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Open Graded Base vs. Traditional Base: Choosing the Right Foundation for Your Landscape Project

Creating a strong foundation for landscape construction projects in London, Ontario can be challenging due to the harsh climate. Therefore, choosing between Open Graded Base (also known as permeable base) and Traditional Base is a critical decision. This choice can significantly impact the durability and performance of the outdoor space. In this blog post, we will explore the characteristics, advantages, disadvantages, and considerations of both options. This information will help you make an informed decision for your next project.


Traditional Base:


Traditional Base typically consists of a engineered well-graded mixture of coarse and fine aggregates. The materials is usually referred to as Granular A or 3/4" minus. Once it is placed, the material is compacted to form a stable and load-bearing foundation. This kind of base is the most commonly used.


Advantages:

  1. Cost-Effective: Traditional Base materials are often more readily available and can be less expensive compared to some alternatives.

  2. Proven Track Record: Traditional bases have been widely used and tested in various construction projects, from landscape construction to heavy civil projects, providing a known level of reliability.

Disadvantages:

  1. Moisture Content Dependent: For achieving 100% compaction, the layer must have the right amount of moisture, which is known as optimum moisture content. This helps to minimize friction and achieve maximum compaction, but excessive moisture can lead to settling, sinking, and uneven surfaces which may compromise the integrity of the construction project.

  2. Drainage: Limited drainage capacity of this option compared to open-graded alternatives can lead to water pooling on the surface, which might not be desirable in some applications.

  3. Potential Heaving: In cold climates, traditional A gravel may be more prone to frost heave. When water within the gravel freezes and expands, it can lead to uneven settling or heaving, potentially causing damage to structures or surfaces.


Considerations:

  1. Drainage: Traditional bases may not offer the same level of water permeability as Open Graded Bases, which can impact drainage efficiency. When installed correctly a drainage plan is essential for the success of this base.

Traditional Base Installed On Pool Pation London Ontario
Traditional Base


Open Graded Base (OGB):


An Open Graded Base consists of engineered 3/4" crushed stone, but with a higher percentage of void spaces between the particles by eliminating all fines. This design allows water to pass through more easily creating a permeable system.


Advantages:

  1. Improved Drainage: OGB promotes better water drainage, reducing the risk of water pooling on the surface and increasing the overall stability of the project.

  2. Less Susceptible to Frost Heave: The open structure of OGB can make it less prone to frost heave issues in colder climates.

  3. Easier Compaction: OGB allows for a much effortless compaction. Without fines the crushed stones "Lock into position" when a vibratory plate tamper is run on the surface.

  4. All-Weather: Without fines to retain any moisture, the OGB can be worked on in all weather conditions.

Disadvantages:

  1. Cost: Installation of a OGB may cost more then the traditional base

  2. May Trap Water: When working in a hard subgrade like tough clay, the water that may accumulate in the base may require a exit path.

  3. May require Reinforcement: When working in a soft subgrade like Sand a separation cloth or Geotextile may be essential to the success by providing a separation barrier between the crushed stone and sand.

Considerations:

  1. Material Costs: Open Graded Base materials might be slightly more expensive, but the long-term benefits may outweigh the initial investment.

  2. Installation Expertise: Proper installation is crucial for the effectiveness of OGB, requiring skilled contractors familiar with its unique characteristics, as well as the characteristics of the existing sub-base.

  3. Drainage System: Consider installing a PVC perforated drainage system on hard surfaces to assist any accumulated moisture to exit the area.

  4. Reinforcements: Consider installing a geotextile base on soft sub-bases to separate the two materials as well as provide a extra layer of strength.


Open graded base reinforced with geotextile in Tilsonburg Ontario
Permeable Base System

Conclusion:


When it comes to choosing between Open Graded Base and Traditional Base for your landscape construction project, there are various factors to consider. These include your project's specific needs, budget constraints, and local climate considerations.


At Hoffman Maintenance & Contracting, we prefer to use an Open-graded system in London Ontario for all our patios, retaining walls, and garden beds, as long as our client's budget allows for it. This permeable system has been gaining popularity among contractors in North America.


Whether you decide to go for the time-tested reliability of a Traditional Base or the enhanced drainage capabilities of an Open Graded Base, it's always a good idea to consult with experienced landscape professionals. They can guide you towards the best choice for your unique project.

If you have any questions or need further guidance on selecting the right base for your landscape construction, don't hesitate to reach out to us at Hoffman Maintenance & Contracting. We're always here to help you create outdoor spaces that stand the test of time.

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