JAHN Basic Forming Information 800-966-4482

revised Nov. 2010
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JAHN Basic Forming Information
12” vertical x 24” horizontal
Snap Tie Spacing
Recommended rate of
placement 4.5 ft./hr. at 70
16” vertical x 24” horizontal
Snap Tie Spacing
Recommended rate of
placement 2.0 ft./hr. at 70
12”
24”
12” vertical x 12” horizontal
Snap Tie Spacing
Recommended rate of
placement 4.5 ft./hr. at 70
SNAP-TIE
SPACING
8”
26”
24”
22”
24”
18”
16”
12”
6”
12”
8 Hole, 24” x 24” Tie Spacing
uses the fewest ties and is for low
walls, slow rate of pour, or where
the work is backfilled.
Recommended rate of
placement 2.0 ft./hr. at 70
24”
12”
Staggered System
uses only 10 ties. Suitable for fast
pours to 8’ heights.
Mark panels for one-way up erection.
Recommended rate of
placement 2.0 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 2 x 4 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.
Snap Tie spacing will depend on the temperature, rate of pour, and plywood thickness.
When in doubt, consult your rate of pour charts.
page 1
PREPARATION
Gang drilling of plywood is the only preparation required with the Jahn Forming Method.
5/8” or 3/4” plywood may be used.
Although 5/8” is slightly lower in cost, 3/4”
is stronger, lasts longer, uses fewer ties and
brackets and is more economical in the long
run.
Holes should be drilled 1/8” larger than
tie end. This will usually be 9/16” or
5/8”.
GANG DRILLING
OF
PLYWOOD
NOTE: The 5/8” take up of the eccentric on
the Jahn A Bracket allows a snap tie with a
dimension of 4-3/4” to be used with either
3/4” or 5/8” plywood.
The 5/8” take up of the eccentric on the
Jahn C Bracket allows it and 8-1/4” snap ties
to be used with either 3/4” or 5/8” plywood.
PROCEDURE
1. FOOTING PLATES OR CLIPS
Good forming requires good level footings or
sub-grade to be used as a starting point for all
forming applications.
Snap a chalk line in back of the plywood thickness and nail down a 2” x 4” plate. Nail down
Jahn Footing Clips, 2 per plywood sheet at 2 ft.
maximum spacing. On heavy pours, put plates
on both sides.
Where footings are not used, the Grade Beam
Clip is an economical reusable item.
page 2
2. PANEL ERECTION
Erect, plumb, nail to plate and
temporarily brace the first sheet of
plywood.
Erect additional sheets of plywood
by nailing them to the 2 x 4 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.
3. INSTALL TIES AND “A” BRACKETS
Place the ends of the snap
ties through the holes in the
plywood. The 4-3/4” Snaptie,
Standard is recommended for
use with the Jahn “A” Brackets,
5/8” or 3/4” plywood and 2 x 4
wales.
Two men can do this job with
speed and economy if one
installs the ties and the other
attaches the Jahn “A” Brackets.
page 3
4. Jahn “A” Bracket
The bracket is made of high strength steel
with a cadmium plated eccentric and painted
body which is rust resistant.
Designed for use with single 2 x 4 waler.
Can be installed either before or after walers
are in place.
Can be used for any type of wall forms and
may be used repeatedly.
5. Proper “A” Bracket Installation
page 4
6. Low Walls
A. Install top waler in “A” Brackets first.
B. Tighten waler by firmly striking eccentric lip with hammer.
C. Plumb and align.
D. Brackets may be installed before or
B
after walers. (see 5. Installation)
E. Work from top to bottom,
tightening as you go.
D
F. Break joint a “A” Bracket or
where there is no vertical
joint in plywood.
E
G. Scab may be installed at
any waler joint by using
“C” Bracket
A
C
F
G
7. Inside Walls
Second wall erection procedure is the same as the outside,
except placement of plywood panels over tie ends.
As shown, this can best be done by two men slipping sheet
of plywood over tie ends, starting at the bottom and moving panel from side to side, or up and down to line the hole
in the plywood with each successive tie.
8. Outside Corners
To eliminate cutting full panels, a corner may be
started on the inside wall first, using full 4 ft. plywood panels. When the outside wall is erected,
full sheets are installed in line with the inside ones
andspecial filler ffanels, the same width as the
wall thickness plus plywood thickness, are used to
fill out the exterior corner.
The Jahn Cornerlock is used to retain the walers
at the outside corners.
(see Number 9. Jahn Cornerlock)
page 5
Jahn Scaffold Jack:
The all steel unit designed to fit 24” x 24” and
16” x 24” tie and waler spacings.
This jack has a built in fuardrail receptacle and
is designed to hold two 2 x 10 planks for a
comfortable working platform. Space jacks at
8’-0” maximum centers.
Note: Snap ties are not designed
to carry scaffold bracket loads.
Single Waler System
SINGLE WALER BRACKET INSTALLATION
Wall Height Considerations
Snaptie spacing is dependent upon form pressure and the type of
forming used. Below are a few typical wall form spacing diagrams
for various wall heights with pertinent notes for each height.
WALL APPLICATIONS
Walls
Over
Wall
Form
Over
8ft. High
8 feet
• Single or Double 2x4
strongbacks with
24
support clamps
Walls
Wall
Formto
4
feet
4 ft. High
Walls
Wall
Formto
8 ft.
8High
feet
• Install 4'x8' plywood
horizontally. Attach
• Attach strongbacks vertically
2x4 walers with
horizontal tie-spacing
to full height of
form.
of 2'-0" on center.
• Use proper
spacing to
engage next row
of ties, while
attaching waler
with form aligner
clamps.
• Easily attach
plywood and
secure with
wrench head
snapties and
fastened to every
other walerprovides a
stable alignment for
walls over 10 ft.
• Nail a waler to top of
last waler at plywood
joint.
• Nail aligner brace to
vertical strongback at
1/3 height from top
of form.
• Only one side
needed for bracing.
• Form aligner brace
spacing at 6 ft. on
center.
single waler
forming
brackets.
page 6
9. Jahn Cornerlock
The Jahn Cornerlock is used at the outside corners to
secure the 2 x 4 walers. Only two nails are needed for
attachment, while barbed plates grip the side of the
2 x 4’s for positive non-slip action.
The locking handle has a “Cam-Action”, drawing the
wales together at true right angles, by rotating the
handle 90 degrees toward the wale.
No special tools are needed for either installation or
stripping.
10. Inside Corners
No special treatment is needed for the inside
corners. Merely alternate the walers, as shown.
Erect Strongbacks
Installation of Strongbacks:
Strongbacks are used to aid in form alignment and to
tie stacked panels together. Loose 2 x 4’s are used in
conjunction with Jahn “C” Brackets and 8-1/4” snap
ties or 4-3/4” snap ties with the Jahn Tie Extenders to
strongback forms.
Normal strongback spacing is 8’-0” on center.
Jahn - C Brackets:
Jahn C brackets are used to attach vertical strongbacks for
form work alignment.
Designed for use with 2 x 4 walers and 8-1/4” end.
Eccentric securely holds form work while compensating for
minor variations in lumber sizes.
Bracket can also be used to support a horizontal plywood joint.
Jahn Tie Extender:
Converts short end snap ties to standard end
snap ties.
With the Jahn “C” Bracket and 2 x 4’s, verical
strongbacks are possible at any point in the
form.
Use well crimped nail through holes in
body to secure extender to snap tie.
page 7
Joint Cover Details:
Alternate A
Drill 9/16” diameter hole 1-1/8”
down from top edge of the lower
sheet of plywood.
Alternate B
Install snap tie in the joint between
the panels.
Alternate C
Nail 4 x 4 wale to lower sheet of
plywood, hold the wale in place with
Installation of
Second Lift of Plywood
Lift the plywood sheet and place it into
position.
Tack bottom to joint cover waler.
Hold the sheet in place with a short 2 x 4
spacing block and Jahn “C” Bracket.
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 snap ties, brackets and walersworking bottom to top.
Brackets can be installed either before or
after walers are in place.
Note: Snap ties are not designed to cary
scaffold bracket loads.
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