To reduce the risk of freezing and condensation on pipework, the following precautions should be taken: Notes for surveyors / building control officers. Properties built during the 1960s and 1970s frequently do not have diagonal bracing and all of the necessary longitudinal bracing. Even if the roof shows no signs of any deformation it is important that such bracing is added retrospectively. All joints should be cut accurately to fit tightly. When they are nailed, care should be taken not to split members.

On most dormers, the DORMER CHEEK STUDS should be supported either by a double rafter or by a double floor joist. 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 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 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.

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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. Provides support to purlins to prevent deflection and to transfer roof loads to the load-bearing structure below. Cavity trays should be linked to the flashing to prevent water penetrating into an enclosed area where a: Trussed rafters should be supported only at the junction between the ceiling tie and rafter, unless specifically designed otherwise, eg as a cantilever. Tiles or slates should overhang to the centre of the gutter. For slates or plain tiles, an under-eaves course should be used.

Trimming members around dormers should be large enough to take the extra load from the cut main roof members and dormer framing and cladding, as detailed in the design. Restraint straps should be fixed to solid noggings with a minimum of four fixings of which one should be in the third rafter. The fixings should be four steel screws or four 75mm x 4mm (8 SWG) round nails. 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).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. 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. For any further information or prices please do call our national sales office. Buy Celotex Insulation fixings for fixing Pitched roof insulation currently unavailable Where roof coverings are of plain tiles or slates, laced and swept valleys may be used or, alternatively, a mitred valley with soakers.

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.

The underlay should be turned up at least 100mm at all abutments to prevent rain and snow being blown into the roof space. CEILING JOIST or TIE: triangulates the rafters, stopping the walls and roof spreading outwards; supports the ceiling finish and any walkways, etc 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.