Facade retention

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Facade retention involves supporting existing façades or party walls for renovation and is often used for works to listed buildings. By retaining the façade, the overall look of a building is preserved while new internal floor structures and layouts can be constructed to meet the needs of modern occupants.

A shoring retention scheme is generally required to support the front façade while construction of the new internal layout takes place. Once construction of the internal structure is complete, the existing façade can be connected to it.

The temporary works involved in façade retention can be significant structures in their own right and play a major role in assessing the financial viability of a project. From the outset, the design team should address the importance of the retention as a critical element of the project and careful feasibility studies should be carried out to to assess its viability and likely costs.

A thorough understanding of the existing building is vital including its age, the overall structural form, the structure of neighbouring properties, details of connections between the façade and the existing internal structure and existing foundation sizes. Site constraints (such as available space) may also affect the location and design of the temporary works.

Types of retention include:

• Scaffolding, suitable for low level facades between 3 and 4 storeys, with sufficient space at their base for installation.
• Proprietary retention, involving props, ties and bracing suitable for higher facades as the general quantity of components are reduced.
• Fabricated steelwork, used when cost of hiring proprietary equipment over long periods of time outweigh the cost of fabricating a structure
• Combinations of fabricated and proprietary retention systems.

The support system must be stiff enough to prevent excessive movement, which could cause cracking to the façade. By pre-loading the façade with a series of flat jacks the likelihood of movement can be reduced and deflection limited. The overall stability of the system must be maintained in all directions taking into consideration wind loads and impact loads. The system must also resist the overturning moment as well as moments generated by eccentric dead load. Kentledges can be incorporated into the design to counteract these moments.

[edit] Find out more

[edit] Related articles on Designing Buildings Wiki

• CDM.
• Crane supports.
• Deleterious materials.
• Designers.
• Design liability.
• Demolition.
• Excavation.
• Façade.
• Falsework.
• Formwork.
• Health and Safety.
• Refurbishment.
• Renovation.
• Scaffolding.
• Shoring.
• Temporary works.
• Trench box.
• Trench support.

[edit] External references

• BS5975:2008 + A1: 2001 Code of Practice for Temporary Works Procedures and the Permissible Stress Design of Falsework (BSI 2011).