Ian Mccarthy, director of Leeds-based roofing specialist, Yorkshire Heritage Roofing, answers some common questions about roofs and the best methods of repair

QThere are a number of slipped slates on our roof – does this indicate that it needs re-covering?

Not necessarily; while slipped slates due to nail sickness/fatigue are usually a sign that the fixings are failing due to the lifespan of the roof, it doesn’t mean that it requires a reroof. The slates that have slipped should be inspected as these themselves may have failed, meaning that a few low-cost repairs should solve the issue. If the slates are intact, further investigation of the roof should be undertaken to find out if the entire roof is suffering from nail sickness. If this is the case, it’s likely that a reroof will be required at some point.

QIs it an issue if the roof undulates significantly? In most cases, this isn’t a problem as undulation usually results from the roof moving and settling over the years. The timbers inside should be inspected to ensure that there are no defects or cracks that may have been caused because of this. Sometimes a structural engineer may need to advise on strengthening the timbers.

QSome of the rafter feet are rotten. How should these be dealt with?

While many roofers do undertake parts of the joinery work, whenever timbers that make up the structure of the roof are found to be damaged, it is wise to employ a carpenter to carry out any repairs alongside the roofer. It is often the case that new feet can be fixed to the existing rafter up to the purlin rather than replacing the entire rafter.

QThe roof timbers have suffered serious beetle infestation, so will they need replacing?

The timbers will need replacing if the wood has become soft and is easily broken apart as they will have lost their structural integrity. An inspection by a carpenter would be beneficial as they may recommend alternatives to replacement.

QWater appears to be getting in at the junction between the roof and parapet wall. What is the likely cause of this?

There may be a broken slate or tile at the side of the parapet, a slipped soaker or a flashing or mortar that has come loose; all of which are relatively simple to repair. In some cases, the parapet will have a damp-proof course made from lead, which can also act as the flashing for the internal and external side of the parapet. If this is the case, the lead may have split or cracked due to the weight of the parapet above, limiting its ability to expand and contract. Generally, the stone or brickwork above the lead would need to be removed to replace the lead. Where this isn’t possible, regular maintenance is vital to ensure all joints within the brickwork or stone are fully pointed to ensure no water can find its way through.

QWhat causes lead flashing to fail? Lead flashings can seem perfectly intact, but small cracks or splits may result in damp occurring internally. These are due to heat expansion and contraction or when the maximum length of lead for the code that is installed has been exceeded.

Qis there a way to solve the problem of condensation on the roof’s underside? Condensation is due to lack of ventilation, so installing roof vents will allow airflow into the roof space. This can be done at the eave and ridge sections of the roof or with slate or tile vents integrated into the roof.

– handmade roofing tiles. Tel: 01424 756777; aldershaw.co.uk

– stone roof slating specialist. Tel 01993 705874; heritageroofingoxford.co.uk

– roofing specialist.

Tel: 01303 265198; johnwilliamsroofing.co.uk – handmade clay tiles in a range of styles. Tel: 01444 232931; keymer.co.uk

– members supply materials and services. leadcontractors.co.uk