and Bracing Bucks
It is important to keep the wall assembly straight,
plumb, and square during wall assembly when concrete
is being placed, and while the concrete is curing. Withstanding
the pressures of wind speeds (including unexpected storms)
during the construction process should be a consideration.
It is also important to provide a safe, adequate, portable,
and temporary working platform so that walls as high
as 12-feet can be constructed. For these reasons it
is very important that the vertical legs of the scaffolding
and bracing system be attached securely to the wall
assembly at every form course, and that the vertical
leg be supported securely by a diagonal brace (kicker)
with a turnbuckle and be securely fastened to the ground
or floor deck.
Scaffolding and bracing bucks should be installed on
the inside of the building, starting 2-feet from corners
and at 6-foot intervals along the length of each wall.
The layout of the scaffolding and bracing system can
vary depending on the location of window and door openings,
and other building details. The regular 6-foot spacing
helps in keeping the wall straight and stable, while
creating a solid base for attaching walk planks and
guardrails where required. The distance between supports
for walk planks and guardrails should not exceed 6-foot.
See: Installation Guide.
Using a level or a plumb bob to check corners for plumb,
use a string line stretched between corners in combination
with bracing bucks and adjustable turnbuckles to straighten
walls prior to and soon after concrete placement.
Walls higher than 12-feet will need to be constructed
in more than one installation. Example: A 16-foot high
wall can be built in two separate 8-foot high installations.
Special scaffolding and bracing considerations need
to be made when constructing walls higher than 12-foot.
Standard ICF Corporation does not manufacture
a scaffolding and bracing system. You can build your
own system using wood, or you can build an inexpensive,
durable, adjustable, and reusable system using standard
structural grade steel studs manufactured by Dietrich
Industries. The component parts are available through
ICF Building Products, LTD. www.icfbp.com Or, there are
several commercially available ICF scaffolding and bracing
systems available through Reech-Craft: www.reechcraft.com,
and ICF Building Products, LTD. www.icfbp.com
It is very important
that all scaffolding and bracing used to construct walls
using Standard Insulating Concrete Forms conform to,
and be in accordance with, Local and State authority,
and Federal OSHA regulations, requirements, and guidelines
set forth in 29 CFR 1926.450 thru 453. Safety First!
(back to top)
Before Concrete Checklist
Prior to placing concrete into the wall forms, check
the entire wall assembly for plumb, straight, and square,
making any needed adjustments using the turnbuckles
on the bracing system. Note:
Keep in mind that once concrete has been placed in the
wall, a wall tilted slightly inward can be plumbed easier
by pushing (rather than pulling) using the turnbuckles
on the bracing system.
Check to make sure that provisions have been made for
all penetrations through the wall. See: Utility, Mechanical,
and Service Penetrations. Make sure that all window
and door frames (bucks) are flanged and braced properly
and that mechanical fasteners have been installed to
anchor the frames to the concrete. Check that all re-bars
are installed and/or wired in place properly with special
attention given to lentils over windows and door openings.
Check to make sure that anchor bolts and ledger connectors
for attaching band joist or ledgers to the wall are
in place. Check to see also, that all other connecting
devices that are to be place into the fresh concrete
are on hand. Fill all gaps with minimum expanding foam
adhesive on both sides of cut forms and openings where
concrete leakage could occur. And check to see that
all wall areas and cut forms that require spices have
had spice pieces added to both side of each form.
Ensure that the scaffolding and bracing system is built
to the manufacture's specifications and anchored securely
while at the same time straightening and plumbing the
walls using a string line. Make sure that scaffolding
provides an adequate working platform, and is installed
with proper safety precautions and in compliance with
the proper governing authority for health and safety.
Instruct workers and crewmembers about the importance
of safe working procedures and conditions. Have an adequate
supply of materials and tools on hand to deal with mishaps
such as spills, blowouts, and other unforeseen problems.
For reasons of safety and convenience, it is a good
idea to have both running water and a telephone on the
This is a partial list. Over time you will develop
a checklist of your own--one that relates to your projects,
to your system and method of building, and one that
will become familiar to your crew. Remember the new
adage "do not order the concrete until you are
ready". (back to top)
Standard Insulation Concrete Forms (ICFs) are
designed to resist the pressure of concrete being place
(pumped) in accordance with Standard ICF Corporation
specifications and American Concrete Institute (ACI)
Although there are several ways to place concrete into
ICFs, years of experience in the field have shown that
the easiest way is with a concrete pump. Both line pumps
and boom pumps can be used. However, it is not practical
to use a line pump with a hose diameter larger than
2-inches because the weight of the hose makes it difficult
to manually handle it around the job site during a continuous
When using a boom pump, we highly recommend reducing
the size of concrete hose to 3-inches and then add two
90-degree elbows (a dog leg) or a Lamberts Loop
to slow the flow rate of the concrete as it is pumped
into the forms. It is also important to add an 8 to
10-foot length of flexible hose (an elephant trunk)
at the end of the pump line to make it easy to maneuver
the hose and direct the flow of concrete. This is especially
important when lowering the hose along the wall assembly
to fill under window and door frames and other difficult
areas of the wall. Although the pump operator will move
the boom along the wall, it is important for the worker
at the end of the hose to have accurate control of where
the concrete is being place. The elephant trunk will
allow the worker to move the hose short distances quickly
when necessary. See: Installation Guide.
The placement of concrete has many variables that must
be considered before pumping begins. The overall size
of the project, the height of the walls, the temperature
and humidity, the concrete mix design, the use of concrete
additives, the concrete slump, the rate (height of each
lift) at which the concrete should be placed, and, if
needed, the method of consolidating the concrete. It
will also be necessary to have materials on hand to
make repairs if an unexpected blowout should occur,
and to have enough workers on the job to perform all
the tasks required to accomplish a quality installation,
in a reasonable length of time, and in a safe manner.
Safety First! In addition, the placement of concrete
should follow guidelines and recommendations of the
American Concrete Institute (ACI).
The environmental factors that will influence the design
of the concrete and that will affect the rate at which
the wall cavity should be filled are temperature, humidity,
wind, and direct or indirect sunlight. Concrete placed
in insulating concrete forms (ICFs) generates heat during
its curing process (hydration) and is retained within
the forms. This eliminates the need for additional insulation
or additives during cold weather applications. ICFs
can also provide a better quality concrete in warmer
climatic conditions. It should also be noted that concrete
could gain up to 50% more compressive strength during
a 28-day moist-cure environment when placed in ICFs.
Environmental factors can also affect the rate of flow
at which concrete should be placed into Standard ICFs.
Concrete should be placed in the wall cavity at a continuous,
moderate, and even flow rate using several lift heights
to gain the desired total wall height.
As a general rule, it is not advisable to place concrete
in lifts higher than 4-foot each. Experience has shown
that the consolidation of the concrete during the placement
process may require a final pass to ensure an adequate
amount of concrete at the top of the wall. Worker judgment
will be required to determine the safe rate of placement
and the number passes required. It is always best to
"lean on the side of caution" to ensure a
quality installation. (back to top)
Concrete Placement Rate Table
Feet per Hour
2.2 (2 ft, 2 ½
2.75 (2 ft, 9 in)
3.03 (3 ft, ½
3.85 (3 ft, 10
4.4 (4 ft, 4 ¾
4.95 (4 ft, 11
It is advisable to have a designated worker(s) to watch
the walls during concrete placement to ensure that pressure
from the placement of the concrete is not deforming
the wall and to ensure that the concrete is flowing
and being consolidated within the wall cavity properly.
It is also important to ensure that all structural components,
connectors, and re-bar are properly aligned.
Concrete strength should meet or exceed that required
by the building design and shall not be less than 3000
psi @ 28 days curing time. The key to good concrete
flow and consolidation is maintaining a proper slump.
A 6-inch slump is best for most applications.
Working together with your concrete supplier to develop
a delivery plan and a concrete mix design that will
work well using the components available in your area
is recommended. Arranging to have ready-mixed concrete
trucks arrive every 45 minutes is a good rule of thumb.
Concrete admixtures, used in accordance with the manufacturer's
recommendations, can be used in formulating a concrete
mix design to accomplish the desired workability and
results. The concrete supplier and the pumping service
will have a lot of experience. Tell them exactly what
you are doing, and don't hesitate to ask them for help
or suggestions when you need it.
Having a designated worker on the job, other than the
pump operator, to keep an eye on the concrete consistency
and slump is good insurance against problems developing.
Examples are: On a hot day the concrete can loose 1-inch
of the slump going from the ready-mixed truck to end
of the pump hose. The segregation of concrete components
caused by dropping concrete may require changes in the
concrete mix design.
Engineering and architectural
specifications and drawings will determine the required
compressive strength of concrete, as well as the size,
grade, and the position of the steel reinforcing bars.
The placement of concrete and design of steel reinforcing
shall be in accordance with local standards and regulations,
and in accordance with ACI 318. (back
Standard ICFs are designed to withstand the pressure
of concrete placement when installed in accordance with
the guidelines set forth in this manual, and when using
generally accepted building practices and common sense.
The term "blowout" is used to describe the
rare instance when a small area involving a portion
of one or two forms, fails during concrete placement.
Blowouts usually occur where a damaged form has been
installed, or where exterior bracing is inadequate.
These situations can further be aggravated when improper
concrete placement occurs. See: Before Concrete Checklist,
and Concrete Placement.
One should not be overly concerned about blowouts,
spills, bulges, or other mishaps because such unforeseen
problems can be easily corrected. Do not panic. Be prepared.
Always have an adequate supply of materials and tools
on hand so that you can deal with the situation immediately.
While the problem area is being repaired, concrete pumping
can continue in other areas of the wall.
A repair can be made by allowing concrete to flow out
of the damaged area relieving enough pressure to push
the form back together. The area should then be reinforced
using screws to secure pieces of wood to the stud flanges.
The area may need to be reinforced on both sides of
the form. In this case, a piece of ¾-inch plywood
placed on both sides of the wall, connected with a length
of all-tread rod, and secured together with large washers
and nuts may be helpful.
Since each situation is different, there will be times
when you may need to improvise and be creative when
solving a problem. To insure quality installations,
remember: 1) do not order the concrete until you are
ready, and 2) maintain a proper concrete slump during
placement. (back to top)
The placement of each lift of concrete must be consolidated
to ensure that all steel reinforcing bar (re-bar) are
fully embedded and that no voids occur in the concrete.
This is especially important in areas around window
and door openings, and in lintels where the positioning
of re-bar may inhibit concrete flow. For this reason
it is always best not to place any concrete into lintels
until the elevation of the concrete lift being placed
can fill the wall and lintel cavities and can be consolidated
into a continuous monolithic pour.
Several different ways to consolidate concrete in Standard
ICFs are: (1) Pushing and pulling up and down,
and/or shaking a length of re-bar in the freshly placed
concrete known as "rodding". This is an old
but effective way to get concrete to move and consolidate.
(2) Tapping with a carpenter's hammer on a 16-inch length
of 2x4 placed over the vertical stud locations marked
on the external surface of the forms. Tapping on the
sides of the wood window and door bucks and bulkheads
can help to consolidate concrete. This method is easy
to accomplish and very effective in consolidating concrete
within the wall cavity. (3) Using an internal "pencil"
vibrator (1-inch diameter or less) can also be used,
but with caution. These vibrators, unless used with
some skill and training, should not be used for consolidating
concrete in Standard ICFs. Internal vibrators
are best used conservatively, and in areas such as lintels
where steel re-bar can constrict the flow of concrete.
The use of internal vibrators can cause extreme and
unnecessary pressure to be placed on the ICFs.
The key to good concrete flow and consolidation is
maintaining a proper slump. A 6-inch slump is best for
most application. (back to top)
After Concrete Placement
Before concrete placement the walls should be checked
for plumb and straight. This should also be done at
the end of the pour by adjusting the turnbuckle on the
bracing. A string line pulled between corners is the
best method for checking the wall for straightness.
At the same time, anchor bolts or structural connectors
can be used to check for alignment. They can also be
installed at the top of the wall. If an additional story
is to be built above the finished surface, the concrete
should be kept slightly below the top of the forms so
the tongue and grooves can be kept clean of concrete
to allow for a good connection. If there are no additional
stories, the surface should be troweled level with the
top of the wall. (back to top)
Concrete Curing and Removal of Bracing
If the walls are below grade and are to be backfilled,
remove the bracing after the wall has developed adequate
strength and is supported laterally at the top by the
floor or roof, and at the bottom by the floor. Above
grade walls should also be allowed to cure properly
to obtain adequate strength. Bracing should be kept
in place as long as required for structural integrity
and safety. Normal building steps and procedures usually
allow enough time for adequate concrete strength to
develop, however it is best not to rush the process.
Environmental factors (temperature, humidity, wind,
and direct or indirect sunlight) will influence the
rate of the strengthening process during curing. Low
temperatures and/or high humidity will slow the concrete
curing rate but allow for increased strength to develop.
High temperatures and/or low humidity will speed up
concrete curing but lower strength development.
Because ICFs are insulated, the heat generated during
the curing of the concrete is retained within the forms
eliminating the need for additional insulation or additives
during cold weather applications. ICFs also provide
a better quality concrete in warmer climatic conditions
because ICFs are sealed containers that inhibit the
loss of moisture, creating a moist-cure environment.
It should also be noted that concrete could gain up
to 50% more compressive strength during a 180-day moist-cure
environment provided in ICFs. (back to
Start by marking (w/ magic marker) the route of all
the planned electrical wiring or conduit and the location
of device boxes on the surface of the walls. Then, by
using a router, with an appropriate size and shape bit,
make a 1 ½-inch deep groove through the foam
and the hard plastic stud flanges. This groove will
allow the wire or conduit to be buried below the surface
of the finished wall, which is sufficient in avoiding
the reach of screws used for attaching furnishings and
wall coverings. The electrical wire or conduit can be
friction fit or held in place with spots of foam adhesive.
Electrical device boxes with surface mounting side
ears are installed similarly by removing a piece of
foam next to a stud flange and using course thread screws
secured to the flange. Device boxes can be held in place
with foam adhesive, or can be anchored to the concrete
Hot wire knives can be used to make grooves and to
remove pieces of foam for installing wiring, conduit
and device boxes. They work with speed and make no dust
in the process. Hot knives will not, however, cut through
the hard plastic flanges, which will need to be cut
and removed with a saw or router. Hot knives are available
from ICF Building Products, LTD.: www.icfbp.com, Windlock
Select: www.windlockselect.com, and Demand Products:
Standard ICFs have a designated electrical wire
and conduit chase, making for easy cuts with a saw or
router while avoiding wall-ties. Standard ICFs
also provide a place in the stud flange for installing
4-inch device boxes where necessary without encountering
the wall-ties in the bracket.
All electrical wiring
and device boxes must be installed in accordance with
appropriate governing electrical authority and code.
(back to top)
Plumbing pipes are usually not located in exterior
walls. The kitchen sink is commonly the only exception
to the rule. In this case, with 2 3/8-inches of foam
on the inside of the wall, there is enough room to make
a channel of sufficient size to accept drain, vent,
and water supply pipes.(back to top)