Flat Roof Insulation - Composite Roof Deck

Flat Roofs

Flat Roof Insulation - Composite Roof Deck
INTRODUCTION For insulating directly over timber joists we recommend the use of Kingspan Thermaroof TR31 zero ODP. Incorporating a 6 mm WBP plywood upper surface and a foil underside, Kingspan Thermaroof TR31 zero ODP combines decking, insulation and vapour control layer in a single product. Suitable for use beneath built–up felt roofing systems this offers all the benefits of a warm roof construction whilst being quick and simple to install. Ideal for both newbuild and refurbishment. Figure 1


PRODUCT DATA		ACHIEVING U–VALUES

1 Thickness does not include 6 mm WBP Plywood. 2 With appropriate waterproofing and chippings. 3 Based on 3 layers of partially bonded built up felt with the surface covered in mineral chippings, a Kingspan Thermaroof TR31 zero ODP board is laid over the timber joists with a skim coated single layer of 12.5 mm plasterboard fixed to the underside. For the purpose of these calculations the standard of workmanship has been assumed good and therefore the correction factor for air gaps has been ignored. 4 Product thickness = insulant thickness + 6 mm ply. 5 Due to limited lengths of fixings, 96 mm overall depth of Kingspan Thermaroof TR31 zero ODP is the maximum practical thickness. In order to achieve 0.22 W/m².K 20 mm Kingspan Thermapitch TP10 zero ODP is required between rafters. (See page 12 for details of Kingspan Thermapitch TP10 zero ODP.) 6 The l–value quoted is in accordance with the Harmonised European Standard BS EN 13165 (urethane) and BS EN 13166 (phenolic) using so called 90/90 principles. Comparison with alternative products may not be appropriate unless the same procedures have been followed.
FIXING DETAILS
Suitable for use over joists at 400 mm and 600 mm centres. Lay boards, plywood facing upwards with long edges following joists and with board joints staggered see figure 2. Insulant thickness 45–50 mm Kingspan Thermaroof TR31 zero ODP should be fixed with suitable galvanised ring shank nails. These are to be placed at 100 mm centres around the board edges and at 300 mm centres along any intermediate supporting timbers. Insulant thickness over 50 mm Kingspan Thermaroof TR31 zero ODP should be fixed with low profile oval head screw fixings. These are to be placed at 200 mm centres around the board edges and at 300 mm centres along any intermediate supporting timbers. Refer: Fixfast 01306 880299 SFS Intec Limited 01132 085500 General All edges of the board should be supported. The use of 50 x 50 mm cross–noggins will ensure this along the boards shorter edges and where boards may be cut at openings or details. A wide bead of non–setting gun–grade mastic sealant, applied along the centre of the joists and cross–noggins will ensure a continuous vapour control layer on the foil underside of the boards. The mastic sealant must be wide enough to accommodate two board edges butted together see figure 3. Refer: Adshead Ratcliffe & Co Ltd 01773 826661, C M Sealants 0208 519 6358. Sheets should be lightly butted (approx. 2 mm gap) whilst maintaining a 20 mm bearing at edges over supporting timbers. Fixings should not be positioned within 10 mm of the board edges or within 50 mm of the corners. Care should be taken to keep the decking dry prior to waterproofing. Always utilise a type 3G felt as the base layer to a 3 layer felt system. To avoid cold bridging ensure the wall insulation around the roof perimeter is carried up 300 mm (min) above to the underside of the insulated deck. This creates a warm roof construction, therefore ventilation is not necessary. Cutting should be carried out using a fine toothed saw.
Figure 2		Figure 3

Staggered board joints over roof joists		Boards laid into non setting mastic