Slate Roof Mortar

A common repair to slate roofs is to apply torching a mortar fillet underneath the slates attaching them to the battens.

Slate roof mortar.

The correct mix ratio is 3 parts sand to 1 part cement this is much stronger than bricklayers use 5 1 as the cement on the roof must withstand more driving rain than a typic. Where slates are particularly heavy the roof may begin to split apart along the roof line. This may applied as either a repair to hold slipping slates or pre emptively on construction. This can be carried out cheaply and it s work you can comfortably undertake yourself.

Roof cement is primarily used to hold roof tiles hip tiles and ridge tiles securely in place it also keeps out rainwater. Slate tiles differ slightly from other stone tile installations in that they require a wet mortar bed made of a mixture of portland cement and sand rather than standard thinset mortars. Foliation may not correspond to the original sedimentary layering but instead is in planes perpendicular to the direction of metamorphic compression. Over the years this torching can crumble and break normally falling with a thud on the floor of the roof space during the middle of the night.

Slate is a fine grained foliated homogeneous metamorphic rock derived from an original shale type sedimentary rock composed of clay or volcanic ash through low grade regional metamorphism it is the finest grained foliated metamorphic rock.