Roof Expansion Joints are customary where a new roof abuts an existing building, as in this case, where there is an expansion joint in the building, or where there is a change in plane of the roof. In this last instance an expansion joint is not always required.
Roof Expansion Joints prevent movement from damaging the roof. Movement is almost always the root cause of roof problems. After eliminating chemical incompatibility and physical damage causes, you are left with movement due to gravity, thermal expansion/contraction (of membrane or building), or shrinkage of membrane.
Some roof membrane types are more susceptible to movement than others. If your project expects a life of more than 40 years, it is prudent to expect that the membrane type will change when re-roofing takes place at some point.
In the roofing condition shown here, the new building had an EIFS finish that we did not want to flash to, so we tucked the counter-flashing under the EIFS. This tactic could be used to flash into an existing unsuitable surface, too.
- This detail is needed to specify the configuration, construction and materials required for the roof expansion joint.
- This detail requires further details and specifications covering these conditions.
- You may want a specification covering the quality and installation aspects of these materials. The notes have specification reference numbers included to help make that connection.
- These details should be placed on the Exterior Details sheet, the A-500 series of sheets per the National CAD Standards, contrary to the designation shown here.
- Download PDF of detail.
Original post date April 26, 2013
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