Blind Side Walls or One Sided Forms
(Sacrificial Forming Systems)

No other forming method works as well as stay-form for this application
Stay-form will save time and money on every blind side wall project.

Blind side walls or one sided forming:

Stay-form is the ideal forming material for blind side walls. Contractors who have tried to build forms inches away from existing structures or rock formations know how difficult form removal can be. Most construction projects will not allow the contractor to leave wooden forms in place because of the vermin problem created by this material. Therefore, the contractor must build concrete forms that can be somehow removed or can stay in place. Stay-form solves this problem better than any other forming system currently on the market.

AMICO has developed a forming system composed of rebars for vertical stud mechanisms, specially developed hook ties that can be installed from the front side of the form, and finally Stay-form that is applied to the rebar studs. Enclosed in this document you will find complete load tables for this installation, detailed drawings that will thoroughly explain the installation, a detail of the hook tie, and finally, photos that shows some typical blind side wall installations. Utilizing a system composed of rebar studs, hook ties, and Stay-form, a blind side call can easily be combined with traditional forming materials on the accessible side, to form a wall only inches from existing structures or rock faces.

Advantages over wood or modular forms:

1. Forms Easily: Stay-form easily forms into multiple configurations to accommodate curves, angles and corners. To make corner bends, ribs are notched to a 90-degree angle by making two 45-degree cuts, and leaving the mesh between the ribs intact. By bending the remaining mesh to the desired angle or radius, a perfectly formed corner or shape is created. Tie wire is utilized to hold the corner shape at the appropriate angle. Curves form easily in a direction parallel to the ribs. A full circle tube can be formed with Stay-form. Such a wide variety of form shapes are possible that it is virtually impossible to describe all the flexibility this product offers. Many more shapes are attainable using Stay-form than by using other materials such as wood, steel or plastic. Multiple sections of Stay-form can be joined end to end with a 3-inch to 4-inch lap. End laps should always be braced with a support. To accomplish a side lap, overlap one or two ribs. Occasionally blindside wall applications such as retaining walls must curve or even turn corners; this can be easily accomplished with Stay-form.

2. Supporting Stay-form is Easy: Utilizing the load tables found in this document the contractor can easily plan for support spacing using rebars and hook ties, that will easily work with any modular forming system that might be used on the front side of the wall. The blindside wall load table also provides information on allowable pour pressures at various tie and stud spacings.

3. Excellent Support for Concrete: When properly supported Stay-form will support concrete pours with only minimal deflection between ribs. Placement devices such as elephant trunks should be used to discharge concrete no more than two feet above the pour surface.

4. Cuts to Size Easily: Stay-form is packaged in five sheet bundles that are wire tied together. Single or multiple lengths or pieces can be cut utilizing a circular saw with an abrasive metal cutting blade. Tin snips or metal shears are used to notch small areas or ribs.

5. Easily Penetrated: Stay-form can easily be snipped (sheared) or punched to allow hook tie placement on rebar supports or for penetration of conduit. Often metal aviation snips are employed for this procedure.

6. No Stripping Required: Stay-form is a stay-in-place concrete form that requires no stripping. This fact is crucial in blind side wall installations that are typically placed within inches of existing structures, rock faces, or grades. Because the Stay-form, hook ties and rebar studs stay in place, wall fabrication a few inches away from existing structures is possible.

7. Concrete Placement and Consolidation is Aided by Stay-form: Since visual inspection of the pour is possible with Stay-form the contractor can feel a greater degree of confidence that no voids exist in the pour without having to over vibrate. With typical forms voids are not visible till the forms are stripped. At this point correction is difficult and costly. Even with blind side wall applications the vibrator operator can look down the backside of the Stay-form and see when the concrete paste blossoms through the form to cover the face of the form. At this point one can be reasonably assured that the concrete has been properly consolidated.

8. Saves Time and Money: All of the above adds up to a savings of time and labor, which translates into financial savings on every project. The old adage rings true, "Time is money". The problem solving capabilities of Stay-form makes even difficult applications easy to accomplish.

Customer Experiences: We would appreciate knowing how contractors use Stay-form. If you have used Stay-form in a unique or unusual forming or shotcrete application please send us your photos, drawings, written descriptions or just phone us, so that we can share your application ideas in a future publication.

Stay-form will save you money on every project.
Installation Techniques:

Installation of Stay-form blind side walls is accomplished by following AMICO's installation details. Installation begins when the footing or mud slab is poured by installing rebar stubs that will protrude from the footing at least 12-inches and be spaced to match the location and spacing of the vertical rebar supports that will form the support for the blind side wall. Next the installer has two options. The blind side wall assembly composed of the rebar studs, Stay-form panels, and hook ties can be assembled on the ground and hoisted as a unit to a vertical position, or the unit can be erected piece by piece if the wall is not too tall. Assembly of sections on the ground (gang forming) seems to be the most popular method of fabricating this type of assembly.

Assembly begins by laying out the rebar studs at the appropriate spacing as show in the blind side wall load table. Once this is completed the Stay-form can be wire tied to the stud members at approximately every six to twelve inches on center. The ribs should be oriented into the pour so the flat side of the sheet rests on the rebar supports. It is recommended that a number four rebar be placed in the bottom rib of the Stay-form to reinforce this area. It is also recommended that the first two laps of Stay-form be lapped two ribs due to the higher pressures at the bottom of the pour and that both ribs be wire tied together at twelve inches on center. The Stay-form sheets should also be oriented with the ribs perpendicular to the rebar studs.

The next step is to install the hook ties at the appropriate spacing along the entire length of each stud member. This is accomplished by making a small slit or hole on each side of the rebar stud. The hook is then inserted through the Stay-form and hooked over the rebar. The threaded end of the hook is then returned through the Stay-form passing through the second hole or slit. A keeper or washer (a specially designed plate with two holes) is then slid down the hook tie to fit over the threaded end of the hook tie. Installing a nut on the threaded end of the hook tie completes this portion of the installation. Once all of the hook ties are in place the assembly is ready to be hoisted into position. A number four rebar can be placed in the top rib of the assembly to reinforce the section at the lift points. The vertical stud members are then welded to the stubs that protrude from the footer. It is a good idea to delay tying the last two ties of the Stay-form to the rebars until this welding is completed.

Once the Stay-form blind side assembly is in place and supported in a plumb position, the installation of the modular or plyform assembly can proceed as with any traditional wall form. All kickers and support mechanisms will be placed on the accessible side of the wall. Once all forming and support mechanisms are in place, concrete placement can begin. All concrete placements should be accomplished utilizing placement devises such as elephant trunks so that concrete in released no more than two feet above the pour surface. Uniform pressures in accordance with the blind side wall load table must be maintained during the pouring process. See the attached load table for other precautions. Normal vibration procedures can be utilized except that the vibrator should be held several inches away from the surface of the Stay-form. By looking down the backside of the wall from above the vibrator operator will be able to see the concrete paste penetrating the openings in the Stay-form. This will be the indication to move the vibrator to another area. Do not vibrate previous lifts more than 4" to 6". This is to avoid increasing the thickness of the liquid head. Once the entire surface of the Stay-form shows the penetration of the paste, the applicator can be reasonably assured that all proper consolidation has occurred.

After concrete has hardened, the forming and bracing on the accessible face of the wall can be removed. Remember that the Stay-form assembly remains in place.

Next Section: Blind Side Wall Drawing >

 
 
 
 
 

Stay-form: the forming and shotcrete problem solver.
Contact AMICO Stay-form
1-800-769-7642 ext. 205 or sales@amico-us.com


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