If you have codes in your area, before making any decisions on material types, make sure you will be allowed to use them, otherwise it's time wasted and you'll be back to the drawing board. An example would be,in our area, that drywall has to be used with one tape coat before covering with other material types.

With metal sidings,depending on your locale, you might want to consider the heat gain you will be getting in the warmer months making it less efficient to cool your house.Your wall system can be designed to combat this gain when using metal panels.The heaviest gauge i've seen offered out here for residential is 26 gauge that we used on an outbuilding for the roof.23 gauge is consideribly heavier and i was happy with the 26.

Money well spent would be to incorporate an indoor air purifying system. Do your reserach before making any final decisions and keep an open mind to what might not be allowed in your area.

I believe almost all codes require a specific fire/vapor/sound rating, as opposed to a specific material. I'm not arguing, just finding it very odd that drywall would be required, when something like plaster would do the same. There are a variety of finish materials available for walls; everything from plaster or even clay to various gypsum and wood products.

As for the steel; I don't think you're really referring to steel siding as much as you are to the steel framework; and yes, it is available. A number of companies make steel structural studs, bents, kits, etc.....like ICF or SIP homes, they aren't as popular, but certainly are fairly commonly available.

OK- I could do the plaster interior walls, but the plaster has to adhere to something- I can only think of drywall, or wood board, both can be condusive to mold. I am trying to figure out what might be available for an interior wall that will not be able to mold- the asthma thing... I have thought of concrete block wall, but how would I insulate?- Have the metal outer wall, some sort of insulation in the middle, then concrete clock on the interior? I know someone who did build with a very heavy.commercial metal, but won't be able to get in touch with him until this winter to ask where he got it. I believe I am supposed to have a 1 inch spacer between the exterior metal wall and the insulation for the condensation to be able to evaporate. In most counties-rural, in Texas, you can use metal exterior. I am just trying to figure out the interior walls. Do any of you know where to find commercial grade products- they are heavier than residential.

Hold on. Drywall is a slightly better contributor to mold, but really; mold is caused by bad construction, not a specific material. Just about ANY material can hold mold; so you really should be focusing on the QUALITY of construction.

And they make mold-resistant drywalls....they even have names like "Mold Guard".

Do you have a designer or architect you're working with? I'm not trying to be offensive....really.....but your questions relate more to the 'idea' of certain materials being bad or something, rather than the fact; ANY material can support or encourage or discourage mold growth....ANY product can be installed so that it functions really well, or not that well. It's about quality, not about the material.

Let's keep this conversation going; I'm not trying to be offensive, but I'm seeing some ideas her (e.g., that drywall = mold), that ARE NOT true.

Your not being offensive! Your helping! I did not know that there were mold resistant drywall- if that is the fact, maybe it wouldn't be so bad to have it. I am aware of the allergy resistant insulation- by Johns Manville is one of the brands- I imagine there are others. Right now I am in Wyoming, where metal buildings are common, but we are dry here- maybe with the high humidity in Texas it might not be the best idea. I have a friend who has a metal apartment in his barn, but it is not insulated, so there is not a condensation problem. I am trying to go with solid materials, as they are better for asthma. For those of you who build- if there is an air space between exterior wall and insulation, with air movement such as an exhaust fan in the attic, would that suffice, do you think? I am not worried about heat gain, because if you have enough insulation, and appropriately faced east/west. north/south, large overhangs, it should not be a problem. Morton Buildings does homes/barns all over the US. (I am talking about building in the rural areas. Talking to them, it should not be a problem- of course they promote their buildings. I have found a couple other metal home sites- I want to do my own, but get info from others. I want to talk to some of their customers. Any ideas for building for asthma is appreciated!

To address the title of this thread, start with a search on google for "gage galvalume" and see how many different returns you get. I did a search on "20 gage galvalume" and had numerous hits.

I'm like Jason, though. I'm not sure if you're looking to build a metal home or if you're looking to build an asthma-proof home, and likely don't have any useful input in that regard anyhow.

To address the gap between the siding and the insulation, though... I'm guessing the metal siding is fastened to "nailers". Since you have horizontal nailers spaced 2' apart, there's likely going to be a gap between the insulation and the metal itself, especially if there's a rigid insulation installed. One way to eliminate that gap would be with spray foam insulation, but I have no idea what that would do to your asthma.

You might also search on "foam core panels", or something of the like, to maybe kill 2 birds with one stone. (Insulation and a more rigid metal wall.)

http://www.healthgoods.com/Education/Healthy_Home_Information/Building_Design_and_Construction/foam_core_panels.htm

Here is a link that might be useful: link

You may want to look into the Green Building Iniative. Many new neighborhoods in our area are going green. This can reduce off gassing, mold, etc. in addition to being energy efficient and less wasteful than some other building materials and methods.

Hope this helps.
Cameron

Here is a link that might be useful: GBI

Thanks guys- I will look with the info you gave me. Bungeeii- I want to kill two birds with one stone- I want a metal home because I won't have a problem with bugs eating wood frame (what a mess in Florida- I fed alot of bugs with my house), and with building with metal, there will be less to trigger an asthma attack. Also minimal maintainence- I broke my neck a few years ago, so I need as little as possible to maintain. I'll get to work searching your recommended sites!!