Landscape Architect Articles

LCN December 2008 Hardscapes12-02-08 | News

Tumbled Hardscapes Challenges

By Michelle Brown, Pavestone Consultant

According to Randy Miller of installer American Interlock and Modular Construction, Inc., the most challenging aspect of the project was the ?EUR??,,????'??stitching?EUR??,,????'?? and the resulting time penalty required. The technique ships mechanically assembled 10 square foot patterned sections to be keyed in with others at the job site. The ?EUR??,,????'??Muster K?EUR??,,????'?? pattern used was a two-piece system, and while a machine mechanically put the pavers down, edge pieces had to be rotated to proper positions and a manufacturing spacer removed. In addition, the edges required inserting manually cut pieces. Images: Pavestone

Tumbled bricks and pavers are a popular method of acquiring that old world look in a new hardscape project. However, what are some challenges encountered with these unique products, and how are they best meet? At LCN, we decided to find out.

North of Fort Worth, Texas is the city of Keller. The District at Uptown is a local development composed of attached homes, town homes and detached homes on 62 individual lots. They average 2,200 square feet and range in size from 30 to 40 feet wide and up to 100 feet in depth. The construction project was notable in that it was the first time Pavestone had applied a mechanical production color blend installation to a residential site.

The District at Uptown, located in Keller, Texas, was the first residential application of a Pavestone mechanically assembled tumbled paver design featuring production blended color. According to the manufacturer, time savings that result reduced one 100,000 square foot bid price from between $1.15 and $1.45 per square foot to $.95 per square foot.

The mechanical production process involves shipping the pavers in 10 square foot sections of the final pattern. The appropriate pavers are adjusted or removed on site to allow the sections to key together. Adjustment of these pieces is known as stitching. Borders also require custom cuts to fill in the space, a time-consuming step in a residential application where narrow streets mean frequent borders.

Randy Miller, of installing company American Interlock and Modular Construction, Inc., says one of the most challenging aspects of this project was this stitching process. ?EUR??,,????'??The project had a mechanical installation, but we also had to go in and manually stitch it together,?EUR??,,????'?? he explains. ?EUR??,,????'??We were laying a Muster K pattern that consisted of a two-piece system. While the machine mechanically puts the pavers down we had to pull out the smaller paver?EUR??,,????'???which is just a spacer piece that is on the pallet for manufacturing purposes?EUR??,,????'??+and stitch it together manually with a rectangle. It was a good learning experience for our company and will be used in future projects.?EUR??,,????'??

The contractor estimates the mechanical installation eliminated 70 percent of the labor requirements with it?EUR??,,????'???s ability to lay about 12 square feet per minute. Another major benefit was a $.50 per square foot savings experienced by the contractor, totaling about $34,000. One man operates the machine while another tightens the paver field. Images:Pavestone

The Spec and Tool Dimension

Compiled by Matthew Doyle

Creating a split faced look to enhance the tumbled appearance of a paver is difficult without a specialized tool. Pave Techs Wall Splitter is designed to create that look with a four-bladed unit that operates at waist level when properly adjusted. The cutting height can range anywhere from 3/8" to 12". Images:Pave Tech

ASTM Specs and Tumbling

As we?EUR??,,????'???re all aware, dimensional consistency can make or break a hardscape project. If the individual blocks don?EUR??,,????'???t go together right, the lines that result can be uneven with unprofessional looking results. As part of our research, LCN interviewed Ted Corvey of Pine Hall Bricks. Dimensional requirements were key in the conversation.

The tumbling process at Pine Hall begins with the initial firing in a football field sized 2,000-degree Fahrenheit kiln over several days to produce a conventional brick. This conventional brick then spends fifteen to twenty minutes or less in a tumbler (essentially a long, angled tube). They then emerge with that battered, chipped and weathered look that?EUR??,,????'???s so distinguishing about this product.

However, one issue with this process is that it inherently degrades dimensional consistency. In fact, regular ASTM standards for chips and corners can no longer be meet. As a result, these bricks are generally sold under a PA classification, which leaves much more room for inconsistency then regular ASTM standards.

In the case of Pine Hall Bricks, Corvey claims they come out of the kiln initially to PX standard, the most stringent in the ASTM system. As a result, while the tumbler will create enough chips and rounded edges to require that the brick be sold under the PA standard, the average dimensions of the faces will still be up to the PX standard. Assembly should therefore be nearly identical to non-tumbled products.

However, other manufacturers may or may not be so scrupulous and take advantage of the openness of the PA standard to loosen up their dimensions. Assembly issues like inconsistent lines and difficult fitting might result, impacting the final aesthetic of the project and customer satisfaction.

As a result, Corvey highly recommends extensive planning before the first brick is ever laid. Just because the specs say 4???8, don?EUR??,,????'???t assume the brick is 4???8, take the time to measure it. Also, make sure to get the actual dimensions on several units from the pile to gauge consistency. Then check these numbers against those demanded by the pattern.

Continue the planning process by utilizing a starting pyramid to get a sense how the actual product will come together and adjust chalk lines accordingly. These lines are another essential step, and should be used to guide the installation process. Measurements, the pyramid assembly, how often the pattern repeats and the perpendicular lines required should all be taken into account. Then move on to the parallel components of the pattern.

While this level of planning should be common to all hardscape projects, the extra potential for dimensional inconsistencies inherent in tumbled products make taking the additional time absolutely crucial.

Another tool specialized for tumbled bricks and pavers is Pave Techs Tumbler Hammer. The face of the hammer is equipped with large teeth designed to rough up the desired section of the paver to get that worn look. It is also optimized to work particularly well on saw-cut faces. Images:Pavestone

Tools and Tumbling

Without a specialized tool, the only way to achieve a split-face look is by saw cutting the block/paver and chiseling the cut until it looks natural. Also, with city ordinances cracking down on noise and dust pollution, splitters offer an advantage that saws simply can?EUR??,,????'???t.

The Wall Splitter from Pave Tech offers the look and texture of a split-faced block, without the wasted labor the chisel requires. When using the tool, lay the material on the double-sided loading table and position the block where the split is needed. When adjusted properly, the four-sided blade should make contact with the block at roughly waist level. To split, work the blade into the block a few times to start the fracture, before lifting up and following through with one quick push. Further splitting of the same height material does not require further adjustment. This tool is able to cut the smallest pavers up to the largest wall block, with a cutting height of 3/8?EUR??,,????'?? to 12?EUR??,,????'??.

Another option for the split-face look from the same company is the Tumbler Hammer. It is designed for use on saw cut surfaces of concrete blocks, caps or pavers to give them the tumbled look. With serrated teeth on both ends, it is the easiest way to create a split face when a splitter is not available.

Building Blocks

8000: Psi. ASTM-936, the standard used for pavers manufactured in the United States, requires that the compressive test strength of the test specimens be at least 8000 psi and that no sample test less than 7200 psi.

Source: ASTM International

1970s: Decade that saw the beginnings of the manufactured paver industry in North America.

Source: McClatchy