14th September 2020

How to Install the Intrim SK800FR Fire Rated Shadowline® System

(This original post was updated 2-8-21 to incorporate Revision B from the CSIRO Short Form Assessment Report FCO-3351, dated 28 July 2021)

We have prepared easy to follow steps together with detailed illustrations to assist you with the installation of the Intrim SK800FR Fire Rated Shadowline® Skirting system to meet the testing application and conditions noted in the CSIRO Short Form Assessment Report FCO-3351 Rev B, “Fire-resistance of various plasterboard lined walls that include an Intrim FR MDF skirting detail when tested in accordance with AS 1530.4-2014,” dated 28 July 2021.

Download Shadowline SK800FR Installation Instructions


Detailed instructions with diagrams are below:

The configuration of the components for this system must be as follows.

Plasterboard lined wall system incorporating 64mm steel stud wall framing, lined on both sides with 16mm thick CSR Fyrchek plasterboard (or another brand with same fire rating standards), and the 18mm thick SK800 Shadowline FR MDF skirting board, screw fixed along the bottom of the steel framing, on both sides of the wall frame.

The bottom of the wall frame cavity must be lined with 50mm thick x 60kg/m3 Bradford Fibretex 350 Rockwool insulation board, continuously behind the skirting board and between the steel studs and must have a minimum distance of 160mm between the top edge of SK800 skirting and the top of the insulation board. (Refer to figure 1 below).


1. Installing the Skirting

Cut SK800 skirting to required lengths to fit neatly between door jambs and internal and external corners of framework. Cut SK800 skirting with 45-degree mitre cuts for internal and external corners.

FR MDF SK800 must be screw fixed to steel frame, into every stud at a maximum distance of 600mm centres. (minimum of 2 fixings per stud up to 90mm wide, minimum of 3 fixings per stud for 135 to 185mm wide, and minimum of 4 fixings per stud for 235 to 285mm wide). These fixing points must include 1 fixing 20mm from base of skirting board and another fixing must be through the centre of ribbed section at top of skirting board. Install with 5mm packers between the bottom edge of skirting and floor to allow for any subframe movement. (Refer to figure 2).  Apply a Bead of Bindex Fire & Acoustic Sealant between base of skirting and floor substrate as shown in Figure 1

2. Rockwool Insulation Installation

50mm CSR Fibretex 350 Rockwool

Cut and fit in between framing studs and rear faces of skirting boards allowing a maximum distance between the face of the insulation and the rear face of skirting of 14mm.

The height of the insulation must be 160mm minimum height above top edge of skirting as per figure 1.

3. Plasterboard Installation

16mm Fire Grade Plasterboard

Install plasterboard sheet to framework as per manufacturer’s specifications. Cut and fit plasterboard sheet as close as possible to door jamb and skirting edges. Preferable to have the factory finish plasterboard edge sitting on the top of SK800 skirting edge. (Refer to figure 3).

4. Setting Skirting & Plasterboard Joint

Brush down the top ribbed section of the skirting to remove all dust prior to plaster setting. Set all plaster joints including the joint where the bottom edge of wall plasterboard sits on top of the shadowline skirting, using paper joint tape or FibaFuse tape. (Any tape used that does not meet the recommended tape types will void all warranty).

The tape should be positioned within the joint so the bottom edge of the tape comes within 5 – 10mm of the bottom edge of the ribbed section of skirting. All plaster set and accessories must be installed to manufacturer’s specifications and instructions. (Refer to Figure 4)

5. Finishing

Apply all coats of plaster set including top coats to all plaster joints and sand. All plaster set and accessories must be installed to manufacturer’s specifications and instructions. (Refer to Figure 5).

Proposed Variations

The proposed construction shall be a steel plasterboard lined wall that includes an Intrim Mouldings FR MDF skirting board backed with 50mm CSR Fibretex 350 rockwool insulation as tested in FSP 1997 and subject to the following variations.

  • The wall linings may vary to include other proprietary brands of 16mm Fire grade plasterboard provided they have been tested or assessed to be fixed to each side of a 64mm steel stud without cavity insulation and achieve an FRL of at least -/60/60.
  • The wall may increase in height.
  • If the wall increases in thickness the maximum difference between the insulation thickness and the cavity size shall be tested at 14mm.
  • Refer to Figure 1 for a summary of the construction.