Ground Screw Load Testing: When and Why You Need It

Ground screws work brilliantly for everything from garden sheds to commercial buildings, but these applications create very different demands on foundations.

Your typical shed weighs maybe 50-100kg and sits on decent garden soil. A modular classroom weighs several tonnes, houses 30 children, and might be placed on challenging ground conditions. 

Solar installations, telecommunications masts, and industrial equipment each bring their own challenges to the table. 

Ground screws handle all these projects successfully, but some require load testing to prove the foundations will safely support what you’re building. Understanding when testing is mandatory for compliance reasons – and when it simply makes good sense – helps you plan your project and avoid complications.

This guide explains when load testing is required, what the process entails, and how to determine whether your project requires it.

Which Projects Require Load Testing?

To put it bluntly, load testing isn’t optional for many projects. Either building regulations demand it, or the consequences of getting it wrong are too serious to risk. 

Building control – responsible for upholding building regulations across the UK (with variations in Wales, Scotland, and NI) won’t approve certain structures without load testing data. 

Other times, load testing may not be strictly required, but is highly recommended to ensure a safe, stable build.

Here’s a deeper look at exactly when you’ll need load testing for ground screws:

Understanding Ground Screw Building Regulations

Building regulations apply to a wide range of structures where safety and structural integrity are paramount. Your local building control department won’t approve these projects without documented proof that your foundations can handle the loads you’re planning to place on them.

The scope of building regulations is broader than many people realise. Garden rooms with sleeping facilities need approval, but so do larger garden offices, commercial buildings, and any structure above certain size thresholds.

Some common projects requiring building control approval include:

• Garden rooms used for sleeping or living accommodation
• Home extensions becoming permanent parts of your property
• Commercial and industrial buildings of any size
• Structures exceeding 30 square metres floor area
• Any building requiring structural load calculations

Building control officers require more than manufacturer specifications – they need site-specific testing data that proves your ground screws can withstand the loads according to British Standards (BS) for geotechnical design. 

Understanding Performance in Different Ground Conditions

Ground conditions impact screw performance, which can be verified with load testing. 

Some examples of ground that warrants load testing analysis include:

• Soft soils or waterlogged ground that might not provide adequate support
• Made ground or contaminated land with unknown characteristics
• Waterside areas or areas with seasonal water table changes that affect soil stability
• Sloping sites where conditions vary significantly across the build area
• Ground with varying soil types that create unpredictable performance

In such conditions, proper load testing reveals what your screws can handle in your ground, helping you adjust screw lengths, add foundation points, or modify your design accordingly. 

Commercial Structures That Push Weight Limits

Commercial buildings – such as retail units, workshops, or office buildings – generate high loads that require stricter testing. Solar installations, telecommunications equipment, and industrial machinery also place their own unique demands on foundations. 

Load testing verifies that structures will withstand various loads, both vertically and horizontally. 

Understand the Load Testing Process

Load testing is relatively quick and straightforward to carry out. We bring hydraulic equipment to your site and systematically test your screws by applying controlled forces while measuring their response.

Most projects undergo compression testing to verify their downward weight capacity. Some structures might also need tension testing for uplift forces and horizontal testing for wind loading. 

Let’s explore each type of load testing in more detail:

1. Compression Testing

Compression testing is the most common type, measuring the downward weight your screws can withstand. We use hydraulic equipment to push down on the screw heads with gradually increasing force. It’s primarily advised for:

• Garden rooms and home offices
• Home extensions and annexes
• Most commercial buildings
• Storage facilities and workshops

2. Tension Testing

Some projects also need tension testing, which measures resistance to upward forces. 

Buildings with large roofs, solar installations, or structures in windy locations can experience uplift forces that try to pull their foundations out of the ground.

Instead of pushing down, we pull upward with the hydraulic equipment to understand how much upward force your screws can resist.

3. Horizontal Testing

Horizontal testing measures resistance to sideways forces from wind loading, ground pressure, or structural systems that push foundations sideways.

We apply measured sideways forces to determine how much lateral load your screws can withstand before they start to move.

Horizontal testing is typically recommended for structures with significant wind exposure, such as taller buildings and solar installations. 

What Your Test Results Tell You

We start with your chosen screw specification (or what we believe will be ideal) and analyse how it performs.

If initial testing indicates that your chosen screws require more capacity, we can switch to different specifications during the testing process itself. 

We continue testing until we achieve the design loadings your project requires. There may also be other modifications to consider:

• Adding more foundation points to distribute loads across additional screws
• Modifying your building design to reduce foundation demands
• Using different installation techniques that perform better in your specific ground conditions

We test and refine until your foundations are proven to work for your specific ground and structural loads. If your project requires building control approval, you’ll gain the detailed, site-specific data they need for sign-off. 

When Load Testing Is the Right Call

Certain projects and site conditions make testing either essential or highly advisable. In these situations, it’s not just added reassurance – it’s smart risk management. You should seriously consider testing if:

• You’re building on unknown, variable, or poor ground: Soft clay, waterlogged soil, made-up ground, or contaminated sites can all significantly reduce the performance of ground screws. Testing shows whether your planned specification can cope.
• You’re building something heavy or high-risk: Garden rooms with sleeping accommodation, modular classrooms, offices, or retail units often involve heavier loads or stricter compliance requirements that justify testing.
• You’re dealing with unusual or concentrated loads: Installations involving heavy equipment, solar systems, or large roof spans may need uplift or lateral testing in addition to standard compression testing.

Remember, if your project requires building control approval, load testing is a legal requirement. 

GSC has extensive experience producing reliable, compliant data for building control, whether for residential or commercial building regulations, temporary works approval, or any other compliance requirement. 

When Load Testing May Not Be Necessary

There are numerous smaller, low-risk projects where formal testing isn’t necessary. These projects tend to follow well-understood patterns, with known ground conditions and predictable loads. For example:

• Lightweight garden structures: Sheds, bin stores, small pergolas, and similar buildings on firm, undisturbed ground.
• Simple decks or low platforms: Decking close to ground level, especially with light use and on stable ground, typically doesn’t require testing unless the site conditions are questionable.
• DIY projects using standard kits: If your design follows standard guidelines and doesn’t introduce concentrated loads or unusual site conditions, ground screw performance is usually well within expected tolerances.

Still, even for smaller builds, testing can offer peace of mind – especially if poor ground, structural modifications, or long-term use might increase the load over time. We can advise on whether you need load testing – so feel free to contact us with any technical queries. 

Making the Right Testing Decision for Your Project

Most straightforward residential projects don’t need formal load testing – established specifications handle typical garden buildings reliably. But when you do need testing, working with a specialist who understands both ground screws and the testing process makes all the difference.

GSC combines 15 years of ground screw expertise with comprehensive load testing services. We know which projects benefit from testing, how to interpret results, and what adjustments improve performance. 

Whether you need simple verification for building control or detailed analysis for challenging conditions, we provide testing that protects your investment.

Explore our comprehensive range of self-install and commercial screws, or contact our friendly team with any questions about load testing. 

Whether you need straightforward DIY screws for a garden shed or professionally tested foundations for a commercial building, our team is waiting to get your project off the ground.