The full 3.5-inch-wide TrimJoist® nailing surface allows for sufficient nailing and optional gluing of the subfloor.

Problem: Joist system not stiff enough.
In addition to the stationary loads on a floor, each step a person takes places a small impact load on the supporting joists. Over time, this seismic stress can cause the whole system to become “loose.” TrimJoist® products are not only designed to withstand these impact loads, they also provide for a strong-back mechanism, which can disperse these loads more evenly through the floor system.

Where can I get TrimJoist® products for my next project?

TrimJoist® products are sold only through authorized dealers and distributors. These dealers typically maintain sufficient inventories to satisfy most customer demands. In geographical areas not presently serviced by a dealer, TrimJoist Corporation may be able to arrange factory-direct delivery in truck-load quantities (typically 8,000 to 11,000 linear feet).

Can I order TrimJoist® with special duct chase placement?

No. For engineering reasons, the center duct chase opening must remain close to the physical center of the truss. Beginning July 1, 1996, new ANSI standards went into effect for wood floor truss design. ANSI standards do not allow the duct chase to be off-center by more than 12 inches even in custom manufactured trusses.

Can I get custom engineering on my particular job?

Yes! TrimJoist Corporation maintains an engineering department for just this purpose. If you can send us a set of plans or adequate drawings via fax, UPS, FedEx, or email, we will assist you in selecting the correct joists for your application. Many of our dealers have in-house engineering capabilities as well.

What about a computer program to analyze a TrimJoist® product for a given loading or support condition?

Any licensed architect or engineer may download a free copy of our analysis program here. This program is Windows-based and is simple to use for anyone who understands uniform and concentrated loadings. The program also analyzes beams from a variety of beam manufacturers.

Can I order free literature from TrimJoist?

Yes! You can order our free literature online or by calling us at 800-844-8281.