Down the street (this is in New England) they’re building a commercial building out of steel studs. I can’t help myself but to look around whenever something’s being built – so I stopped in after hours and actually saw some plans laying tattered on the ground.
It looks like stores downstairs & possbily offices or apartments upstairs (just shows empty space with ‘cathedral’ ceilings) and I didn’t see any plumbing roughed in yet to make a more informed guess.
In the plans I see that they’re going to insulate between 12″ C-stud light gauge steel rafters with 10″ FG batts, with those styrofoam vent channels in the joist cavities at the overhangs where the seat height is less than full 10″. On top it’ll be plywood sheathing, 30# felt, cedar breather, cedar shingles. Underneath it’s calling for poly VB glued to underside of rafters. I have no idea what is going on with the mechanical system. It’ll have ridge & soffit vents, yada yada yada….
So what I’m curious about is whether this is a stupid roof system, or something fairly common. I’m sure nobody has an opinion…….
Any takers?
Replies
Studs don'tmake very good roof rafters. I use them to build walls.
Yer gonna catch hell for snooping around after hours. Do you go into the local bar and grille to check out the alcohol lewvel in the bottles, or are you out to learn something?
If this is my job, you wanna be coming to me directly with your questions and staying off the job. Too many people get hurt doing what you are doing. Ask the builder or architect direct.
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It all depends on what gauge the studs are, the span, the load they are carrying, and how they are secured and tied together. If all of these are within spec. it should work fine.
That being said it also adds up to a lot of variables. I've worked on three schools in the Dallas TX. area that were "hurricane proof". No stud lighter than 18ga; all perimeter walls 14 ga. Heavy duty screws, lots of welding, lots of blocking, lots of red iron purlons, double 14 ga. studs on all openings. The list went on and on and every single item and stud was personally inspected by the head architect who was REAL good at selling these schools to the local school boards.
What I'm trying to say is that all the individual components are just part of an overall system. It's this system that counts. Just reading some "discarded" blue prints is not going to give enough info. to give you this.
Lastly, I've got to agree with Piffin about being on a job site after it has shut down for the day. Although a few builders like Austin Construction, or Centex builders are safety conscientious, most are not. You would be amazed at the dangers of being on a job site entails. Open holes, dead falls, you name it and it is on a job site waiting to kill you. Also lots of stuff gets stolen or vandalized on job sites and if you are found on a job after it is shut down for the day you'll have to do a lot of explaining real fast or spend the night in the local lockup.
Hope this answers some of your questions. If you are looking for info. on this job just saunter on up to the job site, introduce yourself and ask for the GC. He's the man with the plans and the knowledge to work with them.
Cork in Chicago
Cork, you suppose SP was asking for a structural analysis or thoughts about the insulation/ventilation system with all the yada, yada, details?
The steel can be a thermal bridewge if not isolated in some way but I'm not looking at those plans to see how well that is detailed.
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All the yada yada probably means insulation and ventilation. What caught my eye was the "light gauge" studs.
Cork in Chicago
I see your point. I thought about calling it 'cold rolled' but decided that 'light gauge' might be a more familiar term.
Piffin,
I appreciate your $.02 regarding respect for the jobsite. I figured that'd come up in this venue - but old habits die hard. I don't make a habit of going inside other people's jobs without permission/a tour, but seeing drawings blowing around riled my curiousity.
Yup, my question is from a thermal/moisture standpoint. I'm going to watch & see how it goes. I just wonder if this 2nd floor area stays unfinished for a long time, basically visqueen for a ceiling, will it be looked back upon as a bad decision.
Likely to be leased out to be finished by the tenants, or finished to suit. Could have a suspened tiles office type ceiling with mechanicals hung between
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Seems that if the space is finished out, and the "attic space" is not kept above the dew point temp, it'll be a real mess - with the FG insulation up on the roof plane.