Replacing Other Walls with Segmental Retaining Walls

Cost-effective, aesthetically pleasing segmental retaining wall units (SRWs) are rapidly becoming both the design professional and contractors best option for taming transitions in grade and enhancing the overall beauty of landscaping projects.

Equally at home in residential, commercial and heavy highway applications, SRWs are backed by proven design standards and are accepted by the engineering community as viable options to traditional costly poured concrete retaining walls, masonry walls and crib or railroad tie walls. SRWs have the advantage of offering multiple shapes, sizes, colors and textures as well as proven economics, constructability and a proven design methodology.

?EUR??,,????'??The cost comparison of SRWs compares favorably to other type retaining walls,?EUR??,,????'?? according to Sam Miller, P.E., president of Scott Miller Consulting Engineer, in Little Rock, Ark. ?EUR??,,????'??For walls over five to eight feet in height, SRWs typically come in 25 to 40 percent cheaper than properly engineered concrete cast-in-place, natural stone and masonry walls. Fill sites offer the greatest advantage to SRWs and difficult transitions in grade greater than 8 feet in height are almost always more economical with an SRW.?EUR??,,????'??

Slope stabilization and grade transition solutions become part of the overall landscape design beauty when SRWs are the retaining wall selected.

While timber and railroad tie walls are less expensive than SRWs initially, timber walls typically have a much shorter design life on the order of 10 to 20 years when compared to the 75 to 100 year design life for SRWs. So while timber walls are only moderately cheaper in the short term, the life cycle costs and replacement costs of timber walls (typically three to four times over the life of a comparable SRW) are much higher. Additionally, SRWs are much better for the environment and do not contain chemical additives such as creosote, arsenic and nickel like timbers. Across the country treated timbers are increasingly being classified as hazardous waste. Many municipalities are banning timber walls and many landfills will no longer accept them or do so at premium cost.

SRWs are typically more visually appealing than other type walls and are much more versatile. SRWs are available in a multitude of colors and a wide variety of sizes, face patterns and textures including sculptured faces, straight split faces, striated faces, tumbled faces, etc. Multi-piece block systems are becoming very popular and add to the visual appeal. The systems can also be designed to incorporate live plantings within the units. SRWs, because of the face patterns, also resist graffiti extremely well, making them ideal in urban environments. Additionally, SRWs offer much more design flexibility and lend themselves to graceful radiuses, 90-degree corners, stairs and columns and satisfy other complex architectural requirements.

Adds Miller: ?EUR??,,????'??I have designed projects utilizing segmental retaining wall units in a variety of shapes and structures to include steps, planters, walls, columns, retaining walls and parapet walls all incorporated into the same project. Poured concrete was considered but could not provide as aesthetically a pleasing product within the same budget.?EUR??,,????'?? SRW systems incorporate well into landscapes and are often coupled with interlocking concrete pavers around pool decks, patios and walkways.

Being a dry stacked, mortarless wall system, the individual units naturally flex and move with shrink/swell cycles of the soil and can tolerate this movement without affecting the structural performance and aesthetics of the wall. This same movement can detrimentally crack and damage concrete and masonry systems, shortening their life and necessitating repairs. Additionally, SRWs by their virtue of being mortar-less systems are permeable and readily allow movement of water through the wall face, and in combination with a drainage tile this helps to alleviate the build up of hydrostatic pressure. Other wall systems depend primarily upon weep holes and are typically more susceptible to failure due to hydrostatic pressure. Unlike timber walls, SRW blocks are relatively inert and are not affected by wet soils and humidity as natural wood products. They do not attract insects, bugs and rodents which can be destructive to the overall property. However, if damaged, SRWs are normally very easy to repair. Individual blocks that are damaged can be singularly removed and a new face inserted on a block-by-block basis. Projects have been designed with this ease of repair in mind. By constructing an SRW over buried utilities, the wall can be dismantled block by block in a ?EUR??,,????'??V?EUR??,,????'?? pattern over the buried utility, the blocks repalletized, the utility accessed and repaired and the wall reconstructed with the original blocks leaving no visible change to the aesthetics of the wall. This can be very difficult to virtually impossible to accomplish with other types of retaining wall systems.

The multi-stone SRW delivers a beautiful, yet natural look. The texture discourages graffiti, adding to the appeal for urban retaining wall projects.

SRWs can also be installed much quicker than other types of walls including CIP walls, timber walls, stonewalls and masonry walls. An experienced SRW installation crew will lay between 750 and 1,500 square feet of wall per day on larger projects. Which means that a 5,000 square foot wall can be completed in less than one week. An equivalent concrete or masonry wall would require approximately twice as much time considering the form work, rebar placement, concrete placement and curing time, and backfill placement. A significant amount of the savings in time is the fact with an SRW the backfill is placed at the same time the wall is built instead of waiting until after the wall is completed as with other type walls.

Another benefit of SRWs is their ease of constructability in extreme weather. Winter months find concrete pours being limited to days when temperatures are 40 degrees and rising. Mortared systems are also hampered by cold weather with the grout becoming impossible to work with. Hot summertime temperatures also affect concrete and mortared systems, often necessitating in more expensive admixtures and/or ice in the mix to avoid flashset. As long as the soil remains unfrozen SRW?EUR??,,????'???s can be effectively constructed. Adds Mark North of Mark North Erosion Systems in Fort Worth: ?EUR??,,????'??We have kept projects on schedule by converting other retaining wall systems to SRWs. One example is a Denny?EUR??,,????'???s Restaurant in Arlington, Texas. Cold weather was holding up the concrete work, including the specified CIP retaining walls. The retaining walls were crucial to the project, by switching to SRWs we completed the walls in a timely fashion and kept the project on track. The owner received a more aesthetic wall while saving money.?EUR??,,????'??

The ability to backfill a wall at the same time it is built increases project installation speed.

And according to Randy Miller of Concrete Paver Systems in Dallas: ?EUR??,,????'??SRWs are typically installed with much less experienced crews since the technology and training is much lower for SRWs. Generally one or two experienced foreman are present on the job with a crew having three to four relatively unskilled laborers. Concrete or other masonry walls typically require experienced carpenters for the form work, rod busters for the rebar placement and/or concrete finishers or masons.?EUR??,,????'?? As a result, the experience required for an SRW crew is significantly less than concrete or other masonry walls and consequently the labor costs for SRWs are significantly less when compared to other type walls.

An experienced SRW installation crew can lay between 750 and 1,500 square feet of wall per day on large projects.

"The patented rear-lip design of Anchor Wall stones aid in efficient installations due to the fact that mortar and pins are not required," said Alva Logsdon of Pavestone Company. "There are many valuable tools to assist the contractor's success in SRW installation. From NCMA professional certification and manufacturer product knowledge courses, to technical manuals and the new Anchor Assistant?EUR??,,????<

Sam Miller concludes: ?EUR??,,????'??SRWs provide the economics, aesthetics, design flexibility and structural stability required to successfully complete retaining and landscaping projects.?EUR??,,????'??

Compared to other retaining wall choices, SRWs are often the most logical solution for design professionals, owners and contractors.