If the inside of the roof is unlined, check for cracks showing daylight as this will indicate areas needing closer inspection. Shine a torch on the timbers and check for water staining. If stains are found on the timber, try to trace the source of the stain. It is useful to inspect the inner roof space after a long period of rain, as the source of a leak is easier to trace. Slate does deteriorate with age so check for hairline cracks by looking for staining on the tiles.
From ground level
Outside, check the whole roof by inspecting at ground level. It is easy to spot a disjointed or slipped slate against the regular lines of slates. If there is a change to the colour of a section, it could be newly exposed and therefore unweathered. Look for a powdery or flaky surface, known as delamination, which shows deteriorating slate, which is no longer doing its job effectively. Look at the ridge on the skyline and check for gaps in the mortar joints. Check for the state of the flashings at abutments and around chimney stacks. Check for fallen pieces of mortar.
If the roof is too high to allow you comfortable access by ladder for a closer inspection, use binoculars to scan the surface as carefully as possible, from all angles - front, back and sides where applicable.
At the roof level
If you are using a ladder, always make sure it is set up correctly and long enough - at least 3 rungs above the gutter. Always work with someone standing near by when you are working at a height. See our Ladder Users Guide for details on how to use a ladder correctly and safely.
Once at the roof level, only access the surface of the roof using a roof ladder. This is a purpose built ladder that has wheels to allow you to push it up the sloping roof without dislodging or damaging the slates. When the wheels reach the top of the roof ridge, by turning the ladder over a hook securely lodges on the ridge.
You can hire roof ladders. Otherwise, there are wheel and hook sections available to buy which fit onto conventional ladders. If you are going to be working on the house, perhaps a scaffold tower would be worth hiring.
If patch repairs are regularly necessary, it may be time for the roof to be re-covered. It is difficult for an amateur to judge whether a new roof is required. If you need advice about the soundness or safety of your roof, contact one or two builders for their opinion. Alternatively, pay a surveyor or architect for an unbiased report on its condition.
A contractor, who will guarantee the work completed, should undertake major roof repairs or replacement of sections. It is worth checking with your local authority to see if you qualify for a discretionary improvement grant. This will depend on the age of your property plus its rateable value. Planning permission is not required for roof replacements unless the building is a listed property or you live in a conservation area.
A slate roof is expensive and is often replaced with less expensive tiles. Slate is available and it is worth checking supplies with builder’s merchants, roofing companies or demolition contractors.
Simulated slates are available and are less costly than replacing the roof with real slate. Imitation Cornish, Cumbrian, Cotswold and Welsh slate are available in a range of sizes. Flat ones with nail holes are often suitable for replacement on a slate roof, but check the size, colour and thickness carefully. Not all simulated slate tiles are suitable for repairing a slate roof as they are made with nibs and interlocking grooves that would not fit on to an original slate roof.
The type and colour of the tiles can enhance or spoil the appearance of the house. If you live in a terraced or semi-detached property, consider the covering of the neighbouring roof, which can affect the overall appearance of your roof.
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