Frequently Asked Questions
1. What material does Fitzgerald recommend using for backing?
Strips of wood, Foam strips or expanding foam.
2. What adhesive do you recommend to apply the backing to your form liner?
Any type of ABS or Plumbers Glue.
3. What do you use to seal the joints when using plastic?
Plumbers Glue or ABS glue.
4. Why do we need to add wood backing to some of your patterns?
Due to the depth of some of our Fluted Rib patterns, wood backing is required to prevent deflection from concrete pressure.
5. How do you close off the ends on a plastic liner to prevent concrete from getting behind the liner?
Bevel the edge of the plastic and run a chamfer strip along the edge that is the same depth as the pattern.
6. What is the best type of release agent?What will happen if I use a petroleum based release agent?
You always want to use a water based release agent for the best results (contact your sales rep for recommendations). A petroleum based release agent will deteriorate the liner, thus reducing the life and longevity of the liner.
7. How do I attach the liner to my form?
For plastic it is usually a matter of contractor preference but you can use Tek Drywall Screws, Staples or Glue. When using screws or staples we recommend spacing them approximately 6” to 12” on center around the perimeter and 18” to 24” on center throughout the field. For elastomeric urethane you can attach by screwing or bolting through the back of the form face into the back of the liner, or through the front of the liner into the form face using 1/4” diameter fasteners. Fasteners should be placed at 12” centers on all perimeter edges of the form liners and 18″-24” on center throughout the field.
8. How do I cut the elastomeric liners bonded to plywood?
Should trimming of an elastomeric liner be required, the slower the cutting tool used, the easier the liner will be to trim. A crosscut handsaw provides the best trim on elastomeric liners. If a blade type circular handsaw is used, as many as five or six shallow, slow cuts should be made across the path of the trim. Extreme care should be taken to keep the saw blade from binding or from melting the material. Lubricating the blade with WD-40 during the trim may assist the cut.
9. How do I cut the Vac-u-Form plastic?
As a rule of thumb, the liner will expand or contract approximately 1/16 of an inch, in 10 feet with each 20 degree change in temperature during the placement of concrete. Keep this in mind before trimming the liner too small. Vac-U-Form liners trim easily with a circular handsaw and a fine-tooth plywood blade, such as the type used for cutting veneer paneling. If the liner is to be butted against a rustication strip or reveal, the blade angle should be set so that the liner is cut at the same angle as the reveal. These operations should be performed with the liner securely clamped to a steady workbench to prevent any “chatter” that could fracture the form liner surface. Form liners with minimal relief can be trimmed by scoring with a sharp knife and breaking off the excess.
10. How long do shop drawings take?
It depends on the complexity of the project and design but typically 2 to 4 weeks after receipt of all approvals. Larger scope projects may take longer, and are evaluated on a “project-by-project” basis.
11. Why are some patterns only available in Graylastic urethane?
Not all patterns are applicable for the Vac-u-Form process due to potential issues with deflection, stripping, complexity of pattern design, or size restrictions. Deep relief (2”+) patterns do not lend themselves to the best results in a thermal form application.
12. When using form liner on a radius can you use the Vac-U-Form?
Plastic can be used in a radius application depending on the pattern. We can also provide “un-bonded” urethane, OR urethane bonded to thin noodle board backing for flexibility to attach to your form work.
13. Can I use plastic and urethane on a project in conjunction with each other? Will the finished product look the same?
The finish concrete will be slightly different, and you will also need to build up the form face with plastic, to ensure it aligns with the thicker, bonded, urethane product. We recommend using one type of material on your project, unless they will be used in different locations and not adjacent to each other. Your finishes will appear the same, although urethane typically delivers a cleaner, sharper replication.