Check your roof twice-yearly. Reinstate slipped or missing slates or tiles, and replace broken ones before roof timbers or plaster ceilings are harmed. True slates can be refixed with copper wire (‘tingles’), but heavier stone slates must be nailed or pegged. Isolated tiles are re-secured by hooking the pegs or nibs over the battens or laths.

Junctions in roofs are potential trouble spots. Ridge and hip tiles may work loose, needing rebedding in a lime mortar, and lead flashings and mortar fillets at chimneys etc should be inspected for early signs of deterioration. In the loft, look for water staining and other evidence of leaks, remembering that this may be some distance from the point of entry. Be aware that some unscrupulous contractors rely on roofing underlay to compensate for bad workmanship. Ensure that loft insulation does not block eaves ventilation, promoting damp and timber decay.

Mortar fillets with cracks should be repointed or, if cracking is extensive, re-formed. Normally a soft lime mortar should be used, not cement. There should be a presumption in favour of the retention of mortar fillets and other locally traditional details, rather than their replacement with lead.

Where lead or other metal flashings exist and are split or holed, replacement may be necessary using a short length of matching material. Vertical splits, though, can be repaired by covering them with a small section of new matching flashing, wedged and pointed above the original.

Repaired roof with metal straps and new timber

Where lead sheeting still has some life left, holes and splits are best made good with lead-welded patches, not solder, but fire safety must be remembered. Proprietary adhesive tape is available for temporary repairs. Where individual sheets have reached the end of their useful life, they will require replacing.

Copper, stainless steel and aluminium roofs are light and consequently susceptible to wind damage. Sheets should be refixed immediately, otherwise flexing (‘drumming’) can necessitate total replacement. Other minor defects (such as holes) may be addressed by covering with patches of matching material.

Excessive moss is often undesirable on roofs. Moisture retention may cause damage to roof coverings, and acidic rainwater run-off to gutters or roofs below can corrode certain metals. A seasonal brushing down should help control the build-up. Sometimes copper strip growth inhibitors are fitted at every ten courses of slates or tiles, remaining effective for 30-40 years. Alternatively, sacrificial lead flashings can be provided at drip-off points.

Keep your roof moss-free. Horsham roof slabs.