How Structural Insulated Panels (SIPs) are Made – Simplified


Structural Insulated Panels, or SIPs, are a type of construction material that is becoming increasingly popular in both the residential and commercial building industries. SIPs in a nutshell, are made up of two layers of oriented strand board (OSB) with an insulating foam core in between. This results in a strong, lightweight panel that can be used for walls, floors, and roofs.

As we have discussed in a previous article about the reasons why ADU.Works chooses SIP as their construction method of choice over traditional stick-built framing – one of which is that the panels have been shown to reduce heating and cooling costs by up to 50%, in this article we’ll discuss how SIPs are made.


Structural insulated panels, as the name suggests, are made up of two pieces of a type of laminated wood (usually plywood) or an oriented strand board (OSB) as with a layer of insulation in between. They’re available in a range of sizes, (as long as 24-feet) and can be customized to fit the specific dimensions of your project. Given that SIPs are manufactured in factories, this means they can be delivered to the job site ready to install. This saves time and money on the overall construction process.

Oriented Strand Boards have been a popular choice as the interior and exterior sheathing for SIPs because of its versatility and load-bearing capabilities. OSBs are formed by adding adhesives and then compressing layers of wood strands in specific orientations. It uses wood from the crooked, knotty and deformed trees that would otherwise go unused. As strands, they are mixed with waterproof resin and interleaved together in thick mats, which are then bonded together under heat and pressure.  This results insolid, uniform building panels, with enhanced features, and high strength and water resistance – making it an ideal product for a variety of purposes, including sheathing in walls, flooring, and roof decking.  It’s also one of the most environmentally friendly building products on the market today.

The most common type of foam core used in SIPs is expanded polystyrene (EPS). EPS is composed of 98% air, which gives it long-term stability, resistance to heat flow and releasing of chemicals. When it comes to sizes and types of filling, SIPs can be custom-made to meet the specific requirements of a structure. These panels can come in different sizes and thickness along with the type of foam core used depending on the performance property that best fits the project. Some panels are made to be better insulators while others are made to be more constructively tough. The thickness may range from around 3.5 inches up to 11.25 inches, and achieve insulation levels ranging from R-16 to R-49, respectively.


To form the SIP, the OSB and EPS are then bonded tightly by coating both components with structural-grade glue or adhesives and then pressed together with around 4-6 pound per square inch of pressure for a prolonged time to ensure a fully adhered product.

According to SIPs.Org, the structural properties of an SIP can be compared to that of  a steel L-beam. Because of its unique design, the OSB facers pose as the ridge of the I-beam, while the tightly pressed foam core delivers the web. This allows SIPs to handle compressive loads. As a testament to its structural integrity, SIPs are so strong that they are approved for use in Florida’s strict High Velocity Hurricane Zones (HVHZ) withstanding winds with an excess of 180mph. The load-bearing area of SIPs is equivalent to building with 2 x 10 framing at 16 inches on center, making them a great choice for hurricane-resistant construction.


By providing a complete set of plans, this takes away a lot of the guesswork allowing you to focus your attention and resources to other things. In addition, these plan sets are designed to meet all the necessary code requirements, so you can be confident that your ADU will be reliable and of high quality.

This is why having Pre-Engineered ADU Plan Sets is one of the 3 Innovative Factors that ADU.Works has. Though we build Low Cost ADUs, you can be assured that we make No Compromises on our build quality and materials. Rather, we continually strive to find innovative methods to reduce costs by making our processes as efficient as possible so we can help more homeowners in California increase their housing density and/or generate passive income.

If you’re interested in a quick but comprehensive demo, please don’t hesitate to book a consultation with us or give us a quick call through our number +1 (650) 227-4810. Our team looks forward to hearing from you.

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