Flat to Pitch - Propped Rafter
Specifications for FTP System Ltd Propped Rafter framing system
FTP Systems Ltd supply lightweight, high tensile cold rolled steel flat-to-pitched roof conversion systems.
FTP provide a range of lightweight steel framing systems uniquely designed to suit the needs of each roof, converting it to pitched without having to remove the existing flat roof, or constructing a pitched roof in a new build situation. This provides a long-term solution to water ingress caused by weathering. The system has been pre-engineered to incorporate a maximum amount of adjustment, allowing it to accommodate any amount of level variance. The system is designed to suit any specified product for the roof, for example insulation, noise dampening, thermal bridging or cladding type, without any change to the main components.
The system is manufactured from pre-galvanised high yield high tensile cold rolled steel in a range of profiles of a bespoke design exclusively for the use by FTP Systems Ltd.
All materials conform to BSEN 10147:1992. Structural calculations are provided to prove each component, and the finished product.
The system will be erected to meet the Building Regulations 1991 (England and Wales) Standard.
In the design of the system all current codes of practice are considered and proved by calculation:
- BS6399: Part 2:1997 Code of practice for wind loads
- BS6399: Part 3:1988 Code of practice for imposed roof loading
- BS5950: Part 5:1998 Code of practice for design of cold-formed sections
FTP Systems Ltd work closely with a structural engineer ensuring easy exchange of information and allowing all elements from the survey of the sub-structure to the entire design process to be proved by calculation and is included as part of the package.
The FTP Propped Rafter System
The FTP propped rafter system is delivered in kit form, allowing for assembly on site. The system consists of four main components as follows:
- FTP Base Members, 50 x 50 x 2mm thick angle, generally manufactured from Z2 pre-galvanised cold rolled steel.
- FTP Post section, 10 X 40 x 40 x 40 x 10 X 1.2mm thick lipped channel, always manufactured from pre-galvanised Z35 (minimum) high tensile pre-galvanised cold rolled steel. With external sleeve to give approximately 210mm adjustment to establish a level Rafter line.
- FTP Rafters, 20 x 37 x 45 x 37 x 20 x 1.2mm thick always manufactured from Z35 (minimum) high tensile pre-galvanised cold rolled steel. Rafters are supplied cut to length to suit individual projects.
- FTP Longitudinal Bracing/Sag bar, 50 x 50 x 2mm thick angle in 3000mm lengths, generally manufactured from Z2 pre-galvanised cold rolled steel.
All frame connections are generally made by the means of 2no CR19 self-drilling carbon steel screws, unless additional fixings are required to suit load conditions. The number of fixings required are determined by structural analysis.
Base fixings are determined by means of a fixing pullout test to ensure suitability to individual requirements.
FTP Services
A number of services are included in a FTP Systems Ltd package. A full site survey will be carried out including a level survey to determine any variances in existing roof levels. A full fixing pull-out test is performed to determine and prove holding fixings required by taking 6 samples. Regular site visits are then carried out to give technical support and advice to the erection team, ensuring the system is fixed in accordance with our recommendations. Erection details are provided by full and detailed CAD drawings, as is the insurance backed design of proposed new structure. Insurance backed structural calculations are included within the package in order to obtain building regulation approval.
The general contractor is to supply the roof perimeter edge protection, power etc.
Further design conformation can be obtained from:
FTP Systems Ltd
Wilson-Barker House
Severn Road,
Stourport-on-Severn,
Worcestershire,
DY13 9EZ,
UK
Tel: 01299 878558
Fax: 01299 822272
Email: fabs@ftpsystems.com
