While there are many reasons for smooth, featureless walls, when you want the look of stone, brick, wood or other high-end architectural finishes, patterned concrete makes an attractive, inexpensive substitute. Shapes and textures can be easily created by using architectural forms, formliners, formliners that embed thin bricks or blocks, and block forms.
The Arch-Crete textured forming system uses a high-impact and wear-resistant composite material to create lightweight wall panel forms. "Arch-Crete was created to simplify the process of creating decorative concrete for precast, tilt-up and cast-in-place applications," says Paul Munro of Arch-Crete.
Each 3-ft. by 6-ft. panel weighs an average of 57 lbs., making them easy to transport. These forms are assembled by the same methods as steel and aluminum forming systems, although Arch-Crete has designed new forming fasteners and hardware to improve ease of use. A dynamically designed reinforcement grid matrix provides maximum strength during the pouring process, limiting deflection to provide uniform concrete finishes.
The form panels have been lab tested for durability and rated at more than 1,500 pours. These forms do not absorb water, so concrete does not stick to them. Six face textures are available, including boulder stone, castle cut stone and river rock.
Contractors who already own forms or who want a broad choice of surface patterns may prefer formliners. Formliners save contractors time and money compared to placing a stone or brick veneer on a completed smooth wall.
Fitzgerald Formliners offers more than 250 patterns, including brick, rope, fractured fin and wood. The company has five different liner types for use in tilt-up, cast-in-place and precast walls. "Plastic ABS .110 can be reused six to eight times, while Plastic ABS .150 gets 10 to 15 reuses," explains Jill Richards of Fitzgerald Formliners. "Plastic Styrene is a single-use material. GrayLastic urethane is a heavy-duty urethane material and can get up to 100 reuses." A single-use gasket works in tilt-up construction; precasters use urethane.
The plastic liners come in 4-ft. by 8-ft. and 4-ft. by 10-ft. sizes and weigh from 16 to 34 lbs. each. Because the surface being textured is often not exactly the same size, the formliner may need trimming with a circular handsaw. Plastic formliners expand and contract 1/16 in. per 10 ft. with each 20-degree temperature change during concrete placement.
Urethane liner size varies widely, with a standard size of 4 ft. by 10 ft., but they can be much longer. These weigh 5 to 12 lbs. per sq. ft. Some liners are designed for side-to-side and end-to-end matching so when they are butted up together, the pattern will match as it moves across the finished wall. The maximum pour rate for plastic and urethane formliners is 600 to 750 lbs. per sq. ft.; liners with more highly textured patterns require slower placement.
Choosing the right formliner depends on the pattern desired, the liner's intended use and how many times the contractor wishes to use it. If a contractor wants to form up the entire job at once, if the preferred pattern is available, a single use plastic formliner would make economic sense, notes Richards.
Increte Systems Inc. offers the Stone-Crete system for cast-in-place walls. These formliners are used for residential and commercial structural walls, interior basement walls, bridge abutments, retaining walls, subdivision entries and highway sound barriers. All 10 patterns are available in 2-ft. by 6-ft. and 6-ft. by 2-ft. sizes, while the coquina pattern also comes in 4 ft. by 6 ft.
The high reuse urethane rubber forms are good for 100 or more pours and weigh 90 lbs. in the 2-ft. by 6-ft. size. The same size high reuse urethane foam forms weigh only 24 lbs. and will last at least 50 pours. The foam forms are becoming more popular because they are both lighter and easier to cut, Mike Lowe Jr. of Increte Systems notes.
"With most systems, typically you get seams where the forms butt up together where they adjoin," explains Lowe. "We have a patented removable keystone that bridges the gap on each seam. It makes our walls more realistic because you can't really spot the seams. Every set of liners comes with keystones.
"Every pattern we have here was a custom pattern at one time," says Lowe. "The Sedona pattern, which is the most popular, was created for a project in Arizona's Sedona Valley. They sent us some boulders and some stones and we duplicated the texture and shape. It's very realistic looking."
Brick-embedded concrete walls
For clients desiring real brick exteriors with tilt-up or precast concrete wall prices and efficiency, Scott System, Inc. offers a brick inlay system. The company makes three types of formliners used for integrally casting brick into concrete. Workers need no special training to insert 1/2-in. thick bricks into these liners. "Casting brick into concrete is fast, economical and beautiful," explains Dana Scott of Scott System. "When the wall goes up, the brick is already in place. Scaffolding, flashing, lintels and weep cavities are eliminated also."
Made of urethane elastomer, the Brick Gasket Liner comes in a 4-ft. by 8-ft. standard size and custom sizes. Thin bricks are placed into the liner pockets and concrete is poured over the back of the assembly, integrally casting the brick tiles into the concrete. The BGL is guaranteed for 100 uses and lasts longer with proper care. "This is a good alternative for repetitive precast spandrels," says Scott.
Brick Snaps are a single-use product made of polystyrene. They can be assembled in a variety of patterns and can accommodate four different brick sizes. This is a single-use template system for precast or tilt-up applications. A similar product, the Block Snaps, is used for integral casting of 8-in. by 16-in. thin block.
Scott System's newest product, Rim Snaps, are for casting brick vertically, typically in columns, climbing forms and other poured-in-place applications. This product can be reused.
The Scott System templates strip off quickly, but the bricks stay put. "Pull out tests show that the brick itself will shear, but not 'fall out' or 'pull out' of concrete, at 3,000 psi," Scott notes. "The bond is permanent." The finished panels should be washed using high pressure hot water.
Design Pro makes forms that let concrete contractors make their own landscape, V-interlock and knob-style blocks. These large blocks are used for landscaped parking lots, privacy walls and product divider walls at concrete plants. The forms are made of "10-gauge steel with a formed channel running around the outside edge," notes Dan Stocke of Design Pro. They last indefinitely unless they are hit by a hard object or run over. Each form can be used to make two blocks per day by pouring one in the morning and then stripping off the form before pouring another block in the afternoon. The clamps on the corners are used as levers to strip the form.
"All of our forms are created so that you pour face down," Stocke points out. "They are made of two L-shaped halves that clamp together in the corner, so whatever you're pouring them on is going to be the face. Many people pour on top of a cement slab to get a smooth surface." Because decorative faces have become so popular, they manufacture urethane mats in 10 stone patterns. These mats are placed in the bottom of the form to create a patterned finish on the block's face. Custom mats are also available.
"These are wet cast blocks," Stocke points out. "Blocks at supply stores are dry cast and they are quite brittle. If you hit one of our walls with a truck, it's not going anywhere, although it might be chipped. Our blocks are much more massive than what you find elsewhere."
Each landscape block form uses 16 cu. ft. of concrete to make a 2-ft. by 2-ft. by 4-ft. block that weighs 2,400 lbs. They have tapered side walls so they can form a curved wall. Design Pro's newest product is a mid-sized landscape block form. It makes four 1-ft. high by 2-ft. wide by 2-ft. deep blocks at once that each weigh 560 lbs. These smaller blocks look better in residential settings and can be lifted with a small skid steer.
By inserting rebar, the form can be filled as little as 6 in. and added to later, a good use for leftover concrete from other jobs. "The only thing anyone is going to see is the front of the block, so if the sides are a little marred or have pour lines, it doesn't matter," notes Stocke.
Jean Feingold is a Gainesville, Fla.-based freelance writer who frequently covers concrete and other construction-related topics.