Maas slating is a way of covering a roof in which rectangular slates are laid in half bond, so that every slate sits centrally over the joint of the course below. The name refers to the Meuse (Maas) region in the Netherlands and Belgium, where this method is traditional; in Dutch the roof itself is called a maasdak. The result is a calm, strictly horizontal pattern, quite different from the irregular, scale like appearance of German or random slating.
How the covering works
Each slate overlaps the two courses beneath it. Because the joint of one course falls in the middle of the slate below, there is nowhere a continuous vertical joint for water to run into.
- Slate shape — rectangular, with a straight lower edge
- Bond — half bond, so each course is offset by half a slate width
- Head lap — the amount of overlap follows from the pitch: the shallower the roof, the more lap is needed. Work to the slate supplier’s figures and the recognised slating rules; they differ by slate type and pitch
- Fixing — stainless steel or copper hooks, or nails into battens or boarding; nailing is the usual choice on historic work
Points to watch
- Pitch. Slate needs a decent pitch to shed water quickly. Below the minimum recommended pitch the covering does not work and either extra measures or a different covering are needed
- Substrate. A slate roof is comparatively heavy and needs a flat, stable base. If the roof plane deflects, slates rattle and break
- Ventilation. Provide a ventilated layer beneath the slates, or moisture will condense on the underside and rot the boarding
- Maintenance. Loose or broken slates can be replaced one at a time without stripping the whole plane — that is the strength of a slate roof. Leave it to a slater, because it is easy to break the neighbouring slates while lifting one out
- Historic buildings. On a listed building the type of covering is usually fixed. Do not depart from the existing pattern without agreeing it with the conservation officer
Related terms
- Roof slate
- Slate roof
- Slate
- Slate hook
- Slater’s hammer
- Roof pitch
Want to learn more about construction terms? Visit our knowledge base at fredsdiyplans.com.