| 4.2.5 Protection against sound from adjoining |
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dwellings or buildings |
Separating walls, flanking walls, partitions,
and floors should meet the sound insulation requirements of the
Building Regulations.
Junctions between separating elements and other building elements
should be“airtight” and be taped and sealed. All mortar
joints should be filled with mortar.
One way of meeting the regulations is by using constructions
which have been shown by testing to provide the sound insulation
indicated in Tables 2 and 3 below. Pre-completion testing will be required when using this route for compliance.
4.2.6 Separating walls
A cavity wall consisting of two 100mm leaves of Aircrete blockwork
with a minimum density of 600kg/m in general purpose or thin layer mortar
separated by a 75mm cavity
can meet the requirements of the Building Regulations and the NHBC
when supported by a British Board of Agrément Certificate, although pre-completion testing is still required.
Walls can be finished either with 13mm thickness of lightweight
or dense plaster or with 9.5mm plasterboard on dabs (minimum) on
both outside faces. If waIl ties
are required, they should be of a flexible lightweight type, for
example butterfly or proprietary flexible tie.
Approved Document ‘E’ Section 2 includes examples of separating walls
which, when built correctly, should achieve the performance
standards in Table 2 above.
An aircrete solution is given as wall type2.4 for constructions
without separating floors where there is a step and/or stagger of
at least 300mm give:
Two leaves of Aircrete block with 75mm cavity and step/stagger,
plasterboard or plaster on both faces
• minimum surface mass including finish 150kg/m
• minimum cavity width 75mm
• plasterboard, each sheet of min mass per unit area 10kg/m,
to both room faces, or
• 13mm plaster to both room faces
The required surface mass is provided by
• 100mm Aircrete block leaves
• block density of 600kg/m
• 225mm coursing
• plasterboard, each sheet of min mass per unit area 10kg/m,
to both room faces.
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Care should be taken when specifying a dry lining to masonry separating walls. The thickness of plasterboard layers and the methods of fixing and jointing may be critical. For details, reference
should be made to BS 8212 Code of Practice for dry lining and partitioning
using gypsum plasterboard.
Cavity separating walls should be constructed so that any external
cavity wall insulation placed by blown or pumped methods, where permitted,
cannot enter the separating wall cavity.
In masonry cavity separating walls, where the cavity is up to 75mm,
flexible wall ties should be used, such as:
Butterfly wall ties, or proprietary ties assessed for the purpose,
spaced and staggered in alternate courses 900mm horizontally and 450mm
vertically.
Closer spacing would increase sound transmission. Rigid ties would
transmit sound more readily than flexible ties.
Where the dynamic stiffness is used, it should be measured in accordance
with BRE Information Paper IP3/01. Published Feb, 2001.
Sound insulation is improved by approximately 3dB when wall ties are
omitted completely subject to structural requirements.
Teat data assessed by BBA have confirmed that the following aircrete construction, if built correctly, will meet requirements of table 3 of this code of practice for separating walls of purpose-built rooms for residential purposes.
Single leaf of 215 mm blockwork plastered on both room faces
• Minimum block density of 600 kg/m3
4.2.7 Flanking walls
The construction of the flanking wall has an influence on the acoustic
performance of the structure as a whole. Flanking walls should be butted
against the separating wall and tied together at 300mm maximum vertical
spacing or should be bonded to the separating wall in such a way that
the separating wall contributes at least 50% of the bond at the junction.
Where the external wall has a cavity, the cavity should be stopped with a
proprietary flexible closer.
BBA have confirmed that where the following aircrete block constructions
are used in a solid external wall or as the inner leaf of an external
cavity wall subject to Part E of the Building Regulations England and
Wales, and the external wall flanks a separating wall, if built correctly
and in accordance with the conditions given below, they should comply with
the requirements for flanking sound transmission.
A) Aircrete blockwork with a minimum thickness of 100 mm and a minimum density of 440 kg/m3 either traditional or thin layer mortar and finished internally with plaster or plasterboard on dabs.
B) Aircrete blockwork with a minimum thickness of 115 mm and a minimum density of 400 kg/m3 either traditional or thin layer mortar and finished internally with plaster or plasterboard on dabs.
C) Aircrete blockwork of minimum surface mass of 120 kg/m2 excluding finishes.
The three constructions given can be used without any restrictions with
cavity masonry walls complying with Regulation E1 of AD E and BBA Certified
aircrete separating walls. Aircrete flanking walls A and B can be used with
solid masonry walls complying with Regulation E1 of AD E, but the external
wall should have openings on both sides of the separating wall at every
storey, which are at least 1 m high and not more than 700 mm from the face
of the separating wall.
The following Aircrete construction is suitable as flanking walls to
separating floors as defined in Approved Document E.
• A leaf of Aircrete traditional or thin layer mortar blockwork with a
minimum surface mass of 120 kg/m2 excluding finishes.
Details specific to the project should be obtained from the Aircrete
manufacturer.
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