Cullen Restraint Straps Technical Guide 2024

Brands for the offsite industry

Cullen Restraint Straps Technical Guide Innovation. Quality. Service.

Restraint Straps by Cullen Cullen’s restraint straps are engineered for durability and performance, offering essential structural stability across various applications. Interdependent tested to the requirements of BS EN845-1, accepted by the NHBC and compliant with Approved Document A of the UK Building Regulations, these straps meet the highest standards for safety and load resistance in residential and commercial builds. Whether for securing timber or masonry structures, our restraint straps provide effective, code-compliant solutions for preventing lateral movement in walls, floors, and roofs. With rigorous testing and certification, Cullen restraint straps are designed to ensure ease of installation, reliability, and long-term stability.

Parallel Restraint (Domestic Floors)

Parallel restraint refers to the measures taken to prevent lateral movement of walls by transferring external wind forces into the floor diaphragm. This is achieved using straps installed parallel to the floor joists.

Perpendicular Restraint (Domestic Floors)

PFS

PS RANGE

Perpendicular restraint refers to the measures taken to prevent lateral movement of walls by transferring external wind forces into the floor diaphragm. This is achieved using straps installed perpendicular to the floor joists.

Vertical Restraint (Domestic Roofs)

Vertical restraint focuses on preventing uplift forces, such as those caused by wind, from detaching roof elements from the supporting walls. Straps provide a secure connection between the roof and the structure below, ensuring the roof remains firmly in place.

Delivers superior performance and exceptional flexibility, ideal for lateral restraint in floor and roof applications.

The PS range provides required parallel restraint to block work for joist hangers and, where required, build–in details.

RST

VRS

Horizontal Restraint (Domestic Roofs)

Horizontal restraint resists wind forces, maintaining the alignment and stability of the roof structure. This is typically achieved with straps and roof bracing that counteract wind forces and prevent the roof from distorting under load.

*Straps highlighted in blue for visual purposes only

The VRS is an engineered strap that has been designed to provide a convenient and secure method of fixing wall plates to timber and masonry walls.

A high-performance strap developed to resist uplift and provide lateral restraint for timber gables.

The straps are required for compliance with UK building regulations and NHBC technical requirements. Approvals

Compliance The information we provide has been compiled using the minimum requirement from Building Regulations 2010 approved document A, Scottish Building regulation domestic, NHBC standards.

The latest version of the technical guide will always be the digital format on our website.

Technical support: 01592 771132 / technical@itwcp.com / https://www.itwcp-offsite.co.uk 3

Technical support: 01592 771132 / technical@itwcp.com / https://www.itwcp-offsite.co.uk

PFS Pre Formed Strap

PS RANGE Pre Formed Strap

The PS range provides required parallel restraint to block work for joist hangers and, where required, build–in details.

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

Applications can be found on pages 10, 12 and 13

Applications can be found on pages 8 and 9

Features & Benefits — Strap suitable for various blockwork sizes (100-215mm) to include fire and party walls — Higher characteristic capacity values compared to competitor solutions, enabling straps to be installed at a maximum of 2 metre centres — Load values support floor opening details to meet NHBC requirements e.g. stairwell openings — Fewer fixings and connectors are required compared to competitors’ solution — Installation videos available for all detailed applications

Part of the Cullen Gable Restraint System – Pg13

PST–135

Features & Benefits — Typically used for lateral restraint in floor and roof applications — Exceeds minimum performance of 8kN as per BS EN845-1 — 1 solution for floor and roof applications — Engineered strap with reduced thickness and weight compared to traditional straps — Installation videos available for all detailed applications

PST–220

Approvals — CE/UKCA marked in accordance with EN845-1 — Meets NHBC Technical requirements

Engineered bend for increased performance

Material Specification — 35 x 1.5mm Galvanised mild steel – Z600 or Z275 (with edge protection) Approvals — CE/UKCA marked in accordance with EN845-1 — Meets NHBC Technical requirements — Meets Homebond technical requirements

Fixings Code

Description

Box Qty

PSB

Available Sizes

547389 141185

3.4 x 35mm Square Twist Nails – LOOSE 3.4 x 35mm Square Twist Nails – COLLATED*

500

2,500

PSC–220

*For use with Paslode PPNXi

FLAT STRAP

Fixings — Dependant on application

Available Sizes

4mm Ø holes Dimensions (mm)

Minimum Block Work Width (mm)

Maximum Block Work Width (mm)

Strap Material Thickness (mm)

Product Code

B (mm)

F (mm)

T (mm)

PST

Code

Description

Box Qty

547389 141185

3.4 x 35mm Square Twist Nails – LOOSE 3.4 x 35mm Square Twist Nails – COLLATED*

500

PST–135

100

125

100

451.7

135

1.4

2,500

PST–220 PSC–220

140 100 n/a

215 215 n/a

100 100 100

536.7 536.7 451.7

230 220 135

3 3

*For use with Paslode PPNXi

PSC

PSB

1.4

Please refer to page 8 and 9 for guidance on strap requirement

Dimensions (mm)

BENT STRAP

4mm Ø and 6mm Ø holes

PSB

1.5

Strap Selection

I–Joist Depth (mm)

Open Web Joist Depth (mm)

Hanger Depth

Product Code PFS–1000–F PFS–1200–F PFS–1600–F PFS–2000–F

F (mm)

Product Code

F (mm)

B (mm)

195/200

220

240

300

350/360

400

195/202

219/230

253/254

304

375/380

418/424

1000 1200 1600 2000

PFS–900–100–B PFS–1100–100–B PFS–1500–100–B PFS–1900–100–B

900

100 100 100 100

195 225 240 250 300 350 400

PST

195 225 240 250 300 350 400

PST

1100 1500 1900

PST

PSC PST

PST

PSC PST PST

PST

PSC

PST

PSC

Load Data

Fixings

Performance

Characteristic Tensile Capacity (kN)

Fixings

(3.4 x 35mm)

Performance

Characteristic Tensile Capacity (kN)

(3.4 x 35mm)

Built into 3.5N/mm 2 block work & nailed to min C16 grade timber**

8No

8.80

Built into 3.5N/mm 2 block work & nailed to min C16 grade timber** 8.00 **Tested in accordance with the requirements of EN846-4 (with a vertical precompression of 0.4N/mm 2 to the top of the masonry specimen – equivalent to storey height of blockwork) 8No

Flat Strap

n/a

10.80

**Tested in accordance with the requirements of EN846-4 (with a vertical precompression of 0.4N/mm2 to the top of the masonry specimen – equivalent to storey height of blockwork)

The latest version of the technical guide will always be the digital format on our website.

Technical support: 01592 771132 / technical@itwcp.com / https://www.itwcp-offsite.co.uk 5

Technical support: 01592 771132 / technical@itwcp.com / https://www.itwcp-offsite.co.uk

VRS Vertical Restraint Strap Applications can be found on pages 11 and 13

RST Restraint Strap Twist

The VRS is an engineered strap that has been designed to provide a convenient and secure method of fixing wall plates to timber and masonry walls.

The RST is a high performance strap which can be used to resist uplift.

Applications can be found on pages 11 and 13

Part of the Cullen Gable Restraint System – Pg13

Features & Benefits — Unique geometry allows a fixing on two planes without the clash issues of standard twist straps — Suitable for timber frame and masonry walls — Can be used independently or in addition to truss clips/framing anchors/hangers — Also a suitable strap for providing lateral restraint to timber gables (see page 13) — Lighter than traditional twist straps reducing manual handling risk — Achieves greater tensile capacity before reducing centres enabling us to outperform competitors’ solutions — Installation videos available for all detailed applications

Features & Benefits — Engineered to achieve the same performance as a traditional 30 x 2.5mm strap — Thinner profile compared to traditional tie down straps - reducing manual handling risk — Installation videos available for all detailed applications

RST–1

Material Specification — 30 x 1.2mm Galvanised mild steel – Z600 Approvals — CE/UKCA marked in accordance with EN845-1 — Meets NHBC Technical requirements

Engineered bend for increased performance

Material Specification — 30 x 1.2mm Galvanised mild steel – Z275

Available Sizes

Fixings Dependant on application.

RST–2

Fixings To be specified by building designer

Dimensions (mm)

4mm Ø and 6mm Ø holes

Dimensions (mm)

RST–3

150

Available Sizes

Dimensions (mm)

Product Code

RST-1

4mm dia fixing holes

RST–1 RST–2 RST–3

405 848

205 275 275

200 573

RST-2

1350

1075

1.2

Fixing Hole Qty

6mm dia fixing holes

RST-3

Product Code

4mm Ø

6mm Ø

Y 6 8 8

Z 3 8

RST–1 RST–2 RST–3

Product Code VRS–900–100

F (mm)

B (mm)

900

100

Load Data

Fixings (3.4 x 35mm)

Performance

Tensile Capacity (kN)

Characteristic Tensile Capacity (kN)

Performance

Wall Plate (3.4 x 35mm)

Timber Stud (3.4 x 35mm)

Strap only

7.50

11.80

Fixed to 3.5N/mm 2 block work & nailed to min C16 grade timber wall plate*

n/a

4.80

Performance

Fixings (3.4x35mm)

Characteristic Capacity (kN)

3 4 5

5.69 6.23 6.76

Nailed to timber stud & wall plate (min C16 grade)

4.80

Strap attached to truss/solid timber (Min. C16)

*Fixings into masonry wall to be specified by building designer

The latest version of the technical guide will always be the digital format on our website.

Technical support: 01592 771132 / technical@itwcp.com / https://www.itwcp-offsite.co.uk 7

Technical support: 01592 771132 / technical@itwcp.com / https://www.itwcp-offsite.co.uk

Restraint Straps (Domestic Floors)

PST strap with non–restraint hanger

— The strap should be nailed with a minimum of 8No 3.4x35mm Square Twist Nails into the joist top flange/chord

Lateral restraint of the walls can be provided by the floor, the restraint must be provided parallel and perpendicular to the floor joists.

Floor Level

Detail

Region

Ground Floor

1st Floor

2nd Floor

ROOF

Non–Restraint Hangers (JHI/JHIR/ RB–JHI/RB–JHIR)

England & Wales

PST or PSC required at 2m max centres

The type of restraint straps required and the centres at which they are placed depend on the joist end detail and region in which the house is built. Parallel restraint straps run along the same direction as the floor joists. Perpendicular restraint straps run across, or at a right angle to, the floor joists.

PST or PSC required at 2m max centres

PST or PSC required at 1.25m max centres

Scotland

Please refer to page 5 for further information on PST/PSC straps and table for the correct hanger / strap combination.

3RD STOREY

2ND FLOOR

Scan or click to view installation videos

2ND STOREY

1ST FLOOR

PSB strap with restraint hanger

1ST STOREY

— The strap should be nailed with a minimum of 8No 3.4x35mm Square Twist Nails into the joist bottom flange/chord

GROUND FLOOR

Floor Level

Detail

Region

Ground Floor

1st Floor

2nd Floor

3 STOREY HOUSE

PSB required at 2m max centres PSB required at 1.25m max centres

Restraint Hang- ers (RA/HRAD/ RADS)

No additional restraint is required (additional PSB straps required each side of opening where openings exceed 600mm)

England & Wales

Scotland

The information we provide has been compiled using the minimum requirement from Building Regulations 2010 approved document A, Scottish Building regulation domestic, NHBC standards and British Standard BS 5628–1;2005 Annex D.

Please refer to page 5 for further information on PSB straps

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.

Scan or click to view installation videos

Parallel Restraint

PSB strap with built in detail

PSC strap with non–restraint hanger

— The strap should be nailed with a minimum of 8No 3.4x35mm Square Twist Nails into the joist top flange/chord

— The strap should be nailed with a minimum of 8No 3.4x35mm Square Twist Nails into the joist bottom flange /chord

Floor Level

Detail

Region

Detail

Region

Ground Floor

1st Floor

2nd Floor

Ground Floor

1st Floor

2nd Floor

Non–Restraint Hangers (JHI/JHIR/ RB–JHI/RB–JHIR)

England & Wales

PST or PSC required at 2m max centres

Where joists have a minimum bearing of 90mm no additional restraint is required (additional PSB straps required each side of opening where openings exceed 600mm)

PSB straps required at 2m max centres

England & Wales

Built in

PST or PSC required at 2m max centres

PST or PSC required at 1.25m max centres

Scotland

Please refer to page 5 for further information on PST/PSC straps and table for the correct hanger / strap combination.

Please refer to page 5 for further information on PSB straps

Scan or click to view installation videos

The latest version of the technical guide will always be the digital format on our website.

Technical support: 01592 771132 / technical@itwcp.com / https://www.itwcp-offsite.co.uk 9

Technical support: 01592 771132 / technical@itwcp.com / https://www.itwcp-offsite.co.uk

Restraint Straps (Domestic Floors)

Restraint Straps (Domestic Roofs)

Perpendicular Restraint

Lateral restraint of the walls can be provided by the roof, the restraint must be provided perpendicular to the roof trusses.

Floor Level

Detail

Region

Vertical restraint straps counteract uplift forces on roof elements i.e. wall plates and trusses. Horizontal restraint straps provide lateral stability, securing the roof to walls and preventing sideways movement. The information we provide has been compiled using the minimum requirement from Building Regulations 2010 approved document A, Scottish Building regulation domestic, NHBC standards and British Standard BS 5628–1;2005 Annex D.

ROOF

Ground Floor

1st Floor

2nd Floor

England & Wales

PFS required at 2m max centres

3RD STOREY

Perpendicular

PFS required at 1.25m max centres

Scotland

PFS required at 2m max centres

2ND FLOOR

Please refer to page 4 for further information on PFS straps For all applications strap must extend over a minimum 3No Joists PFS surface fixed to I–Joist

2ND STOREY

1ST FLOOR

These have been issued as guidance only, the overall responsibility lies with the Building Designer.

— Noggins to be installed between the I-Joists or Metal Web Joists using 2No UZ-Clips and 2No. 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 8No 3.4 x 35mm square twist nails evenly spaced and into at least every joist

— Only suitable when joists line through with top of block work

1ST STOREY

GROUND FLOOR

3 STOREY HOUSE

Vertical Restraint Bent Strap To Wall Plate

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

Twisted Strap To Truss

RST strap to be nailed to truss with 3.4 x 35mm square twist nails. Nail quantity dependant on uplift value. Fixings into masonry to be specified by building designer. Please refer to page 6 for further information on RST straps

Fix VRS to the wall plate with 2No 3.4 x 35mm square twist nails. Fixings into masonry to be specified by building designer. Please refer to page 7 for further information on VRS straps

PFS through web of I–Joist

— 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 8No 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

Horizontal Restraint (Masonry Gables)

Floor Level

Detail

Region

Up to and including 2 storeys

3 storeys

4 storeys

PFS required at 2m max centres

PFS required at 1.25m max centres

England & Wales

PFS through web of Open Web Joist

Perpendicular

PFS required at 2m max centres

PFS required at 1.25m max centres

Scotland

— 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 8No 3.4 x 35mm square twist nails evenly spaced into the noggins

— 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 3no. 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, 8no. 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.

The latest version of the technical guide will always be the digital format on our website.

Technical support: 01592 771132 / technical@itwcp.com / https://www.itwcp-offsite.co.uk 11

Technical support: 01592 771132 / technical@itwcp.com / https://www.itwcp-offsite.co.uk

Gable Restraint System

Restraint Straps (Domestic Roofs) Horizontal Restraint (Masonry Gables)

ITW Construction Products’ Cullen brand has been a leader in timber engineering connectors for over 40 years. In collaboration with industry partners, Cullen has developed the Gable Restraint System (GRS) featuring the Gable Restraint Bracket and restraint straps. This system ensures secure

transferring lateral wind loads safely into the braced roof diaphragm. Fully compliant with Building Regulations, NHBC Standards, and Scottish regulations, the GRS is a trusted, NHBC-accepted solution underwritten by ITW Construction Products when installed per our detailed guidance.

Fixing to Longitudinal Truss Bracing (Fixed to Truss Web)

— 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.

(2)

(1)

connections between timber gables and masonry walls,

Fixing to Longitudinal Truss Bracing / Additional Longitudinal Binder (Fixed to Truss Web)

For wall tie, panel jointing & cavity tray details see our Gable Restraint System Technical Guide .

(3)

— 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.

(1)

Please note the GRB forms part of a system and must be used in conjunction with the system straps and fixings as shown below.

The Gable Restraint System is comprised of the following specified products:

VRS-900-100

GRB-100

(2)

Fixing to Solid Noggins (Between Trusses)

— 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 8no. 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).

(3)

(1)

Patent: EP567179

(4)

Establishes a verified connection between a timber gable and a masonry wall.

Provides a secure method of fixing wall plates to timber and masonry walls.

(2)

RST-3

PFS-1500-100-B

FT: The Timber Frame Wall Tie

Fixing to Longitudinal Truss Bracing / Additional Longitudinal Binder (Fixed to Truss Ceiling)

— Install PFS on the 25 x 100mm longitudinal truss bracing (1). Bracing to be fixed to each truss with 2no. 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.

(4)

(1)

A high-performance strap developed to resist uplift and provide lateral restraint for timber gables.

Delivers superior performance and exceptional flexibility, ideal for lateral restraint in floor and roof applications.

Restrains the external blockwork or brickwork back to the timber frame structure.

(2)

The latest version of the technical guide will always be the digital format on our website.

Technical support: 01592 771132 / technical@itwcp.com / https://www.itwcp-offsite.co.uk 13

Technical support: 01592 771132 / technical@itwcp.com / https://www.itwcp-offsite.co.uk

Brands for the offsite industry

Cullen Technical Support email: technical@itwcp.com

December 2024*

*Subject to change at discretion of ITW Construction Products Offsite

Cullen Technical Guide

ITW Construction Products 1 Wheatstone Place Southfield Industrial Estate Glenrothes Fife KY6 2SW t +44(0) 1592 771 132 f +44(0) 1592 771 182 e orders@itwcp.com www.itwcp-offsite.co.uk

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