FinnForm Technical Bulletin

FinnForm is a superior product specifically designed for concrete forming. Consistent end-use results are not only dependent on proper form design but also of equal importance on proper care and useage. In this technical bulletin, we review and detail those steps necessary to insure proper care and storage of FinnForm.

MOISTURE PENETRATION - SEALING

FinnForm, as in any other forming plywood, if not properly sealed can absorb water and moisture which could cause the panel to swell unevenly (thicken) in the area of moisture penetration. This swelling although usually less than 1/32" can cause a slight indentation in the concrete.

To prevent moisture penetration it is important that all recut FinnForm edges, all penetrations of the phenolic impregnated faces by fastening devices (nails, screws, header teks, etc.) and any other face damage, be properly sealed or resealed where required. Please note that even with proper sealing, grain raise (swelling) can occur. This is normal with any plywood panel.

a. Areas to be Sealed

All recut edges and all penetrations made in FinnForm plywood for attaching to the backup must be sealed to prevent moistture penetration. If not properly sealed, moisture may cause swelling along the recut edges and around tie, bolt, nail or screw holes.

NOTE: FinnForm plywood has edges completely sealed at the mill. However, in some cases, the mill applied sealer is scraped off due to shipment handling damage. It is, therefore, important to inspect all panels prior to use. (If the edge sealer has been damaged, the edge area effected should be resealed prior to use.) In fact it is recommended that all edges (even factory sealed) be resealed before use, since minor handling damage may not be visible to the eye.

Improper care and storage can also cause heavy scars in the panel face thereby removing the phenolic plastic impregnation of the outer plies. Moisture penetration will also occur in these areas if not properly sealed prior to use.

If swelling has occurrred, allow the panel to dry before applying any sealers, otherwise the moisture will be permanently trapped in the plywood giving a deviation from the normal face plane.

In addition, it is also recommended, when stripping FinnForm from the forms after use, that all sealed areas be inspected and resealed where required prior to storage or reuse.

b. Recommended Types of Sealers

A variety of water repellent sealers are effective. Among those that have proven useful for keeping moisture out of FinnForm are:

1. Urethane Sealers (Exterior)
2. Epoxy Paint (Waterless)
3. 100% Acrylic Resins Paint

NOTE: To insure proper application of sealers, consult the sealer instructions or the sealer manufacturer directly.

CUTTING AND FASTENING

There are a few installation aids that will facilitate the cutting and fastening of FinnForm:

a. Cutting

FinnForm plywood can be cut readily with any sharp saw blade. However, if a large amount of mill work is anticipated, carbide tip saw blades have been the most efficient and economical. Any saw that heels, can cause splintering of either or both faces. FinnForm can be cut with hand held circle saws (skil type). However for high quality form work, table type saws have been the most proficient. When drilling tie holes the best method has been to use a hole saw. If this is not possible, it is suggested that, as with any laminated product, it is best to use some method of back-up blocking to prevent excessive splintering of the back side of the panel.

b. Fastening

Where the surface requirements will allow the use of nails, it is recommended that common rather than box nails be used, since they will hold into the back-up material more effectively. Experience has shown that it is economical to use more sophisticated fastening devices because forms made with FinnForm faces have a greater effective re-use expectancy. Such devices as screw nails, ring shank nails, recessed flat head screws, header teks, split rivets, have been used to fasten FinnForm to the back up material. Blind fastening devices, etc., have been used to fasten FinnForm to back-up material where contractors needed a fair faced concrete. This is feasible because the withdrawal loads of fastening devices (screws, nails, etc.) are much higher in FinnForm than in most other plywoods.

HANDLING AND CLEANING

Carelessness in handling and stripping the form can result in reducing the useful life and reuse capability inherent in FinnForm. Suggested methods for handling and, where required, cleaning and repairing FinnForm are detailed below:

a. Handling

When handling or stripping the forms, care should be taken to prevent damage to FinnForm corners and edges. Do not use metal bars or pries in stripping; use only wooden wedges when necessary. Lower forms and panels from high places with particular care. Fill and seal all saw cuts, dents and other damaged areas as they occur. Re-seal all edges which have to be cut.

Pre-fabricated forms, designed for edge protection of the panels and for easy removal, help to reduce possibility of damage. Use of protecting metal edges and double-headed nails speeds stripping and reduces damage to framework.

NOTE: Easiest removal and minimum damage to forms occur when formwork is stripped from the concrete as soon as possible.

b. Use of Release Agents

Concrete by nature is abrasive. Water by nature is a lubricant. Vibrators by design move the concrete mass with high force and in usually an abrasive motion. Therefore all concrete form surfaces are subject to abrasion. Any abraded surface will tend to collect mechanically, fines (cement particle, silica, etc.) in the minute scratches. This can lead to a fines build which in turn may peel off the formface—blemishing, blotching, and discoloring the concrete face. Release agents tend to reduce the probability of this happening. Therefore we recommend the use of release agents. The phenolic impregnated faces of FinnForm are inert and have not combined chemically with any release agents. FinnForm has been compatible with all recognized release agents.

c. Cleaning and Repairing

Cleaning and repairing the phenolic impregnated face will improve the useful life of FinnForm panels. Cleaning with a wide blunt blade or stiff brush has been the most successful. All face damage should be patched and repaired after each use. Epoxy type plastic and other fillers are useful. Holes may be plugged with cork, metal plates or plastic inserts.

NOTE: FinnForm has the same face surface on both sides and often it is more economical to reverse the panel when repairing the used side is considered excessive. In all cases, lightly apply release agents prior to each use.

STORAGE

In cases where FinnForm will be stored prior to use or re-use, the following procedures should be employed:

a. Cleaning (prior to storage)

In case of storage after use, it is recommended that all FinnForm panels be thoroughly cleaned with a stiff brush and hose to remove particles of concrete and sand. Pull projecting nails and reseal all holes, damaged edges, and other areas as previously defined.

b. Storage

The following procedures will increase the useful life of FinnForm in periods of prolonged storage:

1. Clean, repair, reseal and apply release agents to panels before storage as previously defined.
2. Stack panels off the ground on near level supports—never stack on edges.
3. Stack according to size or type to facilitate rehandling and reuse.
4. Framed panels should be stacked face to face and back to back alternatively to avoid damage to faces from handling bolts, etc.
5. Close or bolt stacking is acceptable for a short period. Always stack panels under cover or preferably in a building.

®FinnForm is a registered trademark of Plywood & Door Manufacturers Corporation, Union, New Jersey.