Construction guidance for acoustic partitions
Even with the correct design details, you need to be very careful to ensure that you don't compromise the integrity of your acoustic partition. Whether you are dividing spaces using floors or walls, then the check list below should provide some useful guidance on the elements that you will need to be aware of. Please note though that a good standard of workmanship is essential. Although following the guidance below will increase your chances of passing a sound test, it is not a substitute for specially tailored advice from a qualified consultant.
- Where fire stops are needed. the should only be attached to one leaf of the cavity (not two), that is, if they are not of the flexible variety.
- All block-work be plastered at least on one side. This is to ensure that all gaps are filled.
- All perpendicular joints in block-work should be filled with mortar; also at junctions, especially with perpendicular surfaces. For block-work with an acoustic rating of Rw50 and higher, the block-work of the inner wall should be bonded into the inner lining of the external wall. If the inner leaf of the external wall is of lightweight block, this should not be carried through past the separating wall.
- All plasterboard joints should be staggered, taped and sealed and all gaps filled with a flexible sealant.
- Partitions, where possible, should be built from the structural slab to soffit. If this is not possible, there should be a break in the ceiling board either side of the partition. These ceilings should be designed acoustically with at least 2 layers of 12.5mm plasterboard with mineral fibre insulation (tile-in-grid systems are unsuitable unless specifically designed to attenuate sound transfer). Generally, advice from an acoustic consultant should be sought for the design of these systems.
- If the structural roof is corrugated and the corrugations run perpendicular to party walls, the holes should be hard-packed with mineral fibre and sealed with mortar pugging.
- Where expansion joints are to be used, this detail should be referred to an acoustic consultant for design guidance.
- Door frames should be airtight. Any air gaps (including those between the door frame and the surrounding wall) should be filled with grout and sealed. Smaller gaps should be tightly packed with mineral wool, and sealed with mastic at least 15mm deep.
- Where acoustically critical timber floors are constructed, plasterboard undersides should not come into direct physical contact with the perimeter wall. Instead, a small gap should remain which should be completely filled with a non-hardening mastic.
- All service penetrations require acoustic detailing. All pipes, ducts, conduits that are to pass through partitions must have vibration breaks in the form of flexible connectors. If the requirement of pipework such as heating systems precludes the use of flexible connectors, the aperture through the partition hosting the pipework should be packed with felt or mineral wool. A false flange may also be built around this aperture and should be caulked with mastic sealant.
- Electrical services entering a room must also be sealed. Continuous back-to-back electrical services across a partition should be avoided as this may form a direct transmission path through the partition.
- Services mounted to walls of noise sensitive rooms should incorporate acoustic hangers to isolate structure-borne sound radiating into the connecting wall or surface, and thereby radiating into the room in question. The type used for this purpose is commonly available (E.g. as listed in the British Gypsum Whitebook).
- Any flexible connections used in ventilation ductwork bridging across partitions should be designed and specified to prevent any additional obstruction to the flow and therefore turbulence-generated noise.
- All materials should be damage-free as acoustic weaknesses can arise through small cracks in concrete, damaged plasterboard, unfilled gaps around door frames and service penetrations.
