straight forward health and safty advice 
Working on roofs results in a substantial number of fatal and serious accidents every year For this reason, no one must go onto any roof or undertake any roof work, no matter how simple it seems, until they are properly trained to do so. There must be a Risk Assessment for the work, which takes into account the hazards likely to be encountered, e.g. process and flue discharges,  fragile materials, etc. This must also consider the emergency rescue arrangements.  Design and plan the working using the guidance that is given in the HSE document “Health and safety in roof work” (ref. HSG33).  When planning the work, and working at height cannot be avoided, apply the safeguards shown below, in the following order: a safe working platform with guardrails and toe boards  - this is the most effective precaution; Only if this first level of protection cannot be achieved in practice, are the following acceptable; safety nets and similar protective systems – as these provide general protection – or lastly; individual protection e.g. safety harnesses with lanyards or inertia reels, attached to suitable anchorage points. Work of short duration i.e. taking minutes rather than hours, may be carried out using individual fall protection. Use a suitable safety harness and lanyard with a shock absorber, or an inertia reel, secured to an anchorage point that is capable of taking the anticipated shock loads if a fall occurs. For other work, suitable edge protection must be provided. This must consist of guardrails and toe boards at the edge, and fencing around any opening or skylight, where a person can fall. There must be a safe means of access to the roof. Check the weather conditions each day before work starts and if necessary, while the work is to be done. Remember that a safe foothold can be difficult in bad weather.
Work precautions