Top Mark Property Improvements > Precast Block Retaining Walls
Precast Block Retaining Walls
Large segmental retaining walls are constructed using precast concrete blocks that weigh in excess of 100 lbs each. These blocks come in a variety of shapes and sizes and some weigh as much as 5,000 lbs. Large precast retaining wall blocks are more suited for building medium to heavy duty retaining walls that are usually above 5′ in height. As these blocks must be placed using heavy equipment adequate site access is a prerequisite.
Precast retaining wall blocks work by interlocking with each other to provide great stability and strength. Each block interlocks with the one beneath it. and every course is offset by half a block so that a running bond is created to provide maximum strength and stability. Each course will often have a slight setback called a batter to improve stability by leaning back into the retained soil.
Unlike Armour stone retaining walls, Segmental retaining walls are fairly rigid, and are incapable of minor movements without undermining the structural integrity of the retaining wall. However, because the entire wall is interlocked, and is acting as one unit, even a comparatively slender wall can withstand more robust lateral earth pressures than an Armour stone retaining wall of the same depth.
A precast block retaining wall reinforced with Geo-Grid can withstand substantial loads and can be built up to 50′ in height. For retaining walls in excess of 6′ in height, or walls that will have to bear additional loads, large precast concrete blocks such as Redi-Rock are better suited. These Types of retaining walls should always be designed by a certified structural engineer.
If your retaining wall project requires a wall in excess of 3′ in height, it is best to contact a specialized retaining wall contractor well in advance as the design and permit phase of the project could take considerable time and resources. We are fully equipped to service residential, commercial and industrial clients in the Mississauga, Oakville. Burlington, Hamilton 8, surrounding areas. Give us a call today to set up a free consultation.
Sandie Dix Wall
The existing wall between the neighbouring properties was a hodgepodge of natural stone, pieces of concrete and cement, reinforced with olde pieces of pipe and wood. The difference in elevation ranged from 4 feet to 10 feet along the length of the 60 feet of wall.
The concern of the neighbours was the erosion and integrity of the existing structure. The homeowner on the high side of the wall was worried about damage to the existing forsythia hedge, while the lady on the low side of the wall was afraid her garden would get trampled during the rebuilding of the wall. Care had to be taken to ensure that the issues expressed by the adjacent property owners were addressed.
The slope of the property dictated that the wall was to be higher at the bottom of the garden, and was to step up with the incline of the land.
As the homes were built close together, sharing single driveways, there was no access for equipment, so the existing wall had to be demolished carefully and removed by hand. The old wall stones were taken away by wheelbarrow and all new materials had to be delivered by wheelbarrow and placed by hand.
The base gravel and all backfill were also brought in and installed manually. Drainage pipe and filter fabric were required behind the wall, and geo-grid mesh was placed every 2 feet of wall height to ensure tieback strength throughout the length of the structure.
The block used is an Oaks Precast product – Hewnstone – a hollow block with a smooth decorative face. The fibreglass (yellow) pins ensure further locking of the blocks. The strength of the wall and drainage is increased by filling the hollow space with clear gravel.
This wall was also built by hand using a rough faced Oaks Precast block. The patterned concrete pool deck and the confined space prevented access by machinery. The previouoly existing railroad tie retaining wall was removed by hand from the property and the new concrete block structure was installed by hand to minimize damage.
The hollow block filled with gravel and pinned retaining system allow for both strength of the wall system as well as sufficient drainage behind the wall. Perforated weeping tile pipe, filter fabric and geo-mesh are all recommended to enhance the integrity of the finished product. The rough split face of the exposed wall offers a decorative appeal.
The original wall, adjacent to the driveway was a brick facing, backed by a concrete block wall. The existing combination had long since outlived its structural life, and was in need of replacement.
Techo-Bloc Suprema Wall System, a one hundred pound block with rough finished split-face a groove and pin locking system, provides the structural integrity for a large wall, while giving a visual appeal.
The block is to be laid on a gravel base, and back-filled with clear ¾ inch aggregate. A layer of heavy filter fabric separates the soil to be retained from the wall and the drainage system installed behind the block. The added weight of the gravel inside the block locks this wall together for years and prevents excessive movement for the life of the wall. Geo-grid re-inforcing is installed along the length of the wall at a height interval of every 24 inches or 3 courses of block.
Piedmonte Onyx Wall cap by Techo is installed atop the wall as a finished coping.
The previous installation had deteriorated to the point of crumbling. Poor drainage and an improper installed base had caused the wall to lean and the pathway atop the wall to shift.
Upon demolition of the wall, a pre-existing layer of railroad tie had been left in the wall, and poorly installed drainage behind the wall had contributed to the shortened life-span of the existing structure.
After installing Techo-Bloc Suprema Wall System to replace the leaning, crumbling existing wall, Unilock Artline Interlocking Stone with an inlaid Black Series 3000 border pathway was installed.
Proper installation of base, backfill, filter fabric, and socked drainage pipe are all essential to the long life of a properly installed retaining wall.
The strength and integrity of this wall will last for decades, as long as proper installation techniques are followed. The installed Piedmont coping has the ability to support a decorative fence or railing for safety, as seen in the accompanying pictures.