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French Footings: Clay-Risk Rules and Site Design

France has a public clay-risk construction route with scoped depth figures. Check that route, the ground study and the designed concrete quantities.

NF DTU 13.1 (Sept 2019); NF P 94-261 (2013, am. 2017) Clause FR NF DTU 13.1 Clause FR NF P94-261

The requirement

France has no one footing depth for every site. But public rules do give minimum depths for a defined clay-risk construction route. It is wrong to say that every depth figure is hidden in a paid standard.

The ministry’s guidance for the prescribed route gives at least 1.20 m in high-exposure clay zones and 0.80 m in medium-exposure zones. It also describes the alternative of following a suitable design ground study. These numbers are not a general frost-depth table for all of France.

Confirm the mapped zone, work type, legal scope and chosen route. The design must cover the ground, loads, nearby trees and water. Depth alone does not settle width, reinforcement or the rest of the foundation detail.

NF DTU 13.1 and the French Eurocode standards may form part of the project specification. Their full licensed text was not reviewed here. Do not infer an exact frost zone, cover or concrete grade from this summary.

Work out the concrete volume

Use the concrete sizes on the approved plan. Embedment is the depth from ground level to the base of the footing. It is not the thickness of concrete to pour. A strip, wall and trench fill each have their own shape. Work out each part on its own. Where parts meet, count that concrete once.

This example uses a straight concrete strip with the same size all along:

  • Total concrete length: 26 m.
  • Concrete width: 0.45 m.
  • Concrete thickness, measured from its top to its underside: 0.60 m.

These are example sizes, not code limits or a footing design. Check the shape and size on the plans. Then check how deep the base must sit. It must meet the soil and frost rules for the site.

Volume = length × concrete width × concrete thickness.

26 × 0.45 × 0.60 = 7.02 m³.

That is the volume before any extra for waste or uneven ground. Measure the trench or forms. Agree the extra amount and final order with the supplier. The tool does the sum. It does not choose safe footing sizes.

Do it in 5 seconds

Sources

Public source scope checked on 6 September 2026. The licensed standards, site study and full project design still need review.

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