INSULATING CONCRETE FORM
The Ultimate Insulating Concrete Form (ICF)
By Ian Giesler, ICF Builder Network
Audience: The NOVICE
ICF Brand Loyalty
The loyalty of installers, distributors, dealers and the people that generate business in conjunction with the use of ICF’s is a truly unique phenomena. The steadfast loyalty does not seem to have any particular cost or performance based logic attached to it. Some of the loyalty that is perceived in the industry (loosely used term) is no doubt bought by the person that is exhibiting it.
Some ICF Manufacturers offer distribution territories for a fee or sales performance promises. This territory incentive typically associates itself with the promise of making a bunch of money. ICF sales and installation businesses may be a short term get rich quick scheme to some, but in due time, reality and competition set in. There is also the perception that there is a ‘learning curve’. This ‘curve’, which is usually touted as being two or three projects long, tends to put the contractor in a peculiar situation. The average contractor is looking for that niche market to make money. This usually means that they are not making a satisfactory amount of money at the present trade they are involved in. Perhaps that is because they haven’t mastered that trade or don’t have the capabilities to do so. The ICF trade is no different. Some contractors are unwilling to admit that they are not cut out for the work and believe that they must continue or otherwise they are a failure.
Some contractors see ICF as “the way to go” and feel they have the chance to get into the market early with hopes of capitalizing on their market position. Many times, they somehow place themselves as a “partner and stakeholder” alongside the manufacturer. After a fall-out with the manufacturer that they aligned themselves with, these contractors cannot say a good word about the specific products. The downplaying of specific products is typically because they feel cheated and can only see red when the manufacturer or product name is mentioned. This rarely has anything to do with the performance of the form. Whatever the reason, beware of brand loyalty or extreme animosity.
The most important consideration of the project is the budget. The budget is based on the total cost of each phase of the construction process. The cost of ICF walls is all too often based on the cost of the form system alone. This is the biggest mistake that grabs most first time users in the checkbook. The DIY only encounters this once. The novice contractor that is making a decision to start offering ICF walls in the lineup is just starting to get the feet wet. The cost of the ICF walls is rarely calculated correctly. The cost of ICF walls involves nearly every rough and finish trade that enters the project. Subcontractors that must interface with the ICF walls whether they are familiar with them or not have to figure for any deviation from the normal process. When the subcontractor discusses these issues with the owner or builder typically statements like “My electrician wanted to charge $500.00 dollars more because it is an ICF house” come to the light. (Yes, pun intended) Some of those statements are absolutely correct and are substantiated by extra labor and materials that the subcontractor must provide to complete the phase of work. Other times, the subcontractor is just trying to substantiate the fact that the price for the work is high, and the ICF walls are an easy target to blame. The subcontractor may also state that they are typically higher cost because the quality of their work is better than the rest. (This is somewhat the same mentality that is noticeable in the brand loyalty discussion) The budget for the ICF walls must consider all of the additional and reduced costs associated with the other trades.
Which ICF to use? Why use ICF?
The choice to use ICF instead of wood frame, etc., is obviously based on the perception that ICF is better. Which ICF system provides the best set of features and benefits that are considered to be valuable for the project? There are only a few types of ICF systems. Each type offers significantly different construction issues and completed results to the owner. Comparisons of the features and benefits of the three types (solid monolithic concrete, waffle grid, and screen grid) are readily available. The comparisons are rarely “apples to apples”, rather based on a variety of different test standards, criteria, and calculations. The actual performance of the ICF’s can be construed as being adequate for constructing energy efficient, durable, disaster resistant, sound concrete walls.
There are significant differences in the three types however. The manufacturers offer a myriad of different sales pitches filled with technical information, facts and emotional text. Buyer beware.
Why different styles?
The reasons for the many different styles probably have roots back to the beginnings of the “Concrete Block vs. Monolithic Concrete” debate. They are all engineered to perform for the required task. Ultimately, cost is the driving force that perpetuates the debate. The volume of concrete to be considered adequate for the average residential structure is typically the basis for the argument to choose one style over another. The solid monolithic (SM) wall obviously uses the most volume of concrete per square foot of wall area, the waffle grid (WG) a little less, and the screen grid (SG) the least amount. Arguments typically favor statements like “decreases in concrete volume and overall strength can be recouped by the addition of more reinforcing steel”. Both the SM and WG systems offer a fire resistance quality that is not available in the SG style. The SG style, which typically uses all Expanded Poly Styrene (EPS) material without cross ties of metal or plastic, requires additional steps for mechanical attachment to the wall.
There are essentially two basic component parts to the SM and WG systems. The form walls consisting of EPS or Extruded Poly Styrene (XPS) and the ties or “webs” that separate and hold the walls in place. The ties are made from metal or plastic. The term ‘plastic’ in this case should be clarified. The different manufacturers utilize “Engineered Polymers” to attain the characteristics required for performance. The term ‘plastic’ refers to the non-metallic ties.
The different systems have ties that terminate either on the surface of the form or are recessed below the surface. The systems that have recessed ties typically have an adequate marking system that allows the user to identify the tie locations. The systems with ties on the surface offer only one real benefit during construction and that is the ability to see them at first glance. The idea that ties on the surface are easily screwed into by drywall installers etc. is not correct. Presumably, the drywall is covering the tie that the installer is intending to screw into. If a tie is half under a sheet of drywall, then the installer should be able to discern the markings on the form that indicate a tie location. The benefit of recessed ties lies primarily with the use of direct applied synthetic stucco systems that require the surface to be rasped to remove dust, dirt and imperfections without having to deal with the ties. The ties that are recessed also do not rust, fall off, weaken from exposure, funnel rainwater into the wall, short circuit or thermal-bridge the insulation, or telegraph through finishes.
The opinion that metal ties are better than plastic ties or vice versa is a hotly contested issue. There are only two major ICF companies that use metallic ties in the U.S. One system utilizes a single piece of sheet metal that is cut, bent and perforated. The other system utilizes a two-component three-piece assembly. A piece of expanded metal is cut and bent to form the tie and two pieces of light gauge sheet metal are pressed onto the ends to create a vertical fastening surface for finish materials. These companies tout several benefits of metal vs. plastic ties:
Won’t weaken over time
Not affected by sunlight
Stronger than plastic overall
Stronger fastener pullout values
Greater durability in a fire
Won’t add fuel to a fire
Won’t add toxic fumes to a fire
Reusable after a fire
Most of these claims have no real benefit with respect to using ICF. The first two issues deal with plastic ties becoming weak over time due to exposure to the elements. The plastic ties can become weak if left exposed to the elements for a prolonged period of time. This timeframe is typically much longer than the time to complete an entire project. The third issue, stronger than plastic overall, is mute since the plastic performs all requirements adequately. In some cases, the plastic ties may actually be stronger than the metal ties. The screw pullout values for some plastic ties are phenomenal. The plastic ties have a significantly greater thickness than the light gauge sheetmetal with emphasis put on screw pull out values. Durability, toxicity, and failure as a result of a fire are also mute points. If ties are failing, burning and adding fuel and toxic fumes, then the fire is well under way. The notion that the fumes could hurt someone or finishes could fall on someone is ludicrous. The idea that the ties are reusable after a fire is absurd. The light gauge sheetmetal would be warped and twisted. If anything, the metal would need to be cleaned from the surface so that total sealing of the wall (if reusable) could be done.
Conversely, the form Manufacturer’s with plastic ties claim:
Plastics won’t rust from the chemicals present in the concrete or bleed water
Stronger pullout values
Don’t fall off over time
Won’t adversely affect finish materials
Will not short-circuit the insulation
Do not sweat
Easier to cut and don’t require special tools
Do not impede concrete placement
Most of these claims are not universal to all systems that incorporate plastic ties. There is some validity to the statements with regard to specific brands.
Another commonly used statement by the purveyors of the metal tie systems is that most conventional forms systems all use metal ties. One important item left out of the argument is that they are being attached to wood forms. The wood has much stronger capabilities than the foam forms on the market. The comparison can be rebutted with, “How many cars have metal bumpers nowadays?”
The claims made on both sides of the argument do have some merit. An open mind with a dose of reality and rationality thrown in makes the plastic vs. metal debate a non-issue. The metal vs. plastic arguments should not be used as a major decision factor for choosing a system to use. The metal tie systems have been on the market for quite some time and have other issues that shadow the plastic vs. metal debate.
In most cases, the tie of a form is the strongest link. The EPS walls are the points that fail under concrete pressure. The spacing of the ties is a critical factor in the success or failure of the systems. Of the popular systems on the market in the U.S., the tie spacings vary from 5 inches on center to 12 inches on center. The systems with the shortest distances between ties are typically stronger than the other extreme. When using the short spaced tie (SST) systems, there is a shift in construction concerns from exceeding form pressures to insuring consolidation and complete filling of the forms with concrete. The SST systems typically install with less waste than the longer spaced tie (LST) since ties are present in more pieces of cut form. The SST systems offer more finish attachment points than LST. SST forms typically do not require the use of supplemental bracing along the bottom of the wall, around openings and at cut locations on the wall. Deflection as a result of concrete pressures is considerably less on SST walls than LST walls. SST walls can withstand internal vibration with standard concrete vibrators whereas LSTs cannot. SST systems typically have a thinner cross sectional area of plastic tie that is easier to cut horizontally for placement above or below openings. The main differences between SST and LST systems have to do with installation costs, overall performance of the form system for withstanding concrete pressures and the additional points for attachment.
There is a multitude of different shapes and sizes of ties in ICF forms. Every manufacturer of ICF’s has a unique tie design. Some ties have slots that lock reinforcing bar in place. This eliminates the need to tie reinforcing bar splices. Some have indexing tabs that keep the bar in line, but it still must be tied at splices. The SG systems offer prefabricated wires that span the cavity of the form. These heavy gauge wires have indentations bent to hold reinforcing in place. These wires are usually set every four feet or so on each row of forms. Other systems do not have any provisions for the accurate placement of reinforcing. The reinforcement should be clear of the EPS by a minimum of ¾ of an inch.
Ties for Fastening Finishes
There are a variety of shapes and sizes of ties when it comes to finding a target to fasten finishes to. Most systems incorporate a 1 inch to 1 ½ inch wide strip that runs vertically on the form. This strip usually does not extend continuously from bottom edge to top edge of form. Several systems have diamonds, squares, rectangles etc. that are intended to be used as fastening points. On the SG systems, several methods are used. Some systems have slots in the EPS foam available for the insertion of wood or plastic strips. Some have allowances for sheetmetal brackets to sit on the top of the form. The sheetmetal is eventually anchored to the concrete via some sort of tab. The exposed portion of the tab usually is in the shape of a square or rectangle that is easily hit with a screw .
The ties are adequate for finish material attachment. The use of embedded anchors, wood recessed into the foam and anchored to the concrete, etc. is probably a good idea for attachment of cabinetry and items that may impose a significant load. This is easily done before drywall is installed.
The Interlock of Forms
The decision to use a form system with interlocking ties, foam or both is crucial only to the installer that will be erecting and placing concrete. Once concrete is placed, the interlocking features do not keep water from leaking through the wall. There is once again a multitude of interlocking features molded into the EPS portion of the systems. Take a moment and think about where the weak link of the form systems is. Typically, the weakness is in the vertical and horizontal joints. Some systems don’t have an interlock at all, they utilize common insulation board with small slots for tie placement along the horizontal and vertical joints. These slots assist the installer in keeping the ties vertical and not staggered about the wall. Some manufacturers claim that these systems are strippable after concrete has been placed. These ties are usually the square, diamond or rectangular type that were referred to earlier. Some systems utilize a simple tongue and groove or close variation. These systems must be installed with care so as to maintain the vertical alignment of the ties. Some manufacturers recommend adhering the forms together as they are stacked. This can be a detriment to the installer if something gets out of whack. The majority of ICF manufacturers have some sort of Lego™ type interlock. The style, size and type of interlock typically doesn’t affect the project outcome. A few of the manufacturers have both interlocking foam with ties inserted on the horizontal and vertical joint also. The smaller interlock systems are more susceptible to damage while transporting and handling. Smaller interlocks are not as forgiving when attempting to build on an imperfect foundation. The systems with smaller interlocks have the most trouble with “interlocking problems”. Many of these problems have to do with the molding of the foam. The systems with smaller interlocks have an advantage over the larger ones when it comes to layout of the walls. The larger interlock systems typically must be laid out on a 2-inch wall length increment, whereas the smaller interlock systems can be laid out on a 1-inch increment. The tongue and groove systems don’t necessarily have a layout requirement, although they are more prone to error in wall length as a result of wall growth or shrinkage as the wall goes up.
Most of the systems have pre-made corner blocks. Several have both 45 and 90-degree blocks. These options are a must. They aid in keeping corners plumb and square.
Pre-Made Accessory Forms
The accessories offered by most of the manufacturers are nice to have, but not totally necessary for the cost. Of the options available, the brickledge form is nice, although it can be misused to the detriment of a quality installation. The brickledge forms have a long way to go in the improvement category. The lack of corner forms, and the labor associated with using them are at issue. The height adjuster forms are convenient for window and door opening adjustments, as well as overall building height on multiple story buildings. With proper planning, and the use of the right system, these options are not a must requirement.
Electrical Installation Considerations
If electrical outlets and switches are to be installed on the ICF walls, be sure to do the due diligence study on electrical box requirements. On some systems, the inexpensive blue or grey plastic box can be anchored to the concrete after foam removal, the concrete behind is flat and parallel to the foam surface. The anchored box will protrude exactly ½ inch from the foam, just enough depth for drywall. On some systems, wide shallow boxes with mud rings must be used. These boxes and accessories can cost a lot more than the regular inexpensive single gang outlet box. On the WG and SG systems, the use of double and triple boxes may require planning in advance of placing concrete unless chipping of concrete is desired.
Assemble on Site or Pre-Made Blocks
The decision to use pre-made blocks or assemble on site blocks is typically decided based solely on the cost of the forms. The main advantage of assemble-on-site (AS) systems vs. the pre-made (PM) is freight cost. A secondary advantage is the ability to build different wall thicknesses with the same system. The advantages of AS systems can easily be disputed by manufacturers of multiple width PM systems that price the product low enough that the additional freight cost combined is close or lower than AS systems. The AS systems still have to insure that the correct ties are delivered with the panels. The costs associated with assembly and moving of AS systems on site are usually overlooked by the installer. The PM systems do not require the assembly time of AS systems. The PM systems can typically be moved in bundles of ten to 15 blocks by one person on the site. AS systems are usually moved 3 or 4 blocks at a time by one person. The AS systems add one more step that has potential to cause a problem later in the project. The AS systems with three part tie systems (those with a part molded into each panel and a separate part that ties the two parts together) are not molded by the manufacturer of the form system. These systems are contract molded. This small detail usually leads to poor quality control by the molder. Several panels of the average job quantity typically arrive missing the part that should be in the panel. This missing part is over-looked quite often. The result is a missing stud in the wall and a bulge or blowout at the time concrete is placed. The AS systems for the most part are not as rigid as the PM systems and are more susceptible to racking and excessive movement at the time concrete is placed.
Most of the systems have been designed with good solid criteria in mind. Nearly every system can be used to build a rectangular basement with one wall height and four or six corners. Not all systems are conducive to building houses with twenty or so openings, three or four plate heights, and thirty to thirty-five corners. The product reviews are based on real life experience, interviews, comparing of notes, and in some cases comparisons to nearly identical products. To make the reviews “equal”, they are based on the following requirements: Construct a single story structure with 2500 square foot of formed wall, thirty four openings adding an additional area of 790 square foot of wall area, three plate heights, 234 feet at 10 foot tall, 45 feet at 12 foot tall and 30 feet at 14 foot tall, and fifty corners (30 at 90 degrees and 20 at 45 degrees. If you are considering building with an ICF, and are wondering about which brand to select, we would be happy to review specific brands. We would like you to provide all relevant information about your projects and your company so that we can tailor the review for your situation. Simply request a product review through this site.
The Ultimate ICF:
The ultimate ICF system combines the best performance features of the many systems on the market.
Solid monolithic concrete wall style
Three basic components: straight block, 90 and 45 corners
Low cost delivered to worksites
Multiple concrete cavities
Surface labeled in English and Spanish for fastening points
1” interlock of the foam
Unisex top and bottom
Panel ends have index alignment feature
Must interlock in a “T” configuration
Index lines for cutting
1-1/2 inch wide by full height fastening surface
Recessed under the EPS surface
Integral reinforcing locking feature to hold two #5 bars in place
Screw pullout value exceeding that of metal studs and OSB plywood
Minimal concrete displacement
Minimal cross section to avoid interruption of concrete flow
Do not impede consolidation of concrete
Easily cut with a handsaw
Low waste generating
Withstand extreme concrete pressures
Withstand 10’ lift of 8” slump concrete placed by a boom pump at a rate of 1 CUYD per minute without an “S” bend and internal vibration
Does not require ANY supplemental bracing at door and window openings
Able to apply all standard finishes to the wall without additional furring requirements.
Accommodate typical electrical boxes with ease.
Eliminate the requirement of tape, zip ties etc. to hold forms in place
The ultimate ICF block can be used for the “model home standard review” as stated previously. This product can be stacked, braced and poured by a three-man crew in three to four days total. The walls can be as straight as a stringline, plumb and square, no matter how difficult the slab or footing quality is.
THE BEST INSULATING CONCRETE FORM (ICF) FOR THE JOB