Scaffolding 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 job.

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)

Concrete Placement

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) 318.

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 concrete pour.

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

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 to top)

Blowouts

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)

Concrete Consolidation

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 top)

Electrical

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 wall.

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: www.demandproduct.com.

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

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)