There are many misconceptions about “big block” units versus SRWs due to misinformation. Here are some perceived advantages of big block units.
- Bigger is better: False - If all walls are designed and constructed properly and based on industry standards outlined in Best Practices for Segmental Retaining Wall Design, they will all perform as required.
- You can build larger gravity walls with big blocks: False - Allan Block with no-fines concrete (NFC) backfill is considered a gravity wall structure and will have a design depth similar to that of big block. Also, the cost of using Allan Block and NFC is consistently $10-$20 a sq ft less than big block when comparing material cost and installation.
- Big blocks can use less geogrid: False - When grid is needed to create reinforced retaining walls, the grid length is equivalent for big block and Allan Block walls, which is roughly 60% of the wall height.
- Big blocks are better when excavation space behind the wall is limited: False Allan Block with no fines concrete backfill can achieve the same wall heights with similar or less structure depth.
With these misconceptions clarified, here are some reasons why Allan Block wins versus big block products.
- Faster manufacturing time using a dry cast concrete block machine
- 1000s/day for AB vs 1-2/day for big block per mold. Block machines produce higher quality product with a much tighter tolerance for block dimension between units.
- Lower freight costs
- Approx. 520 ft² (48 m²) per load for AB vs 15-50 ft² (1.4-4.6 m²) for big block.
- Lower installation cost
- Lower production cost + lower freight cost + the cost of smaller equipment for AB = lower installed cost
- Simplified Scheduling and Installation
- Big block projects need to be produced, staged, shipped and installed in a manner to follow the layout and design parameters of each project. Specific blocks must be shipped at the right time and installed in the correct location within each wall. AB product is simple in that all the product sizes are the same and any unit can go at any spot within the wall which simplifies the scheduling and installation process.
- Large group of AB Certified Contractors
- Thousands of AB Certified Wall Contractors properly trained on SRW installation.
These benefits for Allan Block will most commonly result in a more economical installation cost. Production costs alone may result in up to a 75% reduction when comparing an AB product to a typical big block retaining wall product. When you factor in the additional freight cost due to the additional number of trucks required to ship a big block product, the cost savings can add up quickly.
Another benefit that is often overlooked is the large group of AB Certified Wall Installers. The Allan Block Contractor Certification Program is designed to give contractors the proper training and tools to ensure top quality retaining walls are built. As a leader in the industry, Allan Block Corporation has developed these tools and training programs to help contractors get the knowledge and the resources they need. With the help of our vast network of trained Allan Block representatives, thousands of professionals have already taken advantage of our installation training, technical support, and the many tools we have available to help them plan, design and build with Allan Block products.
SRWs have become a cost effective and reliable option for virtually all retaining wall projects. SRW design, construction and performance have continued to improve, and much of this advancement has been, and will continue to be influenced by Allan Block’s research and development. For more information on AB Walls and NFC, please visit allanblock.com.