Installation on paved surfaces (asphalt, paving, concrete) — standards and requirements

The installation of ground screws on paved surfaces—such as asphalt, paving, or concrete in parking lots and garages—is governed in the EU by Eurocode 7 for the geotechnics of the subgrade beneath the pavement, and Eurocodes 1 and 3 for the loads and structure of the above-ground building (carport), while the actual composition and quality of the pavement are assessed according to national pavement catalogues, which are not harmonized in the EU.

Three levels to distinguish

Foundations on a paved surface combine three separate areas that in practice are often addressed by different specialists:

Subgrade geotechnics — addresses Eurocode 7, just like for foundations on a greenfield site
Composition and condition of the pavement itself (asphalt thickness, base layers, their bearing capacity) — addressed by national pavement catalogues, not Eurocode
Design and loading of the carport over the roadway — covers Eurocode 1 (actions on structures) and Eurocode 3 (steel structures)

The investor and the designer need to coordinate all three areas — the geotechnical survey must also include the pavement structure, not just the soil beneath it.

Eurocode 7 — Geotechnics under the pavement

General overview of the standard is in a separate article: Eurocode 7 and screw piles. Additionally, for installation through a paved surface, the following are relevant:

The survey must include the pavement layer. Geotechnical investigation for a carport in a parking lot includes not only the soil at the depth of the ground screw, but also the composition of the pavement itself (thickness of the asphalt, underlying gravel layers) — without this information, the drilling procedure cannot be properly designed.

Group effect and screw spacing. Eurocode 7 requires the verification of the bearing capacity of a group of piles (including screw piles, if they are designed as pile foundations), in particular the possibility of block failure or the interaction of individual elements.

Documentation for the site operator. The record of installation parameters (e.g., achieved torque and installation depth) can serve as part of the execution quality documentation for the designer, investor, or site operator.

Pavement structure — national catalogues, not Eurocode

Unlike subgrade geotechnics, there is no harmonized European standard for pavement structure and assessment. Each country uses its own pavement catalogue:

Czech Republic Technical Specifications TP 170 (Design of Road Pavements) — determine the thickness and composition of asphalt and base layers according to the traffic load of the area.

Germany: RStO 12 (Guidelines for the Standardization of Pavement Structures of Traffic Areas) — German standard for pavement structure.

Austria: RVS 03.08.63 — Austrian guideline for pavement design.

France: LCPC-SETRA Technical Guide for Pavement Design.

Poland: Catalog of typical pavement structures — the Polish catalog of typical pavement structures.

Practical impact: Prior to execution, it is necessary to determine the actual pavement structure on the specific area (parking lot project documentation, or possibly test pits) — without this information, it is impossible to determine whether a DTH pilot hole is necessary and at what depth.

Eurocode 1 — Carport Loading

EN 1991 (Eurocode 1: Actions on structures) specifies how a carport, as an elevated structure with a large surface area exposed to wind, differs from a low-profile PV mounting system on the ground:

Wind. A carport has a higher wind exposure than a ground-mounted PV structure — the load is calculated according to EN 1991-1-4, including the exposure factor for the given height and surrounding development (open parking lot vs. sheltered location between buildings).

Buoyancy. The flat roof of the carport can generate uplift forces under certain wind directions, which the screw and anchorage detail must transfer — this load plays virtually no role in a ground-mounted PV structure.

Snow. In locations with relevant snow load, it is calculated according to EN 1991-1-3, in combination with wind according to EN 1990.

Eurocode 3 — Steel structures

The carport's load-bearing structure (columns, purlins, frame under the panels) is typically made of steel or aluminum and is designed according to EN 1993 (steel) or EN 1999 (aluminum). The connection detail between the column and the ground screw head is crucial — it must transfer the combination of vertical load, horizontal wind load, and uplift.

Specifics of anchoring into hard surfaces

DTH pre-boring. For thicker asphalt layers or compacted base layers, it may be appropriate to use a DTH pre-bore or another pre-drilling technology depending on the nature of the subgrade.

Local surface repair. After drilling, the area around the screw is finished — with sealant in the case of asphalt, or by replacing the paving stones around the screw head in the case of paving. The scope of the intervention is orders of magnitude smaller than that of a concrete foundation with excavation.

Coordination with operations. Implementation in a functional parking lot requires temporary marking, sector clearance, and often night work—this is an organizational rather than a normative requirement, but it affects the project schedule.

Checklist for installing a carport on a paved surface

Geotechnical survey including pavement structure (asphalt thickness, base layers)
Verification of the actual pavement structure against the national pavement catalog (TP 170, RStO 12, etc.)
Static load calculation according to EN 1991 (wind, uplift, or snow) and EN 1990 (combinations)
Design of steel/aluminium structures according to EN 1993 / EN 1999
Decision on the necessity of DTH pre-boring based on subsoil hardness
Coordination plan with the site operator (marking, sectoring, night work)
Telemetric installation log for each screw
Local surface repair plan around each point

Frequently Asked Questions

Is there a single European standard for pavement structure?
No. Pavement design and assessment are governed by national catalogues (e.g., TP 170 in the Czech Republic, RStO 12 in Germany), not Eurocode. Subgrade geotechnics beneath the pavement are addressed according to Eurocode 7, just like anywhere else in the EU.
Why does a carport have different wind load requirements than a ground-mounted PV structure?
A carport is an elevated structure with a large exposed surface and can generate uplift forces—Eurocode 1 (EN 1991-1-4) calculates these loads differently from a low PV rack, which is closer to the ground.
Is pre-drilling necessary when driving screws through asphalt?
It depends on the thickness and hardness of the asphalt surface and base layers. For thicker or compacted layers, a DTH pre-drill is used to create a pilot hole for the screw.
Who is responsible for repairing the surface after the installation?
The scope and method of the local repair (grouting, tile replacement) are agreed upon with the area operator as part of the implementation contract — this is not normatively regulated by the Eurocode, but by the contractual terms of the project.

Where to continue

How the installation of a solar carport on ground screws practically takes place: Solar carports on ground screws

General overview of geotechnical design according to Eurocode 7: Eurocode 7 and screw piles