Case 1
- Introduction
- Causes of Defects
- Good Practices
- Standards
- Maintenance and Diagnostics
- Remedial
- Similar Cases
- References
Good Practices
Design
When too large an area of the roof is encountered, an expansion joint should be provided. The expansion joint is located wherever there is a change in roof direction, height and material.
Expansion Joint Criteria to be factored into the Design:
- Anticipated thermal movement of the building’s components.
- The type of roof deck framing support.
- The roof system component coefficients.
- Climate conditions to be expected
Twin kerb expansion joints are recommended with a metal cap flashing (Figure below) fixed to one kerb only, or a capping system held by cleats or spring clips.
Construction
The width of the joint should be in accordance with BS 6093. All dust in the joint sealing slots should be blown out with dry, oil-free compressed air. Ensure that the expansion joint filler is tightly packed into the slot. Before sealing the slot insert the backer rod caulked tightly into the base of the sealing groove to prevent the sealant adhering to the base of the slot.
Materials
Sealant should be tolerant of climatic variations and have high movement accommodation. An elastomeric sealant would be suitable for movement. Correct sealant should be used to reduce sealant deterioration:
- Metal – metal = urethane, polysulfide, acrylic
- Metal – concrete = urethane, polysulfide, acrylic, silicone
- Metal – glass = silicon, urethane, polysufide
- Concrete – concrete = urethane, polysulfide, polyurethane