Preparation

Gang drilling the plywood is the only preparation required. Holes need to be drilled 1/8" larger than the snap tie head. Normally a 9/16" diameter drill bit will be required. We recommend you drill a maximum 5 plywood panels.The 5/8" take-up of the eccentric on the Jahn "A" Bracket allows a snap tie with a L&W dimension of 4-3/4" to be used with a 5/8" or 3/4" plywood. The 5/8" take-up on the "C" bracket allows it and 81/4" snap ties to be used on 5/8" plywood.

Gang drilling of Plywood

Snaptie Spacing and Rate Placement:

The most common snap tie spacings being used with the Jahn Forming System are shown below. For different rates or pour and/or other tie spacing, contact Masons Supply. Refer to the back cover for addresses and phone numbers.

12" vertical x 24" horizontal Snaptie Spacing. Recommended rate of placement 4.5 ft/hr at 70°.

16" vertical x 24" horizontal Snaptie Spacing. Recommended rate of placement 2.0 ft/hr at 70°.

12" vertical x 12" horizontal Snaptie Spacing. Recommended rate of placement 4.5 ft/hr at 70°.

Plywood Used Strong Way (Face Grain Parallel to Spacing)

Notes: The above recommendations are based on the use of 3/4" Plyform Class I, and 2x4 S4S studs (Douglas Fir-Larch, Southern Pine or equal having a minimum allowable fibre stress of 1,200 psi). Design is based on all formwork members being continuous over four or more supports. Normal weight concrete made with type 1 cement, no admixtures or pozzolan, slump no more than 4 inches and vibration limited to 4 lineal feet or less.

Footing Plates:

Good forming practices require that a level footing be used as a starting point for all forming applications. Snap a chalk in back of the plywood thickness and nail down a 2x4 plate.

Plywood Panel Erection:

Erect, plumb, nail to plate and temporary brace the first sheet of plywood. Erect additional sheets of plywood by nailing them to the 2x4 plate and temporary wood cleats at the top corners. Make sure the joints are tight. If panels are to be stacked, ensure that the panel tops are level.

Installation of Wales:

Install the Walers into the brackets working from top to bottom of the panel and tightening the eccentric as you go. Waler joints should occur at a bracket or a scab should be utilized to reinforce the joint (see sketch).

Inside Wall Panel Erection:

The inside panel sequence is the same as the outside panel described above except for the placement of the plywood panels over the tie ends. This can be accomplished by two workmen by starting at the bottom and moving the panel from side to side and up and down to align the snap ties with the holes in the plywood.

Inside Corner Forming:

No special treatment is required for inside corners other than the alternating of the wales as shown in the sketch. It is advantageous to start the inside corners with full size plywood panels to facilitate forming the outside corners.

Outside Corner Forming:

Install the first outside panel in line with the first inside panel. Filler panels, the same thickness as the wall plus the plywood thickness, are then used to fill out the exterior corner.

Installation of Jahn Cornerlock:

The cornerlock eliminates costly overlapping and blocking of the wales. Its cam action draws the wales securely together. Place one wale flush at the corner and let the other extend past the flush one. Slip the cornerlock into place with the handle perpendicular to the wale. Nail the cornerlock in place and rotate the handle 90° toward the wale. A snug, tight outside corner is a accomplished.

Installation of Strongbacks:

Strongbacks are used to aid in form alignment and to tie stacked panels together. Loose 2x4's are used in conjunction with Jahn "C" Brackets and 81/4" L&W snap ties or 43/4" L&W snap ties with the Jahn Tie Extenders to strongback the forms. Normal strongback spacing is 8'-0" on center.

Joint Cover Details:

Alternate A - Drill 9/16" diameter hole 11/8" down from top edge of the lower sheet of plywood. Install snap tie, "A" Brackets and wale and then the upper sheet of plywood. Nail the upper sheet of plywood to the wale.

Alternate B - Install snap tie in the joint between the panels. Add double wales and a "C" Bracket.

Alternate C - Nail 4x4 wale to lower sheet of plywood, hold the wale in place with strongbacks and add upper sheet of plywood

Installation Of Second Lift Of Plywood:

Lift the plywood sheet and place it into position. Hold the sheet in place with a short 2x4 spacing block, snap tie and "C" Bracket placed toward the top of the panel and nail the bottom of the sheet to the joint cover wale. Set additional panels by nailing them to the joint cover wale and securing them to the previous panel with a small wood cleat. Install the snapties, brackets and wales - working bottom to top. Note: Snap ties are not to designed to carry scaffold bracket loads.