What are ground screws?
As the name suggests they are literally screws that go into the ground, pretty much like your typical metal screw, only much bigger!
They are made of galvanised steel and weather proofed for longevity.
On top of each screw is a standard or bespoke bracket which the floor joists are fixed to.
How are they installed?
They are screwed into the ground typically to a depth of 1.2m to 5m using specialist equipment.
How do they work?
The surface friction on the shaft of the screw and interaction with the ground around the threaded portion creates stability. Joists are then attached directly to the screws.
How do we know they are strong enough?
Load testing, commonly referred to as a ‘pull test’ is carried out on site to verify capacity. Simply put, this involves using specialist equipment to measure how much force is needed to begin to move an installed ground screw. This provides empirical evidence for engineers and building inspectors.
What can ground screws be used for?
Ground screws come in various sizes and can be installed to varying depths. This makes them suitable for a wide range of projects: a garden room; conservatory; porch; extension.
Why consider ground screws?
Traditional concrete foundations are obviously a tried and trusted method and typically a go to solution for most builders. However, more and more people are finding that ground screws offer a truly alternative and innovative solution. There are many advantages over concrete that make them worthy of consideration for your new build.
No more digging!
Building foundations with concrete involves extensive excavation and a lot of soil moving work. Not only is this a labour extensive process, it uses heavy machinery, fuel and is very messy. It can also damage surrounding soil. And all that soil has to be disposed of somehow!
Ground screws are driven directly into the ground which means there is no waste material and the surrounding area and soil is largely untouched.
No need for soil sealing
Unlike concrete foundations, ground screws avoid unnecessary surface sealing of the soil. The soil ecosystem remains intact and undisturbed. Rainwater is able to trickle underneath the foundations without the need for any separate drainage channels to be installed.
This means that should the building be dismantled, the ground underneath remains intact and quickly reverts to its original condition.
An ideal solution for less than ideal sites!
For some problem sites concrete foundations are not practically or economically viable. Examples could be land that is difficult to access with large machinery: an area that contains underground pipes and cables: a sloping site. Using ground screws enables an installer to access any site and plan precisely where the foundations are placed.
Speedy and simple installation
Laying of traditional foundations involves a great many steps: digging, preparing, reinforcing. And once the concrete is poured and sealed, several days are needed to allow it to dry before anything can be placed on them.
With ground screws, once the foundation points have been measured and marked out, installation can start. This is usually completed in day or two at most. The foundations can then be built upon immediately. On average using ground screws is 70% quicker than concrete foundations.
All year round installation
In a country that has on average 250 rainy days a year, the fact that ground screws can be installed whatever the weather is a huge benefit. In contrast, laying concrete in wet conditions can severely compromise or delay the build.
Whereas removing concrete foundations involves separating and disposing at landfill, ground screws can literally be unscrewed and provided they are undamaged they can simply be used again. Alternatively, they are completely recyclable.
There are many cost savings to be made. Ground screw foundations means there is no need for the hire of heavy machinery and associated fuel costs. Significantly less labour requirements makes for a much cheaper build. Avoiding soil sealing enables rainwater to run under the house and removes the need for costly guttering and drainage systems.
Costs can also be recouped in future by reusing steel trusses and ground screws.
We think ground screws are a really exciting construction development and hope this article has provided useful information on how they can benefit a build. This youtube video https://youtu.be/BeU7dzlh6wk offers a good insight into the technique and shows just how the screws are installed. If you have any queries or have a project that you would like to discuss please feel free to contact us.