Updated: Dec 6, 2020
For joints of plasterboard ceilings with non-load bearing internal walls, there are typically no issues when the walls are built after the plasterboard ceiling as the lining is maintaining a continuous line of protection:
Where the walls are installed before the grid ceiling, and/or for load-bearing walls, there is a breach of the line of protection in this situation. This protection may be reestablished by keeping the same FRR for the wall and ceiling. It is recommended to apply one-way fire protection to both sides of the wall.
Note that these observations are taking into consideration one recommended way for plasterboard ceiling and wall joints. Ultimately, specifications from the manufacturer must always be followed.
However, plasterboard manufacturers do not usually clarify questions regarding penetrations within the wall that penetrates the fire-rated ceiling, and there is still some level of questioning by contractors.
As a good practice, remember that the fire rating of a substrate is continuous and without open penetrations. Therefore, the ceiling must be uninterrupted, with all penetrations fire stopped, and ideally, the construction of the wall would be below the lining.
As a real-scenario example: Consider the picture below.
Is it a requirement for the penetrations to be fire stopped?
The design specifies fire rating is only on the ceiling, and the walls were installed before the ceiling grid. The penetrations are within the non-fire rated wall.
As explained above, when there is a breach on the continuation of the ceiling, the protection must be reinstated.
In this case, there are two breaches on the Fire Rating of the ceiling:
the timber wall that penetrates the ceiling, and
Therefore, the solution chosen must solve the two issues.
Option 1. Creating Fire-rated walls with the same FRR of the ceiling and enclosing the timber in it.
a. In the case of penetrations, they should be fire stopped on the wall
Option 2. Providing a continuity of the Gib Ceiling by encasing the timber
a. Penetrations are fire stopped on the ceiling
Note: The terminology ceiling and wall, in this case, is more related to the orientation of the lining rather than being an actual ceiling or wall. As walls, we are referring to the vertically orientated lining and as a ceiling to the horizontally orientated lining.
Important: On the “ceiling” (inside the wall) you may need at least 1x16mm or 2x13mm plasterboard due to the requirements of the penetrations tested systems. For the lining on the side of the wall, the thickness requirement is defined by the manufacturers manual for one-way systems achieving the same FRR required on the ceiling. Also, for option 2 the lining of the top must be fixed to the floor joist/nogging above.
If you have more questions regarding penetration through junctions on plasterboard walls, have a look in our other post or just send us an e-mail.