Mark Turnquest, CIPM
What Costs More? ICF over CMU
CMU also called Cinder Block or Concrete Block has enjoyed a significant shave of the commercial construction market for more than forty years.
The competition is not one ICF better than the other, the issue is ICF is better than CMU.
ICF is more manageable than CMU, installs are agile contrasting CMU and is by far more stronger and energy efficient than CMU.
In spite of the ICF value in comparison to CMU, one of the major area CMU beats ICF badly is market share! In lue of the CMU head start of many years, ICF continues to grow market share.
The delay in catching up is impeded by some perception among architects, engineers and general contractors that CMU is less expensive than ICF. Conversely, ICF is usually less expensive than CMU - not even including the energy cost payback data factored in.
According to the "Masonry Advisory Council" (USA), a typical installed CMU wall will cost around $9-$11 per sqft . It may seem that ICF install cost may be alot more than CMU. There are numerous reasons this thinking is deceptive.
Red Iron: The CMU contractor rarely includes any steel in his bid number. The red iron provider is usually responsible for the rebar, embeds and lintel steel.
These extra items are typically part of the red iron and not part of the CMU contractor bid. However, the CMU number is actually less than the real cost incurred, the CMU bid does not cover the real cost of building the wall. ICF is therefore greatly more competitive because it produces a reinforced monolithic concrete wall, replacing red-iron as well as CMU water proofing.
Water proofing is sometimes not included in the CMU number (contract amount) as well. It is about a $1 per square foot.
Sheetrock can be attached to most ICF system directly, while fur-out strips of some kind will be required to attach the Sheetrock to the CMU. The cost of these fur-outs are usually in the framers number and will almost certainly not be included in the CMU bid. These additional cost are often eliminated entirely by the ICF.
Fur-Out work - depending on complexity, can cost additional dollars per sqft if they are present. Even if the fur-outs are limited, these numbers still allow CMU to bid low because the CMU contractor does not include fur-outs in his bid.
Thermal Performance - Similarly, insulation cost are not included in block masons bids. CMU construction cannot approach the thermal performance of ICF. Any significant effort to improve thermal performance of CMU to approach that of ICF will drive the cost up.
The strength and weight of monolithic concrete is approximately twice that of CMU. If an architect wants a CMU wall with the strength similar to monolithic concrete, he would consider adding perimeter red-iron column to make the wall stronger and support the roof trusses.
A rule of thumb for the installed cost of red-iron is $2 per pound. Thus, if a 10ft column weighs 20lbs p/ft, it will cost about (10x20x2) or $400 labour and materials to install. Since these columns are often not required for an ICF wall this will always mean that the ICF wins again.
Many general contractors will be concerned about the speed of construction and the impact of other trades. The skills of an ICF installation crew shows that ICF is usually about twice as fast with half the crew when compared to CMU construction.
Trades such as electricians and plumbers would note the advantages of ICF that ICF is generally easier to work with than CMU.
When it comes to making a decision between faster, more efficient, stronger, more flexible and less expensive wall, it is clear there is no comparison between a CMU and an ICF wall.