Bs 5268 Guidelines 5m344b
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MAIN CHANGES – IS193 2006 •
DRAFT ISSUED FOR PUBLIC COMMENT JULY 2005
•
EARLIEST IMPLEMENTATION MID 2006
•
MOVES CLOSER TO BS 5268 Part 3
•
REFERENCES MORE ENs
MAIN CHANGES – IS193 2006 •
MINIMUM TIMBER THICKNESS 35mm TO COMPLY WITH EN 1995 (EUROCODE95)
•
SPAN TABLES OMITTED ALL TRUSSES TO BE DESIGNED
•
MAXIMUM BAY LENGTHS FOR EACH TIMBER SIZE EFFECTIVELY GOVERNS MAXIMUM SPANS FOR EACH CONFIGURATION
MAIN CHANGES – IS193 2006
•
•
•
•
PRINCIPAL GIRDERS Girders ing other girders, trusses, or ing a roof area more than 2.5 times the standard truss CEILING TIE MUST BE BOLTED, OTHER CAN BE NAILED OTHER GIRDERS Typically those in hip systems and multiple trusses around openings of less than 2.4m width ALL CAN BE NAILED
MAIN CHANGES – IS193 2006 •
REFERENCES PRODUCTION CODE EN 14250
•
AND FACTORY PRODUCTION CONTROL (QA)
MAIN CHANGES – IS193 2006 •
SITE INFORMATION PACKAGE REQUIRED TO INCLUDE;
• •
ROOF PLAN SHOWING TRUSS LAYOUT WITH TRUSSES LABELLED NUMBER OF PLIES FOR MULTIPLE TRUSSES
MAIN CHANGES – IS193 2006 •
LOADING FOR SLATES 0.400 kN / sq. m. INCLUDED
•
BRACING SIZE REDUCED FROM 2,500 sq. mm. TO 2,200 sq. mm
•
MINIMUM TARGET THICKNESS OF 25mm (25 x 88 mm.)
SIGNIFICANT CHANGES TO BS5268 •
TIMBER QUALITY “Fissures greater than half the thickness are only permitted at the ends of a member and for a length not greater than the width of the piece”
•
NO LONG FISSURES ACCEPTED
SIGNIFICANT CHANGES TO BS5268 •
LOADING “To recognise the possibility of future conversion of roof trusses where habitable room areas may be provided, the designer should apply to the habitable room area a minimum live load of 1. 5 kN/ sq. m. and an appropriate dead load which should include an allowance for partitions. In the absence of detailed loading information a minimum floor dead load allowance of 0. 55 kN / sq m should be used.”
•
IF IT LOOKS LIKE AN ATTIC, LOAD IT LIKE AN ATTIC
SIGNIFICANT CHANGES TO BS5268 •
LOADING “Uned eaves overhangs 600mm and above in length, measured on plan, should be designed to carry a concentrated load of 0.9kN 300mm from the tip of the overhang measured on plan”
SIGNIFICANT CHANGES TO BS5268
•
LOADING Ceiling tie loads for water tanks should be ; – 2 x 0.45 kN for 230 or 300 litre tanks – 2x 0.675 kN for 450 litre tanks – or design to specific requirements
SIGNIFICANT CHANGES TO BS5268 •
GIRDERS “Gaps greater than 3mm between chord should be packed with suitable material”
SIGNIFICANT CHANGES TO BS5268 •
GIRDERS Effective thickness of the girders shall be Kr x N x B Where; Kr 2 ply = 0.7 Kr 3 ply = 0.6 Kr 4 ply = 0.5 N = number of plies B = thickness of each ply
SIGNIFICANT CHANGES TO BS5268 •
DESIGN RESPONSIBILITIES “It is important that the deflection of wind girders be limited. To avoid structural damage to walls or wall and ceiling finishes the Building Designer should provide the trussed rafter manufacturer with the maximum permitted deflection for the (wind) girders. In the absence of any other guidance, it is suggested that the maximum permitted deflection of wind girders should be taken as 10mm”
LIMIT DEFLECTION OF WIND GIRDERS TO 10mm MAX. UNLESS OTHERWISE INSTRUCTED BY BUILDING DESIGNER
SIGNIFICANT CHANGES TO BS5268 •
STANDARD ROOF BRACING
•
ANNEX A NOW GIVES STANDARD BRACING PATTERN FOR SPANS UP TO 17M
•
APPLICABLE TO ALL BUILDINGS
SIGNIFICANT CHANGES TO BS5268 •
WALL PLATES AND TRUSS FIXINGS
•
Wall Plates – Wall plates less than 3m long in one piece – Wall plates longer than three metres can be in two or more pieces but only two pieces can be shorter than 3.0m and none shorter than 1.5m long.
•
TRUSS FIXING TO WALLPLATE – All trusses should be fixed using proprietary types of fixings nailed in accordance with the manufacturers requirements
•
SKEW NAILING OF TRUSSES TO WALL PLATE BANNED
SIGNIFICANT CHANGES TO BS5268 •
WATER TANKS – Platform should tank over whole area – Platform should be minimum 18mm material – For 450 litre tanks, changed member size minimum, maximum span for finks and maximum bay sizes for other truss configurations – All for tanks should be C16 or better
SIGNIFICANT CHANGES TO BS5268 •
FABRICATION “For trussed rafters manufactured with punched metal plates fasteners the requirements on EN 14250 apply”
SIGNIFICANT CHANGES TO BS5268 •
ERECTION Under “Damage between manufacture and erection” the new 5268 allows; “In any chord or web member, bow of 0.003 of member length or 20mm whichever is the lesser, may remain after erection.
SIGNIFICANT CHANGES TO BS5268 •
INFORMATION TO BE PROVIDED BY THE TRUSSED RAFTER MANUFACTURER TO THE BUILDING DESIGNER Now includes; “The number, type, size and position of all fasteners required to girder trusses together”
•
NAILING AND BOLTING DETAILS FOR GIRDERS REQUIRED
DRAFT ISSUED FOR PUBLIC COMMENT JULY 2005
•
EARLIEST IMPLEMENTATION MID 2006
•
MOVES CLOSER TO BS 5268 Part 3
•
REFERENCES MORE ENs
MAIN CHANGES – IS193 2006 •
MINIMUM TIMBER THICKNESS 35mm TO COMPLY WITH EN 1995 (EUROCODE95)
•
SPAN TABLES OMITTED ALL TRUSSES TO BE DESIGNED
•
MAXIMUM BAY LENGTHS FOR EACH TIMBER SIZE EFFECTIVELY GOVERNS MAXIMUM SPANS FOR EACH CONFIGURATION
MAIN CHANGES – IS193 2006
•
•
•
•
PRINCIPAL GIRDERS Girders ing other girders, trusses, or ing a roof area more than 2.5 times the standard truss CEILING TIE MUST BE BOLTED, OTHER CAN BE NAILED OTHER GIRDERS Typically those in hip systems and multiple trusses around openings of less than 2.4m width ALL CAN BE NAILED
MAIN CHANGES – IS193 2006 •
REFERENCES PRODUCTION CODE EN 14250
•
AND FACTORY PRODUCTION CONTROL (QA)
MAIN CHANGES – IS193 2006 •
SITE INFORMATION PACKAGE REQUIRED TO INCLUDE;
• •
ROOF PLAN SHOWING TRUSS LAYOUT WITH TRUSSES LABELLED NUMBER OF PLIES FOR MULTIPLE TRUSSES
MAIN CHANGES – IS193 2006 •
LOADING FOR SLATES 0.400 kN / sq. m. INCLUDED
•
BRACING SIZE REDUCED FROM 2,500 sq. mm. TO 2,200 sq. mm
•
MINIMUM TARGET THICKNESS OF 25mm (25 x 88 mm.)
SIGNIFICANT CHANGES TO BS5268 •
TIMBER QUALITY “Fissures greater than half the thickness are only permitted at the ends of a member and for a length not greater than the width of the piece”
•
NO LONG FISSURES ACCEPTED
SIGNIFICANT CHANGES TO BS5268 •
LOADING “To recognise the possibility of future conversion of roof trusses where habitable room areas may be provided, the designer should apply to the habitable room area a minimum live load of 1. 5 kN/ sq. m. and an appropriate dead load which should include an allowance for partitions. In the absence of detailed loading information a minimum floor dead load allowance of 0. 55 kN / sq m should be used.”
•
IF IT LOOKS LIKE AN ATTIC, LOAD IT LIKE AN ATTIC
SIGNIFICANT CHANGES TO BS5268 •
LOADING “Uned eaves overhangs 600mm and above in length, measured on plan, should be designed to carry a concentrated load of 0.9kN 300mm from the tip of the overhang measured on plan”
SIGNIFICANT CHANGES TO BS5268
•
LOADING Ceiling tie loads for water tanks should be ; – 2 x 0.45 kN for 230 or 300 litre tanks – 2x 0.675 kN for 450 litre tanks – or design to specific requirements
SIGNIFICANT CHANGES TO BS5268 •
GIRDERS “Gaps greater than 3mm between chord should be packed with suitable material”
SIGNIFICANT CHANGES TO BS5268 •
GIRDERS Effective thickness of the girders shall be Kr x N x B Where; Kr 2 ply = 0.7 Kr 3 ply = 0.6 Kr 4 ply = 0.5 N = number of plies B = thickness of each ply
SIGNIFICANT CHANGES TO BS5268 •
DESIGN RESPONSIBILITIES “It is important that the deflection of wind girders be limited. To avoid structural damage to walls or wall and ceiling finishes the Building Designer should provide the trussed rafter manufacturer with the maximum permitted deflection for the (wind) girders. In the absence of any other guidance, it is suggested that the maximum permitted deflection of wind girders should be taken as 10mm”
LIMIT DEFLECTION OF WIND GIRDERS TO 10mm MAX. UNLESS OTHERWISE INSTRUCTED BY BUILDING DESIGNER
SIGNIFICANT CHANGES TO BS5268 •
STANDARD ROOF BRACING
•
ANNEX A NOW GIVES STANDARD BRACING PATTERN FOR SPANS UP TO 17M
•
APPLICABLE TO ALL BUILDINGS
SIGNIFICANT CHANGES TO BS5268 •
WALL PLATES AND TRUSS FIXINGS
•
Wall Plates – Wall plates less than 3m long in one piece – Wall plates longer than three metres can be in two or more pieces but only two pieces can be shorter than 3.0m and none shorter than 1.5m long.
•
TRUSS FIXING TO WALLPLATE – All trusses should be fixed using proprietary types of fixings nailed in accordance with the manufacturers requirements
•
SKEW NAILING OF TRUSSES TO WALL PLATE BANNED
SIGNIFICANT CHANGES TO BS5268 •
WATER TANKS – Platform should tank over whole area – Platform should be minimum 18mm material – For 450 litre tanks, changed member size minimum, maximum span for finks and maximum bay sizes for other truss configurations – All for tanks should be C16 or better
SIGNIFICANT CHANGES TO BS5268 •
FABRICATION “For trussed rafters manufactured with punched metal plates fasteners the requirements on EN 14250 apply”
SIGNIFICANT CHANGES TO BS5268 •
ERECTION Under “Damage between manufacture and erection” the new 5268 allows; “In any chord or web member, bow of 0.003 of member length or 20mm whichever is the lesser, may remain after erection.
SIGNIFICANT CHANGES TO BS5268 •
INFORMATION TO BE PROVIDED BY THE TRUSSED RAFTER MANUFACTURER TO THE BUILDING DESIGNER Now includes; “The number, type, size and position of all fasteners required to girder trusses together”
•
NAILING AND BOLTING DETAILS FOR GIRDERS REQUIRED
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