Standard Specification for Roof Slating - Eaves, General Laying and Verges

Eaves Course

The eaves course must be supported by a continuous tilting piece or fascia. The slating should overhang by an amount (usually about 50mm) sufficient to ensure that the water discharges into the middle of the gutter. Where the underlay may sag and form a water trap behind the fascia, it should be supported by a wedge-shaped timber fillet, or other means of support. There must be a double course of slates at the eaves, formed by laying a course of short under eave slates, over which the first course of full slates is laid. The under eave course of slates should be laid on their faces and nailed to a slating batten. The length of the under eave slates is calculated by adding the gauge and lap of the slate together.

Laying Slates

Slates should be laid with a broken bond and secured with nails to softwood timber battens or boards, Before fixing, perpendicular lines should be marked giving the correct bond and spacings. Approximately 4mm should be left between the vertical joints of each slate, so that there is a free thoroughfare for water rubbing down the roof. Slating should be started at the eaves and fixed diagonally across and up the roof slope, thus ensuring each slate is fixed with two nails.


The overhang of slate at the verge should be between 40 and 50mm, and wide slates (doubles) should be used in alternate courses to maintain the bond. The minimum width of any one slate in an exposed position should be 115m. If an undercloak slate is used, it should be butt jointed, nailed if possible, and well bedded in mortar, which should then be struck off flush to the external face of the wall. The upper slates forming the verge must be bedded to the undercloak. Battens should carry over the edge of the undercloak slate to give additional support.