Hi all – This week has been a revelation for me here. I thought SIPs were all OSB and EPS – I had never heard of MgO or steel SIPs until now, or that anyone was using polyurethane foam. Some questions: So MgO SIPs are load-bearing? How does that work? Isn't MgO a drywall alternative? I've never touched or seen it in real life, but I assumed it was like a plaster. With MgO SIPs, what material is doing the load-bearing work? As for steel, I'm stumped by what form they usually take. For home construction, are steel SIPs typically fully covered by steel sheets, or do they have steel studs spaced like normal studs? I saw one with steel sheets that uses 26 gauge sheet. That isn't thick enough to satisfy Hardie or Nichiha requirements for steel frame attachment, so how are people attaching siding to these sort of SIPs? Thanks.

The two steel sheets fully cover the EPS, polyurethane, etc. core, except for the ends and edges. The steel skins are usually galvanized (G-40 or better, such as G-90 for coastal use). The bending of the steel sheets plus the insulating core gives it the strength to be used for floors, walls and roof. Tongue and groove edges also add to its strength. Each SIP brand may have its own unique shape. Steel studs are not needed for this type of SIP. Most Steel SIPs can be left exposed as the final finish. Siding can be installed if desired. Stitch screws (short screws closely spaced into only one skin) may be needed to attach furring strips if the siding is heavy. Furring strips can be spaced to meet requirements of the siding while creating an air space and drainage plane. Brick can be attached with the usual clips. To be safe, check with the steel SIP manufacturer about how to attach heavy siding, etc. to the thin steel skins.

All claddings can be applied to the Permatherm steel SIP panels
no furring is required ,
my own personal house has hardi lap siding front and rear with 3/4" cementitious stucco over paper backed wire lath on both side

Chris, Great to hear from you. My wife and I met you several years ago at a trade show in Orlando.

There are many types of MGO and the quality of the magnesia cement board, the SIP connection details and other greatly affect the bearing capacity of a SIP. We manufacture the "Innova Panel" with is a Patented load bearing, impact rated panel that has been Miami Dade NOA approved for use in the high Velocity hurricane wind zones, +200 mph. We do not cut window openings into our panels, instead following masonry principles using header panels, fully developed window and door bucks and other structural detail improvements to common SIP system details. These changes were required in order to develop the panel strength required to pass the impact and wind load testing required for high velocity wind zone certification. SIPs are great in compressive loading, similar to masonry, but like masonry, require structural members for tie downs required to resist uplift loads. Our Miami Dade NOA approved panel has a compressive loading capacity of +27,000 pounds for a 4' x 10' using our approved SIP building system details. A quality magnesia cement board is much stronger than a Hardie or Niche board. Hardie and Niche have low nail and screw pullout ratings, a quality MGO board will be near or more than 400 psi. The screw pullout testing on our impact rated panel is +900 psi and you can use nails guns with ring shank nails. Magnesia cement board is cut with the same blade as plywood, Hardie and Niche require expensive Diablo blades. Most steel panels are actually not a true SIP as they are not compressive load bearing panels without a second structure. Steel panel resist wind loads, but most have low compressive strength on their own. I have used steel panels for commercial projects and they are great for many uses and can provide a finish exterior. They do have more movement with temperature changes than OSB or MGO, but this is generally addressed in the design so as not to be an issue. I think both panels are tools in the box for the designer and have both have their specific benefits and sweetspot when used correctly.

Does PermaThermSips.com have a website, Chris? I'd like to know more about Permathermsips. Best, S

I'm interested in learning more about InnovaPanel as I will be building a duplex in Los Angeles and would like to look at a steel stip. I tried to visit the website but got a warning that it is not certified as safe for browsing. Can you assist? Thanks! Scott