In October the Firth RibRaft® X-Pod® system took another step forward in its meteoric rise as the ‘go to’ foundation system for home builders when it won the Technology Award at the NZ Concrete Awards.
“The judges comments were that they were thoroughly impressed with our ‘environmentally friendly concrete replacement solution’,” says Dene Cook, Divisional Technical Manager for Firth who received the award on behalf of Firth with Fabio Parodi and Aldo Mortola from Cresco Engineers, co-developers of the system.
The judges went on to say that, ‘the pod design allows for easy transportation, installation with results in the reduction of costs. This project uses less overall concrete and more recycled materials and eliminates polystyrene pods for a more environmentally sustainable product.’ The judges also noted that, ‘this system was developed in New Zealand and has high potential impact for foundation systems around New Zealand.’
The award encompassed entries from individuals, firms, research or educational institutions who have made significant contributions to the understanding or use of concrete as evidenced by new technology, research or technical publications, new equipment, new techniques, design innovations or educational activity.
The Evolution of the Firth RibRaft® X-Pod® System
Firth first introduced the polystyrene pod based Firth RibRaft® to the NZ market in the early 1990’s. The system showed exemplary performance in the Canterbury earthquakes. With the aim of continuous improvement a challenge was set within Firth to develop the next generation of foundation system. The outcome of considerable research, development and collaboration with Cresco Engineers NZ Ltd is the Firth RibRaft® X-Pod® System, first launched in 2018.
What were the challenges and how were they met?
To enhance the sustainability of the solution, using recycled materials was a must. With very limited opportunity to reuse plastic the pod design allows the use of 80% recycled plastic. To minimise the volume of concrete required, an innovative adjustable pod system was developed to allow for dimensional flexibility of the foundation system.
Initial value engineering focused on the optimal spacing for the internal ribs of the system. Analysis revealed that ribs at 750mm centres develop the optimal cost vs structural performance solution. This meant that the solution would need to be a completely new concept, rather than simply a substitution of the existing 1100mm pods used in the existing Firth RibRaft. Finite element analysis was undertaken to develop the optimal shape for the pod which provided the required strength while minimising the concrete volume.
Two plastic pods were developed, one which created a grillage of beams at the optimal 750mm centres, which has proven to be an excellent performer in poor ground conditions, and a variant which creates a 1.5m grillage, and is cost effective for good ground sites. The developed Firth RibRaft® X-Pod® solution is the first system on the NZ market which utilises a plastic pod while creating a structural grillage of beams.
Ease of installation
Improved constructability was an important requirement for the design team. The X-Pod’s have been designed to stack making them easy to handle and minimising the volume for transportation. “Now all the components for a house floor can be delivered on a residential trailer,” explains Greg Illing, Construction Systems Specialist for Firth. “The pods are clipped together using a RibRaft Keystone, which holds them firmly in place during construction. The risk of polystyrene pods moving during concrete placement has also been eliminated with the X-Pod®.”
What do we know a year on from the launch of X-Pod®?
“Often on sites with poor ground conditions the Geotech reports require considerable ground improvements to be made for the use of RibRaft® foundations with ribs at 1200 centres,” adds Greg. “Using X-Pod® with 750mm rib spacings can considerably reduce the ground improvements required. For example a current design of the foundation for a 250m2 house initially required an earthworks dig out of 700mm. Using a Firth RibRaft® X-Pod® the amount of material dug out from the site was reduced by 100m3, only requiring a gravel raft of 75 m3 vs 175 m3.”
Fabio from the Cresco Group says, “I have worked with the engineer and the earthworks can be reduced from a 700mm digout and backfill to 300mm with a geotextile and one layer of geogrid. This is thanks to the stiffness of the Firth RibRaft® X-Pod® and our capacity to provide a detailed analysis of the system on soft ground.”
...and happy customers
“I am very familiar with the old polystyrene system and have used it for at least 30 slabs,” says Craig Jensen, Director of Craig Jensen Residential. “When I was shown the Firth RibRaft® X-Pod® system by the architect we discussed it and I was keen to give it try. Now I have used it on the large extension of a home in Mt Eden and there’s no way I’ll go back to the old polystyrene foundation system. Any builder will tell you the stuff is horrible to work with and it’s bad for the environment. X-Pod® arrives on a pallet, it’s made from recycled plastic and it just clips together. There’s no comparison.”
“Once we saw the system we thought it was just better,” says Grant Watson, Director of Capital Homes. “It’s made of recyclable product, we save time in laying it as it’s much quicker to get down and it’s easy to store on site. We are sold on the system and are converting customers over to it. The next two homes we build will be with Firth RibRaft® X-Pod® and the two after that I hope too.”
Construction practices continue to change and develop but the future lies with products which offer enhanced sustainability without taking away from structural integrity, cost effectiveness and performance. In developing the Firth RibRaft X-Pod a set of challenges were set for the development team. The final analysis shows that criteria has been satisfied in a cost effective and sustainable way. We believe that RibRaft® X-Pod® system represents the future for all residential foundation systems.
For more information visit our new dedicated X-Pod® website or call 0800FIRTH1