Health check
A poorly looked after roof can result in serious damage to the rest of your home, so know how to spot and fix problems as a top priority
Expert Roger Hunt advises on maintaining roofs
Old roofs can suffer from issues ranging from the corrosion of fixings, mortar erosion to the ridge, hip and verge tiles, as well as decay of the timber structure. Clay tiles, in particular, are susceptible to the freeze and thaw process that can lead to the face of the tiles breaking down. Although a roof can last a lifetime if installed and maintained correctly, it is vital to select a contractor who understands old buildings. Reroofing work requires building regulations approval.
Maintenance checklist
● Ensure gutters, valleys and run-outs are kept clear of debris
● Check roof slopes for missing, slipped and broken slates or tiles
● Inspect the underside of the roof for chinks of light and rain penetration
● Look for roof debris on the ground and in the loft space
● Deal with any signs of condensation in roof spaces
● Note potential problems with junctions and ridges
● Identify split or decaying roof timbers
Questions and answers Shaun Howland, director of Kent-based John Williams & Company, answers some common questions about roofs and the best repair methods.
Q What can be done about slipping roof slates?
Slipping slates are normally a sign of ‘nail sickness’. The nails corrode over time, so that eventually there is nothing left to hold the slate in place and it will slide out. Other reasons might include the slate breaking due to wind uplift, or a powdery coating – efflorescence – forming due to moisture or a lack of airflow. Individual slates can be fixed back using either a copper strap – not lead – or a proprietary invisible repair clip. In the case of widespread nail sickness, reroofing will be inevitable and replacing a slate with a strap will only be a temporary emergency repair. Q How can condensation in the roof space be cured?
Moist warm air will naturally rise and end up in the roof space, where it will condense on surfaces with
a temperature below the dew point – the point at which the moisture level within the air results in condensation. Ventilation of the roof void at both low and high level is a mandatory requirement when reroofing, although, with older buildings, it is accepted that upgrading to modern standards might not be practical. Retrofit products are available to improve ventilation in roofs where complete reroofing is not anticipated.
Q Some of the rafters are rotten – how should these be dealt with? Defective roof timbers should be repaired during reroofing. With period properties, it is usually appropriate to retain as much of the original structure as possible. Often defective timber can be cut out and new pieces jointed in using the same species of timber as far as possible. In some cases, it might be necessary to have the rafter repair designed by a structural engineer.
Q What can be done about water penetration around a chimney area? First, check the roof covering and flashings and look for evidence of a damp-proof course within the chimney. The pointing and flaunching should be inspected and repaired as necessary, as defective or missing mortar can exacerbate the problem. If rainwater ingress is due to the masonry becoming saturated, the only long-term remedy is to take the stack down to roof level and rebuild with a robust lead damp tray. If the property is listed, consent will be required for this work, but is not guaranteed. Other advice includes using the chimney: warm air from an open fire will assist in drying out the brickwork.
Q Are bats and birds a concern when undertaking roof work?
Bats and some birds are protected, and in the case of bats, if their presence in the roof is suspected, a bat survey will be necessary. Advice will be provided regarding what, when and how work can be carried out. This is mandatory and serious consequences result from non-compliance. Given the potential delays to work, it is prudent to plan well ahead if the existence of bats is suspected. Likewise, if birds are nesting in the roof, take advice and plan ahead to avoid doing work during the breeding season.
Q What should be considered when choosing new slates or tiles?
If the property is listed, then listed building consent will be required and samples must be provided for approval. Otherwise, it is a case of considering the overall aesthetic appearance and appropriateness of materials. The quality and availability of slates and tiles differ greatly. Any competent independent roofing specialist will be able to offer advice across the whole spectrum of materials.
Q The lead of a flat roof is leaking – can it be repaired?
Correctly installed lead has a long life expectancy but can become thin with age due to wear by water erosion or underside corrosion. Lead will also crack if the sections are oversized or over-fixed. Oversized lead sections may expand and contract to such a degree that stress fractures and eventually splitting will occur. In the case of thinning, it is often impossible to achieve a suitable lead weld repair whereas, with a crack, it is possible to weld in a patch. This must be done under strict hot work precautions due to the risk of fire.
Q What are the key things to consider when stone slates cover a roof?
The important consideration is that the mortar used must be breathable to protect the integrity of the stone. Traditionally, stone slates are bedded in a lime mortar. This is a highly specialised form of roofing and incorrect installation can cause serious issues, so employ specialists.