Recovering and repairing existing roofs and the Building Regulations. The following provides guidance on the re covering and repair of pitched and flat roofs with regard to the requirements of the Building Regulations. New roof coverings may impose substantially higher loads on the roof structure compared to the original ones. Occasionally the new material may be substantially lighter than the original material. In both cases a Building Regulation application is required to be deposited with the Building Control Section. Structure Requirement A1When the roof covering imposes higher loads the roof structure may require additional strengthening work to be carried out and could require a structural appraisal by a qualified engineer to ensure it is capable of sustaining the increased load. In older premises, typically terrace type properties, it is not unusual for the rafters and purlins to be under sized and the roof to be inadequately braced to limit the effects of roof spread. The lack of triangulation to a roof can usually be easily identified by the construction of the roof not forming a typical triangle but instead forming a shape similar to that shown in the adjacent diagram. Where the roof timbers are identified as being under sized and or having inadequate or no measures for the limiting of roof spread, you will be required to make provisions to remediate this. The structure is usually re mediated by with the addition of additional purlins and the limiting of roof spread is usually achieved by the addition of ties linking the wall plates together as indicated by the bold line in the above diagram. Resistance to moisture Requirement C2As well as the obvious purpose of a roof to prevent the ingress of moisture from the weather, there is also a requirement to prevent the build up of condensation in a roof space. Adequate permanent ventilation will be required to be provided to the roof void either by the use of an accredited breathable roofing felt or permanent open ventilation via continuous strip at the eaves or other comparable means and where a roof is insulated at the pitch line the rate of ventilation must be increased as shown below. Where other means of ventilation such as tile vents are used, these must be spaced at suitable centres so that the rate of ventilation is at least equivalent to the following Pitched roof of 1. Eaves 2. 5,0. 00 square millimetres per metre run. Ridge 5,0. 00 square millimetres per metre run. Pitched roof in excess of 1. Eaves 1. 0,0. 00 square millimetres per metre run.
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September 2018
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