Wednesday, September 15, 2010

Segmental Retaining Wall Blocks - Are They The Future?

Only through a descriptive analysis of each type of wall can we hope to assess the differences of each.

Flagstone Retaining Walls: Flagstone has been around since the dawn of time and used for everything. They were found to be plentiful in the mountain regions and carried all over because they were so flat and easy to stack. Very easily stacked by homeowners to keep any garden free from livestock, they became permanent parts of any farm or ranch near enough to use them.

Mining operations found the larger stones and soon, especially in Europe and Great Britain, they were being used to construct buildings and even castles. Made of sandstone, a sedimentary stone, they were easily shaped however necessary. Where the larger stones were shaped and used for retaining walls, the structures could be quite sturdy and virtually indestructible.

Segmental Retaining Walls: These retaining wall systems are created by using solid, high density concrete blocks in a variety of manners. Whether using interlocking pins, bars, or lips formed on the back edge of the block, they are all designed to withstand the stresses required of a retaining wall. This is the only thing they were designed to do.

Demanding specifications have been formulated by each manufacturer through rigorous testing to produce systems that will not fail if installed properly. Such conditions as soil density, wall height, load types, back fill, drainage, etc are all calculated when designing the best application for each location. This is the only true case of engineering as relates to residential retaining walls.

Concrete Block Retaining Walls: Concrete blocks have been used by housing contractors to build retaining walls since they first came out. It was easy to hire the same subcontractor who they used for the walls of the house to create the retaining wall. Some contractors take it one step farther by pouring the block cavities full of concrete. This creates a far stronger wall especially when they put re-bar into the block as well. Doing more than building the wall and pushing dirt in behind it is rare.

The walls created in this manner are good to look at and can be bricked, stuccoed or painted to match the house as needed. Unfortunately, the finished product normally has no drainage behind it nor packed back-fill. Many of them fail within the first five years while most of the ones that don't fall down form cracks that are non-repairable to say nothing of ugly.

Field Stone Retaining Walls: Field stones were first used for retaining walls for much the same reason as any other stone. They were plentiful and free. Farmers and ranchers needed to move them up out of the fields so they became natural walls. Ireland has hundreds of miles of these type walls to contain the livestock. They simply unstack and re-stack sections to create openings when needed.

Much has been done with field stone in America because they create a very natural structure even though the structural integrity cannot be measured. No testing has ever been done to provide installers with any type of construction guidelines.

Railroad Tie Retaining Walls: Because of their regular shape, low cost, and easy accessibility, they have been used by almost every installer at one time or another. They have been referred to as the poor mans retaining wall. Some very elaborate walls have been constructed using this material, some even in the commercial construction arena to support buildings.

As with all wood that contacts the ground, it rots from the ground contact side outward. The evidence of the rot is not even visible until the timbers give way. Another issue is the center of any large timber because the treatment is not absorbed that far inside.

If there was ever a case of availability dictating use, railroad ties are the perfect example. The availability was only made possible because they were used by the railroad and removed when damaged or old. They flooded the market as a cheap material and the best use was for outdoor construction. Retaining wall construction was a natural fit. Only recently has the EPA considered the creosote treatment as dangerous for the environment.

Landscape Timber Retaining Walls: These are the round edged timbers sold by many of the large landscape and hardware companies for use in homeowner landscaping. The level of treatment used in these timbers is far below what is necessary for ground contact. But they are cheap and the homeowner is almost always swayed by cost over all other considerations.

Landscape timbers can make a very pretty wall, are very easy to assemble, and will last for up to five years if they are not under any kind of pressure, such as the earth behind them trying to move. Make sure you put in plenty of drainage.

If a retaining wall is in your future, consider the options carefully accounting for durability, dependability, and overall effectiveness. Much has been done in the last 5 years to create an old style look to the new style retaining wall materials. You might be surprised at what you find.

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