Sneak a peak inside Australia’s first hemp spray build as an alternative to tamping inside double-sided form-work.

Had you heard of spray pumping hemp? Well neither had I but I heard that Joe D’Alo from The Hemp Building Co was doing a build and I wanted to check it out! I was lucky to be able to hop in my car and head down the road 30mins to the lovely hamlet of Yandoit in central Victoria to visit Kath and the team hard at work building the first demonstration of a French designed and imported hempcrete spray machine in Australia.

A hempcrete spray pump machine is a specialised piece of equipment used to apply hempcrete made from hemp fibers, lime, and water. The machine facilitates the application of hempcrete in a sprayable form, making it easier to cover large areas quickly and efficiently. The hemp fibers, lime binder, and water are mixed together in the correct proportions to create a workable hempcrete mix. This mix needs to be of a consistent and sprayable texture.

The mix is loaded into the hopper (a smallish container in this case) of the spray pump machine. The hopper is a container that holds the material before it is pumped into the spray system. The pump generates the necessary pressure to push the hempcrete mix through the hose which is held over the cavities and layered on like sticky icing, with each layer gently tamped to ensure it sticks, and excess swept up to save wastage. Hempcrete needs to cure properly, allowing the lime binder to set and harden. This may involve maintaining moisture levels and ensuring proper ventilation.

Joe has been working with hemp for many years as Australia’s first registered builders to offer unparalleled expertise in this innovative and sustainable material. Joe has undertaken a bold move to import this pricey machine from France, with the requisite binder that works to save water as it is more efficient than other lime based binders on the market for hempcrete and has the requisite tackyness to be able to stick to itself without the support of rigid form-work on both sides.

Kath is in the beginning stages of the hempcrete process, with a steady stream of volunteers and some paid labour helping the process along in her 126sqm passive solar home. Hoping the main part of the build (the form-work was already completed by our friend Andy over at Nothing Is Straight) will take 2 weeks, it is a quick time- frame for this build., With a stunning view and aspect, and being totally off grid, I look forward to seeing the progress of the build and whether the cost of hiring the machinery, and Joe, was worth it down the line as her builds progresses. Keep checking our events page to find out if there’s more opportunities to get involved with hempcrete or other methods throughout the year.

Advantages of Using a Spray Pump Machine

Efficiency: Spraying hempcrete is faster than traditional hand application, especially for large surfaces.
Consistency: The machine ensures a uniform application, which can improve the quality of the finished surface.
Reduced Labor: Using a spray pump machine can reduce the amount of manual labor required, making the process more efficient and less physically demanding.

The choice between pumping and traditional tamping methods depends on several factors, including the scale of the project, the desired finish, and practical considerations like labor and time.

Here’s a comparison to help understand the benefits and limitations of each method:

Pumping Hempcrete

Advantages:

Speed and Efficiency:
Faster Application: Pumping hempcrete is generally faster than tamping, especially for large areas. The spray pump machine can cover extensive surfaces quickly, reducing labor time.
Less Manual Labor: Reduces the need for manual handling and compacting, which can be physically demanding.

Uniform Application:
Consistency: A spray pump machine provides a more consistent application thickness, which can lead to a more uniform finish and better thermal performance.
Reduced Gaps: Minimizes the risk of gaps or inconsistencies that might occur with manual tamping.

Accessibility:
Hard-to-Reach Areas: Easier to apply hempcrete in difficult or elevated areas where tamping would be cumbersome.

Disadvantages:

Initial Cost:
Equipment Expense: Investing in a spray pump machine can be expensive, and it may not be justifiable for smaller projects.

Complexity:
Technical Knowledge: Requires proper training and handling to ensure the mix is compatible with the machine and to achieve the desired finish.

Cleaning and Maintenance:
Maintenance: Regular cleaning and maintenance of the equipment are necessary to prevent clogs and ensure longevity.

Traditional Tamping Method

Advantages:

Cost-Effective:
Lower Initial Cost: No need for specialized equipment; the tamping method typically requires basic tools and materials.

Control and Precision:
Detailed Work: Allows for more detailed work in smaller areas or for specific finishing touches that might be more challenging with a spray machine.
Manual Adjustment: Direct control over the compacting process can be beneficial for ensuring the hempcrete is well-integrated with formwork.

Simplicity:
Simplicity of Process: The method is straightforward and doesn’t require sophisticated machinery.

Disadvantages:

Labor-Intensive:
Time-Consuming: Tamping can be labor-intensive and time-consuming, particularly for large surfaces.
Physical Demand: Involves significant physical effort, which can lead to fatigue and slower progress.

Inconsistencies:
Variable Application: Manual tamping might result in inconsistencies in thickness and compaction, potentially affecting thermal performance and structural integrity.

Accessibility Issues:
Hard-to-Reach Areas: More challenging to apply in high or awkward spaces compared to spraying.

Which Method is Better?

For Large Projects: Pumping hempcrete is often more efficient and practical for larger projects where speed and uniformity are critical.
For Small Projects or Specific Details: Traditional tamping might be preferable for smaller-scale work or where detailed control is needed.

Conclusion

Both methods have their merits, and the choice depends on the specific needs of the project. Pumping is advantageous for its speed, efficiency, and uniform application, making it ideal for large-scale projects. Traditional tamping is suitable for projects where cost is a major concern, and detailed control is needed.

Ultimately, the decision may also be influenced by available resources, expertise, and project requirements. In some cases, a combination of both methods might be employed to optimize the construction process.

If you’d like to see the Hempcrete machine in action, check out this video developed by Benjamin Leroux and AM3P.