Sheeting the upper floor ceiling
May 2, 2015
The upper floor ceiling is sheeted with 15mm Gypsum Wallboard to provide the fire protection we require for the JJI roof joists.
This is screwed straight through the airtightness membrane into the joists above, which means that precisely locating the joists in advance of placing the screws is important! We used a string line for accuracy, although as the face of these deeper joists is 63mm wide, there is some room for manoeuvre.
Sheeting the void was interesting but thankfully we managed to fit the plasterboard lifter onto the scaffold tower, which made the job considerably easier, as although the boards are light in comparison to the Fermacell on the ceiling of the ground floor storey below, they are still heavier than a standard 12.5mm plasterboard sheet.
We had two penetrations in the airtightness layer for cabling in the double height space: one for a smoke detector and one for a pendant light fitting. We positioned the fixing points for these two items at the junction between a dwang and a joist to give us two fixings points for these items later.
We had to create a hole in order to feed the cables above the airtightness layer as we had installed the cables first, which we repaired afterwards using pro clima airtight tape, and place an airtightness grommet around each penetration in and out of the membrane. The smoke detector requires two cables so we used a proprietary twin gable grommet here. These photos illustrate the sequence...