Section 3 Separating floors and associated flanking constructions for new buildings

Introduction

3.1 This Section gives examples of floor types which, if built correctly, should achieve the performance standards set out in Section 0: Performance – Table 1a.

3.2 The guidance in this section is not exhaustive and other designs, materials or products may be used to achieve the performance standards set out in Section 0: Performance – Table 1a. Advice should be sought from the manufacturer or other appropriate source.

3.3 The floors are grouped into three main types. See Diagram 3.1.

3.4 Floor type 1: Concrete base with ceiling and soft floor covering

The resistance to airborne sound depends mainly on the mass per unit area of the concrete base and partly on the mass per unit area of the ceiling. The soft floor covering reduces impact sound at source.

3.5 Floor type 2: Concrete base with ceiling and floating floor

The resistance to airborne and impact sound depends on the mass per unit area of the concrete base, as well as the mass per unit area and isolation of the floating layer and the ceiling. The floating floor reduces impact sound at source.

3.6 Floor type 2: Floating floor

Floor type 2 requires one of the floating floors described in this section. The description of floor type 2 contains a suffix (a), (b) or (c) which refers to the floating floor used.

3.7 Floor type 3: Timber frame base with ceiling and platform floor

The resistance to airborne and impact sound depends on the structural floor base and the isolation of the platform floor and the ceiling. The platform floor reduces impact sound at source.

3.8 Ceiling treatment

Each floor type requires one of the ceiling treatments described in this section. The description of each floor type contains a suffix A, B or C that refers to the ceiling treatment used.

3.9 Within each floor type the constructions are ranked, as far as possible, with constructions providing better sound insulation given first.

Ceiling treatment

3.8 Each floor type requires one of the ceiling treatments described in this section. The description of each floor type contains a suffix A, B or C that refers to the ceiling treatment used.

3.9 Within each floor type the constructions are ranked, as far as possible, with constructions providing better sound insulation given first.

Junctions between separating floors and other building elements

3.10 In order for the floor construction to be fully effective, care should be taken to correctly detail the junctions between the separating floor and other elements such as external walls, separating walls and floor penetrations. Recommendations are also given for the construction of these other elements where it is necessary to control flanking transmission. Notes and diagrams explain the junction details for each of the separating floor types.

Diagram 3.1 Types of separating floor

3.11 Table 3.1 indicates the inclusion of guidance in this document on the junctions that may occur between each of the separating floor types and various attached building elements.

Table 3.1 Separating floor junctions reference table

Beam and block floors

3.12 For beam and block separating floors, seek advice from the manufacturer.

Mass per unit area of floors

3.13 The mass per unit area of a floor is expressed in kilograms per square metre (kg/m²). The mass per unit area of floors should be obtained from manufacturer’s data or calculated using the method shown in Annex A.

3.14 The density of the materials used (and on which the mass per unit area of the floor depends) is expressed in kilograms per cubic metre (kg/m³).

3.15 Where appropriate, the mass per unit area of a bonded screed may be included in the calculation of the mass per unit area of the floor.

3.16 The mass per unit area of a floating screed should not be included in the calculation of the mass per unit area of the floor.

Ceiling treatments

3.17 Each floor type should use one of the following three ceiling treatments (A, B or C). See Diagram 3.2.

3.18 The ceiling treatments are ranked, in order of sound insulation performance from A to C, with constructions providing higher sound insulation given first.

Note Use of a better performing ceiling than that described in the guidance should improve the sound insulation of the floor provided there is no significant flanking transmission.

3.19 Ceiling treatment A, independent ceiling with absorbent material

Ceiling treatment A should meet the following specification:

• at least 2 layers of plasterboard with staggered joints;

• minimum total mass per unit area of plasterboard 20kg/m²;

• an absorbent layer of mineral wool (minimum thickness 100mm, minimum density 10kg/m³) laid in the cavity formed above the ceiling.

The ceiling should be supported by one of the following methods:

• Floor types 1, 2 and 3. Use independent joists fixed only to the surrounding walls. A clearance of at least 100mm should be left between the top of the plasterboard forming the ceiling and the underside of the base floor.

• Floor type 3. Use independent joists fixed to the surrounding walls with additional support provided by resilient hangers attached directly to the floor. A clearance of at least 100mm should be left between the top of the ceiling joists and the underside of the base floor.

3.20 Points to watch:

Do

Do seal the perimeter of the independent ceiling with tape or sealant.

Do not

Do not create a rigid or direct connection between the independent ceiling and the floor base.

3.21 Ceiling treatment B plasterboard on proprietary resilient bars with absorbent material

Ceiling treatment B should meet the following specification:

• single layer of plasterboard, minimum mass per unit area of plasterboard 10kg/m²;

• fixed using proprietary resilient metal bars. On concrete floors, these resilient metal bars should be fixed to timber battens. For fixing details, seek advice from the manufacturer;

• an absorbent layer of mineral wool (minimum density 10kg/m³) that fills the ceiling void.

3.22 Ceiling treatment C, plasterboard on timber battens or proprietary resilient channels with absorbent material

Ceiling treatment C should meet the following specification:

• single layer of plasterboard, minimum mass per unit area 10kg/m²;

• fixed using timber battens or proprietary resilient channels;

• if resilient channels are used, incorporate an absorbent layer of mineral wool minimum density 10kg/m³) that fills the ceiling void.

Note: Electrical cables give off heat when in use and special precautions may be required when they are covered by thermally insulating materials. See BRE BR 262, Thermal Insulation: avoiding risks, section 2.4. Installing recessed light fittings in ceiling treatments A to C can reduce their resistance to the passage of airborne and impact sound.

Diagram 3.2 Ceiling treatments A, B and C

Floor type 1: concrete base with ceiling and soft floor covering

3.23 The resistance to airborne sound depends mainly on the mass per unit area of the concrete base and partly on the mass per unit area of the ceiling. The soft floor covering reduces impact sound at source.

Constructions

3.24 The construction consists of a concrete floor base with a soft floor covering and a ceiling.

3.25 Two floor type 1 constructions (types 1.1C and 1.2B) are described in this guidance which should be combined with the appropriate ceiling and soft floor covering.

3.26 Details of how junctions should be made to limit flanking transmission are also described in this guidance.

3.27 Points to watch

Do

a. Do fix or glue the soft floor covering to the floor. (N.B. allow for future replacement.)

b. Do fill all joints between parts of the floor to avoid air paths.

c. Do give special attention to workmanship and detailing at the perimeter and wherever a pipe or duct penetrates the floor in order to reduce flanking transmission and to avoid air paths.

d. Do build a separating concrete floor into the walls around its entire perimeter where the walls are masonry.

e. Do fill with mortar any gap that may form between the head of a masonry wall and the underside of the concrete floor.

f. Do control flanking transmission from walls connected to the separating floor as described in the guidance on junctions.

Do not

a. Do not allow the floor base to bridge a cavity in a cavity masonry wall.

b. Do not use non-resilient floor finishes that are rigidly connected to the floor base.

3.28 Soft floor covering The soft floor covering should meet the following specification:

• any resilient material, or material with a resilient base, with an overall uncompressed thickness of at least 4.5mm; or

• any floor covering with a weighted reduction in impact sound pressure level (DLw) of not less than 17dB when measured in accordance with BS EN ISO 140-8:1998 and calculated in accordance with BS EN ISO 717-2:1997.

Floor type 1.1C

3.29 Floor type 1.1C Solid concrete slab (cast in situ, with or without permanent shuttering), soft floor covering, ceiling treatment C (see Diagram 3.3)

• minimum mass per unit area of 365kg/m² (including shuttering only if it is solid concrete or metal) and including any bonded screed;

• soft floor covering essential;

• ceiling treatment C (or better) essential.

Diagram 3.3 Floor type 1.1C - floor type 1.1 with ceiling treatment C

*Floor Type 1.2B

3.30 Floor Type 1.2B Concrete planks (solid or hollow), soft floor covering, ceiling treatment B (see Diagram 3.4)

• minimum mass per unit area of planks and` any bonded screed of 365kg/m²;

• use a regulating floor screed;

• all floor joints fully grouted to ensure air tightness;

• soft floor covering essential;

• ceiling treatment B (or better) essential.

Diagram 3.4 Floor type 1.2B - floor type 1.2 with ceiling treatment B

Junctions with an external cavity wall with masonry inner leaf

3.31 Where the external wall is a cavity wall:

a. the outer leaf of the wall may be of any construction; and

b. the cavity should be stopped with a flexible closer (see Diagram 3.5) ensuring adequate drainage, unless the cavity is fully filled with mineral wool or expanded polystyrene beads (seek manufacturer's advice for other suitable materials).

3.32 The masonry inner leaf of an external cavity wall should have a mass per unit area of at least 120kg/m² excluding finish.

3.33 The floor base (excluding any screed) should be built into a cavity masonry external wall and carried through to the cavity face of the inner leaf. The cavity should not be bridged.

Floor type 1.2B

3.34 Where floor type 1.2B is used and the planks are parallel to the external wall the first joint should be a minimum of 300mm from the cavity face of the inner leaf. See Diagram 3.5.

3.35 See details in Section 2 concerning the use of wall ties in external masonry cavity walls.

Diagram 3.5 Floor type 1.2B - external cavity wall with masonry inner leaf

Junctions with an external cavity wall with timber frame inner leaf

3.36 Where the external wall is a cavity wall:

a. the outer leaf of the wall may be of any construction; and

b. the cavity should be stopped with a flexible closer;

c. the wall finish of the inner leaf of the external wall should be two layers of plasterboard, each sheet of plasterboard to be of minimum mass per unit area 10kg/m², and all joints should be sealed with tape or caulked with sealent.

Junctions with an external solid masonry wall

3.37 No guidance available (seek specialist advice).

Junctions with internal framed walls

3.38 There are no restrictions on internal framed walls meeting a type 1 separating floor.

Junctions with internal masonry walls

3.39 The floor base should be continuous through, or above, an internal masonry wall.

3.40 The mass per unit area of any load-bearing internal wall or any internal wall rigidly connected to a separating floor should be at least 120kg/m² excluding finish.

Junctions with floor penetrations (excluding gas pipes)

3.41 Pipes and ducts that penetrate a floor separating habitable rooms in different flats should be enclosed for their full height in each flat. See Diagram 3.6.

3.42 The enclosure should be constructed of material having a mass per unit area of at least 15kg/m². Either line the enclosure or wrap the duct or pipe within the enclosure with 25mm unfaced mineral fibre.

3.43 Penetrations through a separating floor by ducts and pipes should have fire protection to satisfy Building Regulation Part B - Fire safety. Fire stopping should be flexible and prevent rigid contact between the pipe and floor.

Diagram 3.6 Floor type 1 - floor penetrations

Note There are requirements for ventilation of ducts at each floor where they contain gas pipes. Gas pipes may be contained in a separate ventilated duct or they can remain unenclosed. Where a gas service is installed, it shall comply with relevant codes and standards to ensure safe and satisfactory operation. See The Gas Safety (Installation and Use) Regulations 1998, SI 1998 No.2451.

For flats where there are separating walls the following may apply:

Junctions with separating wall type 1 - solid masonry

Floor type 1.1C

Diagram 3.7 Floor type 1.1C- wall type 1

3.44 A separating floor type 1.1C base (excluding any screed) should pass through a separating wall type 1. See Diagram 3.7.

Floor type 1.2B

Diagram 3.8 Floor type 1.2B - wall type 1

3.45 A separating floor type 1.2B base (excluding any screed) should not be continuous through a separating wall type 1. See Diagram 3.8.

Junctions with separating wall type 2 - cavity masonry

3.46 The mass per unit area of any leaf that is supporting or adjoining the floor should be at least 120kg/m² excluding finish.

3.47 The floor base (excluding any screed) should be carried through to the cavity face of the leaf. The wall cavity should not be bridged. See Diagram 3.9.

Floor type 1.2B

3.48 Where floor type 1.2B is used and the planks are parallel to the separating wall the first joint should be a minimum of 300mm from the inner face of the adjacent cavity leaf. See Diagram 3.9.

Diagram 3.9 Floor type 1.1C and 1.2B - wall type 2

Junctions with separating wall type 3 - masonry between independent panels

Junctions with separating wall type 3.1 and 3.2 (solid masonry core)

Floor type 1.1C

3.49 A separating floor type 1.1C base (excluding any screed) should pass through separating wall types 3.1 and 3.2. See Diagram 3.10.

Diagram 3.10 Floor type 1.1C - wall type 3.1 and 3.2

Floor type 1.2B

3.50 A separating floor type 1.2B base (excluding any screed) should not be continuous through a separating wall type 3.

3.51 Where separating wall type **3.2 is used with floor type 1.2B and the planks are parallel to the separating wall the first joint should be a minimum of 300mm from the centreline of the masonry core.

Junctions with separating wall type 3.3 (cavity masonry core)

3.52 The mass per unit area of any leaf that is supporting or adjoining the floor should be at least 120kg/m² excluding finish.

3.53 The floor base (excluding any screed) should be carried through to the cavity face of the leaf of the core. The cavity should not be bridged.

3.54 Where floor type 1.2B is used and the planks are parallel to the separating wall the first joint should be a minimum of 300mm from the inner face of the adjacent cavity leaf of the masonry core.

Junctions with separating wall type 4 - timber frames with absorbent material

3.55No guidance available (seek specialist advice).

Floor type 2: concrete base with ceiling and floating floor

3.56 The resistance to airborne and impact sound depends on the mass per unit area of the concrete base, as well as the mass per unit area and isolation of the floating layer and the ceiling. The floating floor reduces impact sound at source.

Constructions

3.57 The construction consists of a concrete floor base with a floating floor and a ceiling. The floating floor consists of a floating layer and a resilient layer.

3.58 Two floor type 2 constructions (types 2.1C and 2.2B) are described in this guidance, which should be combined with the appropriate ceiling and any one of the three floating floor options (a), (b) or (c).

3.59 Details of how junctions should be made to limit flanking transmission are also described in this guidance.

Limitations

3.60 Where resistance to airborne sound only is required the full construction should still be used.

3.61 Points to watch

Do

a. Do fill all joints between parts of the floor to avoid air paths.

b. Do give special attention to workmanship and detailing at the perimeter and wherever a pipe or duct penetrates the floor in order to reduce flanking transmission and to avoid air paths.

c. Do build a separating concrete floor base into the walls around its entire perimeter where the walls are masonry.

d. Do fill with mortar any gap that may form between the head of a masonry wall and the underside of the concrete floor.

e. Do control flanking transmission from walls connected to the separating floor as described in the guidance on junctions.

Do not

Do not allow the floor base to bridge a cavity in a cavity masonry wall.

Floating floors (floating layers and resilient layers)

3.62 The floating floor consists of a floating layer and resilient layer. See Diagram 3.11.

3.63 Points to watch

Do

a. Do leave a small gap (as advised by the manufacturer) between the floating layer and wall at all room edges and fill with a flexible sealant.

b. Do leave a small gap (approx. 5mm) between skirting and floating layer and fill with a flexible sealant.

c. Do lay resilient materials in rolls or sheets with lapped joints or with joints tightly butted and taped.

d. Do use paper facing on the upper side of fibrous materials to prevent screed entering the resilient layer.

Do not

a. Do not bridge between the floating layer and the base or surrounding walls (e.g. with services or fixings that penetrate the resilient layer).

b. Do not let the floating screed create a bridge (for example through a gap in the resilient layer) to the concrete floor base or surrounding walls.

Diagram 3.11 Floating floors (a) and (b)

3.64 Floating floor (a) Timber raft floating layer with resilient layer

Floating floor (a) should meet the following specification:

• timber raft of board material (with bonded edges, e.g. tongued and grooved) of minimum mass per unit area 12kg/m², fixed to 45mm x 45mm battens;

• timber raft to be laid loose on the resilient layer, battens should not be laid along any joints in the resilient layer;

• resilient layer of mineral wool with density 36kg/m³ and minimum thickness 25mm. The resilient layer may be paper faced on the underside.

3.65 Floating floor (b) Sand cement screed floating layer with resilient layer

Floating floor (b) should meet the following specification:

• floating layer of 65mm sand cement screed or a suitable proprietary creed product with a mass per unit area of at least 80kg/m². Ensure that the resilient layer is protected while the screed is being laid. A 20–50mm wire mesh may be used for this purpose;

• resilient layer consisting of either:

a. a layer of mineral wool of minimum thickness 25mm with density 36kg/m³, paper faced on the upper side to prevent the screed entering the resilient layer, or

b. an alternative type of resilient layer which meets the following two requirements:

maximum dynamic stiffness (measured according to BS EN 29052-1:1992) of 15MN/m³, and
minimum thickness of 5mm under the load specified in the measurement procedure of BS EN 29052-1:1992, 8kPa to 2.1kPa.

Note: For proprietary screed products, seek advice from the manufacturer.

3.66 Floating floor (c) Performance based approach

Floating floor (c) should meet the following specification:

• rigid boarding above a resilient and/or damping layer(s); with

• weighted reduction in impact sound pressure level (DLw) of not less than 29dB when measured according to BS EN ISO 140-8:1998 and rated according to BS EN ISO 717-2:1997. (See Annex B: Supplementary guidance on acoustic measurement standards.) The performance value DLw should be achieved when the floating floor is both loaded and unloaded as described in BS EN ISO 140-8:1998 for category II systems.

Note: For details on the performance and installation of proprietary floating floors, seek advice from the manufacturer.

3.67 Floor type 2.1C Solid concrete slab (cast in-situ, with or without permanent shuttering), floating floor, ceiling treatment C (see Diagrams 3.12 and 3.13)

• minimum mass per unit area of 300kg/m² (including shuttering only if it is solid concrete or metal), and including any bonded screed;

• regulating floor screed optional;

• floating floor (a), (b) or (c) essential;

• ceiling treatment C (or better) essential.

Diagram 3.12 Floor type 2.1C(a) - floor type 2.1 with ceiling treatment C and floating floor (a)

Diagram 3.13 Floor type 2.1C(b) - floor type 2.1 with ceiling treatment C and floating floor (b)

3.68 Floor type 2.2B Concrete planks (solid or hollow), floating floor, ceiling treatment B (see Diagrams 3.14 and 3.15)

• minimum mass per unit area of planks and any bonded screed of 300g/m²;

• use a regulating floor screed;

• all floor joints fully grouted to ensure air tightness;

• floating floor (a), (b) or (c) essential;

• ceiling treatment B (or better) essential.

Diagram 3.14 Floor type 2.2B(a) - floor type 2.2 with ceiling treatment B and floating floor (a)

Diagram 3.15 Floor type 2.2B(b) - floor type 2.2 with ceiling treatment B and floating floor (b)

Junction requirements for. floor type 2

Junctions with an external cavity wall with masonry inner leaf

3.69 Where the external wall is a cavity wall:

a. the outer leaf of the wall may be of any construction; and

b. the cavity should be stopped with a flexible closer (see Diagram 3.16) ensuring adequate drainage, unless the cavity is fully filled with mineral wool or expanded polystyrene beads (seek manufacturer's advice for other suitable materials).

3.70 The masonry inner leaf of an external cavity wall should have a mass per unit area of at least 120kg/m² excluding finish.

3.71 The floor base (excluding any screed) should be built into a cavity masonry external wall and carried through to the cavity face of the inner leaf. The cavity should not be bridged.

Floor 2.2B

3.72 Where floor 2.2B is used and the planks are parallel to the external wall the first joint should be a minimum of 300mm from the cavity face of the inner leaf. See Diagram 3.16.

3.73 See details in Section 2 concerning the use of wall ties in external masonry cavity walls.

Diagram 3.16 Floor type 2 - external cavity wall with masonry internal leaf

Junctions with an external cavity wall with timber frame inner leaf

3.74 Where the external wall is a cavity wall:

a. the outer leaf of the wall may be of any construction;

b. the cavity should be stopped with a flexible closer; and

c. the wall finish of the inner leaf of the external wall should be two layers of plasterboard, each sheet of plasterboard to be of minimum mass per unit area 10kg/m², and all joints should be sealed with tape or caulked with sealant.

Junctions with an external solid masonry wall

3.75 Junctions with an external solid masonry wall

Junctions with internal framed walls

3.76 There are no restrictions on internal framed walls meeting a type 2 separating floor.

Junctions with internal masonry walls

3.77 The floor base should be continuous through, or above an internal masonry wall.

3.78 The mass per unit area of any load-bearing internal wall or any internal wall rigidly connected to a separating floor should be at least 120kg/m² excluding finish.

Junctions with floor penetrations (excluding gas pipes)

3.79 Pipes and ducts that penetrate a floor separating habitable rooms in different flats should be enclosed for their full height in each flat. See Diagram 3.17.

3.80 The enclosure should be constructed of material having a mass per unit area of at least 15kg/m². Either line the enclosure, or wrap the duct or pipe within the enclosure, with 25mm unfaced mineral wool.

3.81 Leave a small gap (approx. 5mm) between the enclosure and floating layer and seal with sealant or neoprene. Where floating floor (a) or (b) is used the enclosure may go down to the floor base, but ensure that the enclosure is isolated from the floating layer.

3.82 Penetrations through a separating floor by ducts and pipes should have fire protection to satisfy Building Regulation Part B - Fire safety. Fire stopping should be flexible and also prevent rigid contact between the pipe and floor.

Note There are requirements for ventilation of ducts at each floor where they contain gas pipes. Gas pipes may be contained in a separate ventilated duct or they can remain unenclosed. Where a gas service is installed, it shall comply with relevant codes and standards to ensure safe and satisfactory operation. See The Gas Safety (Installation and Use) Regulations 1998, SI 1998/2451.

Diagram 3.17 Floor type 2 - floor penetrations

For flats where there are separating walls the following may also apply:

Junctions with a separating wall type 1 - solid masonry

Floor type 2.1C

3.83 A separating floor type 2.1C base (excluding any screed) should pass through a separating wall type 1.
`
Floor type 2.2B

3.84 A separating floor type 2.2B base (excluding any screed) should not be continuous through a separating wall type 1. See Diagram 3.18.

Diagram 3.18 Floor types 2.2B(a) and 2.2B(b) - wall type 1

Junctions with a separating wall type 2 - cavity masonry

3.85 The floor base (excluding any screed) should be carried through to the cavity face of the leaf. The cavity should not be bridged.

Floor type 2.2B

3.86 Where floor type 2.2B is used and the planks are parallel to the separating wall the first joint should be a minimum of 300mm from the cavity face of the leaf.

Junctions with a separating wall type 3 – masonry between independent panels Junctions with separating wall type 3.1 and

3.2 (solid masonry core)

Floor type 2.1C

3.87 A separating floor type 2.1C base (excluding any screed) should pass through separating wall types 3.1 and 3.2. See Diagram 3.19.

Diagram 3.19 Floor types 2.2B(a) and 2.1C - wall types 3.1 and 3.2

Floor type 2.2B

3.88 A separating floor type 2.2B base (excluding any screed) should not be continuous through a separating wall type 3.

3.89 Where separating wall type 3.2 is used with floor type 2.2B and the planks are parallel to the separating wall the first joint should be a minimum of 300mm from the centreline of the masonry core.

Junctions with separating wall type 3.3 (cavity masonry core)

3.90 The mass per unit area of any leaf that is supporting or adjoining the floor should be at least 120kg/m² excluding finish.

3.91 The floor base (excluding any screed) should be carried through to the cavity face of the leaf of the core. The cavity should not be bridged.

Floor type 2.2B

3.92 Where floor type 2.2B is used and the planks are parallel to the separating wall the first joint should be a minimum of 300mm from the inner face of the adjacent cavity leaf of the masonry core.

Junctions with separating wall type 4 – timber frames with absorbent material

3.93 No guidance available (seek specialist advice).

Floor type 3: timber frame base with ceiling and platform floor

3.94 The resistance to airborne and impact sound depends on the structural floor base and the isolation of the platform floor and the ceiling. The platform floor reduces impact sound at source.

Construction

3.95 The construction consists of a timber frame structural floor base with a deck, platform floor and ceiling treatment A. The platform floor consists of a floating layer and a resilient layer

3.96 One floor type 3 construction (type 3.1A) is described in this guidance.

3.97 Details of how junctions should be made to limit flanking transmission are also described in this guidance.

Limitations

3.98 Where resistance to airborne sound only is required the full construction should still be used.

3.99 Points to watch

Do

a. Do give special attention to workmanship and detailing at the perimeter and wherever the floor is penetrated, to reduce flanking transmission and to avoid air paths.

b. Do give special attention to workmanship and detailing at the perimeter and wherever the floor is penetrated, to reduce flanking transmission and to avoid air paths.

Platform floor

c. Do use the correct density of resilient layer and ensure it can carry the anticipated load.

d. Do use an expanded or extruded polystyrene strip (or similar resilient material) around the perimeter which is approx. 4mm higher than the upper surface of the floating layer to ensure that during construction a gap is maintained between the wall and the floating layer. This gap may be filled with a flexible sealant.

e. Do lay resilient materials in sheets with joints tightly butted and taped.

Do not

Do not bridge between the floating layer and the base or surrounding walls (e.g. with services or fixings that penetrate the resilient layer).

3.100 Floor type 3.1A Timber frame base with ceiling treatment A and platform floor (see Diagram 3.20)

• timber joists with a deck;

• the deck should be of any suitable material with a minimum mass per unit area of 20kg/m²;

• platform floor (including resilient layer) essential;

• ceiling treatment A essential.

Diagram 3.20 Floor type 3.1A

3.101 Platform floor

The floating layer should be:

• a minimum of two layers of board material;

• minimum total mass per unit area 25kg/m²;

• each layer of minimum thickness 8mm;

• fixed together (e.g. spot bonded with a resilient adhesive or glued/screwed) with joints staggered.

The floating layer should be laid loose on a resilient layer.

Example 1

• 18mm timber or wood based board

• tongued and grooved edges and glued joints

• spot bonded to a substrate of 19mm plasterboard with joints staggered

• minimum total mass per unit area 25kg/m²

Example 2

• two layers of cement bonded particle board with staggered joints

• total thickness 24mm

• boards glued and screwed together

• minimum total mass per unit area 25kg/m²

3.102 Resilient layer

The resilient layer specification is:

• mineral wool, minimum thickness 25mm, density 60 to 100kg/m³;

• the mineral wool may be paper faced on the underside.

Note The lower figure of density for the resilient layer gives a higher resistance to impact sound but a 'softer' floor. In such cases additional support can be provided around the perimeter of the floor by using a timber batten with a foam strip along the top attached to the wall.

Junction requirements for floor type 3

Junctions with an external cavity wall with masonry inner leaf

3.103 Where the external wall is a cavity wall:

a. the outer leaf of the wall may be of any construction; and

b. the cavity should be stopped with a flexible closer unless the cavity is fully filled with mineral wool or expanded polystyrene beads (seek manufacturer's advice for other suitable materials).

3.104 The masonry inner leaf of a cavity wall should be lined with an independent panel as described for wall type 3.

3.105 The ceiling should be taken through to the masonry. The junction between the ceiling and the independent panel should be sealed with tape or caulked with sealant.

3.106 Use any normal method of connecting floor base to wall but block air paths between floor and wall cavities.

3.107 Where the mass per unit area of the inner leaf is greater than 375kg/m² the independent panels are not required.

3.108 See details in Section 2 concerning the use of wall ties in external masonry cavity walls.

Junctions with an external cavity wall with timber frame inner leaf

3.109 Where the external wall is a cavity wall:

a. the outer leaf of the wall may be of any construction; and

b. the cavity should be stopped with a flexible closer.

3.110 The wall finish of the inner leaf of the external wall should be:

a. two layers of plasterboard;

b. each sheet of plasterboard of minimum mass per unit area 10kg/m²; and

c. all joints should be sealed with tape or caulked with sealant.

3.111 Use any normal method of connecting floor base to wall. Where the joists are at right angles to the wall, spaces between the floor joists should be sealed with full depth timber blocking.

3.112 The junction between the ceiling and wall lining should be sealed with tape or caulked with sealant.

Junctions with an external solid masonry wall

3.113 No guidance available (seek specialist advice).

Junctions with internal framed walls

3.114 Where the joists are at right angles to the wall, spaces between the floor joists should be sealed with full depth timber blocking.

3.115 The junction between the ceiling and the internal framed wall should be sealed with tape or caulked with sealant.

Junctions with internal masonry walls

3.116 No guidance available (seek specialist advice).

Junctions with floor penetrations (excluding gas pipes)

3.117 Pipes and ducts that penetrate a floor separating habitable rooms in different flats should be enclosed for their full height in each flat. See Diagram 3.21.

3.118 The enclosure should be constructed of material having a mass per unit area of at least 15kg/m². Either line the enclosure, or wrap the duct or pipe within the enclosure, with 25mm unfaced mineral wool.

3.119 Leave a small gap (approx. 5mm) between enclosure and floating layer and seal with sealant or neoprene. The enclosure may go down to the floor base, but ensure that the enclosure is isolated from the floating layer.

3.120 Penetrations through a separating floor by ducts and pipes should have fire protection to satisfy Building Regulation Part B - Fire safety. Fire stopping should be flexible and also prevent rigid contact between the pipe and floor.

Note There are requirements for ventilation of ducts at each floor where they contain gas pipes. Gas pipes may be contained in a separate ventilated duct or they can remain unenclosed. Where a gas service is installed, it shall comply with relevant codes and standards to ensure safe and satisfactory operation. See The Gas Safety (Installation and Use) Regulations 1998, SI 1998/2451.

Diagram 3.21 Floor type 3 - floor penetrations

For flats where there are separating walls the following may also apply:

Junctions with a separating wall type 1 - solid masonry

3.121 If floor joists are to be supported on the separating wall then they should be supported on hangers and should not be built in. See Diagram 3.22.

3.122 The junction between the ceiling and wall should be sealed with tape or caulked with sealant.

Diagram 3.22 Floor type 3 - wall type 1

Junctions with a separating wall type 2 - cavity masonry

3.123 If floor joists are to be supported on the separating wall then they should be supported on hangers and should not be built in. See Diagram 3.23.

3.124 The adjacent leaf of a cavity separating wall should be lined with an independent panel as described in wall type 3.

3.125 The ceiling should be taken through to the masonry. The junction between the ceiling and the independent panel should be sealed with tape or caulked with sealant.

3.126 Where the mass per unit area of the adjacent leaf is greater than 375kg/m² the independent panels are not required.

Diagram 3.23 Floor type 3 - wall type 2

Junctions with a separating wall type 3 - masonry between independent panels

3.127 If floor joists are to be supported on the separating wall then they should be supported on hangers and should not be built in.

3.128 The ceiling should be taken through to the masonry. The junction between the ceiling and the independent panel should be sealed with tape or caulked with sealant.

Junctions with a separating wall type 4 - timber frames with absorbent material

3.129 Where the joists are at right angles to the wall, spaces between the floor joists should be sealed with full depth timber blocking.

3.130 The junction of the ceiling and wall lining should be sealed with tape or caulked with sealant.

Section 3: Separating floors and associated flanking construction for new buildings