Q: Do we have to use truss clips to fix the trusses down to the wallplate?

A: Truss clips are generally the prefered option and will be obligatory by mid 2006. An alternative method is to use a minimum of two 4.5mm diameter by 100mm long galvanized round wire nails at each bearing position, skew nailed from each side of the trussed rafter into the wallplate or bearing.

Q: EC5: What is EC5?

A: EC5 is an abbreviation for Eurocode 5: Design of timber structures. It is European Standard BS EN 1995-1-1:2004 and has the status of a British Standard. Each Country within the Euro area has adopted this code and either has or will produce an Annex for its use. For the UK this is UK National Annex to Eurocode 5: Design of timber structures – Part 1-1:General – Common rules and rules for buildings.

Q: EC5: How does EC5 affect me?

A: SpaceJoist has been implemented within VIEW under EC5 this means that when you design such a beam by default you will be designing under EC5.

Q: EC5: So what are service classes and do I need to do anything?

A: For SpaceJoist you will only be using Service class 1 and 2. View has been defaulted to 1 as this is appropriate for most floors under the NA this covers Intermediate floors. You will need to change this to Service class 2 if you are designing a Ground floor. This affects the structural design properties of the beam and it is important that this is set for the type of Floor construction you have.

Q: EC5: What are the benefits of EC5?

A: The concept behind all Eurocode is to produce economic designs by standardising design through the Euro zone to limit state design. This means that you as a supplier will be able to design elements for other countries simply with one integrated package from ITW Alpine.

Q: EC5: What are the diferences in load combinations?

A: For SpaceJoist you might notice that the usual load cases have been replaced by something called ULS and SLS. ULS is an acronym Ultimate Limit State and SLS is Service Limit State. To comply with EC5 the beam will have to design for all the combinations that the program produces.

Q: How do I turn my metalwork on/off for any particular job in AiMS?

A: From the main AiMS menu, load the Standard Inventory settings and browse to the Metalwork tab. Notice on this tab that there is a checkbox entitled "Only Show Stocked Items" which when selected will display only the Metalwork items that are currently stocked and hence turned on. Unselecting this checkbox will result in all Metalwork items being displayed with each non-stocked item returning with red text formatting. To turn the metalwork on/off you simply need to select and edit items, switching the Stocked checkbox as necessary.

Q: How do I turn my metalwork pricing on/off for any particular job in AiMS?

A: From the AiMS Job List, load the Job Details for the job you wish to turn Metalwork pricing off / on and browse to the Designed Items tab. Here notice two checkboxes: "Do not use designed metalwork" and "Do not use designed bracing / strongbacks". Selecting these checkboxes will turn the pricing off for each respective item.

Q: Is it allowable for trusses to be drilled or notched for the installation of services?

A: Alpine strongly recommends that holes are never to be drilled in trusses for services as doing so will severely compromise the design of the entire truss. If holes or notches are to be made, it should be with the consent of the truss designer or remedial work for repair will be inevitable. There are two sources for information about drilling holes in the bottom chord members of attic trusses: 1) NHBC’s Technical Letter – Issue 31, Dec 2004. 2) TRA Information Sheet No. 2003-1 These both specify within certain limits where holes of a given size may be made.

Q: What Certification does SpaceJoist have?

A: SpaceJoist have been assessed under CUAP (Common Understanding Assessment Procedure) by BM TRADA Certification, this process will continue until an ETA (European Technical Approval) has been ratified.

Q: What gap is allowed in joints?

A: Within the area of the fastener, the average gap between adjacent members should be no more than 1.5mm

Q: What is the tolerance for fastener positioning?

A: It has been recommeded by the TRA that fastener misplacement should not exceed 5mm in any direction, as is current practice. Under EN 14250 fastener misplacement is tolerated up to 10mm in any direction. If you choose this however, the settings in View will need to be changed and will result in the specification of larger plates.

Q: What precautions need to be taken when installing a trussed roof over a swimming pool?

A: The roof must be adequately ventilated to ensure that the moisture content never exceeds 20% for any significant period. It may be likely that the trusses will be subjected to chemical attack from the pool addatives, so special consideration must be given to the possibility of corrosion of nailplates and other fixings. In any event it is the building designer’s task to ensure that the ceiling detail effectively seals the roof from the pool area and that adequate ventilation of the roof space by natural or mechanical means is achieved. The design must allow for reasonble access to the roof space for periodic inspection of the timber and fasteners.

Q: What tolerances are allowed in the dimensions of trusses?

A: The overall horizontal and vertical dimensions of a truss should not differ from the design by more than the following limits: > up to 10m: plus or minus 10mm > more than 10m: 1mm for each metre. The overall dimensions on a batch of trusses should not differ in excess of 10mm.

Q: What width and depth of wallplate should be used?

A: As a rule, the bearing length should be a minimum of 75mm, and no less than 0.008 times the span unless design calculations show otherwise. On ocasions when wallplates are bedded on masonry they should have a minimum target thickness of 47mm.

Q: Who is responsible for detailing all elements of bracing required in the roof, including that necessary to provide the lateral restraints to the truss members?

A: The responsibility lies with the Building Designer. He or she should also provide suitable fixing details for both the trussed rafters and the wallplates to give restraint against uplift required by the trussed rafter designer.