Decorative slip facings

Executive summary

The use of slips is becoming increasingly popular in the construction industry. Typically when the term ‘slip’ is used we think of ‘brick slips’. However, slips could be made from a variety of materials, such as concrete (artificial stone) or natural stone.

Typically, they will provide an external decorative finish to an existing or new wall substrate.  They will not be considered as a watertight barrier to prevent water ingress, however they may contribute to providing a degree of weather protection to an external wall. 

The following guidance is written in regards to low-rise domestic properties, up to three stories in height.

Typical uses

The Functional Requirements of the LABC Warranty Technical Manual states under the ‘Materials’ heading:

‘Decorative Claddings': Whilst there is and can be no policy responsibility and/or liability for a performance life of 60 years or less for a 'cladding' which has a 'decorative function only' (i.e. with the main substrate wall or roof construction, providing the main weatherproof barrier); a 'decorative' type cladding shall be designed and constructed so they have an intended life of not less than 15 years.’

The slips could be intended to be installed on a variety of construction types, including masonry construction, both light and heavy gauge steel framing, timber frame, concrete frame, or even part of a rainscreen cladding system on any of the aforementioned constructions. Furthermore, slips could be proposed to be installed on an element of construction, such as a chimney or lintel. Some examples are listed below:

1. As part of a cladding system/rainscreen cladding system
2. Adhered to masonry
3. Slip claddings onto framed construction onto a board
4. Lintels
5. GRP chimneys

Warranty position

Slips

• Clay masonry units must conform to BS EN 771-1 and be CE marked
• Calcium silicate masonry units must conform to BS EN 771-2 and be CE marked
• Concrete brick slips (Aggregate concrete masonry units) must be CE marked and conform to BS EN 771-3
• Agglomerated stone. Slabs and tiles for wall finishes BS EN 15286 and be CE marked (artificial stone)
• Natural stone masonry units must conform to BS EN 771-6 and be CE marked

If alternative standards are referred to then please liaise with the technical team.

In addition to the above, the method of attachment to the construction element must meet the following criteria:

Claddings system/rainscreen cladding

Where a cladding system is proposed which includes slips, i.e., a ‘brick slip cladding system’, the system must hold a valid third-party accreditation (e.g. BBA, BDA and BRE) and be deemed acceptable as meeting our insurance requirements.

• The framed structure (backing wall) must be watertight and protected with a suitable breather membrane
• A drained cavity, ventilated where required must be provided in accordance with the LABC Warranty Technical Manual

Masonry cavity walls

Where slips are to be bonded onto masonry walls, the following must be met:

• The cladding system, i.e., slip, adhesive and associated ancillary products such as clips, strapping, etc., must hold a valid third-party accreditation (e.g. BBA, BDA, BRE)
• The design and fixing of the slip system must be in strict accordance with the third-party accreditation with any adhesion tests, pull-out tests completed, satisfactorily, as per the requirements of the certificate
• Any slip is considered to provide a ‘decorative’ finish only to a wall, therefore the design of the external wall (to meet weather resistance requirements) must be in strict accordance with Building Regulations for the wind-driven rain exposure zone location, as if the slip was not to be installed
• The backing wall to which the slips are to be adhered is typically blockwork and therefore the blockwork is considered to be ‘C2 - High risk of saturation’ and must be of the correct classification, i.e., classified as MX3.2, MX4 or MX5 built in M4 mortar. (See Appendix C.1 of the Technical Manual/PD6697)
• The cavity width must be correct and comply with Building Standards for a ‘facing masonry’ wall type, not ‘rendered finish’ or ‘impervious cladding’ finish
• Slips should not be applied to render unless covered by a valid third-party accreditation (e.g. BBA, BDA and BRE) which is deemed acceptable as meeting our insurance requirements. Any third-party accreditation for such construction must confirm the permitted maximum exposure zone the system can be used, if reliance is to be placed on the system to provide weather resistance
• Slips must not bridge the damp proof course. The damp proof course must extend through the slip to the outside face of the slip cladding
• Movement joints in the substrate must be installed in strict accordance with the LABC Warranty Technical Manual and extend through the decorative slip cladding
• Cavity trays must be present, as per the requirements of the LABC Warranty Technical Manual
• Weep holes must be installed, as per the requirements of the LABC Warranty Technical Manual and extend through the decorative slip cladding
• Where ventilation is required, e.g., for timber frame construction, then the full height weep vents must be installed, as per the requirements of the LABC Warranty Technical Manual and extend through the decorative slip cladding
• Where checked reveals are required (very severe exposure zone), the design must be assessed and deemed compliant. The check must be formed by the masonry substrate, not slips or render. Windows must be sealed prior to the slip installation
• Any mortar pointing of the slips must be full depth, with the mortar suitable for the environment, please refer to Appendix C.1 of the LABC Warranty Technical Manual for guidance
• Any systems utilising clips, strapping, screws and other such components when used in a coastal location within 500m of the shoreline must be grade A4 stainless steel
• Any fixings of ancillary rainwater goods, satellite dishes, clothes lines, hanging baskets and similar items must go through the slips and into the substrate to ensure adequate fixing

Slip claddings onto framed construction onto a board

• Where slip claddings are to be used in conjunction with a framed structure and bonded onto a board, the ‘cladding system’, i.e., slip, adhesive, board and associated ancillary products such as clips, must all be covered by a valid third-party accreditation (e.g. BBA, BDA, BRE), the system as a whole
• The framed structure (backing wall) must be watertight and protected with a suitable breather membrane
• A drained cavity, ventilated where required must be provided in accordance with the LABC Warranty Technical Manual
• MgO boards are not acceptable for warranty use
  

Insulated Concrete Formwork (ICF)

• Where slips are to be adhered to cavity blockwork outer leaf, please refer to the ‘masonry walls’ section above
• Where slip cladding is to be placed on a framing onto a board, please see the ‘slip claddings onto framed construction onto a board’ section above
• Where slips are to be installed either a) directly onto the ICF, or b) onto render which is directly applied to the ICF then the slip cladding system must:
  • Have a valid and current third-party product approval (e.g. BBA, BDA and BRE) confirming it has been assessed to provide the weatherproof protection to an ICF substrate consisting of EPS, EPX, etc., or
  • There is a combined named slip, render and ICF system/slip and ICF system which jointly hold a valid and current third-party product approval (e.g. BBA, BDA, BRE), which is deemed acceptable to ourselves

Note

• The third-party product approval for the slip cladding must confirm the slip cladding finish will provide the ‘weather resistance’ to the ICF for a 15 year minimum life expectancy/durability, and
• The third-party product approval certificate clearly identifies the maximum wind-driven rain exposure zone** permitted by the assessment, and
• The certificate holder provides a project specific specification for the render installation, and
• Installers trained and approved by the certificate holder should only install the direct render finish

** If the project location is situated in a wind-driven rain exposure zone exceeding that stated in the third party accreditation, the certificate holder must also provide confirmation at completion to the warranty provider that the installation meets the project specific specification.

External Wall Insulation (EWI)

• The EWI system must hold a valid third-party accreditation (e.g. BBA, BDA, BRE), which is deemed acceptable as meeting our insurance requirements. The third-party accreditation approval must be for the substrate construction proposed
• The backing wall behind the EWI system must be watertight, protected with an appropriate third-party accredited breather membrane (e.g. BBA, BDA, BRE)
• A drained cavity must be provided
  

Slips on lintels

• Slips used in conjunction with either concrete or lightweight (SIP) lintels must hold a valid third-party accreditation (e.g. BBA, BDA, BRE) covering the lintels and slips system as a whole
• Slips used in conjunction with steel lintels must hold a valid third-party accreditation (e.g. BBA, BDA, BRE) covering the lintels and slips system as a whole
  
  

Slips on GRP chimneys

All GRP chimney systems must either:

• Hold a valid third-party accreditation (e.g. BBA, BDA, BRE) confirming a minimum life expectancy of 15 years and be deemed acceptable to the warranty provider, or
• The GRP chimney manufacturer must be a current Accredited Member for the Production of GRP Brick Slip Chimneys from the Construction Glass Fibre Manufacturers Association
  

Slips on soffits

• Where soffit slips are used in conjunction with lintels, the product must hold a valid third-party accreditation (e.g. BBA, BDA, BRE) confirming a minimum life expectancy of 60 years and be deemed acceptable to the warranty provider

Summary

This article may not cover all the potential areas where slips could be used, however it provides guidance on areas where often the use of slips are commonly proposed. For areas outside of this guidance please request a copy of the third-party accreditation (e.g. BBA, BDA, BRE) for the given product and forward to the technical team, if considered necessary, for appraisal.