What is the NF DTU 31.2 standard for wood construction used for?

Defining the rules for the construction of wooden houses, the NF DTU 31.2 standard applies to all structures whose load-bearing structure is made of wood.

Timber constructions: focus on the NF DTU 31.2 standard

Updated several times by amendment (NF P 21-204), the NF DTU 31.2 standard constitutes the construction benchmark for wooden buildings. Intended for construction professionals, it defines all the rules to be followed when carrying out a work whose load-bearing elements are made of wood.

What are the NF DTU 31.2 and NF P 21-204 standards ? 

Updated for the last time in 2019, the NF DTU 31.2 standard is the reference document for the construction of houses and buildings with wooden frames. This Unified Technical Document (DTU), drawn up under the control of the French Standardization Association (AFNOR), is intended for all construction industry players involved in the creation of wooden buildings :

• craftsmen and building professionals;
• the contracting authorities;
• project managers;
• or the control bodies.

What constructions doex NF DTU 31.2 apply to ?

The NF DTU 31.2 standard applies to any structure or part of a structure whose main load-bearing structure is made of wood. More precisely, it concerns three modes of implementation involving wooden elements:

• construction on site with usual construction materials;
• the prefabrication of structural elements manufactured in the workshop and then assembled on the site (wall, floor and roof);
• the prefabrication of three-dimensional elements;
• the construction mixing the three modes of implementation discussed previously.

Consequently, this benchmark can target a large typology of buildings, including :

• individual houses;
• collective housing buildings;
• tertiary premises (shops, offices, schools, hospitals, etc.);
• or industrial buildings.

On the other hand, some wooden constructions fall outside the scope of NF DTU 31.2. This is particularly the case for wooden foundation walls and facade elements resting on a masonry or steel supporting structure.

What does the NF DTU 31.2 standard define?

To provide a benchmark for construction professionals, the NF DTU 31.2 standard lists all the requirements that wooden constructions must meet, for each of their facets.

• Materials: this chapter details the standards that each of the materials used (wood, plywood, particle board, etc.) must meet.
• Basement work: the wooden structural elements must not rest directly on the ground, this section defines the qualities that the foundation work must have.
• Structural construction: the specifics to be fulfilled by the vertical walls, floors and stairs in particular are detailed.
• Covering or waterproofing: this chapter details the rules to be followed to ensure the collection of rainwater and its discharge, in particular to protect the building against any infiltration.
• Carpentry: DTU 31.2 also addresses the conditions to be met by windows, doors and other carpentry work.
• Technical equipment works: the rules to be observed with regard to plumbing, electricity or heating are indicated.
• Insulation structures: the rules for installing the vapor barrier film and insulating filling materials are explained in this chapter.
• The laying of coverings: lastly, the NF DTU 31.2 standard addresses the principles to be followed for the creation of interior coverings (walls and ceilings), exterior coverings and floor coverings.