INSTALLATION
TOLERANCES The designer should consider the installation tolerances of the structure, and the installation tolerances of the SFS, when designing and detailing the through-wall system. Manufacturing tolerances and installation tolerances can vary dramatically, and the design team should consider this. The building and installation tolerances can affect the details, making it more challenging to maintain the fire resistance and water resistance elements at the SFS deflection head and other joints. Early engagement is recommended with the system owner to review these interfaces. There must be an understanding of the tolerances permitted within the various structural systems. The relevant documents related to tolerances are listed below for each structure type. It is important to review the tolerances of the structure and compare them to the tolerances achievable for the through-wall. CONCRETE • BS EN 13670-2009 Execution of concrete structures MASONRY • BS 8000-3: 2001 Workmanship on building sites – Part 3: Code of practice for masonry • Brick Development Association – Good site practice and workmanship SFS • The National structural steelwork specification for building construction • BS EN 1090-4 – Execution of steel structures and aluminium structures - Technical requirements for cold-formed structural steel elements and cold- formed structures for roof, ceiling, floor and wall applications
GENERAL INDUSTRY GUIDELINES OF INSTALLATION TOLERANCES OF SFS Below are the industry-accepted tolerances for SFS through-wall systems: • The structural opening size is taken as 10mm wider and deeper than the actual window or door dimensions to allow for tolerances and for the thickness of the connecting plates to support the windows (Note: it may be necessary to increase the 10mm allowance to 15mm if the thickness of the fixing plate exceeds 3mm.) Allowances for deflections should be made in the window design. • Infill SFS requires a minimum of two thirds bearing onto the primary structural frame. If variation in the line of the frame reduces this bearing, additional ancillary components may be required to correct it to provide the required support. • Maximum projection over the slab edge: one third of section width or 20mm for sections equal or less than 100mm wide. • Tolerances in straightness of wall: +/-5mm in 3m length. • Out of verticality of wall: +/-5mm in 3m height (H) or H/600 for walls over 3m. • Minimum allowance for deflection head allowance: • +/- L/400 for edge beam span (L) of less than 5m or L/500 for spans equal to or longer than 5m, for steel-framed buildings • +/- L/400 for edge beam span (L) of equal to or longer than 4m, for renovation of existing concrete-framed buildings • +/- L/200 for edge beam span (L) of equal to or longer than 4m, for new built in-situ or precast concrete-framed buildings. (Note: the higher deflection allowance for new build concrete buildings is to take account of the long-term creep and shrinkage effects of the concrete.) Alternatively use the table from ED017, setting out tolerances and movement. For more guidance on the design of external wall systems refer to the SFS Guide thefis.org/membership-hub/publications/sfs-guide/
STRUCTURAL STEEL • SCI 178 Design for construction
TIMBER • NA to BS EN 1995-1-1:2004+A1-2008 Design of timber structures – Common rules for buildings
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