Custom Rock formliners require the use of formwork to back up the liners and support the concrete for a quality end result. Formwork must be used with Custom Rock Formliners and there are specific requirements for attaching our liners to the formwork, depending on the type of liner purchased.
If using elastomeric formliners in your project you will need to assemble and brace the architectural side of the formwork first, then attach the formliner before setting ties or opposite formwork.
Position the formliner against the formwork so that edges, pattern, and joints are square. Work with one liner at a time.
Elastomeric formliners can be attached to the forms from the front or back of the form with bolts or lag screws. The head of the bolt can be screwed into the face of the liner and covered with a silicon or urethane caulking material.
Should joints be required, compress the joint as tightly as possible, without buckling or distorting the pattern. Seal all joints by caulking or gasketing to prevent grout joint leakage.
Dress the joints and edges with a utility knife or sander to match pattern features as closely as possible.
Cover the formliner when it is not in use to prolong the life of the material and pattern.
When using plastic formliners, make sure that the correct side goes toward the formwork or casting bed. The glossy side of the formliner is placed against the formwork or casting bed and the concrete is poured against the textured (haircell) side.
Level and square the formwork to ensure proper alignment of the formliners. Dimensions should be marked to square edges, patterns and joints. Working with one sheet at a time, position the formliner against the formwork so that edges and joints are square.
Screws or nails should be spaced approximately 6” to 12” on center around the perimeter of the formliner and 18” to 24” in the center. Tek drywall screws work very well, as they are self-drilling and easy to install.
Pneumatic staplers are also easy to install. However, they do not hold as well as screws or nails and should be spaced closer together.
In tilt-up wall applications, a common method of attachment is to place the formliner on the slab, drill a hole through the formliner and into the concrete, place a wooden dowel into the drilled hole, break the dowel off flush with the surface, and then use a large-headed roofing nail to hold the formliner in place. The dowels are drilled out and the holes are patched after the job is complete.
On tilt-up jobs, double-coated foam tape provides an easy way to secure the formliner to the casting bed. On most patterns the tape should be centered on the formliner seams. Carpet tape 1/32” – 1/16” is recommended. Both formliner and concrete must be clean and dry.
When adhering plastic formliners to metal forms, use “Formica Top” adhesive or an adhesive for bonding plastic to metal. As a rule, glues and adhesives are not recommended. Some have excellent holding power, but are difficult to work with on the jobsite.
To prevent deflection from the pressure of the concrete, some formliner patterns will require additional support. Generally patterns with ribs wider than ¾” or a depth greater than ¾” should have backing strips installed. The need for backing strips should be confirmed from the test pour. Wood or styrene foam insulation board should be used between the formliner and the formwork.