• Timber frame lintels for use in an external timber frame cavity wall construction above window and door openings.
• Cavity widths greater than 50 mm.
• Lintels should be installed with a minimum end bearing of 150 mm, bedded on mortar and levelled along its length and across its width.
• The masonry above the lintel should be built in accordance with BS EN 1996-2.
• All timber frame lintels must be installed with restraining clips and a timber pinch batten to prevent rotation of the lintel during the building stage.
• Keystone timber frame restraint clips are supplied free of charge and must be fixed to the timber frame structure by 3.3 x 50 mm galvanized nails. Lateral restraint clips should be placed at 500 mm centres each side of mid span.  
• NHBC & LABC recommend a damp proof course (DPC) or cavity tray should be installed over all openings in external cavity walls.
• Allowance should be made for the movement of the timber frame structure due to settlement and shrinkage. 
• Masonry should be laid on a mortar bed and all perpendicular joints should be filled.
• The external lintel flange must project beyond the window/door frame and it is recommended that a flexible sealing compound is used between the underside of the lintel flange and the frame.
• Do not cut lintels to length or modify them in any way without consulting a Keystone engineer.
• Masonry should not overhang any flange by more than 25 mm.
• The practice of propping a lintel is sometimes used to facilitate speed of construction. It should only be introduced after initial masonry load has been applied to the lintel.
• Stop ends are required at each end of a lintel to prevent moisture cascading over the ends into the cavity and onto the inside wall.
• At least two weep vents are required per opening and positioned not more than 450 mm apart.

All Keystone timber frame lintels satisfy the thermal performance requirements of Approved Document L of the Building Regulations (E & W), Northern Ireland’s Technical Booklet F and Scotland’s Technical Handbook, section 6. Provide a damp proof course / cavity tray over all lintels. For more detailed information applicable to a particular wall construction, contact Keystone Lintels Technical Department.

Refer to manufacturers literature for details regarding lintel ranges, height, thickness and Uniformly Distributed Load (UDL) figures.

Performance:

Fire:

• Keystone lintels have been subjected to a fire test (WARRES No. 101263) in accordance with BS 476-20 and (Report No. 508704/R) in accordance with BS EN 1363-1 at Exova Warrington Fire and achieved a one hour fire performance.

Corrosion:

• Keystone’s timber frame range of lintels are manufactured from high quality grade pre-galvanized mild steel to BS EN 10346 DX51D with a zinc coating of 600 g/m² (including both sides) conforming to BS EN 845-2.
• The use of austenitic stainless steel is ideal when the life expectancy and maintenance programme of a building are key considerations. 
• Material / coating specification in buildings exceeding three storeys in a non-aggressive environment should be limited to austenitic stainless steel (chrome nickel alloys). 
• Material / coating specification for buildings in an aggressive environment (e.g. coastal sites) should be limited to austenitic stainless steel (molybdenum chrome nickel alloys). 

Structural:

• The Keystone lintel range has safe working loads as detailed in each applicable loading table in the Keystone Steel Lintel Manual.
• The structural performance figures within each table have been ascertained by testing in accordance with the requirements of standards BS EN 5977-2, BS EN 846-9 and BS EN 845-2.

Certification:

• BBA Agrement certificate 98/3493 including regular assessment of production.
• UKCA Assessment of performance, System 3.
• CE Assessment of performance, System 3.
• EN 1090-2 Execution Class 2, Declaration method 1,2,3a & 3b, Certificate 14/F106 & 14/F107.
• ISO 9001 Quality Management Systems, Certificate 18/Q059.
• ISO 14001 Environmental Management Systems, Certificate 18/E019.

Special lintels:

Keystone lintels can be supplied to suit a wide range of wall types, loading scenarios and bespoke custom made specials:

• Arch lintels,
• Bay lintels (square or splayed),
• Corner lintels,
• Bow lintels,
• Sunlounge lintels.

Contact Keystone Lintels Technical Department for further information.

Stainless steel:

• All Keystone’s range of lintels can be manufactured from austenitic stainless steel, grade 304 2b BS EN 10088-Part 2 Astm 240 (European Grade 1.4307).
• Upon request, other grades of stainless steel lintels are available conforming to BS EN 845-2.

Additional features:

• Free scheduling and specification service.
• Keystone Steel lintels have a service life commensurate with that of the building in which they are installed.
• Keying options to suit required plastering applications.
• Cant brick. 
• Powder coating.
• Soffit cladding.
• Brick slip cladding. 
• Universal arch.
• Weep holes.
• Stop ends.
• Bespoke.

Contact Keystone Lintels Technical Department for further information