The following overview illustrates the differences between the 3 basic designs of Insulating Concrete Forms: Flat, Waffle and Screen Grid, and details why Reddi Form chose the more flexible Screen Grid for the Reddi Form patented design.

System 1: Flat Wall

Flat wall ICFs are systems in which the concrete within the form is of uniform thickness throughout. There are several different types. Some require a machine to cut slots in the foam at certain intervals, while others have the tie slots molded into the EPS.

Flat wall systems require a substantial amount of bracing . They are prone to bulging between the plastic ties which can create a wavy wall. To avoid this problem, concrete must also be placed with great care and time. Low slump concrete is very important to successful pours in Flat Wall Systems, and the concrete should not be poured in lifts that are greater than four feet.

Creating corners, angles, T-walls and curves with a Flat Wall system is much more difficult and time consuming than with almost any other ICF system.

A second option is a “flat wall design” which comes with molded EPS insertion ties. Plastic ties or parts of ties are placed in a mold at the plant and are actually fused within the EPS. Some companies ship them as finished blocks. These types tend to be more stable than the machine slotted because the tie is rigid, however, substantial bracing is still required for uniformity.

System 2: Waffle Grids

Waffle grid systems have closely spaced vertical and horizontal concrete members (cores) with a concrete web between the members created by the form design. The thicker vertical and horizontal concrete cores and the thinner concrete webs create the appearance of a waffle.

All of these designs are insertionmolded products.

Waffle grid systems are difficult to mold because of the insertion process. As with any insertion product, the cost to manufacture is greater due to the cost of the insertion, labor cycle time on the machine, and the need for different molds to create the different shapes such as corners and angles (in most cases they need left corners and right corners).

Added time and expense on the job site is also incurred because of the difficulty in cutting the inserted plastic or metal webbing. Waffle grids interlocking mechanism is of a “post and channel” design so extra care must be taken during erection so as not to misalign the vertical cores.

A major engineering deficiency with any type of inserted form is the surface bonding of the tie to the foam, which is quite small when compared to screen grids.

In most cases, the plastic or metal tie is only 1½" wide by 8" or 10" long, or approximately 15 square inches of surface bonding as compared to approximately 48 square inches of bonding with screen grids. This results in 1/3 as much connection holding the forms together. This also applies to flat wall systems.

System 3: Screen Grids (Reddi Form’s patented design)

Reddi Form’s Screen Grid approach to Insulated Concrete Form design is the ideal concrete masonry unit (CMU) replacement. Screen Grid Insulating Concrete Forms (ICFs) were initially conceived as replacements for cinder or concrete blocks since they actually resemble large concrete masonry units.

Screen grid ICF layout, and the tasks related to getting started, are the same as standard CMUs. You start from the corners and work towards the center to establish the bond.

The major differences between screen grid ICFs and actual CMUs are product size (1' x 4' ICF vs. 8” x 16” CMU) and product weight (3 pounds for 4 square feet of ICF vs. approximately 280 pounds for 4 square foot of CMU wall space).

Coupled with the fact that block work is not as strong as reinforced concrete - most codes now require them to be both grouted and reinforced – hence ICFs become an ideal alternative for current and future building technology.

Advantages of Reddi Form – Screen Grids

Stability. Screen grids are much more stable than any other type of ICF system. Due to their design, they do not flex when concrete is poured into them, and they do not have ties that could cause bulging. They distribute the pressure developed by the concrete better than other system types by reducing the pressure against the corners and thus reducing distortion. Less overall bracing and no corner bracing is required.

The fact that the “liquid head” pressure of the concrete needs to be calculated in each column only, versus the entire wall, Reddi Form walls can be poured in lifts of up to 10 feet. The large integrated web design eliminates lateral movement between the sides of the form, which increases the form's stability and insures flat and plumb walls and corners!

Versatility. Because of their stability and strength, screen grid ICFs can be used for “slab-on-grade” and “frost walls”. Simply place and level the forms on the footing in the trench and evenly back-fill both sides so as not to move them off the building line. Then pour the floor and wall monolithically. (Not possible with flat wall systems.)

Accuracy. Because of the larger foam surface area of the foam ties, concrete flow over the top of these ties creates pressure, which holds the form down. This makes gluing unnecessary throughout most of the wall.

Only at the very top of the wall is extra adhesion necessary. (Here there is more concrete under the tie than over which may cause the top form to float.) Another benefit of the large “distributed” Reddi Form interior is that as the concrete flows it pushes the blocks deeper into the locks of the adjoining form, causing the wall to actually straighten under pressure!

No Moving Parts. Pure screen grids are much easier to work with since there are no dissimilar parts (plastic or metal) which makes cutting simple. Since the forms are easy to cut, slopes, angles, curves and elevation changes are simple to produce. They can even be installed either side up or down!

Lighter Weight. While structurally stronger, Screen grids when filled are actually lighter in overall weight than other ICFs. This factor makes them better in seismic areas as well as being of great benefit in high-rise construction.

Reddi Form Construction & Assembly

Angles. Any angle can be achieved by first cutting the block at one half the degrees of the desired angle, flip the cut off piece over and since there is no top or bottom simply glue the pieces together, and you have the angled form you need.

Curves. One cut between each cell does it. With your hot wire cutter or saw, cut the block almost all the way through at the cell on the line outside of the block, leaving about ¾ of an inch. Layout the arc and bend the block to conform to the arc. Once the first row is established, repeat.

Brick and stone shelves. Cut a standard block on a diagonal lengthwise (you will get 2 pieces from one block). Then cut holes in the cells at the desired height to allow the concrete to flow into the brick shelf. Then glue the angled piece to the wall. This capability allows you to place the shelf where you need it reducing the need for extra brick and/or stone.

T-walls. Simply run your outside wall where the “T” occurs, cut out the foam in that cell, and butt the block at that point when fully erected. Plumb both walls and glue each side of the block vertically. No bracing is required. If the “T” falls on a cell line, use a corner block and cut out the foam on both sides and interlock on the second course then alternate to form the “T”.

Design Simplicity. Openings for doors and windows are simple and easy. Following are a number of ways that Screen grids have the advantage of accomplishing this:

Glue 1 ½” or 2” rigid foam to the sides of the opening and use a 2x10 or 2x12 as the header. This can only be done with screen grids because of the reduced pressures of the concrete. Once the wall is poured and the concrete has set, strip the foam and wood from the opening to complete the process. All major window and door manufacturers have masonry clips to fasten directly to the concrete eliminating extra costs for labor and wolmanized wood or plastic. Additional savings can be realized by finishing up to the door or window unit with sheet rock rather than using wood extension jambs and wood casing.

Plastic buck and ¾ plywood materials are available and work well too. Metal door bucks are very simple to install. Just install the frame in the opening prior to pouring and glue it to the foam, making sure it is plumb and level in the wall.

Since Reddi Form walls are able to contain cement poured in 10-foot lifts, pour times are reduced which helps prevent cold joints in the concrete. Reddi Form warranties both 6 inch and 8-inch core blocks to 10 feet pours in single lifts.

Reddi Form is one of the few block systems that can be placed in the ground and back-filled on both sides before pouring concrete. This makes it ideal for slab-on-grade or frost walls, and it saves time and money by allowing the floors and walls to be poured monolithically.

Remember: Reddi Form blocks are all foam, with no moving parts!

These advantages provide significant cost savings to Reddi Form users!

• Warranties for EIFS systems.
• Single pricing structure for all parts: standard, corner, pilaster and closed end.
• Ideal for high-rise buildings by reducing the design load on spanual beams and support columns through lighter weight, hence reducing costs.
• Positive placement of vertical and horizontal rebar with the use of our rebar chairs. No other ICF company can make vertical placement positive without additional tying.
• Concrete can be poured in Insulated Concrete Forms even during extreme weather conditions, below 32°, without using heated tents, hot water, or anti-hydro. Simply pour concrete into the ICF, protect the exposed top and you are done. This greatly extends the building season!
• In hot climates, ICFs protect the concrete from drying too fast (controlled hydration) which helps prevent heat cracking.
• Concrete within ICFs cures stronger than in conventional metal or wood forming systems. Studies done by PCA show that because water is kept within the concrete mix longer (controlled hydration) the concrete develops PSI strength above the design mix. Concrete placed at 3,000 PSI in an ICF will test out at or above 4,000 PSI in 28 days.
• Finally, because of its distributed, lighter weight design, Reddi Form takes the least amount of concrete of any ICF meeting the Prescriptive Codes while not sacrificing any structural strength. This is much like a truss that uses less material but produces more strength through its advanced engineering.