Friday, January 28, 2011

Aluminum Foundation, Steel Foundation for Residential Construction

So lets start figuring out these metal foundations for basements applications:

This is actually a wood foundation clad with a thick layer of galvanized steel.  There would be a poured concrete base.  Then the actual foundaiton would be a wood stud structure, double-shelled, filled with insulation.  Then towards the outside, there would be an air space of about 1.5 inches created with something like Unistrut, though I prefer something cheaper (unistrut is so expensive).
then the galv steel cladding.  We're talking about 11 gauge (0.120 inches thick), welded or screwed (that would be annoying) to the unistrut from the outside.  Stich welded between panels.  Zinc oxide gases coming off everywhere fromo the welding, - gas masks for the welders -
I got a price on the galv steel sheet from North York Iron - $107.25/sheet (thats $.67/lb), 37 sheets (148ft perimeter on my building).  This is for a total cost for the sheets of $3968.  The sheets are heavy, 160lbs each, so not fun to handle - maybe some kind of small crane....But this way, one could make a very thin, and durable exterior shell for a building without suffering the 8 or 10 inches of concrete, probably for a competitive price.  The total shell thickness including the airspace can be about 2" or less.  On ecan get another 6" of insulation in the same space as for a concrete foundation.  The steel can be sprayed and a dimpled poly membrane installed just like a concrete foundation - for better corrosion resistance, though I've found galvanzied steel (doesn't have to be hot-dipped) holds up well.  No poisonous pressure-treated lumber involved, and carbon footprint could be similar or better than the poured concrete.  Thermal expansion co-efficient of the steel is similar to concrete, so not an issue.

Now:  Aluminum foundation:  Same idea as the steel, but no corrosion issue, unless you have a very salty and wet soil....Using the same 1/8" thick sheets, the weight of each sheet will only be about 53lb.  Lighter than a sheet of fiber-cement or drywall - much thinner, of course.  I would not weld these in place, I would use aluminum brazing, although corrosion-resistance of the braze would need to be checked.  This way, the foundation would be sealed entirely, and fastened well at the same time.  I would skip the dimpled membrane and spray.  Apparently the price of Aluminum is about $.65/lb - at this price we are looking about $35/sheet of 4'x8' - cheaper than 3/4" S1S fir plywood!
At first I thought thermal expansion would be an issue, but note that the ground temperatures are pretty stable - fluctuating only some 10 degrees C or so throughout the year.  But thermal conductivity of Al being so high, one might start to wonder if the ground around the foundation would get quite cold, even at the bottom - Hello Therm simulation.


  1. Aluminum and steel have been the primary support of our houses, and they are used in different areas of the house. Some people prefer to use steel while others prefer aluminum. Whatever the preference, it is safe to say that both of them will provide you and your house a good foundation, if properly used. There's no need for much debate; they have the same function.

  2. Thanks for your comment, Lawrence.
    I'm not clear what you are referring to. Some links to what you mean would be useful. I've never seen a wood foundation clad in metal.