Aggregate and concrete block refer, on most French construction sites, to the same type of concrete block. The confusion between these two terms masks real technical distinctions, particularly in terms of strength, thermal insulation, and adaptation to the requirements of RE2020. This article compares their measurable characteristics to guide the choice according to the type of structure.
Strength and thermal insulation: comparative table of aggregate and concrete block
| Criterion | Hollow concrete block (B40 standard) | Insulating / rectified concrete block (R+) |
|---|---|---|
| Mechanical strength | Sufficient for common load-bearing walls | Equivalent or superior depending on the class |
| Raw thermal insulation | Low (requires insulating lining) | Significantly improved thanks to the integrated insulating insert |
| Unit weight | Relatively heavy | Variable, sometimes lighter |
| RE2020 compatibility | Limited without additional insulation | Designed to meet Bbio requirements |
| Unit cost | The lowest on the market | Higher, offset by reduced lining costs |
The hollow B40 concrete block, which everyone calls “aggregate” on site, remains the most commonly used block in France. Its mechanical strength is suitable for the majority of load-bearing walls in individual houses.
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However, its thermal conductivity systematically requires an insulating lining either from the inside or the outside. Comparing a bare hollow block to an insulating block without considering the cost of this additional insulation skews the financial analysis of the project.
To better understand the advantages of aggregate and concrete block according to each construction configuration, the distinction between load-bearing block and insulating block serves as the first decision filter.
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RE2020 and concrete blocks: what changes for material choice
Since the implementation of RE2020 on January 1, 2022, for individual houses, the requirements focus on both energy performance (Bbio) and the carbon footprint of the building. The traditional B40 concrete block is not banned, but it becomes more challenging to integrate into a new project without heavy compensation on the insulating envelope.
Professional federations, notably CERIB, report a significant increase in concrete blocks with improved thermal performance in the markets for individual houses and small collectives. This trend can be explained by a simple calculation: a rectified block or one with integrated insulation reduces the number of items to address during the construction phase.
Low carbon concrete blocks and recycled aggregates
The concrete block sector is also transforming environmentally. Several French manufacturers now market blocks with reduced clinker binders or low carbon cements, and a portion of recycled aggregates. Feedback from public construction sites (schools, social housing) shows a growing adoption of these blocks to meet the Life Cycle Analysis criteria imposed by RE2020.
For a new project, the choice between a classic concrete block and a new generation concrete block is no longer just a matter of price per square meter. The carbon footprint of the material now weighs in on obtaining the building permit.
Hollow, solid, or formwork blocks: which block for which wall
The term “aggregate” actually encompasses several block formats, each suited for a specific structural use. Choosing the wrong type for a given structure results in either additional costs or a lack of strength.
- Hollow concrete block: the most common, used for load-bearing walls and partitions in individual houses. Its low cost and ease of installation make it the standard for residential construction sites.
- Solid concrete block: reserved for structures subjected to heavy loads (foundations, retaining walls). Its high weight complicates handling but guarantees superior mechanical strength.
- Formwork block: serves as lost formwork into which reinforced concrete is poured. This system is preferred for buried walls, swimming pools, and structures exposed to earth pressure.
- Insulating block (type R+): incorporates an insert of polystyrene or mineral wool. It combines load-bearing function and insulation, reducing the number of steps on site.
A garden wall does not require the same strength class as a load-bearing wall of R+1. Installing a solid block where a hollow one suffices increases the cost without structural gain. Conversely, using a hollow block in a buried foundation exposes the wall to infiltrations that mortar alone will not correct.
Implementation and overall cost: concrete block alone or integrated insulating block
The price of a hollow B40 concrete block remains the lowest on the market for load-bearing construction materials. However, this attractive price masks part of the actual cost of the finished wall.
With a traditional block, you must add the installation of insulation (expanded polystyrene, rock wool, or other), rails, plasterboard, and associated labor. The overall cost of the insulated wall often exceeds that of a block with integrated insulation, once these items are accounted for.
Speed of installation and thin joints
Rectified blocks are installed with a thin joint (adhesive) instead of a thick mortar. This technique speeds up implementation and reduces thermal bridges at the joints. The time saved on site offsets part of the additional cost of purchasing the block.
For an uninsulated interior partition wall, the classic hollow concrete block remains the most rational choice. For a facade wall subject to RE2020 requirements, the insulating or rectified block deserves a complete estimate, including insulation, before any decision.
The choice between traditional aggregate and new generation concrete block depends on three measurable variables: the structural function of the wall, the level of insulation required by the current thermal regulations, and the overall cost once all finishing items are integrated. Comparing the unit price of blocks without including insulation systematically skews the decision-making.