Perhaps one of the most important parts of any house, bungalow or block of flats is the main, pitched roof, which not only plays a primary role in keeping the inside of dwellings dry, but also substantially affects the appearance and character of a building.
Most residential properties either have a covering of tiles or slates, and within those broad types there are many different materials, shapes, sizes and colours, which not only look different, but perform differently.
The lifespan for a roof covering varies according to a range of factors, including type, maintenance, building location and exposure, as well as the quality of the original installation and structure. Typical lifespans are:
Natural slates 70-100 years
Fibre cement slates 50-60 years
Clay tiles 60-80 years
Concrete tiles 60-80 years
Roof covering problems
All roof coverings tend to be most vulnerable to failure or water ingress at junctions and ends, including around chimney stacks, pipes and rooflights, to valley gutters and where there are changes in angle or direction, or terminations. If correctly laid, tiles and slates tend to perform reliably away from these vulnerable positions, although can slip or break due to failed fixing nails or as a result of storm damage.
Dilapidated tiled roof covering
For the past 90 years or so, roof coverings have tended to be laid above sarking felt, which provides a second line of defence against water ingress, and also helps keep the interior of the building free from excessive draughts and dust. The felt tends to fail before the tile or slate covering and, in some cases, may be the main reason to re-roof, even though the covering itself might still have some useful remaining life. In more recent times, bitumen-type sarking felts have tended to be replaced with breathable membranes, to help prevent condensation to the roof void or structure.
Tiles and slates have different primary modes of failure. Slates can delaminate, deteriorate due to chemical reaction or corrosion of metal roof features and very commonly the failure of the covering is due to rusting of the fixing nails and dilapidated fixing battens. Tiles tends to become porous and can fail due to frost damage through freeze-thaw action, as well as coverings becoming dilapidated due to defective fixings or battens. The pitch (angle) of the roof will also influence failure, as well as the susceptibility to rainwater ingress.
Slate roof with "Nail sickness"
One of the worst remedial measures for a roof covering, but something that we rarely see, is where modern closed-cell foam is sprayed to the underside of tiles or slates to “lock” the roof covering is place, and supposedly prevent leaks and draughts, and improve insulation. These systems are a very bad idea and can cause more problems than they solve. If present, the only solution is to start-again with a new roof covering, properly chosen and installed by a competent roofing contractor.
Maintenance of roof coverings and replacement considerations
As with any part of a building, regular maintenance is required in order to ensure a long-life of reliable service. It is a good idea to visually check a roof during the warmer months of the year so that any issues can be dealt with before autumn/winter. This might include replacing slipped or broken tiles or slates, attending to defective flashings or repairing cracked pointing.
When replacing a roof covering, there will be different options in terms of type and for a range of costs. The work will give the opportunity to repair or improve parts of the roof structure, as well as other parts of the building that will be accessible. If the new covering is heavier than that being replaced (for example concrete tiles replacing slates) then strengthening of the roof structure might be necessary. As most heat lost from a building is through the roof, the Building Regulations requires a certain level of performance be met when a roof covering is replaced, and so increased thermal insulation may be required.
An increasingly common problem at roof level is with condensation and it is therefore important that there is sufficient provision for natural ventilation.
Surveys and inspections
When undertaking pre-purchase Homebuyer or Building Surveys, inspection for maintenance plans or lease dilapidations, we frequently encounter problems with roof coverings, either due to design, age-related deterioration, or most commonly inadequate maintenance. Often it is possible to have minor works of repair or improvement undertaken to extend the life of the roof covering, and this illustrates the value of having a survey or maintenance inspection.
Kingston Morehen uses a telescopic polecam, with enables some concealed roof features to be seen and photographed, which would not otherwise be visible other than by employing a roofing contractor or paying for a drone survey or other means of access.
Example of roof that can be viewed using Polecam
Polecam in action with one of our surveyors
Please contact one of our Chartered Building Surveyors if we can be of assistance.
