Installing a drywall partition on a classic concrete or cinder block frame is well documented. But what happens when the support is a solid glued laminated timber panel (CLT), a material that is becoming increasingly common in new constructions and extensions?
The constraints change: wood hygrometry, structural movements, rail fixation. Comparing these two situations helps to understand what in drywall installation is standard and what requires real technical adaptation.
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Drywall partition on concrete support or on CLT: what really changes
On a classic concrete floor, the bottom rail is fixed to the ground with knock-in anchors, and the metal frame is anchored directly into the slab. The support is stable, rigid, and structural movements remain low once the concrete shrinkage is completed.
On a CLT floor, the solid wood works according to the ambient humidity. Dimensional variations of the panel can reach several millimeters over the height of a floor. A rail rigidly fixed to the floor and ceiling transmits these movements to the drywall panels, causing cracks at the joints.
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| Criterion | Concrete support | CLT support (solid wood) |
|---|---|---|
| Bottom rail fixation | Knock-in anchor in the slab | Wood screws with washer, pre-drilling recommended |
| Structural movements | Low after drying | Variable depending on humidity |
| Expansion joint | Recommended every 8 meters | Recommended more frequently, with sliding connection at the top |
| Risk of early cracking | Moderate | High without specific precautions |
| Vapor barrier | Not required on the partition side | To be checked according to the existing insulation complex |
To deepen the basics of installing an interior partition and choose the right type of panel, you can consult Les Embellies Déco online before moving on to the construction phase.
Sliding connection at the top of the partition: the technique that prevents cracks
The sliding connection at the top of the partition is the most underestimated technical point in wood construction. The principle: the top rail is not screwed directly into the CLT floor of the upper level. It rests in a slightly oversized U-profile, or the studs are cut a few millimeters shorter than the ceiling height.
This vertical play allows the wood structure to expand or contract without transmitting stress to the drywall panels. Without this precaution, cracks appear as early as the first heating winter, when the indoor air dries the wood and the floor loses thickness.
Concrete implementation
- Leave a gap of a few millimeters between the top of the stud and the upper rail, filled with a flexible joint (polyethylene foam or acrylic sealant)
- Never screw the top rail completely with long screws that would bond the partition to the CLT floor
- Provide an expansion joint at least every 8 linear meters of partition, as recommended for unstable supports
- Check that the vapor barrier of the wall-wood frame complex is not pierced by the fixation of the lateral rails
This technique is not only relevant for high-end wooden frame houses. CLT extensions on existing buildings, increasingly common in urban areas, impose the same precautions for interior distribution partitions.
Sound insulation of drywall partitions: the regulatory threshold that changes the game
Since January 2026, partitions separating wet rooms and dry rooms in new or renovated housing under MaPrimeRénov’ Copropriété must achieve a sound insulation Rw of at least 50 dB. This requirement, published in the Official Journal, modifies the sizing of drywall partitions for many renovation projects.
Reaching this threshold with a simple 72 mm partition (48 mm rail, one BA13 panel on each side, mineral wool in the cavity) is insufficient in most configurations. It is necessary to switch to a wider frame or double the panels on one side.
Acoustic performance comparison
| Configuration | Approximate total thickness | Acoustic performance |
|---|---|---|
| 1 BA13 + 48 rail + 45 mm wool + 1 BA13 | About 72 mm | Below 50 dB in most cases |
| 2 BA13 + 48 rail + 45 mm wool + 1 BA13 | About 85 mm | Close to the 50 dB threshold |
| 2 BA13 + 70 rail + 60 mm wool + 2 BA13 | About 120 mm | Above 50 dB |
The choice of insulation is as important as thickness. A high-density mineral wool improves sound insulation at the same rail thickness, where a lightweight insulation allows more noise through solid transmission.
Indoor air quality: the forgotten criterion in panel choice
Low-emission volatile organic compound (VOC) drywall panels are gaining ground since the implementation of new certifications in 2025. The CSTB report published in March 2026 confirms this trend, driven by increasing demands for indoor air quality in renovated homes.
For a drywall partition project, the choice of panel is no longer limited to moisture resistance (H1 type) or fire resistance. The A+ labeling of indoor air emissions, already mandatory for construction products, pushes manufacturers to reformulate their standard panels.
Checking the VOC emission class of your panels before purchase adds a few minutes to the project preparation. On a children’s room partition or poorly ventilated room, this criterion weighs as much as acoustic performance in the daily comfort of the home.
Drywall remains the most accessible partition material for a DIYer, but technical requirements have significantly increased in recent years. On a CLT support, the sliding connection conditions the durability of the joints. In renovations under public aid, the acoustic threshold of 50 dB requires a review of the classic sizing. Two parameters to integrate from the layout stage, not after the first crack.