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Design
Criteria |
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Moisture Control | Roof
Decks | Rigid Insulation
| Roof Membranes
| 1. |
Expansion joints that extend from the building's framing system through the roof assembly facilitate structural movements that are caused from such events as seismic forces; thermal induced expansion and contraction of the roof assembly; and accommodation of minimal planned settlement. |
| 2. |
Expansion joints are installed so as to allow for the differential movement of various structural components that result from different coefficients of thermal expansion and contraction. Each building's components have different coefficients of expansion and contraction, and each component is subjected to varying temperature changes, with the result of different thermal induced movements between the roof components. |
| 3. | Expansion joints are to alleviate BUR membrane fatigue along continuous locations of discontinuity, and hence to prevent BUR membrane ridging and splitting. Expansion joints are installed to reduce the damage from the stresses and the movements between a building's components; and to prevent those stresses from damaging the roof system. |
Roof expansion joints shall be provided at the following locations:
| 1. |
Where an expansion joint is installed in the building's framing system. |
| 2. |
Where steel framing or roof decking changes direction. |
| 3. | Where separate wings of "L", "U", "T", or similar building configurations are constructed. |
| 4. | Where the type of decking changes such as the abutting of precast concrete and steel. |
| 5. | Where additions are connected to the building. |
| 6. | Where heating or cooling changes significantly, such as a heated office abutting an unheated warehouse. |
| 7. | Where movement between vertical walls and the roof deck is planned. |
Expansion Joint Criteria to be factored into the Design:
| 1. |
Anticipated thermal movement of the building's components. |
| 2. |
The type of roof deck framing support. |
| 3. | The roof system component coefficients. |
| 4. | Climate conditions to be expected. |