Knauf Ceiling Linings Direct to Joists

Download Ceiling Linings Direct to Joists Manual PDF

Knauf Ceiling Linings Direct to Joists

High quality Knauf Plasterboards are designed to be easy to cut, lift and fix to the underside of timber joists to complete a floor that meets all the relevant fire and acoustic regulations.

Designed to work with modern timber construction

Modern timber joist floors come in a variety of guises from traditionally-based solid timber joists to composite engineered I-Beam solutions. We have developed products such as our high acoustic performance plasterboard, Knauf Soundshield and Knauf Resilient Bar around the requirements of flooring as well as partitions, and have tested our products with the majority of common solutions.


Tried and tested solutions

Floors in general, and timber floors in particular create a number of challenges for the ceiling below. All floors will deflect and it is essential from a decoration point of view that the correct materials are used to resist cracking at joints. Knauf Jointing Compounds and Knauf Joint Tapes have been rigorously tested and developed to provide a robust lining that resists cracking. Specifying Knauf Drywall Wood Screws also minimises the chances of ‘nail popping’, caused when the timber itself warps or shrinks due to moisture changes.

Timber joist floors incorporating Knauf Plasterboards have been substantively tested for fire, acoustic and robustness performance.

Typical Knauf direct to joist design detail:



Nogging layout for Knauf Ceiling Lining direct to joists

Noggings are required to support board edges when using 12.5mm thick plasterboard with joists at 600mm centres. No noggings are required where joist centres are at 450mm or lower centres, or when installing 15mm Knauf Plasterboard onto joists at 600mm centres. See the diagram below.


Optimised Solutions - Knauf Ceiling Linings direct to joists


Internal Floors for Residential Projects

Internal Floors IFR1/08 Sound Fire**
22mm T&G Floor Boarding over solid timber joists. 1 layer of 12.5mm Knauf Soundshield* fixed to underside of joists 40 dB(Rw) 30 mins
Internal Floors IFR2/08 Sound Fire**
22mm T&G Floor Boarding over solid timber joists. 1 layer of 15mm Knauf Wallboard fixed to underside of joists 40 dB(Rw) 30 mins
Internal Floors IFR3/08 Sound Fire**
22mm T&G Floor Boarding over timber ‘I’ joists. 1 layer of 15mm Knauf Wallboard fixed to underside of joists 40 dB(Rw) 30 mins

* If joists are at greater than 450mm centres, timber noggings of nominal size 38mm x 38mm are required between joists and at ceiling perimeter to support board edges.
** Fire ratings quoted in accordance with BS 476 Part 22:1987. For ratings in accordance with EN1364 - 1:1999, please contact Knauf Drywall Technical Services.