Read the video transcript below
This short video explains how deflection heads work and the importance of installing them correctly, specifically in relation to fire resistance, sound insulation and structural stability.
The term “deflection” means to move in either direction (downwards and/or upwards), and we call these live loads and dead loads. Dead loads generally relate to a one-off downward deflection only, whereas live loads can relate to deflection that moves downwards and then returns back upwards to its original position due to changes in loading on a floor. Live loads can also be deflection that moves upwards and then returns back downwards to its original position due to uplift in a building’s structure.
We use Gypframe channels where deflection heads are installed. We call these DC (deep channel) and EDC (extra deep channels), and they’re available in various widths for our range of partition systems.
In this video we'll be installing a 15mm downward deflection head with a 60-minute fire rating, incorporating single layer 15mm Gyproc FireLine plasterboard.
Cut and fix 19mm Gyproc CoreBoard to the back of 72 DC 60 Channel with 35mm drywall screws. Details that have been fire tested incorporate Gyproc CoreBoard, Glasroc F FireCase, and timber, but it may be possible to use double layer 12.5mm Gyproc FireLine subject to actual criteria.
Apply a continuous line of Gyproc FireStrip to the CoreBoard.
Fix the channels to the structure at 600mm centres. Note that two rows of staggered fixings at 300mm centres is required for channels wider than 72mm.
Install the metal studs, which should be 15mm short from the top of the channel. Note that the stud should have a minimum engagement into the track of 20mm. This detail is based on 15mm downward deflection, so there will be a minimum plasterboard overlap of 7mm onto the CoreBoard.
Cut and fix GFS1 Fixing Strap to the metal studs with Wafer Head Drywall Screws. The top or uppermost part of the fixing strap should be 15mm below the bottom edge of the channel.
Cut and fix the FireLine plasterboard. Remember that the drywall screw at the top of the board should be fixed into the fixing strap, not the head channel. It’s important to run a continuous bead of Gyproc Sealant along the junction between the floor slab and CoreBoard to provide optimum sound insulation. Don’t fully fill the deflection gap with sealant as this will prevent any deflection taking place.
Where high levels of sound insulation need to be maintained, it’s very common to see cloaking angles. These are fitted to the underside of the floor slab, and hold the plasterboard tight against the head channel on the partition. This can minimise the loss of sound insulation of the partition to one to two decibels, as opposed to four to five decibels.
Where double layer plasterboard is used, the fixing strap is installed between the layer of boards.
Where a two-hour deflection head detail is required, short lengths of metal stud are cut and fixed between the vertical studs 15mm below the channel, installing the stone mineral wool into the web of the stud at the same time.
There you have it... a quick guide on how to form deflection heads.
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