OSCB Contractors’ Guide
16Pages

OSCB Contractors’ Guide Installation of ROCKWOOL SP Firestop OSCB

Introduction This guide is intended to assist with the installation of ROCKWOOL SP Firestop OSCB. Note that OSCB is only compatible for use in conjunction with ROCKWOOL RAINSCREEN DUO SLAB® and NyRock Rainscreen 032. Guidance for details which fall outside the scope of ASFP TGD-19 is based on test evidence carried out to the principles of TGD-19, and is provided only as best-practice.

Installation instructions OSCB 25 Note that for cavities below 75mm, the barrier should be fixed directly to the substrate using No.10 stainless steel screws at 250mm centres. For cavities 75mm and above, follow the steps given below. 1. Form the supplied brackets into an L shape and snap by hand to the required length*. The bracket must penetrate a minimum of 50% into the barrier width, but should not penetrate the intumescent layer. 2. Fix the brackets at maximum 500mm centres, ensuring non-combustible and corrosion resistant fixings are used – e.g. DeWalt Wall Dog, 6mm diameter thread x...

OSCB 44 Note that for cavities below 100mm, the barrier should be fixed directly to the substrate using No.10 stainless steel screws at 250mm centres. For cavities 100mm and above, follow the steps given below. 1. Form the supplied brackets into an L shape and snap by hand to the required length*. The bracket must penetrate a minimum of 50% into the barrier width, but should not penetrate the intumescent layer. 2. Fix the brackets at maximum 500mm centres, ensuring non-combustible and corrosion resistant fixings are used – e.g. DeWalt Wall Dog, 6mm diameter thread x 32mm long or similar....

General installation notes ■ Do not remove the weatherproofing polythene layer. ■ Ensure that OSCB is installed with the intumescent strip facing outwards, towards the cladding panel. Do not apply tape over the face of the barrier. ■ Make sure that OSCB is flush to the substrate with no gaps present. Any voids of up to 10mm should be filled with ROCKWOOL Acoustic Intumescent Sealant. ■ Ensure there are no gaps between adjacent sections of OSCB. ■ Ensure that the intumescent strip is free to expand to the rear of the cladding without obstruction, e.g. vertical cladding rails preventing free...

Cutting of OSCB Perpendicular to length When cutting OSCB into smaller sections: ■ Do not cut into sections smaller than 200mm; ■ There should be a minimum of two brackets and two pigtail screws (where applicable) per cut section. Parallel to length ■ Between the minimum and maximum, OSCB is available in any width and should be ordered appropriately to ensure that the product does not need to be cut down on site. ■ OSCB can be supplied pre-cut to accommodate a continuous angle – for more information please contact your local ROCKWOOL representative. ■ There may however be occasions where it...

Other details Interface with SP Firestop ■ Vertical runs of SP Firestop should be uninterrupted, with OSCB tightly abutting. ■ Around windows, SP Firestop OSCB should be used horizontally top and bottom, with SP Firestop fitted vertically along the sides. ■ In situations where the minimum fire ratings required from the vertical and horizontal barriers are not the same, it is recommended that the higher rating takes prevalence and is applied to both. ■ For example, if the vertical barrier requires at least 60 minutes and the horizontal barrier at least 120 minutes, then both the vertical and...

Corner details ■ External: One run of OSCB oversails the other and is tightly butted against the cladding. The oversailing barrier should have a minimum bearing on the substrate of 200mm or 40% of the section length (whichever is greater), and should be supported by a minimum of two brackets. ■ Internal: Internal corner joints should be mitred. Cassette panels In the first instance, the cladding manufacturer should be approached for specific guidance on how their product can be used in a way that complies with Part B of the Building Regulations with respect to cavity barriers. Generic...

Penetrations T-rails Ideally, vertical rails should not run continuously through a cavity barrier and should instead be stopped either side. In situations where this is not possible, the guidance below will apply. Please note that running a metal rail through OSCB 44 will limit the product’s performance to a maximum of 60 minutes integrity-only, owing to conductive heat transfer through the metal rails; however in our opinion the risk presented by this heat transfer is mitigated by using the product in conjunction with non-combustible ROCKWOOL Rainscreen Duo Slab or NyRock Rainscreen 032...

OSCB installation checklist Fire resistance of substrate It is important that the structures that are supporting and surrounding the fire barrier are capable of resisting a fire for a period no less than the rating required of the fire barrier itself. For example, a fire barrier fixed to a combustible substrate will be limited in a fire situation if the substrate provides a medium for fire spread that bypasses the barrier. Position of intumescent strip OSCB should be installed so that the intumescent strip faces the outer cladding. Intact polythene sleeve The polythene sleeve allows easy...

Adjacent sections of OSCB tightly abutting To maintain an effective seal the barriers must tightly abut one another. Ensure that a bracket or 1mm x 25mm metal strip is unable to slide between adjacent sections. Intumescent free to expand to the façade The intumescent component of OSCB is designed to expand directly away from the barrier, and whilst it will intumesce into tight angles (i.e. 90°), it cannot flow around corners. Check that the vertical cladding rails won’t prevent the barrier expanding. There can also be an issue with cassette panels where small lips will prevent the barrier...

Fire resistance When it comes to our approach to sustainability, it is, simply put, a matter of living our purpose to address the challenges of modern living in a sustainable manner. This means using natural materials to make products that have a positive impact on society. Acoustic comfort Circularity Durability Health and safety The safety of ROCKWOOL stone wool is confirmed by current UK and Republic of Ireland health & safety regulations and EU directive 97/69/EC:ROCKWOOL fibres are not classified as a possible human carcinogen. A Material Safety Data Sheet is available and can be...