Eurocode 7 and Ground Screws: What the Standard Says About Foundation Design Using Screws

Eurocode 7 (ČSN EN 1997) is the European standard for geotechnical design, which also applies to foundations using ground screws (screw piles). If you are planning a photovoltaic power plant, timber-frame building, or industrial facility and are considering ground screws as an alternative to concrete, Eurocode 7 is the document that both your structural engineer and the building authority will reference.

This guide explains what the standard requires, how it applies to working with the screwdriving machine, and what it means in practice for EPC contractors.

What is Eurocode 7?

Eurocode 7 (EN 1997-1 and EN 1997-2) is part of the Eurocode series of European standards for structural design. Part 1 covers general rules for geotechnical design, and Part 2 covers ground investigation and testing.

It is implemented in the Czech Republic as EN 1997-1 a CSN EN 1997-2. Since 2010, it has replaced the older national standards for foundation engineering.

Key areas for ground screws:

Geotechnical categories (GK1–GK3) — which surveys are mandatory
Design Approaches (DA1, DA2, DA3) — How to Calculate the Ultimate Load-Carrying Capacity
Requirements for pile foundations (Section 7) — direct basis for ground screw calculations
Testing and Monitoring — When Is a Test Pilot Needed?

How does Eurocode 7 classify screw piles?

Ground screws (screw piles or helical piles) are classified in Eurocode 7 as pile foundations (pile foundations). Section 7 of EN 1997-1 applies to them.

Specifically, the following are relevant:

§7.4 — Vertical Load-Carrying Capacity of Piles — calculation of the ultimate bearing capacity based on the geotechnical parameters of the soil
§7.5 — Horizontal Bearing Capacity of Piles — relevant for wind-loaded structures (solar power plants, carports)
§7.6 — Pilot Testing — when static or dynamic load testing is necessary
§2.8 — Geotechnical Categories — determines the scope of the survey

Geotechnical Categories and What They Mean in Practice

Eurocode 7 classifies projects into three geotechnical categories (GK) based on complexity:

Category	Typical Projects	Requirements
GK1	Simple structures, uniform conditions, PV systems on flat terrain	Minimal research required; experience is sufficient
GK2	Standard construction projects involving terrain of a certain complexity, industrial buildings	Routine Geotechnical Survey + Calculation
GK3	Unusual conditions, unstable slopes, heavy loads	Comprehensive survey, specialized geotechnical engineer

The vast majority of projects using ground-source heat pumps (solar power plants of 1–10 MWp, wooden buildings, and industrial facilities on standard soil) fall under GK1 or GK2. This involves a geotechnical survey consisting of 1–3 boreholes at the site and a standard bearing capacity calculation.

Design Approach DA1 — How to Calculate Load-Bearing Capacity

The Czech National Annex to EN 1997-1 prescribes design approach DA1, combinations 1 and 2, for piles:

DA1 Combination 1 (DA1/1): load × 1.35/1.5, geotechnical parameters without reduction → deformation is evaluated
DA1 Combination 2 (DA1/2): load without reduction, geotechnical parameters × 1.25 → the limit state of bearing capacity is evaluated

In practice, this means the following for ground anchors: the designer needs the soil shear strength values (φ, c) from a geotechnical investigation, typically CPT tests or borehole investigations with SPT tests.

Based on this data, the following is calculated: characteristic load-carrying capacity of the screw R_k and it is verified whether the resulting design load-bearing capacity R_d = R_k / γ_t exceeds the design load.

For a PV plant project in standard loamy-sandy soil without anomalies, this calculation generally demonstrates sufficient load-bearing capacity for screws with a diameter of 76–110 mm.

When is a probationary period necessary?

Eurocode 7 §7.6 establishes the conditions for mandatory pile load testing. For ground screws, the following are particularly relevant:

A test pilot is recommended or required if:

The project is in complex geotechnical conditions (GK3)
The soil resistivity cannot be reliably determined by calculation from the available data.
This is a high-risk project (bridges, high-rise buildings)
The investor or insurance company requires proof of bearing capacity by measurement.

A test pilot is generally not required if:

GK1 or GK2, standard soil, investigation conducted
PV project or light industrial building with low loads
There is experience with similar projects at the site (reference pilots).

In practice: for typical PV plants up to 10 MWp on flat terrain in the Czech Republic, the test pilot generally does not have to be omitted — but it depends on the specific soil. Trial drilling of the first 3–5 piles with torque measurement is a standard procedure that most pile-driving machines (including Glentor B80 a Glentor C65) enables thanks to data recording from the telematics unit.

Machine certification vs. foundation certification

Eurocode 7 addresses the design and verification of the foundation, whereas the CE mark addresses machine safety. CE certification of a driving machine confirms its safe operation, not the load-bearing capacity of the installed foundation. The load-bearing capacity of a pile or ground screw must always be assessed separately according to the geotechnical and structural requirements of the given project.

The bearing capacity of the foundation is proven by:

By geotechnical survey (CPT, CPT probes, laboratory tests)
By structural calculation per EN 1997-1 (to be prepared by the designer)
Minutes of installation - recording the moment and depth of each screw (machine telematics)

Glentor B80 i Glentor C65 they are equipped with a telematics unit that records the torque curve during screwing. This record serves as proof of achieving geotechnical resistance at each point — a key document for both the designer and the building authority.

What this means for the EPC contractor: a practical checklist

If you are building on ground screws and the project is subject to a building permit, you typically need:

Geotechnical investigation (scope according to GK — typically 1–3 boreholes/CPT tests)
Static calculation according to ČSN EN 1997-1 (to be prepared by an authorized geotechnical engineer)
Certification of screws as a product (ETA or compliance with EN 14199)
CE machine certification document (drilling machine complies with 2006/42/EC)
Machine telematics installation logs (torque × depth at each point)
Building permit or notification according to the local building authority (depends on the project)

For PV plants and light industrial buildings on standard soil, the entire process can typically be handled within a matter of weeks and does not require non-standard measures.

EN 14199 — standard specifically for grouted anchors (or screw piles, depending on context, but "grouting/micropiles" is more accurate for EN 14199. Wait, standard EN 14199 is for Execution of special geotechnical works - Micropiles). Let's use the precise engineering term: EN 14199 — the standard specifically for micropiles

In addition to Eurocode 7, there is also EN 14199:2015 (Execution of special geotechnical works — Micropiles), which applies to minipiles and screw piles. This standard specifies:

Material and design requirements
Installation logs (monitoring)
Acceptance tests

EN 14199 complements Eurocode 7 at the performance level — while EC7 states what is to be achieved, EN 14199 states how it is to be executed. Both documents are relevant for projects where the foundation design documentation is part of the building permit.

Frequently Asked Questions

Must every project on ground screws have a geotechnical survey?
For GK1 projects (simple structures, PV systems on standard soil), the designer can use available data (geological map, local experience). For GK2 and above, the investigation is mandatory. In practice, we always recommend performing at least a test driving of the first 5 ground screws with torque recording.
Does the Czech construction administration recognize ground screws as a full-fledged foundation?
Yes. Ground screws are a recognized foundation method in the Czech Republic in accordance with ČSN EN 1997. Any rejection by a building authority is non-standard and is usually based on insufficient documentation, not on a principled ban.
Is an ETA (European Technical Assessment) required for ground screws?
The ETA applies to the product (the screw as a structural element), not to the machine. For standard installation, the compliance of the screw with EN 14199 or an ETA issued by the screw manufacturer is sufficient. The screw-driving machine itself does not need an ETA — it is CE-certified as machinery.
What to do if the building authority rejects ground screws?
As a rule, it is insufficient documentation. The solution is: to supplement the geotechnical survey, submit a static calculation from an authorized geotechnical engineer, and provide installation records from the machine's telematics. In the event of persistent refusal, an opinion from ČKAIT may be requested.

Where to continue

Technical comparison of ground screws and concrete in terms of cost, speed, and ecology: Ground screws vs. concrete foundations

Which screwdriving machine do you need for your project: Glentor B80 for standard conditions, Glentor C65 for demanding terrain with a hydraulic breaker.