Firewalls

Construction of an External Firewall

In accordance with Building Regulations, it is sometimes necessary for certain elements of a building to have a specified period of fire resistance. The regulations vary according to the element and the distance from the boundary.

The systems that Euroclad have had tested at approved fire research centres are applicable given that the following criteria are met.

Position: The firewall must be 1m or more from the boundary measured from the outer face of the cladding.

Type of Building: In accordance with regulation B2 of the Building Regulations it must be as defined.

Height: Paragraph 13.7, Section 13, Part B4 of theBuilding Regulations states that "In a building with a storey 18m or more above ground level, insulation material used in ventilated cavities in the external wall construction should be of limited combustibility…" (Or be non-combustible)

Special requirements by local authorities: It may be that local interpretations of building regulations vary or that the building merits special consideration. It is essential that the building designer confirms that the Euroclad system selected complies with the relevant local authority requirements.

Direction: Euroclad's standard firewall systems offer protection from the inside of the building.  However, symmetrical firewall systems are also available which protect against fire attack from either direction, inside to out, or outside to in.

Structural Frame: the fire resistant system must be fixed to sheeting rails, which are fixed to supporting cleats through slotted holes with the bolt incorporating a plastic or low-melt washer - both elements having the purpose of assisting movement due to thermal expansion in the event of a fire. The rails are to be at maximum 2080mm centres, and all bottom sheeting rails should be single span. All sheeting rails should be shorter than standard to allow an expansion gap. The remainder of the frame must be protected to the same period of protection as the rest of the wall.

Support of Wall: When the sheeting rails heat up during a fire they will no longer function as a structural member. To prevent the wall moving downwards under its own weight, either a base support or securing to a protected eaves beam is required. This will allow the wall to continue to be supported during a fire, even when the sheeting rails are no longer providing adequate support.

In general terms the actual construction of a built up system firewall is relatively simple as laid out below. Please note that this information is intended as a summary only, and full detailed information should be obtained from the Euroclad Firewall technical publication.

Vertical sheeting - stone wool insulation

Utilising a Rockwool cladding roll a simple fire wall construction is achieved, offering a typical rating of 4 hours integrity and 15 minutes insulation. Where 30 minutes insulation rating is required (as standard for Scottish regulations) the additional precaution of liner sheet stitching is required.

Vertical sheeting - glass wool insulation

When a glass fibre insulation quilt is used, it is necessary to introduce a minimum 20mm air gap between the insulation and the liner sheet. As the insulation is therefore normally compressed over the spacer bar, this system has fallen out of favour with most contractors as it is more awkward to install and is deeper than an equivalent U value normal construction.

Vertical sheeting - symmetrical fire wall

This system uses the same principles as a rock fibre insulation construction, by has the added precautions of stitching the liner sheet, and sealing the liner with an intumescent sealant strip to the end and side laps.

Horizontal sheeting - stone wool insulation

Due to the orientation of the spacer bar (vertically installed), the support of the insulation has, in the past, proved an issue in providing a horizontal firewall construction. However, by using a flexible slab stone wool insulation, this issue is over come, and a quick and easy horizontal firewall cladding solution is now available. Note that the spacer bar does require a thermal break strip installed to the face of the bar, 12mm deep x 50mm wide continuous strip. It is therefore essential that torque settings on fixing guns are correctly set and care taken during installation to prevent 'dishing' around fixings.

Horizontal sheeting - symmetrical fire wall

As with the vertical symmetrical fire wall, the added precaution of stitching the liner sidelaps, and using an intumescent sealant to the end and side laps enables a symmetrical fire wall construction, offering protection against fire attack from either inside or outside the building.