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Advice & Guidance

Roofs

All roofs should be checked to ensure that they are in good order. Neglect of a faulty roof will quickly lead to damage in other building elements. If damp patches are apparent inside they are not necessarily an indication of where the roof failure is located as water can travel a considerable distance from the point of ingress before it is seen.

Clay tile roof

Clay tiles, natural slate and stone: Check the roofs for frost, snow and wind damage. Not all colour changes, minor cracks or delamination (flaking) mean that the roof is in poor repair, but debris on the ground from broken slates and tiles might indicate a problem. Have dislodged or missing slates and tiles reinstated before damage occurs to roof timbers or ceilings. This is a straightforward task but will require a contractor who has the appropriate equipment to allow access to the roof slope.

Welsh slates You should also look out for large areas of moss, which can harbour damp and cause slates and tiles to deteriorate. If moss growth is a problem it can be carefully removed by a knowledgeable contractor. Avoid bitumen coatings and spray-on foam at all costs. These hinder proper inspection and prevent the re-use of slates or tiles. They also reduce ventilation, thereby increasing the risk of timber decay.

 

Action point: Keep a record of the location of slipped slates and tiles in your logbook. A pattern of multiple slipped slates on a particular roof slope may be a clue that the fixings are starting to deteriorate. If this is the case, the slates or tiles may need to be stripped off and relaid.

Stone slates and ridge tilesRidges and hips: Ridge and hip tiles provide protection to the vulnerable areas where different roof slopes meet. They can be dislodged by high winds or stormy conditions so you should check for missing sections, which should be replaced without delay. Ridge and hip tiles are often pointed with mortar to provide further weather protection. This mortar will eventually fail and drop out due to the exposed location. Look out for areas of missing pointing and seek guidance on their repair, as water will quickly penetrate any gaps.

 

Sheet metal roofing: Flat roofs and roof gutters should have a slight fall to allow water to drain away. Check for splits and cracks in areas of flat or sloping sheet roofing as these will let in water even if the defect is only small. Splits and pinholes in lead can usually be repaired by ‘burning in' a new piece of lead but this type of work requires an experienced contractor, who will take the necessary fire precautions.

Lead roof

Action point: Mastic or repair tapes can be used as an emergency measure to prevent water seeping through cracks and splits; however, these are only appropriate as a short-term solution.

Action point: You might also consider having an electrician fit heating tapes in inaccessible gutters. These are activated during cold weather using an external thermostat and warm up to help snow and ice melt away, preventing a build up around hopper heads or against flashings.

Eave detail of a thatched roofThatch: Thatch is usually of long straw, combed wheat reed or water reed, depending on the regional building tradition. It is not always necessary to dismantle and re-cover an entire roof so the advice of a skilled and experienced local thatcher is essential. Patch repairs and overlays are both possible without wholesale stripping, depending on the condition of the roof. Do not worry about the roof looking patchy, as repairs will soon blend in.

 

If you think moss growth may be a problem, seek the advice of a thatcher as you may do more harm by trying to remove it yourself. Galvanised wire netting can prevent birds and vermin stealing the straw for their nests. Any re-thatching should always be carried out in the local tradition, preferably using local materials.

Moss on stone slatesAction point: Think about fire prevention and keep the roof space draught-free and clear of straw dust and old thatch. Ensure that there is a suitably sized access hatch for fire fighting. Ensure that any electrical wiring in roof spaces is checked regularly by a qualified electrician. Spray-on chemicals designed to increase fire resistance or improve spread of flame characteristics are not recommended.

Asphalt: Bituminous compounds have been used to cover roofs for at least 150 years. Failures are usually caused by poor workmanship or design and faults can sometimes be corrected if there is found to be a leak. As with sheet metal roofing look out for splits and cracks, however, it is not necessarily the case that all unsightly faults such as blisters or bumps will need immediate attention.

Overflow from a hidden gutter

Roof valleys and parapet gutters: Valley and parapet gutters frequently become clogged with leaves and other debris. It is not unusual for tennis balls, footballs, birds' nests and even dead birds to be the cause of a blockage. Seeds blown by the wind can quickly establish themselves in small amounts of silt. Once established, grass and plant roots can cause extensive damage to masonry as well as impeding the flow of water away from the building. These gutters therefore need to be inspected and cleared of accumulated debris on a regular basis to ensure the effective discharge of rainwater and to prevent overflowing.

Clean lead gutterAction point: Clear roof valleys and parapet gutters at least twice a year in spring and autumn. During heavy leaf fall, it is worth removing dead leaves on a weekly basis. In cold weather, any water that cannot drain away is liable to freeze, causing damage to the fabric of the building when it expands.

Action point: During the winter, parapet and valley gutters also need to be cleared of snow to prevent melt water rising above them and causing damp internally. Use wooden or plastic tools for snow clearance to avoid damage to leadwork.

 

Take extra care to ensure your safety in icy conditions. You should also be aware that north facing flat roofs and gutters can be very slippery all year round.

Lead used to protect the jointAbutments: The most vulnerable areas of the building fabric often occur where one part of the building meets another i.e. where a vent pipe penetrates through a roof of where the roof meets the wall. These junctions will often have lead or zinc ‘flashings' to protect the joint from the weather. Inspect these flashings to check that they are in good condition, without holes or splits.

 

You should also make sure that they are securely fixed. Sometimes a mortarfillet' is used to protect these junctions with lead ‘soakers' underneath the slates or tiles. Check the mortar fillets for signs of decay. If they are loose or missing, they will need to be replaced.

Access: Duckboards are useful as they allow a space for melting snow to flow away whilst maintaining a safe and dry walkway in gutters and across other areas of flat roofing. You should inspect the duckboards to ensure that they are in a good state of repair and have them repaired or replaced if necessary. Other aids such as handrails and platforms should also be inspected to make sure that they remain safe and usable.

Action point: Remove trapped leaves and other debris from underneath duckboards to ensure that water can drain freely from the roof.

Roof spaces:Roof space without safe access If your roof space has a safe means of access and has a boarded floor, check whether there is evidence of leaks or damage to the roof covering during heavy rain, especially below gutters. Where daylight can be seen from inside through gaps in the roof covering, moisture may well be able to enter. Make sure that any roof insulation is not restricting ventilation at the eaves. If there is an insufficient gap and there is a risk of condensation this may lead to timber decay. If your roof space is not boarded or access is difficult then it is better to have this part of the inspection carried out by a professional.

Further information

© SPAB 2010