I want to build an all metal, self-designed building. Are metal frame and joists really that infeasible?

Question

I have been putting together plans for my dream house. First an architect friend of mine said she might help, but right now she's got too much business and she hasn't even had time to look at a drawing. Then lumber prices were sky high and someone suggested I use metal. So I redrew my draft plans with metal in mind, but I keep finding a lack of information. Like span tables. They exist for wood, but I can barely find the math for calculating maximum deflections in metal. As soon as I run into any questions, I'm left in the dark.

So I took this to an engineer in town and he said that wood construction is standard. There are fixed tables and placements that you just need to look up in the code. It's easy precisely because you don't have to do any math. Engineering a metal building is tough and the spacings, etc. used for wood won't work because the dead loads are much heavier. I might overengineer the building to support massive loads, at higher cost, but I can't prove it without the math.

An interested engineer could do the math and give me a set of drawings, but the county building inspector won't know how to read them or what to do if we have to deviate in the least. I would have to take them to the state's steel engineering expert, along with the math, to get his approval. If I change anything, we are literally back to the drawing board.

I've started looking back at my wood drawings, but even then I wanted a steel beam to go over the 20' span in the kitchen and great room. I would definitely need 2x12x20s across those expanses and not all species of wood would be strong enough. Everywhere else, I could get by with 10' spans following the length of the house.

Now that I've looked at it, I'm actually more interested in steel and especially in its anti-rot, anti-bug, anti-water capabilities. Is this all completely hopeless or is there a way to finish the construction in steel? Where do I go to get the right kind of architect or engineer?

Answer 1

You're probably thinking of the wrong sort of metal

When most people think of "metal buildings", they think of I-beams, columns, and open-web joists, as found in large-scale construction. While these are used effectively in high-rises, big-boxes, and factory buildings where structural engineers can work everything out, precalculated span and loading charts for them are indeed harder to find (open-web K-joists have them, but you won't find anything of that ilk for I-beams or columns).

Instead, what you want are cold-formed steel joists and studs -- these are the steel equivalent of the dimensional lumber members you are familiar with, and thus have fully prescriptive design methods and span charts available for them.

This is even provided for in the IRC itself -- IRC R603 contains a simplified version of the AISI S230 prescriptive requirements linked above. (It's right next to the wood section!) Furthermore, the dead-loads for CFS are in many ways lighter than even wood, due to member shapes that use metal efficiently; you can even get cold-formed steel roof and floor trusses if you need more span than a CFS joist provides.

There are seven major differences that you need to be aware of with cold-formed steel light-frame construction, though:

1. Screws and a screwgun are to steel as nails and a nailgun are to wood, as you can't nail into a steel stud. This means that you not only need to screw your frame members to their mating counterparts, but you have to screw your sheathing, subflooring, and drywall to the studs and joists as well.
2. Since steel studs can be made in near-arbitrary lengths without compromising straightness, cold-formed steel structures are universally balloon framed; floor tracks are screwed to the inside of the studs, and if noncombustible sheathing is used, there's no need for fireblocking at the floor levels, either.
3. While you can use wood sheathing and subflooring (plywood or OSB) with cold-formed steel studs and joists, most cold-formed steel construction uses noncombustible structural sheathing boards instead. These can either be made of sheet steel laminated to gypsum sheathing (Sure-Board) or a special structural fiber-reinforced cement material (USG/StructoCrete, Armoroc); while the latter in particular are somewhat heavier than plywood or OSB, they maintain the rotproof, bugproof, and water-damage-resistant capabilities of the steel structure they're hung on.
4. Since steel is a far more effective conductor of heat (translation: thermal bridge) than wood is, steel structures generally rely far more on continuous exterior insulation than wood structures do. The good news is that you have all the same options for exterior insulation materials available to you as you do on a wood structure: foamboards provide a low-cost option that can double as structural sheathing and an air/vapor barrier, while mineral wool rigid insulation is waterproof and bugproof while being air-permeable and vapor open.
5. Cold-formed steel has absolutely 0 capacity to store moisture in it. This means that you need good water-resistive and air barriers at the outer sheathing, as well as proper flashing details at openings, or else that moisture will wind up in the form of a puddle in the bottom track or structural sill. While this isn't completely disastrous due to CFS being universally made from galvanized steel, it's something you're best off avoiding, just as in wood construction.
6. While steel won't burn if a fire gets into a cavity space, it will basically "cook" and lose strength when heated by fire, much like what happens if you stick it in a forge. As a result, you'll want to be quite fastidious about keeping combustible bits out of concealed spaces; this means that blocking and mounting members should be metal or other noncombustible materials, not wood, and you'll want to use armored or metal-clad cables for the electrical wiring instead of NM (this also avoids jacket damage risks with NM in steel stud openings). The use of cast-iron drainpipe instead of ABS or PVC completes this removal of combustibles from concealed bays, as water-filled piping is generally not an issue in a fire.
7. Finally, spanning longer distances with simple joists (vs. trusses) is far easier with steel than wood, as the joist makers have far more control over the product. Upgauging the steel to a thicker "wall" and using higher-strength steel (50ksi vs 33ksi) lets you do things, like span 20' with 12" deep joists, that would require transitioning out of dimensional lumber altogether in a wood-framed building.

Answer 2

There are loads of pre-designed steel building shells out there. Use one.

These are offered by commercial building companies for farm and industrial buildings. They have gotten a family of designs pre-approved, and they pre-manufacture all the required beam sections. You take one of their stock widths, and any length you want as long as it's a multiple of X feet. They can get pretty sophisticated, but all the engineering is pre-computed and pre-approved.

As long as you don't mess with the structural envelope, you can do anything you want inside it.

Answer 3

Background: My father was a structural engineer in the steel building industry and did exactly what you are asking for - calculate the statics of buildings and other large constructions, dimension struts, bolts and so on.

Is this all completely hopeless or is there a way to finish the construction in steel?

Yes, this is completely hopeless.

You will not, as a layperson, get this right.

Now hear me out. You may in fact, given enough time and money, be able to build a steel building. You might cobble some plan together and convince yourself in your CAD program that it should all be fine. But you have slim to zero chance to get it past the relevant authorities in whichever country you are living, and unless you also have nerves of steel, you might not last through the building phase before going crazy.

What you are describing (what that engineer told you) is spot on. This is exactly what you can expect, there is no way around it.

The problem is not only to get past "code", but also to dimension everything correctly in the first place. Engineers learn this for years (plus sometimes many additional years on the job to optimize the basics - mostly concerning more economic solutions).

If you are not going to build everything by hand yourself, you will probably also not be able to tell your building company what to do as you are not speaking their language (aside from the fact that you will not find a serious company doing this for you without an architect or engineer at your side).

For many parts, you can not economically do whatever dimensions you want, but you need to take stock material (i.e., types of beams, bolts, fastening constructions, whatever it is); that means that you need to know them and their properties intimately to be able to pick the best one, it's not just about finding the proper row in some table of "code".

When my father used to calculate such a building, the output would be dozens to hundreds of pages of paper, thinly printed with formulae, numbers, drawings; later in the computer area, there would be finite element calculations in there as well. You could expect a whole chapter just to describe a specific joint. These documents would then be sent to the authorities and they literally took them apart; everything that was not 100% watertight was sent back and had to be re-done, over and over until finished.

Even if your local code may make this easier for private homes, you still do not want your roof to come down on your kids, right?

Where do I go to get the right kind of architect or engineer?

In your area that would be called a "structural engineer", i.e. a person who does static analysis for a living. They do not generally work for or are particularly visible to private customers, but are mostly employees of larger companies and working in multifunctional teams, alongside architects and other engineering professions.

If you find an architect who does the design for you, they will take care of the engineering (by knowing or finding the correct engineers) and also will instruct and supervise the executing firm(s) properly.

So, get an architect.

Answer 4

Prefab metal shed.

These are popular and durable. They are used on farms and workyards everywhere. Many, many sizes and shapes are available. Quonset huts many decades old are still in service. If you want a metal building why not buy one from a company that makes and sells them. There will be people from the company available to help you put it up. There will be a standard way to assemble them. Then you can concentrate on creative aspects and not worry if the pieces you used are robust enough to do what you are asking of them.

Hopefully you don't have a neighborhood association.

Answer 5

It absolutely can be done! I don’t have the expertise, but my father did. He had a mechanical engineering degree and worked in construction of commercial buildings until he was able to begin his own construction company building metal buildings….. notably homes. I grew up filling screw holes and taping and bedding those CFS studded walls.

My father and step mother built their house with only themselves and family…. It took a long time and it has a combination of giant red steel I beams and CFS as the structure. I’ve always been proud of their house knowing we all had a hand in building it and it’s far more durable than the wooden houses that are mass produced around me.

Just wish he was still around to ask. Don’t give up. It can be done.

Answer 6

The only way to truly do something like this is to forget about steel. Has iron and rust. As well as stainless steel develop blotchy rust spots from acidic rain. Aluminum is a better alternative. But slightly more costly. Mixing of two metals can cause huge corrosion on both. So if using aluminum stick with aluminum screws but they break easily... Could do it out of copper but with exponentially more cost and it will turn green. But highly sanitary for its antibacterial emviromemt of the metal...but steel such as galvanize or even gold will turn your hands black after messing with it so long. Cleaning chemicals will be drastically different due to metal reactivate compare to certain chemicals... They made an aluminum car a delorean. They made aluminum rvs. An rv may just be the way to hi