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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 Ridge and hip tiles, for a distance of at least 900mm from the face of rigid masonry supports such as gables, abutments and separating walls, should be mechanically fixed. Purpose-made tile-and-a-half, or half-tiles, should be used at verges. Cut tiles at verges are not acceptable. It is essential when installing celotex rigid insulation boards in cut to fit roof applications to ensure they are secured firmly. Insulation boards falling down on your head is no fun and also you really don’t want the weight of the boards resting on your plasterboard finish. Celotex insulation clips are and ideal purpose made fixing that ensures the PIR insulation boards are kept firmly in their place. The advantage of these clips is that if you have uneven timbers or if you are unable to cut the insulation to fit tightly in between the timbers. Then these fixings will work perfectly holding the insulation in position.
However in many other instances trusses are simply laid flat upon the floor. Such a practice is satisfactory provided that the trusses have a firm and level support of the ground. However this again would involve some preparation. The system owner’s software is very sophisticated and not only designs the trusses, but also produces quotations, manufacturing information and production data. Advantages of Trussed Rafters Where the flat roof is over a dormer, it is recommended that the flat roof should be designed and constructed with a fall to the front or sides. When using the following materials, the detailing and workmanship should follow the design and recognised good building practice:
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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. Cavity trays should be linked to the flashing to prevent water penetrating into an enclosed area where a: 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.
Where a pitched roof abuts the wall at an angle, a stepped cavity tray linked to a stepped flashing should be used. To reduce the risk of freezing and condensation on pipework, the following precautions should be taken: To prevent the underlay sagging at the eaves and forming a water trap behind the fascia, it is recommended that the underlay is supported by a continuous fillet. Where the pitch is below 30°, a continuous fillet should always be used. Plain tiles are unsuitable for pitches less than 35°. (b) verges
Trusses are made by some forty four manufacturing companies dotted around the country. Trusses are engineered to suit the particular application requested. The software used by each manufacturer will be supplied by one of three companies who also make the connector plates used to fasten the members together (often referred to as “the system owners”). The major System Owners are Roof truss clips generally come in two different sizes, 38mm and 50mm. The most suitable size clip to use will depend on the size of the timber used to make the trusses. It is best to speak to your truss provider to make sure that you have the correct size clips. They can advise you further. Provides support to purlins to prevent deflection and to transfer roof loads to the load-bearing structure below. Where necessary to protect the heads of timber features, the underlay should extend 50mm beyond gable walls, bargeboards, 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).
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. 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. For any further information or prices please do call our national sales office. Buy Celotex Insulation fixings for fixing Pitched roof insulation currently unavailable Battens should be set out in straight lines, parallel to the ridge and to the gauge required by the tile or slate. The lap should not be decreased because this would reduce weathertightness. The lowest batten should be fixed so that the tile projects halfway across the gutter. 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.A strip of underlay, at least 600mm wide, should be laid over hips and above the underlay to the main roof. For cold roofs that incorporate a low water vapour resistance (type LR) underlay, (e.g. a vapour permeable underlay) ridge or high level ventilation equivalent to a continuous opening of 5mm should be provided in accordance with the design. (b) underlays Ridge and hip tiles are bedded in 1:3 cement : sharp sand with plasticiser mortar or mechanically fixed using a proprietary dry ridge fixing system following the manufacturer's instructions. The method shown in the design should always be used. Where cheek framing does not extend to floor level, a double rafter will give necessary support to the cheek. The two rafters must be fixed together. Celotex insulation fixings are a perfect solution when installing rigid insulation boards in between timbers.
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