How to specify a formliner: a plain guide for architects

Start with the pattern, then get specific

A formliner is a textured rubber mat that goes in the form so the finished concrete carries a pattern. Rope rib, board form, ashlar stone, brick, a custom graphic, whatever the wall calls for. The spec is where you tell the plant what you want and how you want it built.

The first line is easy. Name the pattern or profile. But a pattern name alone does not build a panel. A few other things have to be in the spec so the precaster and the liner maker are all reading the same page.

What to put in the spec

Here is a plain checklist. Cover these and the plant knows what to make.

• Pattern or profile. Name it. If it is a stock pattern, name the stock pattern. If it is custom, say so and reference the drawing.
• Depth of relief. How deep the pattern cuts into the face. A shallow board form and a deep fractured rib are very different jobs.
• Draft. The slight angle on the side walls of the relief so the panel releases from the liner. More on this below because it is the one people forget.
• Panel and joint layout. Where the panels break and where the joints fall. The pattern has to work with the joints, not fight them. A rib that runs off the edge of a panel at a random spot looks like a mistake.
• Finish. Are you leaving the concrete as cast, or is there an acid etch, sandblast, stain, or sealer. The finish changes how the pattern reads.
• Sample and mockup requirements. Say what you want to see and when. A small sample for the texture, a full mockup panel if the job is big enough to warrant one. Spell out who approves it.
• Single use or multi use, if it matters. Liners can be built for one pour or for many. If reuse count matters to your budget or your finish consistency, put it in the spec.

Why depth and draft carry the job

Depth and draft are the two that decide whether the panels strip clean, so they deserve their own paragraph.

Depth of relief is how deep the pattern is. A deeper pattern casts a stronger shadow and reads bolder from a distance. It also means the concrete has to pull out of a deeper pocket when the panel strips.

Draft is the slight taper on the walls of that pocket. Think of an ice cube tray. The sides angle out a little so the cube pops loose. A formliner works the same way. If a deep relief has straight walls with no draft, the concrete locks into the liner and you get tearing, chipping, or a liner that will not release. Enough draft lets the panel let go clean.

PCI guidance for architectural precast recommends building adequate draft into any deep relief for exactly this reason, so the panel and the liner separate without damage. If your pattern is deep, talk draft with your rep early.

Samples and mockups, no form required

You spec better when you can see and feel the real thing. Advanced ships spec sheets and samples with no form to fill out. You do not trade your contact info for a PDF. You ask, they send.

Get a physical sample of the pattern in your hand before you finalize the spec. Texture reads differently in person than in a catalog photo. For bigger jobs, plan on a mockup panel so the owner and the design team sign off on the real finish, at real scale, in real light.

A note on references and files

A quick, honest note. MasterFormat section references and downloadable CAD files are on the roadmap and not posted yet. If you need a section number or a CAD block for your drawing set right now, ask your rep and they will tell you where things stand.

Cover the checklist, get depth and draft right, and hold a real sample before you commit. Do that and the spec does its job, the plant builds what you drew, and the panels strip clean.