I’m curious if anyone has any experience with building an addition within a steel skeleton. I’m thinking about a 2 story 24′ square addition with flat rubber roof. I was looking at a CVS store’s frame being put up in a town nearby and thought it would be a nice alternative- no load bearing walls, I could have a set of tube columns and I-beams spec’d, and have it bolted together on my foundation, then fill in wood framed panels.
I like the existing cape’s curb appeal and am trying to keep that look the way it is without a new roof popping up behind it. I also like the look of a few mill buildings in town and am trying to go with a mill building look for this new addition.
Edited 12/17/2006 11:54 am ET by byrnsie
Replies
2 words.
Sub- it-out.
See? the problem?
Spheramid Enterprises Architectural Woodworks
I have irriatable Vowel syndrome.
I don't see subbing out the assembly of a very small frame a problem.
Oh, you are serious. Bar joist and steel decking. Or precast hiway slabs will work.
Spheramid Enterprises Architectural Woodworks
I have irriatable Vowel syndrome.
Byrnsie,
That is not a flat roof you are are looking at. All roofs are pitched towards a scupper or drain. Most commercial buildings have a parapet wall that conceals the pitch and any roof top mechanical equipment.
Why a flat roof?
Chuck S
live, work, build, ...better with wood
the house currently has a flat roof that I think is the best on house. It is the most energy efficient as there isn't a giant mass of air volume above the heated or cooled space below. I realize the roof needs a slight pitch but I can get that from the wood framing I'd do or ridgid insulation panels are even made in wedge formation to shed water being another possible way.
Cha-ching.....
You'd spend more in engineering and upsizing your footings for the point loads than you would to frame the whole addition in wood. 24' isn't too big of a span for composites/engineered lumber/trusses these days.
Bob
my thinking is that I can't be the first person to do this- someone out there must have done this. The eingineering seems pretty simple and I'll still have to do it if I use LVL's only they'll be long, sloppy and very tall at 24'-0. I'd also have basically the same point loads if I use LVL's.
Edited 12/17/2006 11:55 am ET by byrnsie
The 2000 IRC has tables and connection details for structural steel framing.I have not been through the details, so I am not going to give any ideas of how easy/hard it is.Structural steel framing is one of those things that becomes "popular" everytime the price of wood goes up. But then either steel prices rise or the lumber prices fall and interest is lost again..
.
Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Thanks Bill- the box I saw assembled had simple bolting flanges welded to the structural square tubes, the I-beams were drilled and bolted to them.
>> Structural steel framing is one of those things that becomes "popular" everytime the price of wood goes up. But then either steel prices rise or the lumber prices fall and interest is lost again. <<
For now and here, steel prices are up and lumber prices are down.
I guess I don't really understand what you're asking.
But a couple things do come to mind:
1. Just because you can, doesn't mean you should.
2. If you are planning on doing it yourself, then knock yourself out. As long as it meets code you can build it out of peanut shells and rubber bands if it tickles you.
3. If you are planning on subbing it out... I'd stick with conventional methods that most available trades will be familiar with. As it is you're already adding at least one additional sub to the mix by using the steel. Conventional methods will usually get you better pricing from subs. And you're going to need it as a homeowner/GC.
4. Steel ain't cheap these days.
5. If your motivation is simply to avoid perimeter footings, or a foundation, or a slab and just go with piers, please realize that this doesn't mean you're limited to working with steel. Part of a house I just finished framing had a 22' x 18' 'bumpout' on the back of the home that was constructed on piers. The perimeter was all lvl beam work and the outboard end of this thing was a half-octagon..... so working with LVL's isn't quite as "sloppy" as you think it is. It was really quite simple in fact.
6. "Flat" (none of them should truly be flat) roofs are framed in wood all the time. Personally, I feel that that flat roofs on residential homes should only be used in design as a last resort where nothing else will work. But that's just me.
Thanks Diesel,
My real motivation here is to have a rock solid frame to lay a super simple wood structure on and between. I saw the CVS structure in place- a simple bolt together kit that I see steel contractors put up everyday. It's just that a tiny version like this would seem like a super fast job for a guy that puts up huge big box stores every day. I would find a sub that does this to do it and it seems to me there are lots of guys out there that assemble these things everyday.
My question is: is there someone out there who has done a steel super structure in a residential application. Is it worth it? Drawbacks? Tips? I've installed steel i-beams in a carriage house from 1900 recently, supported with 4X4 structural tubes and wondered why we never do an entire super structure with them.
I saw the CVS structure in place- a simple bolt together kit that I see steel contractors put up everyday
Ah, there's the rub.
That "simple" structure is engineered, and just about every AHJ wants a local engineer to wet stamp the drawings first. Then the drawings go down to the steel supplier by way of the GC for the job. The steel man then (typically) fabricates the steel to order. The fab is then put on a flatbed and trucked to the job site. Once there, it can look like a "kit," but is almost always run off on a per-job basis.
None of which means you cannot use an engineered metal frame for a residential addition.
Just that the steel fabricator doesn't exaclty have a pile of parts for W x Y x T box frame laying about (and in some cases, if they do, get a different fabricator--you do not want to know why the steel was returned, trust me).
Now, to your original post/idea--the trickiest part about what you want to do is in the transition from old to new. While that's not a 'new' worry with addition/remodel work; in this case, instead of a 16" OC wall butting the existing structure, you could have 3-4' from the new column to the old building to "span" to. Ok, not rocket surgery, but definitely a good thing to detail in advance, as opposed to when every trade and the BI are all stopped to sketch out an answer on some scrap plywood.
Now, for probably about the same effort, you could timber frame the addition in the same fashion as you are suggesting using metal (which might have gotten a bit less static here, or not).Occupational hazard of my occupation not being around (sorry Bubba)
I'm using the term "kit" as a complete set of assembleable parts- I know I can't find this building's frame sitting on a shelf somewhere. It is going to require eingineering and I have been to a steel fabrication shop where they do this, I'm just hoping to get some good ideas and experience someone here may already have.
I drove by the CVS frame tonight- it's on to the carpentry stage- the 2X nailers are in place and the trusses are getting attached. I was just hoping someone would jump in and say- I did that it was....
I've never built a whole house where steel wasn't a part of the structural frame. The last one we did had a package that included eleven heavy members, each of which required a crane to set.
They all had to integrate in some way with the adjacent wood framing, and the fab plant detailed everything as specified with holes, flanges, clips, and baseplates.
I really enjoy working with structural steel, partly because it was my concentration when getting my engineering degree, partly because working in the biz helped pay tuition bills, and mostly because I am a pre-fab-aholic . . . I get a kick out of a preengineered package that goes together quickly, wood or steel.
My advice is to do what you want, structure-wise, but cost it out both with some steel, and also with timbers and steel connectors, to see what is most cost-effective.
Your complete cost analysis must include field work, which might be a whole lot less for the steel package. Hanging, pinning, and bolting up a steel frame can typically take a whole lot less time than when doing it in wood.
was just hoping someone would jump in and say- I did that it was....
Which may be the tough part, it's not a common procedure. I've worked with metal in light commercial; both mixed red iron and galv. studs, and all galvanized construction--both have their plusses and minsuses. I've worked with "pole" construction for barns and farm structures, too.
Just never did any as add-on remodel work.Occupational hazard of my occupation not being around (sorry Bubba)
The last house I built had 13 steel I-beams. It was mostly conventionally framed, but the design necessitated lots of steel and LVL's. It was tricky to figure out all the connections and best order to assemble things, but looking back it wasn't so bad.
A super-simple structure like you want could be easy to put up, but like the other guys have said it only makes financial sense if you need the clear span. I do like the industrial/loft look though, so I can see using steel and exposing the structure just for aesthetic reasons. Stress skin panels go well with timber frames; I don't see why they wouldn't make sense on a steel frame.
thanks Woodguy- you're reinforcing my idea. 13 i-beams in a house seems like alot. were they possibly partly along a wall with alot of tall windows or allowing clear spans? I'm wondering why your house used so much steel. Were they bolted or welded in place- supported by tubes? At 13 I-beams it sounds like you might be talking about a superstructure.
It was a big house, designed to look cottagy on the outside but with big, open rooms on the inside, including the basement. It was also a "fast tracked" design job, so the architect was always just one step ahead of us on the design end.
All the connections were bolted, with specialized plates welded to W-beams at the steel shop. Posts were a mix of 3 1/2" and 4" round steel tube and 6x6 LVL posts.
It was by far the most complicated project I've worked on. Your simple steel skeleton sounds like a dream in comparison.
It sounds like you did the assembly of the steel yourself- or did you hire a steel erector? I'm begining to think a compromise may be the way to go- steel for the center only, joists and rafters bridging to walls at both ends from the middle I-beams, but I'm still not convinced it doesn't make sense to do a superstructure.
Today I'm working in an 8 year old house doing the basement and I can just see the pressure on the the (3)2X12 carry beams- this is my motivation. And this is a pretty well-built house. I figure with steel that kind of thing is something you'd never worry about.
Thanks for the info. Anything else you think of would be appreciated.
I work on a carpentry crew--we had an excavator set the biggest beams, one about 2500 lbs, and genie lifts (hand-cranked forklifts) for the others. An architect designed the house, an engineer spec'd the beam sizes and connection details, and I drew everything up in Autocad to make sure all the puzzle pieces would fit.
Steel can definately be a great material to work with, and the more I work with it the less afraid of it I am. There is nothing magic about it though. If you can see the pressure on your (3) 2x12 beam then maybe it was undersized, and additional 2x stock, additional posts, or LVL's would have made a difference?
Good luck!
Mike Maines
Thanks Mike- I wasn't thinking of the excavator being useful. Now you have me thinking of having him set the main beam while on the backfill visit. It would help support the walls. I'd love to see the autocad details of the connections if there's any possiblity.
Edited 12/20/2006 11:10 pm ET by byrnsie
Check with a steel/metal building company that engineers it's own product. Basically the sheet metal skin isn't really structural, you may find one who would engineer a frame and roof, and erect it. Leaving you to sheath it with plywood or whatever is architecturally pleasing to you.
Big mistake, very big mistake. The sheet metal skin is absolutely structural. In an efficient metal building the sheet metal braces the secondary structural (i.e. girts, purlins, and eave struts), and the secondaries brace the primaries (beams, rafter beams, and columns). Remove or reduce any one and the structure MAY be subject to catastrophic collapse. If the unbraced length of any member is increased then that member must be reinforced.
Jim Hannah (almost 14 years in the metal building business)
Jim, isn't the skin acting in shear, and couldn't T1-11, or CDX plywood in some thickness achieve the same strengths? All of the frames I have seen, the frame is statically determinate.
I'm wondering what glass does for that effect when it's the curtain wall!
The metal skin could be a shear membrane if it is stiff enough and fastened often enough around the perimeter. In the size structure being discussed T-11 or cdx would probably work just fine especially if it can be continuous over several secondaries. Note the metal panel is usually base to eave and eave to ridge as one panel each, with 5' to 8' secondary spacing. Where as the plywood panels are on 16" to 24" centers.
The size of building I normally work on; the panel serves mainly to brace the secondaries (girts, eave struts, and purlins) and provides very little shear capacity, as there are not enough fasteners around the edges and across the secondaries to provide shear capacity. There is an entire bracing system of rods and struts to provide bracing that is independent of the panel. In post frame buildings the metal or plywood panel does act in shear.
On your second point, if the frame is a three hinge arch frame it could be determinate but if it is a rigid frame with moment connections then it is statically indeterminate and needs a stiffness matrix and finite difference iterations to solve of the forces and deflections.
H T H; Jim
thanks for that tidbit- I actually was reading your comment going "wow- I never even mentioned sheet metal skin- where is this going"- but really that's something I wouldn't have thought of. We have Space Metal Building here, I'm going to visit thier site. Ironically I've gone to them years ago to buy their galvanized painted panels and I never thought of the opposite. Thanks alot.
If you pursue this I would recommend you have an engineer detail out all the connections and sizes for you .
I don't know about residential steel frames but on the commercial jobs it is done this way .
Engineer sizes out beams, posts, connection details. Engineer's plans are turned over to a steel detailer (A specialized drafts person) who draws up shop drawings ( which the arch./engineer/G.C. review) for the fabricator.
Detailers plans will give all the dimensions/weld sizes/ bolt lengths etc. for every item that has to be dealt with on the beams or posts so the fab shop can manufacture them according to the code.
Fab shop fabricates the pieces and everything is then turned over to the erectors.
Last job I supered was relatively of small size for commercial work and had 21 pgs. of drawings just for the steel components. Done right everything fits perfectly, miss something (or have something happen like having the concrete not be poured exactly to plans, or anchor bolts not placed precisely) and it can be a real pain .
Thanks to everyone contributing here! I appreciate all the advice- I figured if I could even get just a couple of tips it was worth the inquiry here and I got more!
I appreciate everyone's warning that I need engineering for this- I wouldn't do it without. My plan is to adapt plans I have which are stamped, and adapt to my use, then of course I'll have an engineer recheck and certify those plans.
I'm still hoping someone will see this thread and a buzzer will go off. I know there alot of guys posting here that have been on really unique projects that must have built an addition within a steel superstructure.
it is simple... but with the cost of steel I'm not sure if it's cheaper now... all you have to do is call or ck the web for someone who makes steel buildings... they sell the frame only all the time or will build you a frame to your specs... or most of the demo guys arounf here always take apart the metal buildings they are removing and will sell the frame...
p
There are details you should keep in mind if you are going to put a steel frame. One of which is thermal-breaks. If you are going to butt wood up to steel, for example, you'll need a separation to combat moisture/condensation.
Another is pipe/wire routing. If anything is going to be routed around the perimeter walls, you'll have to punch the column or move the walls in so wire can run past the steel.
You'll also want to have subs (electrical,plumbing, HVAC) that are familiar with steel construction and how to hang stuff off of members..
In essence you are building a small commercial project and you'll need archys and subs who are familiar with this type of work..
Are you saying it's not okay to fasten a wood 2X on top of an I-beam to be a nailer for the joists and rafters? I was thinking of spray on insulation to seperate the frame from outside temps and central AC to dry the building to the inside.
It's okay to mate the two materials. There just has to be some sort of barrier between them, like Tyvek, or something...
24' x 24' with no load bearing walls.
why do you need a steel frame to accomplish this ?
a 24' span can be done with wood I joists.
at a tremendous savings over steel.
it sounds like a neat idea, but when you go to price it, the steel will open your eyes.
and then all the details get more complicated with a steel structure.
attachments, steel sizing not aligning with wood sizing, difficulty insulating. on an on.
carpenter in transition