INSULATED CONCRETE FORMS
COST:
Stick wall will cost $4.00 to $8.00 per square foot, not
including vapor barrier, insulation, or house wrap, which is
unnecessary for ICF.
For the formwork, the cheapest ICF I could buy was right at
$20/block, or about $3.45/s.f., average was probably closer to
$3.55, not including tax.
Now if you count one horizontal rebar/course, and one every 16"
vertical (way over code) but typical around here, you are looking
at just under 10 lin.ft. of rebar for every block, or about
$4.00.
One cubic meter of concrete will fill between nine and eleven 6"
core blocks.
At today’s prices about $140.00/cu.m. for concrete, or about
$2.60/s.f. for 6" core.
This puts us right at $5.75/s.f. for 8" core block and
$5.25/s.f. for 6" core block. Please note that this is wall
material only, and doesn't include window or door bucks (I used PT
wood for my project - VBuck is easier but pricey), bracing rental,
concrete pump (this is not a cheap unit), and concrete vibrator
rental, and this is all with free technical assistance. If you can
do ICF walls for $6/s.f. DIY, you are doing very well.
The common misconception is that the bracing reinforces the wall
to protect against blowouts, etc. This was probably true at one
time (all ICF is so stout now that bracing is probably unnecessary
to prevent blowouts as long as you don't use short pieces near the
bottom of a lift), but now the bracing is so you end up with a
straight plumb wall, and have a place to stand when pumping the
concrete. If you have to rent scaffolding to fill the walls, you
might as well rent ICF bracing as it is a lot easier to use.
They claim the blocks are strong enough to frame your first
floor, so you could use this as your first floor scaffolding. Many
of the ICF block installers started out trying just this, and if
you go to kerryteri.com this is exactly what he did for his
basement pour. However, a local guy did this DIY (decided he could
purchase a lot of lumber for the cost of bracing rental) for his
basement and swore he would never do it again - for his first floor
he rented the bracing and went without incident.
If you talk to very many professionals doing this, they will
universally recommend getting the bracing.
You can buy block-loc that goes in the interior of ICF that
serves the same purpose - it just doesn't work as well as bracing
and it won't keep your walls straight.
Another apparent savings is time savings because the walls go up
quickly when you are using big panels. This is another hollow
benefit, as with stacking and gluing ICF block the walls go up very
quickly.
My entire basement stacked, glued, and with internal rebar went
up in one day, with a crew of three experienced people. My point is
that stacking block is very quick, it is the rest of the stuff that
takes time.
The next question I would ask is how do you install the interior
and exterior finish system? With a normal ICF, the webs are located
every 6-8" and have good screw holding power (part of the reason
they are so strong now). With the 12" widths, the metal studs serve
this same purpose. The key is to look at the corners, how close is
a metal piece to screw exterior finish in to? This looks like at
least a couple of feet. This makes it difficult if you wish to
install siding, and you must compensate for this.
I would stick with tried, true, and locally available. What
happens if you underestimated and you need another pallet of block?
If you purchase too much can you return it for a refund? If you run
into a snag, how quickly can you get technical assistance? Since
you are purchasing remotely, do you need to purchase your entire
order at once? Can you phase your deliveries, or do you have enough
storage space that this isn't an issue?
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