How to improve the sound insulation of a plasterboard partition

A "well-built" plasterboard partition can still transmit noise if a single perimeter detail fails. Sound insulation doesn't depend on a single material, but on several elements working together — and if one is missing, the whole loses effectiveness even if the rest is perfect.

The three elements to combine

For separations between homes, combine wide stud (70–100 mm), rock wool and perimeter sealing tape. Any one of the three on its own isn't enough: a wide stud without sealing tape still transmits vibration through rigid contact with the slab, and sealing tape without rock wool doesn't absorb the airborne noise that crosses the cavity.

Sealing tape: stops vibration through rigid contact

The sealing tape is a self-adhesive strip stuck onto the channel before fixing it to floor and ceiling. Without it, the partition transmits vibration straight to the slab through the rigid metal-to-structure contact, which reduces insulation against impact noise even if the rest of the partition is well built. It carries a 5% purchase margin for overlaps.

Perimeter sealant: a CTE-DB-HR requirement

The elastic seal between the edge of the board and the adjoining surface (floor, ceiling, side wall) is a usual requirement of the CTE-DB-HR (Spain's noise-protection code) in partitions with acoustic requirements. A perfectly built partition that isn't sealed around its perimeter loses part of its insulation through the contact gaps — a detail that is invisible once painted, but is noticed when living in the home.

Expansion profile: for long partitions

In very long partitions (more than about 15 metres) or those crossing expansion joints of the building itself, include an expansion profile instead of treating the partition as continuous — without it, the building's structural movement can crack the board over time.

Frequently asked questions

Is it enough to fit rock wool to get good sound insulation? No: rock wool absorbs airborne noise, but if the stud isn't wide or the perimeter sealing tape is missing, vibration is still transmitted through rigid contact.

Is the perimeter sealant mandatory? In partitions with acoustic requirements, yes — it's a usual CTE-DB-HR requirement, not an optional extra.

When do I need an expansion profile in a plasterboard partition? In partitions longer than about 15 metres, or that cross the building's own expansion joints.

Conclusion

The sound insulation of a plasterboard partition isn't a single product added at the end: it's the combination of wide stud, rock wool, sealing tape and perimeter sealing working together. Quoting each element separately, explaining why they're inseparable, stops the client misunderstanding why "just adding wool" doesn't solve the noise problem.