A Building Regulation application will be required in every instance (unless the work is to be carried out by a member of the National Federation of Roofing Contractors), normally a Building Notice will be the best approach and should also be acceptable when re-roofing shops or office buildings unless the new works would affect the Building Regulation B1. The majority of Eden district is classed as being in a severe exposure area, this needs to be considered when carrying out this work.
A thorough survey should be carried out, which is not only restricted to checking member sizes but should include observations of how the roof has performed to date, including checks for overall stability.
This appraisal should include checks for:
- Alignment, signs of decay, insect attack, corrosion of fasteners and fixing, evidence of movement around eaves and at all other connections. Check supporting structure, bracing and for instances where the bearing of timber has been impaired.
- Check for under design of timber, in particular purlins
- Check for inadequate strutting
- Check restraint at foot of rafters (raised tie roofs will need careful consideration)
- Compare weight of new roof covering with the existing, making allowances where the appropriate for any additional loadings which may be applicable due to water absorption (this can be particularly relevant when replacing existing slates with concrete tiles).
After carrying out the above procedures, your Surveyor / Engineer will be in a position to decide what action is to be taken, this can include:
- The roof structure is found to be satisfactory and no further action is necessary.
- Some degree of strengthening is required, details and calculations will need to be provided from your Surveyor / Engineer.
- The roof can be re-covered and the required levels of insulation and ventilation provided. Slating must be carried out in accordance with British Standard 5534, slate laps for different types / sizes of slates and various roof pitches are detailed in the attached document.