Hello all. I am re-designing a commercial structure that was originally designed for CMU. The builder and owner appreciate the long term benefits of ICF, but have concern as to how long the construction process will take. Are there any ICF installers out there that previously came from a CMU background? If so, I need some selling points and specific instances that make ICF construction more friendly than CMU for the contractor. How much time can they expect to save by using ICF? Do you have any real world for instances where you built an ICF building while one of the same size and type was being built simultaneously with CMU, and what were the results? Your advise and experience is greatly appreciated.

-JW

What is your location?

I ask because in California CMU's must be built no more then 4' high then grout filled, then another 4' and fill again...all the way to the top. ICF's can be built to any height and poured that is acceptable to the engineer, generally 12' is the rule of thumb. Advantage number 2 is once built and poured it is already insulated saving you the time of furring or straping the CMU walls for insulation and then insulating after all the mechanicals are completed. Advantage number 3 assuming this is a commercial location such as storage area and what have you...how many times have you seen large crater size holes in drywall between studs/furring from someone running a skid of product or backing a forklift into a wall, with ICF the wall below the drywall is firm, drywall will be damaged but no gapping holes and this also cuts back on rodents living in the walls

As for speed...well that all depends on who is doing the job

We have built ICF perimeter walls with CMU crews on the same job. One was on a school job, where we had more wall footage with window openings (4 sides of the building) whereas the CMU had to only do the length of the building twice, for interior hallway.

Our crew of six ran circles around them, the schedule was held up because they were "too slow" according to the superintendent. Actually they did great work and I am kindof sorry we made them look slow. They had close to 20 people tending and stacking and grouting the block, with an operator and lift running full time, also 4 electricians running conduit and boxes.

I worked on a storage facility where we built 3 of their storage buildings with ICF for climate control while the others were being built with CMU. On the first building, we had a 3 man crew putting up a building right next to a crew putting up a CMU with 10 or more workers. When we showed up, they were close to shin level. In three days we were finished with the block and braced- ready for pour while they had poured thier first four feet the day before and were starting to stack for thier next lift.

Chris mentioned one advantage ICF has over CMU is that with CMU's you have to pour every 4 feet, where as with ICF you can pour up to 12 feet, which helps keep your production going and saves you the cost of having to pay your pumper to come more than one time. On some jobs we had there would be an inspector who has never seen ICF's before that has a CMU mentality that won't let us pour from 10 feet. So we had to cut holes about 4 rows high every other cell to stick the hose and vibrator in, brought the concrete up to about 3 and a half rows, put the foam piece that was cut out back in place with a cleet over it to keep it in place, and then pour the rest from the top, which can be easily done in the same day. Some times we would do that where we were not required to but knew it would be better for our situation. With the CMU's, that's not an option. Just another benefit of Insulated concrete forms pertaining to construction time.

It has been my experience that ICF is about 2x faster than CMU.   For reasons unknown to me, the engineer tends to add extra steel to the ICF monolithic concrete - steel that would be virtually impossible to add if you were attempting to build the same structure out of CMU.    When similar rebar schedules are maintained the ICF is at least 2x faster.

An article about convincing architects to specify ICf vs CMU is in the forthcoming February/March 2010 issue of ICF Builder Magazine on page 8. Cameron Ware wrote an insightful article titled Know the Real Competition: Specifying ICF over CMU . Several good points are included on quantifying the actual cost of a CMU wall as a system. Apparently many CMU estimates appear low due to the fact that they normally do not cover costs for item like red iron and furring materials if required. Other considerations when making comparisons are thermal performance and sound attenuation.

My experience with Italian brick and CMU layers in the Ontario/Canada area has been extreme positive in that they are usually a very well organized and oiled machine to maximize production. So, these guys will run circles around an ICF wall crew that is new to the trade and have to figure out the ins and outs to pro.

A simple question about ICF vs. CMU labor time and cost needs then to be further examined to be fair.

A CMU crew takes more workers and to lay block than it does an ICF crew to lay ICF considering experience equivalency. In order for a CMU crew to build the same strenght wall as an ICF crew regarding the rebar schedule they have to include a bond-beam course for every horizontal rebar placement in order for the rebar to embedded in concrete. This takes time! Then there is the revelation about installing the vertical rebar "as you go up". As a previous poster suggested an engineered CMU wall does not equal that of an ICF wall.

To sum things up: A workman requirement comparison of CMU is 2.5 vs ICF 1 in terms of ability to build the wall. Time factor is CMU 3 vs. ICF 1. Strenght factor is CMU 30-40% vs. ICF 100%. Insulation CMU 0% vs. ICF 100%. Prep for insulation CMU 100% (furring strips) vs. ICF 0%. Insulation install CMU 100% vs. ICF 0%. Effectiveness of furring strip insulation at best 75% vs. ICF 100%. Subtrade friendlyness CMU 50% vs. ICF 100%....and the list goes on.

Initial overall cost considering all systems installed (insulation, furring strips etc.) ICF and CMU is a wash with ICF being installed faster than CMU and ICF providing a better structural base to build from for floor systems or roofing.

Further CMU will loose vs. ICF when it comes to super structures or multi story buildings when ICF is being used as a structural wall system or infill system depending how high one wants to go. If you consider going higher than 2 stories ICF will always win out vs. CMU.

This is just my humble opinion collected from the past few years in commercial installations. There is always a cost/benefit ratio whether you are a DIY or a government agency building with ICF. THanks.

Manfred, very interesting to say the least - i like the way you've broken out each ratio. If I understand them correctly, i agree on almost all of your points. I would like to add a couple of thoughts:

re: "In order for a CMU crew to build the same strenght wall as an ICF crew regarding the rebar schedule they have to include a bond-beam course" I personally, don't think this is possible without making the entire wall a bond beam and that's not going to happen. Also, from what i've seen it very difficult to place enough rebar in a CMU wall without creating a problem -- e.g. not enough concrete around the steel. Thus, my opinion is that it is not possible for a CMU wall to approach the strength of the ICF wall. Actually, I believe you do say that as well in a different way.

re: "Effectiveness of furring strip insulation at best 75% vs. ICF 100%" I do agree with at best 75% but believe it would be extremely difficult and expensive for CMU to reach 50% (at least with furring strips which are usally conductors of metal or wood). Use of full panels between CMU and brick etc. are a possibility but even then very difficult to get there. REgards.

TexasICF, you are correct - CMU wall will lose out against ICF when it comes to strenght and "monolithic" performance. Often times mortar beds for CMU are not complete and create the "mosaic" effect, especially when there are voids in the cavities.

I agree with you on your second point as I was thinking things without writing them out. With the effectiveness I was considering the "air tightness" not the actual insulation value. Again CMU would lose out, since the furring strips inside would have to be "substantial" to make up the inherent insulation value of ICF, even if we would just consider it to be R22.

welcome to south florida, cmu territory, and where i have been banging my head against the (cmu) wall as an icf distributor since 1995. some of the reasons why cmu (called cbs = concrete block stucco) is so widespread here are:
durability and wide spread use, ease and low cost of stucco application, low cost of labor and materials, local availability and free delivery/placement on slab on the same day of ordering, perceived speed (4-6 masons put up a 2000 sf house in one to two days), while re-enforced structures (the code) with tiebeams and filled cells at 4' o/c have not sustained any damage either during the recent hurricanes. and since most of the heat load during summer is coming through the roof, a well insulated attic sealed with spray foam, roof overhangs and shading plants are more important than 4" of eps on the walls. add to that required installation of hurricane shutters or impact windows near the coast (with tap-cons, easier on cmu than icf) and cmu again is less expensive.

dont get me wrong, i believe the end product of icf is better, stronger and more efficient, but the price difference is just to much for developers and builders to accept, especially when customers are usually not willing to pay for the difference. and for the buyer a corian or granite countertop has more value and appeal than a solid concrete wall, when cmu is perceived as strong concrete concstruction also, and counts as such when shopping for insurance.

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If not addressed, the furring strips between the cmu and dry wall can create a "chimney effect" within the walls.  If the attic roof is not sealed out goes your cool or heat. 

Peter,

your message is well received. Slab-on-grade is the most simple sub-structure for any house depending on soil bearing conditions. I concur with you saying that a masonry crew could build a 2000sqf house in 2 days - first floor. Not 2 floors for sure! The higher you go with CMU it will get more complex vs. ICF, whether it be labor intensivity or material logistics. Also, I like to content that a CMU house build in the "2 day fashion" is lacking its inherent quality promised and actual installation control - unless you have the building inspector or engineer there most of the time - and we all know that is not going to happen on a "residence build". There is more and better control for ICF installation since the inspection is done before the concrete is poured.

I understand the mind-set of the Florida building industry. Similar to the NC situation. Builders and developers don't want to change a method that has been in place for over 100 years however "backwards" it is. We are in a paradigm shift when it comes to construction. The emphasis will be on a total energy map (including embodied product energy and occupant behaviour), comfort, and carbon foot print. SIPS, ICF, Passivhaus and other integrated building methodolgies are here "today". Costs for this "system" approach will come down. Death, taxes and increased energy cost are certain. It is like adding 1+1. Ignorant people are still coming up with 3 - but ignorance is fading quickly. Our housing collapse, banking "re-adjustment", economic downturn is a blessing in disguise. The slogan "business as usual" is an expression of the past. Housing will need to come into the twenty-first century with all inovations sum-totalled today. Meaning: ignoring trends (increased un-sustainable practices, earth's burps etc) will lead to the certain death of a society as it exists today. In other words " incrementation will lead to death" (of business, way of life, government, society) - gloomy, eh?! But true.

It baffles my mind how builders, developers and GC's alike still build with practices developed 150 years ago. Ranting - I know.

Manfred - rant on!       Icfblocks - chimney effect very interesting and it makes sense.

Peter -- help us by keeping those guys in Florida! But seriously, in this neck of the woods, when someone says "a mason" -- they are actually talking about "a mason, a helper and some percentage of a bobcat or forklift operator -- how many "people" are you talking about? How many guys constitute a team?

Futhermore, there are CMU stacking limits here (i don't know about Florida) -- for example although it is possible to get a large crew on a small house and one might theorectically stack the whole thing in one day -- this is going to create serious problems because the mortar will squeeze out of the bottom courses due to the weight of the CMU. Thus with enough guys it may be possible to at least approach ICF speeds -- it is not possible to get there and do it properly. Frankly, i personally don't think it can be done at all.  If you have that level of talent stacking CMU, i maintain they will be able to stack ICF at least twice as fast.

Peter,  You may want to look at the now generally accepted IECC (International Energy and Conservation Code).   See commerical wall thermal envelope.   I'm not sure about Florida but for many areas of the country ICF will be less expensive than CMU.   E.g. foam inserts in CMU will no longer count toward R-value and thus many must resort to continuous external (mechanically) attached foam to meet code.    I don't have to tell you why this is a big deal - but for starters if you put foam on a CMU building you can not long stop with the CMU - now you have to finish it out with stucco, brick or etc.  Regards.

there are CMU's out there which can compete very well with ICF in speed of construction and strenght. insulation is what will establish a winner in this comparison. how cheap can you install 4" or foam on your wall? just have a look at dry stack CMUs.

here is one example:
http://www.azarblock.com/

good luck
adi
http://torontonetzerohouse.blogspot.com/

Ah yes, Manfred, quality control. My AAC house, built in 2.5 months with the help of a moonlighting mason, a helper and myself, is right on the money 30 courses up. The corners are 90 degrees and the walls are straight. The only problem we had was the ICF stem wall. The contractor, recommended by the distributor, couldn't keep a straight line. The forms lifted 1 inch in two locations. This was a 32-inch wall. Two courses!!!

The chances of finding a good mason in Pa are much better than finding a good ICF contractor, and my advice is go with the flow.

Adi, dry stack is not as DIY friendly as it seems. If that first course isn't perfect, things are destined to get worse, much worse.