Resilient Bar Calculator — Bars, Screws & Acoustic Gain

British Gypsum Gypframe RB1 resilient bars are fixed at a maximum of 600mm centres on walls and partitions, and a maximum of 450mm centres on ceilings; 400mm centres are reserved for ceramic tiling or where 2400mm board lengths are used. Centres are a structural and board-support requirement, not an acoustic tuning lever — they do not improve sound performance. In fact, fixing bars closer together adds rigid contact points and stiffens the system, which reduces the decoupling and slightly worsens isolation. Always follow the specific product installation guide.

A single layer of 15mm plasterboard on resilient bar over a standard masonry or stud wall typically improves airborne sound insulation by 5-8 dB. Double-boarding (two layers of 15mm) on resilient bar can achieve 8-12 dB improvement. The exact gain depends on the existing wall construction, the quality of installation and whether all flanking paths are addressed.

Yes, resilient bars are widely used on ceilings to reduce impact and airborne sound transmission from the floor above. They are screwed across the joists at up to 450mm centres (Gypframe RB1 ceiling maximum), and plasterboard is then screwed to the bars (not the joists). This decouples the ceiling from the structure. Combined with mineral wool insulation between joists, this is one of the most effective ceiling acoustic treatments.

Use 25mm drywall screws to fix the resilient bar to timber studs or joists. Fix plasterboard to the bar using 32mm drywall screws for single boards or 42mm for double boards. Critical: board screws must only go into the bar, never into the studs or joists behind, as this would create a rigid bridge and destroy the acoustic decoupling.

Yes, resilient bars are commonly used on party walls to improve sound insulation. For a masonry party wall, a system of resilient bar + 2 × 15mm board + mineral wool can help achieve good laboratory performance. Approved Document E sets the airborne requirement for separating walls as DnT,w + Ctr ≥ 45 dB for new-build (43 dB for conversions / material change of use) — note the Ctr spectrum-adaptation term, which penalises low-frequency performance, so it is more demanding than the bare DnT,w figure. The key is to ensure no rigid connections between the new lining and the party wall except through the resilient bars, and to confirm performance against a tested system.