Updated: Dec 8, 2020
A common issue in Passive Fire Protection is penetrations through wall joints where a fire-rated wall connects to a non-fire-rated wall.
While most people can identify penetrations on a firewall and point it as an item to be fire-stopped, there is still a misunderstanding regarding the penetrations inside non-fire-rated walls. For the joints of two firewalls (walls A and B) or where the lining of the firewall (Wall A) is continuous, there are typically no issues regarding passive fire protection (see Figures 1 and 2).
Figure 1 - Continuous lining wall
Figure 2 - Junction of two firewalls
There are also no issues on penetrations through two firewalls junction, as long as the penetration is fire-stopped correctly on the wall (see Figure 3).
Figure 3 - Penetration through firewalls junction
In reality, no project is perfect, so what if there is penetration from a non-fire-rated wall through the nogging of the firewall? Then we have a breach on the fire protection (Figure 4).
However, plasterboard manufacturers do not usually clarify questions regarding penetrations within a wall that penetrates a firewall, and there is still some level of questioning by contractors.
Figure 4 - Breach of the fire protection on wall junctions
This breach can be reinstated by extending the fire protection to the non-fire-rated wall, which would convert it into a fire-rated wall. Then, the solution in Figure 3 would apply.
This solution’s downside is: by converting the wall into a firewall, all the other penetrations through this wall also have to be fire-rated. Plus, this wall may also be connected to other partitions which could generate the new or the same issues again.
Usually, it is not common to find a passive fire system tested for penetrations in timber, then lining is also applied on the nogging and a solution tested on a firewall is applied. Locally fire rateing the nogging may also be acceptable when the difference on the FRR between the two walls is up to 30 minutes.
Figure 5 - Local Fire Stopping applied on the nogging.
Note that the small section of lining around the nogging (in pink) may be formed by the same lining forming the wall, as long as this lining achieves the required FRR. Also, the internal local lining should be properly fixed to the nogging as required by the plasterboard manufacturer.
As a real-scenario example on a FRR -/30/30 wall, consider the picture below. Can you see the explicit requirement for the penetrations to be fire stopped even before the lining is installed?
Figure 6 - Real case example
Note that the fire stopping here will have to be performed before the lining of the non-fire-rated wall. Therefore, It is crucial to have good coordination between the passive fire installers with the lining installer. Also, in all cases, the recommendation of plasterboard and passive fire manufacturers shall be followed.
If you have more questions regarding penetrations through junctions on plasterboard ceilings, have a look in our other post or just send us an e-mail.