Fixing Guide

Slating is a specialist trade and it takes many years of training and experience to become a competent slater. To the untrained eye, it is difficult to spot work of an inexperienced roofer until it is too late.

For a detailed description of the process of slating, reference should be made to BS 5534: 2003 Codes of Practice for Slating and Tiling. However, the following checklist should provide you with a few pointers to ensure you achieve a satisfactory finished roof:

Pitch and Size

Check roof pitch and make sure that the correct size slate and lap are used.


The proper grading and selection of slates is extremely important to achieve a neat and attractive finish. All slates must be sorted regardless of what grade they are. The Best grade are more consistent, but will still have to be put into at least 3 separate thicknesses. Any twisted or broken slates should be set aside for cutting down as under-eaves, tops etc. Make sure sufficient room is available on site to enable sorting to be done.

Marking Out

It is critical that the roof is marked out. If the slates are laid "free hand" then it is very likely the lines will be not be straight. A chalk line running from top to bottom for every third row is a sufficient mark to work to.

Eaves Course

The under-eave slate should be cut to the correct length, for example, a 500x250 slate laid to a 75mm headlap should be cut to 288mm long, (gauge + lap). A common short cut is not to cut the full slate but to turn it around and lay it along its length; the under-eave will be 250mm rather than 288mm and could well cause problems. The under-eave should be laid "back to front" although not critical; it gives a neater appearance and is a good indication of a trained Slater.

Laying Slates

If the slate has been sorted and the roof marked out properly, then laying the slate is straight forward. However, the recent trend is to forklift a pallet on to the scaffold and lay the slates straight out of the pallet without grading. It is unlikely to achieve satisfactory finish this way.

When laying slates, if they do not lay flat, sometimes it helps to crop off one corner or both corners, where they sit on the batten. If that does not remedy the situation, don't lay it, it will not flatten out over the time. Either, use the slate as a cut elsewhere, or don't fix it at all. Wastage will be about 4 to 5% on Best grade slates and up to double that on Second grade.

Broken Slates

Slates should not be walked on. Fixed slates may also get broken by other trades accessing the roof. We recommend slates should be replaced using a stainless steel slate hook of the appropriate size, not stuck down with adhesive as they will very likely fall out over time.

Cutting Slates, Valleys and Hips

Slates should be cut with proper slating tools; Slates should not be cut too small, the narrowest part at the head or the tail should be no less than 50mm, to enable a proper fixing. If this cannot be achieved, then a slate and half must be used.

For further information please contact the Technical department or download the Slate Fixing Guide.

For information on Hook Fixing please contact the Technical department.

For any other technical literature please check the Technical Library.

All in all, natural slate is the most aesthetically pleasing, reliable and cost effective roof covering to use.