Slate shingles: the pros and cons of the roof

Recommendation points

• The essence of the material and production features
• Appearance
• Performance
• Application area
• Installation features
• Cost and main suppliers

In our progressive era, there are many fans of natural finishing materials. Among roofing coverings, slate shingles occupy a separate position not only due to their origin, but also due to their unique appearance and performance..

The essence of the material and production features

Slate shingles are a piece of roofing material that consists entirely of processed rock – slate. The key feature of this stone lies in its structure – it is a set of thin scales that easily exfoliate under mechanical and erosional action. This property of slate is used in the production of tiles: massive blocks are easily split into plates, which are subsequently processed to give the desired shape.

The homeland of slate roofing is England, western and northern Europe during the Middle and Late Middle Ages. Slate was ubiquitous and could be easily processed even in households. At that time, tiles made of natural stone and baked clay were the only type of roofing that could be used for a long time. The only alternative was roofing copper, but the cost of this material is prohibitively high to this day, while slate shingles at that time were even more affordable than ceramic..

It is noteworthy that slate roofing has been successfully used on the roofs of not only private houses, but also mansions and urban infrastructure due to its very high aesthetic value. In addition, stone shingles are perfect for keeled, domed and other curved roofs, where a completely unique appearance is formed..

Appearance

The main drawback that is most often attributed to slate roofing is the extremely poor variety of appearance. Slate cannot be dyed in bulk, and the application of a film-forming coating to the surface does not make sense due to low adhesion and tendency to peel off. In fact, colored slate exists, it is produced by impregnating natural stone in a pigment suspension, but the resistance to fading of such paint is extremely low: after 5-7 years the coating fades and its color is almost indistinguishable from gray.

But even the natural color of slate can be very diverse. Depending on the source of the raw material, the tiles can have muted shades from light blue to almost graphite, sometimes with notes of green and red. The more pronounced the natural shade, the more expensive the tiles are: in the process of their manufacture, the shards are carefully sorted and selected to ensure color uniformity.

Also, a variety of sizes, shapes of shards and laying patterns give the uniqueness to the appearance. The range of coverage includes tiles with a width of 60–80 mm (for covering complex roofs) to 40–60 cm (for wide flat slopes). The shape of the tiles is predominantly rectangular, however, diamond-shaped shards and plates with rounded edges are common. In total, up to a dozen layouts can be distinguished: from the classic checkerboard to diagonal and scaly, you can often find a completely chaotic pattern of the coating, made of shards of mixed sizes.

Performance

Stone shingles have the highest durability of all known roofing materials with the exception of copper roofing. It is noteworthy at least the fact that slate tiles, dismantled from some old buildings, go on sale after a defect, and often their quality turns out to be much higher than that of inexpensive modern ones..

The slate roof is quite massive, due to which it has a high resistance to wind loads. In addition, due to its significant thickness and low thermal conductivity, it warms up much more slowly in the open sun compared to metal coatings and slate. Slate is a very durable material, it tolerates mechanical stress well and provides high-quality sound insulation.

Slate roofing does not form an airtight hydro-barrier, which contributes to limited ventilation of the roof space. The water absorption of oil shale is extremely low, which is the reason for its high frost resistance. However, shale is still subject to erosion: under the influence of oxygen, moisture and temperature changes, the upper layers gradually flake off and crumble. However, this process is quite lengthy: with a tile thickness of 8-10 mm, any pronounced destruction will take tens, if not hundreds of years.

Application area

Like most roofing materials, slate shingles are very versatile. The main limitation for its use is the slope angle of the slopes. Due to the relatively small overlap between the rows, water seepage through the roof is guaranteed to be excluded only at slopes above 25 °. In practice, slate tiles are usually covered with slopes with a slope of 40 ° and higher..

Certain difficulties are also introduced by the significant mass of the slate roof, which requires the installation of a reinforced supporting system and lathing. For most types of slate tiles, the specific weight of the coating is 40-50 kg / m², however, small-format coatings can be even heavier – up to 65-70 kg / m².

The ability to cover the roof with slate tiles may also be limited by the exterior of the building and the general architectural style. Slate roofs are most typical of Romanesque and Gothic architecture. You can also bet on a combination with other natural materials: a stone roof will look appropriate on a house made of timber or with wood-like facade trim.

Installation features

Slate shingles are delivered ready-to-install. It has pre-drilled holes with counterbores for fastening with copper roofing nails with a wide head. The shingles are installed in a standard way for piece coverings: in horizontal rows from the bottom of the slope to the ridge. It is also common to lay the tiles in inclined rows to form a fish scale pattern..

During installation, adjacent rows are offset by half the width of the shard. The overlap between the rows is made in such a way that the shard covers not only the previous row, but also the upper edge of the tile one row lower. For this, the overlap between the rows must be performed at least half the height of the shards..

There is also a more authentic way of installing a slate roof. After delamination, the plates do not undergo additional processing and are not calibrated to size. The roofer sorts the shards by size before starting work, and then manually shapes them into the desired shape and makes holes for fastening immediately before laying. This method of installation is mainly used when covering roofs of complex shapes, when it is required not only to perform the correct alignment of the slopes, but also to maintain the unity of the pattern. At the same time, the cost of the roofer’s services can be comparable to the price of the material itself.

Cost and main suppliers

Slate shingles are one of the most expensive types of roofing. The cost is calculated per piece – about $ 1.5–2.5 per shard. At the same time, up to 40–60 shards can be used to cover a square meter. Average cost of covering 1 m² roofing with high-quality slate tiles ranges from $ 70 to $ 120, depending on the manufacturer.

The most popular slate tile is the English Penryhn Welsh Slate, the raw material for which is mined in the quarries of North Wales. This is the highest quality slate roofing, it is enough just to mention that Buckingham Palace is covered with this tile..

CUPA shingles are from Spain and Moselschiefer from Germany is a more budget-friendly roofing option. In terms of quality and durability, it is not inferior to English, however, the constancy and uniformity of color, as well as the texture of slate, is somewhat poorer.

The cheapest slate shingles are produced in China. The density of the stone is slightly lower than that of European manufacturers; moreover, younger rocks are used in the production. Because of this, the coating is more susceptible to erosion; the actual service life of such tiles is limited to 70–80 years. In addition, due to the relatively low quality and difficulties in logistics, a significant part of the material during delivery turns into scrap..