GROUND SCREW PROS AND CONS
When building a garden Annexe, fundamentally the most important part of the build is to get right in the foundation. I have experienced first hand the consequences of not getting this right, and the results of any mistakes in this area are huge and often, as surprising as this may sound, difficult to hold people accountable for. It is therefore prudent and strongly advisable to request advice from experts like the team here at ANX to assist and ensure your “once in a lifetime” investment is placed in safe hands….. and on solid foundations.
One of the more innovative options on the market today is ground screws, and we are seeing them being used more and more often in the garden annexe market. Ground screws offer a modern alternative to traditional concrete foundations, but are they right for your project? In this blog, I’ll explore the advantages and disadvantages of using ground screws for construction foundations to help you make an informed decision.
What Are Ground Screws?
Ground screws are steel or galvanized screws that are driven directly into the ground using specialised equipment. They provide a stable base on which structures can be built, eliminating the need for concrete or deep digging. Ground screws come in various lengths and diameters, making them adaptable to different soil types and load requirements.
Are they any good?
Ground Screws have many benefits over their rival foundation solutions, however, when answering “Yes…” to the above questions, one must be cautious and caveat that answer with “….., when done properly…”.
The Pros
Environmentally Friendly and Sustainable
One of the biggest benefits of using ground screws is their low environmental impact. Unlike traditional concrete foundations, which require significant energy to produce and install, ground screws have a smaller carbon footprint. There’s no need for concrete pouring, which means less disruption to the surrounding soil and a reduced impact on local ecosystems. This makes them a great choice for eco-conscious projects or areas with delicate landscapes.
Quick and Easy Installation
Ground screws can be installed rapidly, often within a few hours, depending on the size and complexity of the project. This is a stark contrast to concrete foundations, which may take days or even weeks to complete, factoring in the time needed for excavation, formwork, and curing. The speed of ground screw installation can help keep projects on schedule, especially in areas with unpredictable weather that could otherwise delay traditional foundation work.
Versatility in Challenging Terrain
Ground screws are adaptable to various types of terrain and soil conditions, including slopes, sandy soil, or areas with limited access. This versatility makes them ideal for remote locations or projects on uneven ground. Additionally, because ground screws can be adjusted, they allow for precise levelling of the structure.
Reusable and Reversible
If you decide to remove or relocate your structure, ground screws can be unscrewed and reused, leaving the land almost as it was before installation. This is a major advantage over concrete, which is permanent and difficult to remove. Ground screws can therefore be a more sustainable choice for temporary structures or for projects where flexibility is a priority.
The Cons
Limited Load-Bearing Capacity
Ground Screws are generally best suited for lighter structures. Whilst that doesn’t really effect our Garden Room market as the structures are on the smaller end of the scale (as opposed to multi-story buildings), as the building increases in size, then other options do become more competitive and suitable.
The underside of your building is required to be 150mm off the ground
Whilst 150mm might not seem like a big gap between the existing ground and your floor, by the time you’ve counted for the floor build up, your finished floor level will be approx. 0.5m off the ground, making the use of decking necessary to make the building work.
Requires Specialized Equipment for Installation
Ground screws are not something you can install with basic DIY tools. They require specialized machinery and expertise to ensure correct placement and alignment. This means that, while installation is generally faster, it’s also necessary to hire experienced professionals, which can add to the overall project cost.
Pioneering Construction Innovation
Whilst this type of heading should normally belong in the “Pro’s” section, I am pointing out that using new technology does generally pose its own risks as opposed to using tried and tested techniques that we have learned from over years and years. I strongly recommend that when using Ground screws that you employ a design and build contractor that are happy to 100% responsibility for the design and install of their product.
Summary
There are many advantages to screw piles, however the key to a successful installation is thorough due diligence. Make sure you work with an experienced installer, this can be done by reviewing previous projects; checking their insurance, risk assessments and method statements; asking for their quality management policy and relevant qualifications. Once that’s done, the on site testing is critical. Installer’s should complete a survey of the site for power, water, gas supplies and any drainage; if a public sewer is in situ then a build over agreement will be required . Tests must be completed in the exact location of the proposed building, complete multiple tests if the results are inconsistent, and review the reports before briefing the structural engineer.
Just like the installer back ground checks must be done on the structural engineer, ask for examples of similar work; they must be chartered with a relevant body, such as The Institution of Structural Engineers with certification to prove membership; copies of relevant qualifications along with insurance which must include professional indemnity. Its the engineers job to determine what screw piles are required. For this the building design and specifications are needed, along with site information for weather influences and the screw test results. If the project requires building control the structural engineering and test reports will be required for compliance.
ANX have the experience and services to undertake the due diligence and installation.
Follow this link for more information on build overs and building control.
