Slate  Roof  Editorial

By :- Shane Simmonds QbE. (Wits.) - Progressive Roofing cc (Sole Member)

Founder Member of A.R.C. - Association of Roofing Contractors

SLATE OFFERS ARCHITECTURAL ELEGANCE

There are a variety of different materials and methods of, to roofing. Shane Simmonds from Progressive Roofing and founder member of the Association of Roofing Contractors explains the pros and cons of the various applications of Slate Roofs.

Slate is arguably one of the most prestigious roof coverings and can be seen in a wide cross section of developments and private homes. The roofs are popular and aesthetically appealing.

Slate allows the roof to blend into the natural surrounding whilst not detracting from its superior functional and sturdy serviceability qualities. The Slate roof offers a host of excellent qualities such as the aesthetically natural finish detail in the various colours and attributes of Slate.

There are essentially Three Slate Colours, each with it’s own particular characteristics.

1. Silver Blue, a strong and versatile slate more suitable for lower pitch roofs, a good all rounder; suitable for all Slate Roof’s.

2. Western Country, a softer, medium to hard wearing, colour variable Slate, suitable for most Slating applications; 

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3. Multicolour, a softer Slate suited to higher pitched roofs to counteract harsh weather conditions and to highlight the colour elegance of Slate.

A Slate roof finish offers an extended lasting roof covering fulfilling numerous designs from vertical cladding, radiused eave overhangs, dormer window ‘eye brow’ details to both maximum and down to a minimum of 17 degree roof pitch’s.

The solar benefits of the naturally dark Slate roof in conjunction with usual ceiling insulation can dramatically influence moderate internal temperature condition. The Home Security is also enhanced by the close spacing of the roof Slate securing timbers.


Roof Slating Systems

There are essentially two Roof Slating Systems, the Conventional and the Peter low Slating Systems.

1. The Conventional Slating System suitable for roof’s having pitch’s greater than 30 degrees and where the roof waterproofing relies on the secured Slate pieces on their own. This method is notably a heavy roof where one finds the Slate piece overlap detail as much a three layers in places and where architects must pay particular attention to the required timber specifications to support the Slate and the relative cost thereof. It is important to replace broken Slates. Every broken Slate is a leak. Home owners may not always be aware of the smaller leaks when the roof timbers soak up the water leakage, slowly rotting the wood away and which can result in much more costly repairs. 

Slate roof owners should enter into an Annual Maintenance Service Relationship with a reputable Slate Roof Specialist.

2. The Peter low Slating System accommodates all roof pitches and is specific to pitches below 30 degrees. Roof Conversions from a Tiled concrete or clay roof cover to a Slated roof using the Peter Low Slating System is a popular choice because the necessary roof supporting timber specifications are compatible. The Peter low Slating System, roof weight is approximately half the weight of the Conventional Slating System, weighing less per meter square when compared to a Tiled conventional roof and reduces the supporting timber specifications and the relative costs thereof.

The success of the Peter low Slating System was achieved by reducing the Slate piece overlap detail and the overall weight of the roof cover in conjunction with the installation of a Roof Felt Waterproof Underlay fixed below each row of Slate. 

Guarding against the weather’s extremes

The Roof Felt Waterproof Underlay of a Peter low Slating system is the absolute waterproof layer. The Slate piece detail essentially becomes a cosmetic protective overcoat to the Roof Felt Waterproof Underlay.

The life span of the Peter low Roof Felt Waterproof Underlay has been subject to much discussion and research. In recent year’s there has been significant improvement to the Peter low Slating System’s useful life span. The inclusion of an Aluminium Foil laid above the Roof Felt Waterproof Underlay and below the Slate pieces serves as a Ultra-Violet protection overcoat to the roof felt waterproof underlay. Prior to the inclusion of the Aluminium Foil Ultra-Violet protection overcoat the Roof Felt Waterproof Underlay was found to last in the region of between 18 and 25 years. This variable was dependant on the severity of the prevailing weather conditions. A Life Span of 32 years had also been recorded. Research found that the useful life span of a Peter low Slating System was dependant on the amount of exposure of the Roof Felt Waterproof Underlay to the sun’s ultra-violet ray’s that brake down the Roof Felt Waterproof Underlay waterproofing properties.

The Roof Felt Waterproof Underlay is as good as it’s Slate overcoat. The annual replacement of broken and damaged Slates by a reputable Slate Specialist will ensure the maximum lifespan out of the Roof Felt Waterproof Underlay.


Slate Specifications

Slates are used in such a manner that all slates in each row are of the same thickness reducing in thickness in successive rows towards the ridge.

When Slates of different thickness are laid next to each other they result in uneven contact stress points and results in an unnecessarily high number of Slate breakages. This situation is compared to the putting of a marble underneath a sheet of glass – it takes less pressure to break the glass / Slate in comparison to when a sheet of glass / Slate is laid down flat on the floor. 

Three main conditions influence the functional state of a Slate Roof System. 

Slate Grading, Temperature and Hail.

Slate Grading : Slate pieces are hand cut and sized which makes each Slate piece unique in size and weight. Before usage, all Slate pieces must be graded for thickness and should be carried out by a Slate Specialist. The standard of grading will be directly reflected in the quantity of broken Slates replaced during any Maintenance Service program. Slate Thickness Grading is of paramount importance. Slate piece Grading falling outside the normally acceptable tolerance will result in unusually high number of Slate breakages.

Temperature : A piece of slate is comprised of varying rock layers fused together where the number and size of the layers determines the thickness of the Slate. The fused layer joins of the Slate pieces are sufficient to allow water to penetrate inside of a Slate. During high sun, Slate roof temperatures can exceed boiling point followed by a quick reduction in temperature, usually as a result of rain thunderstorms or cloud bursts. This rapid expansion and contraction of Slate pieces causing flaking of layers or complete breakages.

Hail : Slates laid next to each other in rows and fall outside the normally acceptable thickness tolerance are particularly vulnerable to Hail damage. 

New Slate roof Home Owners should be aware that Slate roofs are susceptible to broken slates and should enter into an Annual maintenance relationship with a reputable Slate Specialist to maintain the classic standard of their Prestigious Roof detail. This type of roof has special appeal to both homeowners and architects as it offers architectural elegance while affording a number of individual options on both application and cost.

‘ In Other Words, Slate Roofs Sell Houses’

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