6.9 Curtain walling and cladding

SITEWORK STANDARDS

6.9 - S1-S2 Sitework standards
6.9 - S3 Handling and storage
Curtain walling
6.9 - S4 Location and fixing
6.9 - S5 Weather resistance
6.9 - S6 Glazing
6.9 - S7 Control of condensation
6.9 - S8 Allowance for movement
6.9 - S9 Tolerances
6.9 - S10 Testing
Rainscreen cladding
6.9 - S11 Location and fixing
6.9 - S12 Weather resistance
6.9 - S13 Allowance for movement
6.9 - S14 Tolerances
Insulated render systems
6.9 - S15 Fixing
6.9 - S16 Weather resistance
6.9 - S17 Tolerances
Brick slip cladding systems
6.9 - S18 Fixing
6.9 - S19 Weather resistance
6.9 - S20 Tolerances

6.9 - S1
All sitework shall:
(a) meet the Technical Requirements
(b) take account of the design
(c) follow established good practice and workmanship
 

Sitework that complies with the design and guidance below will be acceptable for curtain walling and cladding systems.

All relevant information in a form suitable for the use of site operatives should be available on site before work on the curtain walling or cladding system starts, including:

  • full set of drawings
  • schedule of revisions
  • manufacturer's specification
  • fixing schedules
  • specific details of all interfaces
  • manufacturer's recommendations relating to proprietary items
  • on-site testing regime.
6.9 - S2
Curtain walling and cladding systems shall be installed by competent operatives
 

Curtain walling, rainscreen cladding, insulated render and brick slip cladding systems should be installed by operatives who:

  • are competent
  • are familiar with the system being installed
  • hold a certificate confirming they have been trained by the system manufacturer, supplier or installer.

HANDLING AND STORAGE

6.9 - S3
Materials, products and systems shall be protected and stored in a satisfactory manner to prevent damage, distortion, uneven weathering and degradation
 

Items to be taken into account include:

(a) handling and storage

The curtain walling or cladding system should be transported, lifted, handled and stored in accordance with the manufacturer's recommendations.

Insulated glass units should be carefully stored and protected in a sheltered dry area.

(b) protection

All practical steps should be taken to avoid the risk of damage to the curtain walling or cladding system during construction.

Curtain walling

LOCATION AND FIXING

6.9 - S4
Curtain walling systems shall be correctly located and securely fixed in accordance with the design
 

Curtain walling systems should be correctly located and securely fixed in accordance with the manufacturer's specification and the design details.

The type, size and positioning of all fixings should be in accordance with the design.

Proprietary fixings should be used in accordance with the manufacturer's recommendations with particular attention given to:

  • the correct embedment, spacing and edge distances
  • correct torque settings
  • the provision of suitable locking nuts and washers
  • the isolation of dissimilar metals
  • the isolation of aluminium from cementitious material.

WEATHER RESISTANCE

6.9 - S5
Curtain walling systems shall be correctly installed to prevent moisture entering the building
 

Items to be taken into account include:

(a) weathertightness

Curtain walling systems including doors, windows and other components should be installed correctly to ensure satisfactory in-service performance.

(b) gaskets and sealants

Appropriate gaskets and sealants should be installed and used to ensure satisfactory performance. Gaskets and sealants should be used in accordance with the design and the manufacturer's recommendations.

Pre-formed factory-moulded 'picture frame' type vulcanised epdm or silicone internal gaskets should be used.

Picture frame gasket and typical profile

External and internal air and water seals and a drained cavity should be provided at all interfaces. Guidance on interfaces is provided in Appendix 6.9-A.

(c) dpcs/dpms

Dpcs/dpms should be installed correctly to provide a physical barrier to the passage of moisture. Dpc/dpm arrangements which rely solely on sealant should not be used. Guidance on the use of dpcs/dpms at interfaces is provided in Appendix 6.9-A.

Dpc/dpm arrangements should extend the full height of the curtain walling system and have appropriate details at all interfaces including floors, walls, roofs, balconies and terraces, to ensure moisture is directed to the outside.

(d) opening doors and lights

Opening doors and lights should be fitted in accordance with the design, hang square within the curtain wall frame and fit neatly with minimum gaps to ensure effective weatherproofing.

GLAZING

6.9 - S6
Glazing shall be carried out in accordance with relevant standards
 

Glazing should be carried out in accordance with Chapter 6.7 'Doors, windows and glazing' (Design and Sitework).

CONTROL OF CONDENSATION

6.9 - S7
Installation shall ensure that the risk of condensation is minimised
 

Insulation should be installed in accordance with the design, ensuring that all interfaces are adequately insulated.

A continuous, durable vapour control layer should be provided in accordance with the design.

ALLOWANCE FOR MOVEMENT

6.9 - S8
Installation shall allow movement of the curtain walling system and the building without causing damage or deformation
 

Allowance for movement should be provided in accordance with the design.

TOLERANCES

6.9 - S9
Installation shall achieve the design tolerances
 

The line, level, plumb and plane of the completed curtain walling system should be in accordance with the design. See Chapter 1.2 ' A consistent approach to finishes'.

TESTING

6.9 - S10
Site hose testing shall be carried out on the curtain walling system to confirm satisfactory performance
 

On-site testing should be carried out to determine the resistance to water penetration of the curtain walling system, including all joints and interfaces which are designed to be permanently closed and watertight.

Representative samples of the finished installation should be hose tested on site in accordance with the current CWCT Standard for curtain walling.

Hose test of typical interface

At least 5% of the completed curtain walling system should be tested, with particular focus on vulnerable areas such as joints and interfaces.

Other testing may be acceptable if it is considered by NHBC to be a suitable alternative.

The results of all testing should be made available to NHBC.

Rainscreen cladding

LOCATION AND FIXING

6.9 - S11
Rainscreen cladding systems shall be correctly located and securely fixed in accordance with the design
 

Rainscreen cladding systems should be correctly located and securely fixed in accordance with the manufacturer's specification and the design details.

The type, size and positioning of all anchors, fixing rails, frames, fixings and fasteners should be in accordance with the design.

Bonded fixings should only be used in accordance with the design.

Anchors, fixings and bracketry should normally be stainless steel or a suitable non-ferrous metal.

Proprietary fixings should be used in accordance with the manufacturer's recommendations with particular attention given to:

  • the correct embedment, spacing and edge distances
  • correct torque levels
  • the provision of suitable locking nuts and washers
  • the isolation of dissimilar metals
  • the isolation of aluminium from
    cementitious material.

WEATHER RESISTANCE

6.9 - S12
Rainscreen cladding systems shall be correctly installed to prevent moisture entering the building
 

Items to be taken into account include:

(a) weathertightness

Rainscreen cladding systems including door, window and other openings and cover flashings, should be installed correctly to ensure satisfactory in-service performance.

Installation should prevent water reaching any parts of the wall that could be adversely affected by the presence of moisture.

The following minimum air gap should be maintained behind all rainscreen panels:

  • 50mm for panels with open joints, or
  • 38mm for panels with baffle or labyrinth (rebated) joints.

open joints and baffled or labyrinth (rebated) joints

Unless specified otherwise in the design, all open, baffled or labyrinth (rebated) joints should have a minimum opening of 10mm.


Open joint and baffled joint

labyrinth (rebated) joint

Where required by the design a screen to prevent birds and animals entering the cavity should be provided at the top and bottom of the rainscreen and to penetrations through the cladding.

Where required by the design, dpcs/dpms should be installed correctly to provide a physical barrier to the passage of moisture. Dpc/dpm arrangements which rely solely on sealant should not be used.

To ensure moisture is directed to the outside, dpc/dpm arrangements should be correctly formed with suitable upstands and stop ends including at the junction between the rainscreen cladding and any other component or system. External and internal air and water seals and a drained cavity should be provided at all interfaces. Guidance on interfaces is provided in Appendix 6.9-A.

Appropriate sealants should be used in accordance with the design and the manufacturer's recommendations to ensure satisfactory performance.

(b) insulation and condensation

Where insulation forms part of the rainscreen, it should be installed in accordance with the design and the manufacturer's recommendations, ensuring that all parts of the backing wall are adequately insulated.

Where the rainscreen panel joints are open and the insulation could be adversely affected by the presence of water, a continuous durable breather membrane should be provided to the outer face of the insulation.

Where the insulation is fixed to the backing wall, a minimum of one non-combustible fixing per square metre or per batt, whichever is the lesser, should be provided in addition to the other fixings.

Installation should ensure that the insulation is continuous around penetrations through the rainscreen.

The rainscreen cladding system should be installed to minimise the risk of thermal bridging and surface and interstitial condensation.

(c) air infiltration

The rainscreen cladding system should be fixed to a backing wall that is reasonably airtight, e.g:

  • masonry walls jointed to a high standard with all joints filled
  • framed walls with a rigid sheathing on the cavity face with all joints taped or sealed.

Where reasonable airtightness cannot be achieved, a separate continuous vapour permeable air barrier with joints taped or sealed should be provided on the outer face of the backing wall.

(d) compartmentation

To help achieve pressure equalisation in open jointed rainscreen cladding systems, the cavity should be compartmented by:

  • a horizontal cavity closer at each floor level, and
  • vertical cavity closers at centres not exceeding 6.0m, and
  • vertical cavity closers at centres not exceeding 1.5m in the area within 6.0m of an internal or external corner, and
  • a vertical cavity closer as close as possible to an external corner, normally within 300mm.

Horizontal cavity closer at each floor level

This compartmentation is in addition to the requirements of the Building Regulations for cavity barriers to control the spread of smoke and fire. However, the same cavity barriers may be used for the compartmentation.

Cavity closers should be rigid and be installed in accordance with the manufacturer's recommendations with particular attention given to maintaining ventilation and drainage in accordance with the design.

(e) durability

The rainscreen cladding system should be fabricated and installed with corrosion resistant or adequately protected materials.

Fixings and bracketry should normally be stainless steel or suitable non-ferrous metal.

The risk of bimetallic corrosion should be avoided by the isolation of dissimilar metals.

Aluminium components should be separated from direct contact with cementitious surfaces.

The rainscreen cladding system should not include materials liable to infestation attack by micro-organisms, fungi, insects or vermin.

(f) testing

On-site hose or sparge bar testing should be carried out with particular emphasis on interfaces that are designed to be permanently closed and watertight.

The building should remain watertight during and after the test.

ALLOWANCE FOR MOVEMENT

6.9 - S13
Installation shall allow movement of the rainscreen cladding system and the building without causing damage or deformation
 

Allowance for movement e.g. at interfaces and at gaps between panels, should be provided in accordance with the design.

TOLERANCES

6.9 - S14
Installation shall achieve the design tolerances
 

Installation should allow for the line, level, plumb and plane of the completed rainscreen cladding system to be within reasonable tolerances for the materials involved. See Chapter 1.2 ' A consistent approach to finishes'.

Insulated Render Systems

FIXING

6.9 - S15
Insulated render systems shall be securely fixed in accordance with the design
 

Insulated render systems should be securely fixed in accordance with the design and the manufacturer's recommendations.

The type, size and positioning of all anchors, fixing rails, frames, fixings, fasteners and bonded joints should be in accordance with the design.

Anchors, fixings and bracketry should normally be stainless steel, suitable non-ferrous metal or appropriate plastics.

For mechanically-fixed systems particular attention should be given to:

  • correct embedment, spacing and edge distances
  • correct torque settings
  • provision of suitable locking nuts and washers
  • the isolation of dissimilar metals
  • the isolation of aluminium from cementitious material.

For adhesive-fixed systems particular attention should be given to:

  • thorough assessment of the backing wall to confirm adhesive fixing is suitable
  • suitable preparation of the backing wall to receive the adhesive
  • the provision of supplementary mechanical fixings as required by the design.

WEATHER RESISTANCE

6.9 - S16
Insulated render systems shall be correctly installed to prevent moisture entering the building
 

Items to be taken into account include:

(a) weathertightness

Insulated render systems should be installed correctly to ensure satisfactory in-service performance.

Insulated render systems should prevent water reaching any parts of the wall that could be adversely affected by the presence of moisture.

Where the backing wall is timber or steel framed a cavity of at least 15mm should be provided between the wall and the insulation to allow moisture to drain away.

Where the backing wall is timber framed the cavity should be ventilated in accordance with Chapter 6.2 'External timber framed walls' (Design).

Steel frame and timber frame

Suitable precautions to resist impact damage should be provided in accordance with the design.

Where required by the design a screen should be provided to prevent birds and animals entering the cavity through the ventilation and drainage openings.

Insulated render systems can be applied direct to masonry backing walls without a cavity being provided.

Where required by the design, dpcs/dpms should be installed correctly to provide a physical barrier to the passage of moisture. Dpc/dpm arrangements which rely solely on sealant should not be used.

To ensure moisture is directed to the outside, dpc/dpm arrangements should be correctly formed with suitable upstands and stop ends including at the junction between the insulated render system and any other component or system.

Guidance on interfaces is provided in Appendix 6.9-A.

Appropriate tapes and sealant should be used in accordance with the design and the manufacturer's recommendations to ensure satisfactory performance.

(b) insulation and condensation

Insulation should be installed in accordance with the design and the manufacturer's recommendations, ensuring that all parts of the backing wall are adequately insulated.

Insulation should be returned into window and door openings and be continuous around penetrations through the wall.

All layers neatly cut around flue outlet

(c) air infiltration

The backing wall should be reasonably airtight before installation of the insulated render system, e.g.

  • masonry walls jointed to a high standard with all joints etc filled
  • framed walls with a rigid sheathing on the cavity face with all joints taped and sealed.

(d) reinforcement

Reinforcement mesh should be provided in accordance with the design taking account of the following:

  • laps between sheets of reinforcement mesh should be not less than 100mm
  • openings, corners, angles, interfaces and movement joints should be formed with appropriate trims
  • additional mesh should normally be provided at points where there is a likelihood of increased stress in the render system, e.g. at the corners of window and door openings
  • movement joints in the backing wall should continue through the insulated render system.

Reinforcement

(e) render

The surface to be rendered should be free from contamination, dust and loose particles. The number and thickness of coats should be in accordance with the design.

Where coloured pigments are specified, batching should be undertaken with care to ensure colour consistency.

TOLERANCES

6.9 - S17
Installation shall achieve the design tolerances
 

Installation should allow for the line, level, plumb and plane of the completed insulated render system to be within reasonable tolerances for the materials involved. See Chapter 1.2 ' A consistent approach to finishes'.

Brick Slip Cladding Systems

FIXING

6.9 - S18
Brick slip cladding systems shall be securely fixed in accordance with the design
 

Brick slip cladding systems should be securely fixed in accordance with the design and the manufacturer's recommendations.

The type, size and positioning of all anchors, fixing rails, frames, fixings, fasteners and bonded joints should be in accordance with the design.

Anchors, fixings and bracketry should normally be stainless steel, suitable non-ferrous metal or appropriate plastics.

Particular attention should be given to:

  • correct embedment, spacing and edge distances
  • correct torque levels
  • provision of suitable locking nuts and washers
  • the isolation of dissimilar metals
  • the isolation of aluminium from cementitious material.

Fixing systems should be accurately set out to ensure brick slips suit storey heights, lintels, corners and openings.

WEATHER RESISTANCE

6.9 - S19
Brick slip cladding systems shall be correctly installed to prevent moisture entering the building
 

Items to be taken into account include:

(a) weathertightness

Brick slip cladding systems should be installed correctly to ensure satisfactory in-service performance.

The brick slip cladding system should prevent water reaching any parts of the wall that could be adversely affected by the presence of moisture.

Where the backing wall is timber or steel framed, a cavity of at least 15mm should be provided between the wall and the insulation to allow moisture to drain away.

Where the backing wall is timber framed, the cavity should be ventilated in accordance with Chapter 6.2 'External timber framed walls' (Design).

Steel frame and timber frame

Suitable precautions to resist impact damage should be provided in accordance with the design.

A screen should be provided to prevent birds and animals entering the cavity through the ventilation and drainage openings.

Brick slip cladding systems can be applied direct to masonry backing walls without a cavity being provided.

Where required by the design, dpcs/dpms should be installed correctly to provide a physical barrier to the passage of moisture. Dpc/dpm arrangements which rely solely on sealant should not be used.

To ensure moisture is directed to the outside, dpc/dpm arrangements should be correctly formed with suitable upstands and stop ends including at the junction between the brick slip cladding system and any other component or system.

Guidance on interfaces is provided in Appendix 6.9-A.

Appropriate tapes and sealants should be used in accordance with the design and the manufacturer's recommendations to ensure satisfactory performance.

(b) insulation and condensation

Insulation should be installed in accordance with the design and the manufacturer's recommendations, ensuring that all parts of the backing wall are adequately insulated.

Insulation should be returned into window and door openings and be continuous around penetrations through the wall.

Insulation (carrier) neatly cut around openings

(c) air infiltration

The backing wall should be reasonably airtight before installation of the brick slip cladding system, e.g.

  • masonry walls jointed to a high standard with all joints etc filled
  • framed walls with a rigid sheathing on the cavity face with all joints taped and sealed.

(d) brick slips

Brick slips should be fixed in accordance with the design and manufacturer's recommendations, taking account of relevant height restrictions.

Excessive cutting of brick slips should be avoided.

Insulation (carrier) positioned to avoid excess cutting of slips

(e) joints

Proprietary mortars and grouts should be used in accordance with the design and the manufacturer's recommendations. Each joint should be adequately filled and appropriately struck.

TOLERANCES

6.9 - S20
Installation shall achieve satisfactory appearance
 

Installation should allow for the line, level, plumb and plane of the completed brick slip cladding system to be within reasonable tolerances for the materials involved. See Chapter 1.2 ' A consistent approach to finishes'.