How Strong is the InSoFast Stud?

We understand the initial concerns people have in learning our panels’ structural framing is made of plastic…and that it’s designed to be glued. It’s no small matter, which is why we’ve worked like mad scientists to perfect the multiple engineered features that make our panels so dependable, including the stud load capacity. If you have any concerns we’re just talking the talk, watch us walk the walk…

If you’re still skeptical, keep reading. The information below is an in-depth examination of the numbers behind our test reports. We’ll explain how strength is determined in construction, draw comparisons to traditional materials and describe how you can achieve the best performance from our studs.

How do objects attach and stay?

Our panels are made of two major materials: EPS foam and polypropylene plastic. The EPS foam forms the body of the panel. While it is a rigid structure, it should not be used to hold weight. Instead, it is intended to support important features like electrical channels, moisture control, panel alignment, continuous interlock and, of course, insulation. The embedded studs should be considered the only load-bearing component of the panels, just like regular studs. They can be nailed, screwed, and glued.

fig1-stud

The InSoFast stud is made of a high-strength recycled polypropylene plastic. Polypropylene becomes malleable above a certain temperature and solidifies during cooling. Our stud is formed through an injection-molding process. Later, a special co-molding process expands the foam body around three separate studs to be formed as one solid panel.

The back surface of the stud features ribbed dovetails for adhesive application. The front surface is flat and designed to be nailed or screwed. The UX panel’s stud surface is exposed and features three inset markers for attachment. The inset simply prevents a screw head from messing up your flush drywall surface.

What metrics are used to determine strength in the InSoFast stud?

We derive our strength from the ASTM results of two reports conducted on our panels. The independent Stork Twin City Testing Corporation measured adhesive capacities in their report. We received our Code Compliance Research Report from Intertek, one of the world’s leading quality assurance testing corporations. Among other things, their report includes measurements on mechanical (screw and nail) capacities. Both companies rigorously tested the capabilities of our studs and came up with some profoundly assuring results.

fig2-strength-measurement

The Intertek report focuses on two specific metrics for testing stud strength, Withdrawal and Lateral Strength. Withdrawal Strength is the capacity of the stud to hold weight without pulling the screw directly out of the material. Lateral Strength, or Shear Strength is the capacity of the stud to hold weight without shattering the material. These metrics are measured in lbf or Pound Force. This is a measuring unit that describes the amount of force exerted under earth’s gravitational pull. 1lbf = 1lb of mass…easy enough.

The Stork report looks at Pull-Off strength. We use the peak stress measurement to determine how much weight in pounds that a square inch of the stud’s surface area can hold.

Property ASTM Result
#6 1¼in Standard Drywall Screws Pull Out (Fastener Withdrawal) D1761-06 325.4 lb/ft
#6 1¼in Standard Drywall Screws Shear (Lateral Screw Resistance) D1761-06 470.6 lb/ft
Adhesion of PL Premium Adhesive and Stud (Peak Stress) D4541-02 108psi (972ps/lf)

In the next couple of sections, we will describe how these measurements relate to some real-world feats of strength. Bear in mind, no house exists in the perfect vacuum of a testing facility and there are many complex variables at work in every building situation. We will take a look at the meaning of each test result, but in practice they should be considered simultaneously.

Will the glue be strong enough to hold drywall?

Yes, in fact, the glue will be strong enough to hold far more than drywall! Technically, glue is stronger than screws because it adheres along the length of the wall as opposed to specific points.

gluestud

The bond strength between adhesive and stud forms as a mechanical lock between the dovetailed ribs. Third-party testing confirms that adhering an InSoFast panel to a concrete wall can hold 108psi. There are about 16 square inches of adherable surface per stud. If you add up the adherable space on a single panel, you’d have over 5,000-lbs of holding power!

It’s important to note the test was conducted with Loctite’s PL Premium 3X Construction Adhesive on a clean concrete wall in a laboratory setting. You can find more information about using this product here. It is the only adhesive we recommend. Please refer to the manufacturer’s recommendations if using another adhesive or adhering to a substrate other than concrete.

Will the studs hold the same weight that a traditional 2×4 holds?

Comparatively, no. A traditional wood 2×4 contains a lot more material for a nail or screw to pull against, which makes it stronger. The strength of the InSoFast stud is more comparable to that of a commercial-grade steel stud. That’s still pretty strong and, in terms of industrial safety factors, probably stronger than you’ll ever need it to be.

Want some other good news before we dig into the numbers? Unlike wood, our plastic stud will never rot, warp, or decay. Unlike metal, it won’t rust or act as a conductive pathway for heat.

Will screws be strong enough to hold drywall, cabinets and big screen TVs?

Yes. If you’re adhering to a masonry surface you get to start out with that amazing full-surface strength. If, instead, you’re screwing the panels into a structural wall you still start out with significant strength factors. Intertek reports that you can safely add up to 96-lbf of Withdrawal and 37-lbf of Lateral force for every screw that attaches the InSoFast studs to the wall.

As an example, consider that the weight of a kitchen cabinet hanging on three screws could apply up to 864-lbf Withdrawal and 333-lbf Lateral. For a little perspective, 333-lbs equates to roughly 20 maximum-size regulation bowling balls.

fig3-bowlingballs

Perhaps a more relevant thought experiment would be to ask yourself how often you intend to buy more than one 50-lb sack of rice to store in a cabinet above your head?

Side note: InSoFast panels are the perfect insulation for your masonry or metal SHTF Survival Shelter!

The final numbers to look at are the strength factors for attaching materials to the InSoFast studs. Per screw, Intertek reports 65-lbf Withdrawal and 94-lbf Lateral. This means you could hang a 65-lb cabinet (or four bowling balls) on your wall with just one screw.

Is it safe to exceed the load capacities by a little bit?

We would never ever recommend it. It is always best to respect the load capacity. However, the Intertek report adds a safety factor of 5:1 to all of its measurements. While it wouldn’t be the best practice to hang that 65-lb cabinet with one screw, the safety factor actually ensures the cabinet can exceed that force by 5x (325-lbs) before causing trouble.

So technically speaking, you would need to add the weight of 16 bowling balls to this single-screw cabinet before it crashed to the ground, wrecking everything in its path. And most likely, the screw would break first.

If you’re still a bit wary, take a deeper look at our Intertek Code Compliance reports and order a sample panel to get a feel for the construction of the stud. As always, feel free to add any questions or comments in the section below.