Concrete Forming

Frequently Asked Questions


I. What is overlaid plywood?

Olympic Panel® overlaid concrete forming plywood is made by bonding resin-impregnated paper sheets onto one or both surfaces of specially engineered plywood panels. The resulting "overlay" reduces defects in the cured concrete by masking defects and grain patterns commonly found in non-overlay plywood. The overlay provides a smoother finish than is possible with BB Plyform or CDX sheathing. Overlays allow the plywood to be stripped easily from the concrete and permit multiple reuses of the panels as long as proper care is given to preparing and handling the panels before, during, and after the pour.

II. What are the different types of overlaid plywood?

There are three types of overlaid concrete forming panels made by Olympic Panel®: MDO, HDO, and PSF. The difference among them lies in the quantity of resin used within the overlay paper, the plywood construction, the type of surface finish given to the concrete, and the number of reuses possible with each.

MDO (medium density overlay) has a resin content of 34 to 35 percent and gives a "matte" finish to the concrete. Olympic Panel®'s most popular MDO is B-Matte® 333, a one-sided overlaid panel with a veneer back. MDO is commonly used on jobs where a uniform matte finish is required. MDO is frequently used for high rise buildings of six to twelve stories, parking ramps, bridges, support columns, or other applications where a matte finish and multiple reuses are required. Contractors can expect 10-25 reuses from MDO depending on the application, proper handling, care and treatment with an appropriate release agent.

HDO (high density overlay) has a resin content of 52 to 58 percent and appears smoother to the touch than does MDO. HDO is typically used where a smooth finish and a high number of reuses is desired. Hotels, high rise office buildings, museums, power plants, civil projects and large-scale residential projects are common applications for HDO concrete forming panels. Olympic Panel® HDO panels are manufactured as one-sided or two-sided panels ranging from 3/8" to 1-1/2" in thickness. Contractors can expect 25-50 reuses depending on the application, proper handling, care, and treatment with an appropriate release agent (See Section V).

PSF (phenolic surface film) has a resin content of approximately 64 percent. PSF overlays provide a high number of reuses and are used on a variety of projects requiring architectural finishes. PSF overlaid plywood is usually engineered for a specific project. Layups and paper combinations can be varied to fit specific end use requirements-from a high grade, high cost product to a lower grade, economical panel. The number of reuses will vary depending on the panel layup and paper configurations, and on the application for which the panel is to be used.

III. Why Do Contractors Use MDO and HDO panels?

Olympic Panel® overlaid concrete forming panels are less expensive to use on a cost-per-pour basis than non-overlaid plywood such as BB Plyform or CDX plywood. Although the initial cost per sheet for non-overlay panels is less, these low reuse panels add time and money to projects in the long run. For example, a contractor may need to use his forming panels twenty times over several jobs. To make twenty pours, he would need to purchase only one Olympic Panel® B-Matte® 333 panel (at twenty pours per sheet). However, he would have to purchase three BB plyform panels (at seven pours per sheet), or five CDX panels (at four pours per sheet) to get twenty pours. As the table below shows, the cost per pour of the one B-Matte® panel needed for twenty pours is just 31% of the cost of the five CDX panels required. Similarly, the cost of the one Olympic Panel® Classic HDO™ panel needed for forty reuses is just 20% of the ten CDX panels needed for the same number of pours, and 27% of the six BB Plyform panels required.

¾" 4' x 8' MDO B-Matte® 333
Product Cost-per-sheet1 # of panels needed for 20 pours Est. # of pours per panel total panel cost for 20 pours Cost-per-pour, 5 pours Cost-per-pour, 10 pours Cost-per-pour, 15 pours Cost-per-pour, 20 pours % of total CDX cost
B-Matte® $28.00 1 10-25 $28.00 $5.60 $2.80 $1.87 $1.40 31%
BB Plyform $22.00 3 5-7 $66.00 $13.00 $6.60 $4.40 $3.30 73%
CDX $18.00 5 2-4 $90.00 $18.00 $9.00 $6.00 $4.50 100%

1Prices are for comparative purposes only. They do not reflect actual pricing.

¾" x 4' x 8' HDO 100/30
Product Cost-per-sheet1 # of panels needed for 40 pours Est. # of pours per panel total panel cost for 40 pours Cost-per-pour, 10 pours Cost-per-pour, 20 pours Cost-per-pour, 30 pours Cost-per-pour, 40 pours % of total CDX cost
Classic™ $35.00 1 25-75 $35.00 $3.50 $1.75 $1.17 $.88 27%
BB Plyform $22.00 6 5-7 $132.00 $13.20 $6.60 $4.40 $3.30 73%
CDX $18.00 10 2-4 $180.00 $18.00 $9.00 $6.00 $4.50 100%

1Prices are for comparative purposes only. They do not reflect actual pricing.

IV. The Olympic Panel® Product Line

Olympic Panel® manufactures a variety of concrete forming panels for different applications. In addition to its standard products, Olympic Panel® can design panels of various thicknesses, overlay configurations, and veneer layups to suit specific requirements. The most widely used panels today are as follows.

MDO B-Matte® 333 is a one-sided medium density overlaid plywood panel designed to provide a matte finish to the concrete. B-Matte® 333 is specifically designed for concrete forming applications, while competing MDOs will give the user 10-25 reuses depending on application, proper care, and treatment with a release agent.
Dimensions 4' x 8' x ½", 5/8", 11/16", ¾", 1", 1-1/8". 2' x 8' & 4' x 10' panels available on request.

Classic™ 100/30 is a one-sided high density overlaid plywood panel designed to provide a smooth finish to concrete. Contractors can expect 25-50 reuses in job built and gang forms, and up to one hundred reuses in system forms depending on the application, care, and treatment with an appropriate release agent.
Dimensions 4' x 8' x ½", 5/8", 11/16", ¾", 1", 1-1/8". 2' x 8' & 4' x 10' panels available on request.

Classic™ 100/100 is a two-sided high density overlaid plywood panel. Contractors can expect 30-50 reuses in job-built and gang forms, or up to fifty reuses in systems forms, depending on the application, proper care, and treatment with an appropriate release agent.
Dimensions 4x8 x 3/8", ½, 5/8, 11/16", ¾, 1", 1-1/8", 1-3/8", 1-1/2". 2' x 8' & 4' x 10' panels available on request.

Multipour® is a high density overlaid plywood panel that is designed to provide an exceptionally smooth, "architectural" finish to concrete. Due to both the increased amount of HDO overlay on the panel surface and to its special plywood layup, Multipour® can give up to 30-50 reuses depending on application, proper handling, and treatment with an appropriate release agent.
Dimensions 4' x 8' x ½", 5/8", ¾", 1-1/8". 2' x 8' & 4' x 10' panels available on request.

Multipour® Plus provides the smoothest finish possible to concrete surfaces. Multipour® Plus can give its users up to 30-50 reuses depending on the application, care, and treatment with an apprpriate release agent.
Dimensions 4'x8' x ½", 5/8", ¾", 1", 1-1/8". 2 ' x 8' panels available on request.

V. Release Agents

Olympic Panel®' concrete forming panels are a cost effective alternative to BB Plyform or CDX plywood due to the multiple reuses that overlaid panels provide. A chemically reactive release agent must be applied prior to use in order to insure that the panels will perform as designed. Olympic Panel® will warrant the performance of its panels only if a chemically reactive release agent is applied according to the release agent manufacturer's instructions prior to each use. Using a chemically reactive release agent as directed will facilitate stripping and will help to provide a smooth finish to the cured concrete. Olympic Panel®'s MDO B-Matte® 333 panels are lightly coated with a chemically reactive release agent prior to leaving the factory. Olympic Panel® HDO panels are not coated at the factory. However, both must be coated at the job site prior to pouring.

There are two major types of release agents-barrier release agents, and chemically reactive release agents. The following description provides a brief account of each. More detailed information is available in the Olympic Panel® Technical Bulletin # OPP-TB-9712, "Form Oil/Release Agents".

Barrier release agents form a barrier between the concrete forming panel and the concrete. Diesel oil or paraffin are commonly used barrier release agents and are often used with non-overlaid plywood. Although oil-based barrier agents help the panel strip easily from the concrete, the oil tends to coagulate on the panel causing air pockets (or "bugholes") in the hardened surface. In addition, the paraffin in oil remains on the cured concrete after stripping, making adherence of paint, stucco or other surfacing materials difficult. These defects may result in expensive repairs, additional job time, and increased material and labor costs. For these reasons, barrier release agents (such as diesel or motor oils) must not be used with overlaid plywood or where a smooth, minimal defect finish is desired.

Chemically reactive release agents are sprayed in a thin film onto the surface of the plywood. Unlike barrier release agents, chemically reactive release agents react with alkalis in the concrete to form a soapy film between the forming panel and the concrete. By preventing the set of the concrete along the surface of the forming panel, this soapy film does two things: it makes stripping of the panels from the cured concrete easier, and it minimizes "bugholes" or other surface imperfections caused by coagulated material. Chemically reactive release agents should always be used where a smooth, minimal defect finish is desired.

Chemically reactive release agents are easy to obtain and apply. Olympic Panel® can provide information on several reputable brands. Chemically reactive release agents come in drums of several sizes, or can be supplied to the job site in easy-to-use five-gallon "sprayers" with spray attachment and nozzle included.

Chemically reactive release agents are applied to the panels before each use in a variety of ways. Among these are as a fine mist from a sprayer provided by the release agent manufacturer, or by hand with lightly soaked rags. However they are applied, the release agent manufacturer's instructions should be carefully followed. Care should be taken to remove any pooled or excess chemical with a cloth lightly moistened with the agent. Non-overlay plywood requires about one gallon per 1,000 square feet (thirty-two 4' x 8' panels). Olympic Panel® MDO requires about one gallon per 2,000 square feet (sixty-four 4' x 8' panels). Olympic Panel® HDO requires about one gallon per 3,000 square feet (ninety-six 4' x 8' panels).

Olympic Panel® overlay panels can be easily cleaned if a chemically reactive release agent has been applied. Applying release agent to the panel after stripping it from the concrete can also soften concrete hardened on the panel surface. The softened residue can then be cleaned away with a wooden wedge and/or a fiber (not wire) brush.

After the panels have been washed down they should be stored out of the direct sunlight, preferably where they won't be soaked by rain and left to dry in the sun. Covering the panels with a plastic sheet and storing them flat in a cool, shaded place is usually sufficient to prevent warping or other damage that may affect panel performance.

Following these simple steps will allow contractors to use MDO from 10-25 times, and HDO from 30-50 times, providing that the panels are properly handled, stored, and edge sealed. The number of reuses obtained will depend on whether the panels are used in job-built forms or in system configurations.

VI. Edge Sealing

All Olympic Panel® concrete forming panels are edge sealed with a styrene acrylic paint prior to leaving the factory. This helps to prevent water in the concrete from being absorbed into the edges of the plywood while the concrete is curing. Water absorption occurs rapidly with non-overlaid panels and is one of the reasons why they cannot be used more than a few times. The MDO and HDO overlays on Olympic Panel® panels prevent moisture from entering both surfaces of the plywood on two-sided panels. Edge sealant prevents moisture from penetrating the edges.

Any high-quality edge sealer such as a polyurethane or aluminum-based paint can be used to touch up the edges when the panel is cut or damaged. Contractors often cut panels to make them into sizes that will fit their forming needs. With overlaid plywood panels, the contractor needs only to coat the exposed plywood edges of the panels with an aluminum-based paint after cutting. These sealers are commonly carried by most building supply dealers. Please request that your local building materials supplier stock aluminum paint if it is not available in your area.

Any damage to the overlaid surfaces of the panels should be repaired prior to reuse. Auto body putty found at auto parts stores may be used for this purpose. When dry, the putty should be sanded smooth before release agent is reapplied.

 
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