Plasterboard: Hush hush

In order to ensure compliance with Part E of the Building Regulations, drywall partitions are required to provide a minimum acoustic performance in a variety of locations, from homes to schools and hospitals. The introduction of the latest amendment of Part E this year has important implications for the drywall industry and the way that products and systems are made and installed.

Part E (fully implemented on 1 July 2004) has set down minimum mass ratios for plasterboard. This means that manufacturers have had to produce products to fit three new grades – 8 kg/m2, 10 kg/m2 and 22 kg/m2. The lightest of these is suitable only for direct bonding to masonry, the 10 kg/m2 board is intended to provide a satisfactory airborne sound insulation performance in private dwellings, and the and 22 kg/m2 combination of wallboard is designed to separate elements within a dwelling, such as walls and floors. Lafarge’s Echeck wallboard is a good example of innovation to meet the new regulation requirement of 10 kg/m2 for wallboard, and the larger mass construction is made up of a combination of two plasterboards.

The new Part E also introduces Robust Details – RDs – for separating partitions and floors in new houses; these avoid the need to carry out pre-completion acoustic field-testing on the installed system. These are specific construction types that are deemed suitable for use in certain applications without the requirement for on-site testing. Chris Walker, systems development manager at Lafarge Plasterboard, says: “RDs don’t prevent the use of materials that don’t have RD status but these installations will be subject to on-site testing. It is important that contractors keep abreast of the drywall systems they are using, so that they don’t get caught out with unforeseen testing costs.”

RD-compliance means the systems are tested in 30 construction locations and must achieve the appropriate performance standard in each case. Only then will they be deemed as suitable. Lafarge Plasterboard is currently testing two drywall systems for RD status.

RDs specify the plasterboards and studs that must be used, and no deviation is tolerated. This makes it of paramount importance that contractors buy and use the correct metals and boards. Stephanie Warren, the product manager of Lafarge’s Cormet brand of metal systems, says: “The market for metals used in drywall systems is very competitive. Many look very similar, but fixing flanges, knurling patterns, profiles and gauges differ from manufacturer to manufacturer. Switching from one metal to another, even though both have product warranties, will undoubtedly invalidate the overall system warranty. At best, this means the system would require on-site testing; at worst, it could result in a system failing to achieve its specified performance – with crippling remedial work costs for the contractor.”

The products

Echeck is a 10 kg/m2 plasterboard for domestic work that contains mass-increasing additives to increase its density. This means that, when used in conjunction with 25 mm mineral-fibre insulation, it will meets the 40 RwdB performance standard required by Part E.

The board, which is 12.5 mm thick, is suitable for partition and ceiling applications, and is “deemed to satisfy” both Part E and RD wall details for partition walls.

To ensure that Echeck is not mixed up with other board types, especially when being used to construct RDs, it is covered in a blue facing paper for easy identification. Other than that, the product is of a standard 2400 × 1200 mm size and has tapered edges for tape-and-joint or plaster finish.

Megadeco

Lafarge’s Megadeco board offers a range of performance features. This heavy-duty 15 mm plasterboard offers high levels of sound insulation, but it also has high fire and impact resistance when built into a system using a metal stud with a single layer on each side.

This product is used extensively in hospitals. A typical specification would be a single layer of Megadeco fixed either side of a 90 mm Omega Acoustic Stud installed at 600 mm centres, with a 75 mm mineral fibre quilt within the cavity. The system is 120 mm thick, and it offers a 60 minute fire rating, severe impact resistance to BS 5234, and airborne sound insulation of 52 RwdB.

The versatility of Megadeco means that the board will meet a cross-section of hospital partition requirements. This enables the contractor to install a single partition system across the entire project, providing it with material, logistical and administrative benefits. The board is also pre-sealed and matched to the joint compound, helping to reduce the amount of decoration required.

Acoustic Homespan

Lafarge Plasterboard’s Acoustic Homespan partition system is another method of achieving sound efficiency in domestic partitions. It combines the high performance Cormet Homespan metal studs with 900 mm wide, 15 mm thick plasterboards.

Acoustic homespan boards are fixed to vibration-damping 44 mm C-section metal studs at four 50 mm centres. These studs have a “dual spring” design that minimises sound bridging across the web of the stud. The boards are fixed with staggered joints to optimise performance and achieve the sound requirements of Part E, even without the requirement for additional insulation. The introduction of 25 mm of 19 kg/m3 mineral wool insulation will increase accoustic sound insulation to 43 RwdB.

The Acoustic Homespan partition is stronger than other C-stud designs, enabling it to match heavy duty classifications and to provide half hour fire protection as listed in BS EN 1364 Part 1. And, if the 15 mm boards are used in conjunction with 50 mm studs, giving an overall partition width of 80 mm, the partition will match the usual specification for multi-occupancy developments.

Cormet Omega Acoustic Stud

The performance of construction elements with regards to sound insulation is not restricted to domestic premises. Specifiers are now becoming more demanding in other areas, including schools and hospitals, where sound privacy is vital. Lafarge Plasterboard has recently developed the 70 mm and 90 mm Omega Acoustic Stud, within its Cormet range of products, to give a greater sound insulating performance within the speech frequency band of 250-1000 Hz.

Although traditional C-section studs offer excellent structural and impact strength, they do form a sound bridge. The Omega design breaks this bridge, thanks to its unique bulb cut-out design. In tandem with engineered twin slots, this creates a resilient central “spring” section. As a result, less sound energy can be transmitted through the stud and more airborne sound is absorbed within the partition.

The stud is designed to work at its best at the frequency bands of common noise such as speech and the sound generated by stereos and televisions. It can also enable acoustic requirements to be met with fewer plasterboard layers, making the partition slimmer in footprint, thus saving space and installation time.