PFS

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PFS

Pre Formed Strap (Perpendicular)

The PFS is an engineered strap that has been designed to provide enhanced performance and greater flexibility while laterally restraining floors and roofs.

Suitable for use with I-Joist, Open Web & Trusses
Engineered strap with reduced thickness and weight compared to traditional straps
One solution for floor and roof applications

Z600 or Z275

35 x 1.5mm

Galvanised Mild Steel with

Edge Protection

Up to 10.80kN

Characteristic Tensile Capacity (flat strap)

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CULLEN TECHNICAL GUIDE

Materials & Resources

Typically used for lateral restraint in floor and roof applications

Exceeds minimum performance of 8kN as per BS EN845-1

One solution for floor and roof applications

Engineered strap with reduced thickness and weight compared to traditional straps

Installation videos available for all detailed applications

Paslode 3.4 x 35mm Electrogalvanised Square Twist Nail

Cullen products have been tested and CE marked to the requirements of ETAG015 using 3.4 x 35mm square twist nails.

Floors

Roofs

Gable Restraint System

The strap should be nailed with a minimum of 8 no. 3.4 x 35mm square twist nails evenly spaced

Refer to the Cullen Restraint Straps Technical Guide

Floors

Surface Fixed I-Joist

Noggins to be installed between the I-Joists or Metal Web Joists using 2 no. UZ-Clips and 2 no. skew nails staggered either side.
After fitting all noggins the PFS strap can then be located tight to the block work and centred on the noggins.
The strap should be nailed with a minimum of 8 no. 3.4 x 35mm square twist nails evenly spaced and into at least every joist.

Only suitable when joists line through with top of blockwork

Noggins: NHBC Requirements

Width: min. ½ I-Joist depth, max. 150mm
Depth: min. 38mm
Timber: min. C16 grade

Noggins to be installed between the I-Joists or Metal Web Joists using 2 no. UZ-Clips and 2 no. skew nails staggered either side
After fitting all noggins the PFS strap can then be located tight to the block work and centred on the noggins
The strap should be nailed with a minimum of 8 no. 3.4 x 35mm square twist nails evenly spaced and into at least every joist

Only suitable when joists line through with top of blockwork

Noggins: NHBC Requirements

Width: min. ½ I-Joist depth, max. 150mm
Depth: min. 38mm
Timber: min. C16 grade

Cut a small slot in the I–Joist web, just under the top flange
Slide the PFS through the slots and position tight against the block work
To provide a fixing for the PFS, noggins must be nailed in place between the I-Joists through the I-Joist web
The strap should be nailed with a minimum of 8 no. 3.4 x 35mm square twist nails evenly spaced into the noggins

Not suitable when joists line through with top of block work

Noggins: NHBC Requirements

Width: min. 38mm
Depth: min. ½ I-Joist depth, max. 150mm
Timber: min. C16 grade

Strongback/additional noggins to be installed as per manufacturer’s guidelines
Position PFS tight to block work and centred on block
The strap should be nailed with a minimum of 8 no. 3.4 x 35mm square twist nails evenly spaced into the noggins

Roofs

Install PFS on the 25 x 100mm longitudinal truss bracing (1).
Ensure the position of the longitudinal bracing and strap coincide with the blocks vertical joint.
The 90deg bend of the strap is to be held tight against the cavity face of the inner leaf of blockwork (2), preferably located on the full block. Notch the blocks to accommodate the angle of the strap and ensure notch is fully mortared.

Install PFS on the 25 x 100mm longitudinal truss bracing (1).
Ensure the position of the longitudinal bracing and strap coincide with a horizontal blockwork joint.
The 90deg bend of the strap is to be held tight against the cavity face of the inner leaf of blockwork (2), preferably located on a substantial piece of blockwork, i.e. over the centre of a full block, with a single cut block over the strap (3). Notch the blocks to accommodate the angle of the strap and ensure notch is fully mortared.

Ensure the position of the straps coincides with the horizontal blockwork joint.
Install PFS to underside of solid noggins (1). Noggins to be fixed horizontally to avoid twisting of the restraint straps.
The 90deg bend of the strap is to be held tight against the cavity face of the inner leaf of blockwork (2), preferably located on a substantial piece of blockwork, i.e. over the centre of a full block, with a single cut block over the strap (3). Notch the blocks to accommodate the angle of the strap and ensure notch is fully mortared.
Fix straps to noggins/trusses with 8 no. 3.4 x 35mm square twist nails, evenly spaced along the length of the strap. Ensure a minimum of 2 fixings into noggin beyond the 3rd rafter (4).

Install PFS on the 25 x 100mm longitudinal truss bracing (1). Bracing to be fixed to each truss with 2 no. 3.35 x 65mm round wire nails.
Ensure the position of the longitudinal bracing and strap coincide with a horizontal blockwork joint, where this is not possible inserted a cut block to suit strap location (4).
The 90deg bend of the strap is to be held tight against the cavity face of the inner leaf of blockwork (2), preferably located on a substantial piece of blockwork, i.e. over the centre of a full block.

Guidance

Straps to be installed at not more than 2m centres (or 1.25m where appropriate) along gable end

Strap to be of sufficient length to be fixed to a minimum of 3 no. trusses

Blockwork to be built up to suit strap location

Longitudinal bracing to be fixed to each truss with 2no. 3.35 x 65mm round wire nails (in all details 3.1 x 90mm long mechanically driven nails may be substituted for 3.35 x 65mm long wire nails)

Where the position of the strap does not coincide with an existing longitudinal truss brace, then the strap may be fixed to an additional 25 x 100mm longitudinal binder (as shown in following details). The binder to be fixed over a minimum of four trusses and fixed to each truss with 2no. 3.35 x 65mm round wire nails.

Fix straps to longitudinal bracing with 8no. 3.4 x 35mm square twist nails, evenly spaced along the length of the strap (for NHBC warrantied buildings, in accordance with NHBC Standards 2017 section 7.2.8, 8 no. 25 x 4mm steel screws shall be used instead of square twist nails)

Parallel restraint straps are not required to roof trusses unless specified by building designer

These have been issued as guidance only, the overall responsibility lies with the Building Designer. For 3rd floor and above please refer to the building standards or building designer for guidance. All straps require a full storey of block work above to achieve the full 8kN declared load capacity.

Gable Restraint System

Cullen PFS restraint straps fixed to solid timber noggins between trusses at maximum 2000mm centres with 3.4 x 35mm square twist nails, 8 no. to noggins and 4 no. to gable panel (2 no. top face & 2 no. cavity face)

Installation Guidance

Explore the step-by-step PFS installation video

The video demonstrates best practice on site, highlighting each stage of the installation process to help ensure accuracy, consistency, and compliance during fitting.

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