Directory of Traditional Building Skills - Mourne Heritage Trust

2 ROOFING – SLATING, TILING AND THATCHThatch is the traditional roofing material of Ireland and was almost universal in modest housesuntil the mid nineteenth century. Locally available split stone or slate was used but it was notuntil the widespread availability of cheap Welsh slate that the major changes occurred. Slaterequired little maintenance, was easily worked, attractive, and remained the main roofingmaterial until very recent times. Widespread use of clay and concrete tiles has surpassed theuse of slate but it remains the best material for repairs and extensions to old buildings.Thatch has declined alarmingly – there are now fewer than 150 inhabited thatched buildings inNorthern Ireland. Concern is so great for their survival outside museums that the Environmentand Heritage Service are offering 75% grants towards thatching and maintenance. Oldproblems of damp and mould are easily solved today and while regular maintenance is requiredthe benefits of beauty and character plus the grant available can swing the financial balance.There has been a great revival of interest in thatching in Britain and this is spreading toNorthern Ireland. Thatchers are now more easily found and there is no doubt that the craft willdevelop with the revival of interest in thatching.Natural slate is also enjoying a revival and with the high cost of new slate a market led demandfor salvaged slate has emerged. When re-roofing is necessary careful choice is required toavoid a patchwork quilt of blues and greys as there are considerable differences in colour. It iswise to avoid mixing slates from different sources so the original ones should be kept togetherand used on the most prominent elevations. Delaminated slates or ones with splits or overlargenail holes should be discarded. Variations in detail in the roofscape such as rows of particularlylarge slates at the eaves, called queens, diminishing courses, that is slates getting graduallysmaller towards the ridge, and the ridge materials (stone, clay or lead) are of immenseimportance to the character of the building and should be retained. It is vital to check roofsregularly for slipped or missing slates and to repair promptly.Westmoreland or Norwegian green slates were popular in Ireland in the inter-war years and itis still possible to get new slates to match. Clay tiles are a very old roofing material rarely foundin Northern Ireland until modern times when the ‘Rosemary’ small plain tile became popular.Cedar shingles enjoyed a brief boom in the 1950s but in general have not fared well in thedamp climate.In general natural slate roofs should have a minimum of 35° pitch, rising to 45° or greater forsmall slates. Where it is not possible to lay natural slate, a different material such as lead shouldbe used.Finally, painted corrugated metal sheeting is a traditional roof in the country, mainly over barnsand out-buildings, but often over the top of thatch on houses. Black, green or red lead are thecommon colours and their use should be considered on all rural building groups.See also Section 3 Leadwork (for flashings) p. 82Section 11 Remedial works (for chimneys) p. 126Appendix 1: Further reading p. 14977