Although any SIP construction will save 50 – 60% in energy costs, are 3 times stronger than frame, and are more environmentally friendly. Steel is a better choice for the following reasons

Advantages of Steel SIPs vs.OSB

v  Steel will not warp, swell, twist, rot

v  Rain during construction do not affect materials in any way

v  No cranes needed for installation a steel SIPs are lighter than OSB

v  The underside of the roof panel automatically forms an attractive finished soffit overhang or exterior porch ceiling.

v  Joints are a T&G friction fit they do not require splines, mastic or fasteners greatly speeding installation time

v  Steel is more stable during manufacturing and panels are held to 1/16” tolerance

v  OSB is limited to 24ft. in length …Steel SIPs are available up to 53ft. in length, eliminating butt joints

v  Steel panels are manufactured on a continuous line making them available in square pre-cut lengths in  ¼ ” increments, but only charged to the nearest  ½ ft., OSB often rounds up to the nearest 2 ft. increment – making you pay for waste that gets thrown away

v  Higher ” R – Value” denser foam provides a 4.25 R- value per inch of foam

v  No Termites … Impervious to termites and carpenter ants , foam core is borate treated

v  No foam grooving is required for window and door openings, after cutouts are made, openings are simply “picture framed” with 18.ga. steel channels

v  The steel skin is the “vapor barrier” on walls no additional covering is required before siding is applied

v  Eave overhangs can be 4 feet with no additional support

v  Sound Control – utilizing a 1-1/2” steel furring strip creates a dead air space for improved STC ratings.

v  Wiring – utilizing that same air space, wiring is much easier than fishing wire thru OSB and any future retrofit wiring is easier.

v  Will not support mold growth – painted galvalume steel skins are UDSA approved

v  Indoor air quality is better due to the tighter and cleaner construction material of the interior

v  Any steel building is safer from lightning strikes

v  “Monocoque construction” All connections and attachments are with screws having greater pullout strength than nailing

v  For economy or insulated utility buildings, steel SIPs have been left exposed as the finished siding and roofing.

v  Zurich Ins. In partnership with the Steel Framing Alliance offer reduced builders risk insurance premiums

v  In Florida and other hurricane prone regions Steel SIPs are 30% less to insure that block/truss and  53% less to insure than wood frame construction

Stan,

If I understand the problem, from your description the beams are going to still be exposed and the 2" pine is on top of the beams presumably as the decor of the ceiling.  If this is so then your only option would be to place the sip panels directly onto the beams and then put your decking that is the ceiling, between the beams hiding the sip roof.  This allows you the ability to get at the underneath side of the Sip panels to apply the fasteners.

However if this is to be an almost flat roof, aren’t you opening yourself up to future problems with the OSB.  If water has any opportunity to sit, or if something gets up on the roof and allows the water to pool at all for any length of time it will eventually find a way to the under decking.  I live in FL the land of flat roofs and I don't know why they are so popular.  I haven't seen one that didn’t develop a leak at some point.  This would be another reason why steel sips are you best option.  But I am not trying to sell you anything as was assumed by a previous poster,  I don't work for any company, I am just an owner builder who has had the luxury of working with both types of sips and love the whole idea of building with them over anything conventional.