Please contact your representative to determine quantities. Refer to appropriate sections of the Specifier Guide for installation guidelines and construction details.The subfloor must be glued as per APA Specification AFG-01 or ASTM D3498 and nailed as per NDS, ICC IBC/IRC code. and is a “24 oc APA rated panel” for joist’s spacing of 24″ o.c. The considered subfloor is a “20 oc APA rated panel” for joist’s spacing of 12″, 16″ and 19.2″ o.c.The indicated spans are based on the Allowable Stress Design method as per NDS, ICC IBC/IRC code. Live Load deflection is limited to L/480.Total Load deflection is limited to L/240.Maximum spans are measured centerline to centerline of bearing and are based on uniformly loaded joists.Minimum end bearing length is 1½”, spans in bold require web stiffeners at OSB end panel.The indicated spans are based on simple span joists.Regulations to any project we do not have first hand knowledge of.Live load: 100 psf / Dead Load: 15 psf / Depth: 16″ – Span table Live load Us to specify your timbers as mistakes in dimensions etc can be very dangerous and we will not apply definitive Suitable, 250mm fibreglass, 120mm cellotex or 140mm styrofoam) (Note – the following insulation thickness would be In most instances it would be recomended that EPDM be used due to the ease of installation The following stages depend on the method you choose to use as a finalĬovering on the roof. It shouldīe noted that all boards should lie half way on a joist were it is to meet another board if it does not it should be cut The decking boards can now be fitted along with the facia boards. Firings can be obtained at all good timber merchants. This fall being directly proportional to the thickness of the firing Lifting the one side of the roof creating a fall. Firings are lengths of timber cutĭown the length from corner to corner forming very long triangles so that they go from full thickness to nothing and Noggins should be installed for every 2 metres of span this will stop the joists from twistingĪs well as keeping the gap between joists constant.Ī firing should be fitted to each joist. Joists are fitted level, usually 400mm spacing but can be 450mm, or 600mm depending on the size of the joists that haveīeen chosen. Not always the case a small discrepancy can be allowed especially if the fall produced is in the right direction The It is usually necessary to have the wall plates level with each other as well as along the length of the wall, but this is Wall plates allow easy, secure fixings when fitting With a combination of cement and fixings to make sure it is level. Wall plates, this is usually 1" x 4" rough cut timber which is fixed to the top of the wall, usually In any other situation you should refer to theĪpproved Document Part A of the Building Regulations or ask your Building Control Surveyor for advice.īefore the joists are fitted it is usually necessary to fit a All figures are based on normal loading conditions found Install, and if fitted as a single membrane as there are no joints to worry about, even when done DIY it will out lastįollowing tables give details of the allowable spans and spacing for some of the more common timber sizes used in flat You will get a guarantee and that is worth its weight in gold. This purlin will require 74 mm minimum end. From the table above, a 75 mm x 175 mm C18 purlin will span 1.97 m. Example: A purlin is required to span 1.95 m, supporting a 2.5 m maximum rafter span on the slope either side. In the case of a felt or fibreglass covered roof, we very strongly advise the Roof purlins in heavy roofs SLC 1 27 m/s with wind pressure qp (10) Table D5 - Sizing of roof timbers - purlins. I t is therefore important, before building your structure that you have the Of the Building Regulations (Structure) where the possible snow loadings, depending on area of the country and heightĪbove the ordinance datum, are taken into consideration. A further part of this equation is discovered in Approved document A Of the calculation for the size of joists required. The weight of these last two coverings, together with the span, form the basis In the case of timberĪ further, waterproof cover is required. Plate to wall as is the case with a lot of extensions, covered by sheet timber or other material. Flat roofs are constructed basically with joists spanning the gap between two walls, or wall
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