Where roof coverings are of plain tiles or slates, laced and swept valleys may be used or, alternatively, a mitred valley with soakers. The design should specify the number of fixings for clay and concrete tiles. Tables 2 and 3 of Appendix 7.2-B contain minimum fixings for tiles. Additional nails and clips may be necessary in accordance with the design. A fixing schedule produced by the tile manufacturer, based on The Zonal Method, is acceptable. If a roof is not a simple triangle, all members should be fully supported and tied together. If necessary, temporary support to long span members should be used until the framing is complete. (c) valley and hip construction Where half-round tiles are used at hips, they should be supported at the base of the hip by a galvanized hip iron. (d) valleys and hidden gutters

CEILING JOIST or TIE: triangulates the rafters, stopping the walls and roof spreading outwards; supports the ceiling finish and any walkways, etc If the design specifies holding down straps to prevent the roof being lifted off the supporting structure, they should be at 2.0m centres (maximum). All joints should be cut accurately to fit tightly. When they are nailed, care should be taken not to split members. A strip of underlay, at least 600mm wide, should be laid over hips and above the underlay to the main roof.

Objective

Battens should be fixed with cut or wire nails. The nail shank can be smooth, annular ringed or helically threaded. Nails can be steel or aluminium. In coastal areas, steel nails should be hot dip galvanized. (d) slates and tiles

Where the width of gable ladders exceeds that of the trussed rafter centres, noggings should be provided to reduce the span of the roofing tile battens. All members should be accurately located. Purlins and binders should be built in, where necessary. In a typical traditional roof, the basic timber members are: When the author has inspected roofs there have been some occasions when the householder has to be advised to remove or lessen the amounts of goods stored in the roof for danger of overloading it. Typically the bottom chord of a truss is designed for a superimposed load of 0.25 kN/m2 which the author often refers to as empty cardboard boxes loading. Two clips are used per roof truss. One is placed on either side, where the truss is fixed to the wall plate. Usually, the roof truss clip is installed on the inside wall plate. However, you can also fit these on the outside wall plate if the detail of the truss heel allows.RAFTERS to ceiling joists: nailed lapped joint. The rafter should be birdsmouthed over and skew nailed to the wall plate A truss clip should always be fitted vertically to a wall plate, never lying flat or horizontally. You must make use of every hole on the face of the roof truss clip, and nail all of these in. Some installers may only use four of the thirteen holes which are on the clip – this is not utilising the strength of the clip fully. For any further information or prices please do call our national sales office. Buy Celotex Insulation fixings for fixing Pitched roof insulation currently unavailable The guidance above will assist in reducing the risk of condensation occurring but is not acceptable as an alternative to cross ventilation of the roof space.

Where straps are fixed to masonry, hardened nails 4mm in diameter x 75mm long or No 12 wood screws x 50mm long into plugs should be used. Cavity trays should be linked to the flashing to prevent water penetrating into an enclosed area where a: Conservative estimates would suggest there is somewhere in excess of 60 million trussed rafters in service in the UK. To date, there has been no known failure of a trussed rafter in its “ex factory” condition, a remarkable safety record. However, experience has shown that trussed rafters are not always well understood by the people who specify them or who erect them. Such misunderstanding can, in some circumstances, lead to poor installation or worse unsuitable alteration. Objective All verge tiles and slates should be bedded on an undercloak. Alternatively, proprietary dry verge systems should be fixed in accordance with manufacturers' recommendations. Battens on rigid sarking boards should be supported on counter battens to allow free drainage of any water that may reach the underlay. Counter battens should be fixed through to the rafters and not to the sarking boards alone. Battens should be fixed through counter battens to rafters.Where bedded in 1:3 cement : sharp sand with plasticiser mortar the following tiles should also be nailed: Proprietary gutter or valley systems should be fixed in accordance with the manufacturer's recommendations. (e) flat roof intersection

At valleys, a similar strip should be laid under the main roof underlay and held down by the valley battens, where used. The main roof underlay should be dressed over the valley battens. Where necessary to protect the heads of timber features, the underlay should extend 50mm beyond gable walls, bargeboards, etc. Vertical laps in the underlay should occur only over rafters and be securely fixed. Where the pitch is below 30°, the underlay should be supported at eaves level by a tilting fillet. The underlay should be dressed into the gutter and pulled tight to ensure there are no troughs to retain water.Particular care is needed where pipes project through the underlay. Torn underlay around pipes can lead to the ceiling becoming wet and stained. Cut a small cross in the underlay and sleeve over the pipe so that the tongues turn up.