Timber shingles and shakes have established a reputation in North America and Europe as a beautiful and practical form of timber cladding for both roofs and walls.
Shingles and shakes are made in different ways and each has its own distinct appearance.
Shingles are taper sawn from blocks of timber and have a relatively smooth face and back. On the other hand, shakes are split by hand or machine along the natural grain of the wood and have a strongly textured surface. Some shakes are re-sawn to give a split face and a sawn back.
Most shingles and shakes used in Australia are made from western red cedar and are imported from Canada. Some are also produced locally from species such as rose sheoak and hardwoods. They can be applied to exterior roofs and walls on any type of building where a solid nailing base is provided.
Sizes and Grades
North American producers have set standard sizes for western red cedar shingles and shakes, and these sizes have been generally adopted by
Shingles and shakes are mostly supplied in random widths and only length and butt thickness is specified. Table 3 sets out standard lengths and thicknesses for Western red cedar shingles.
Although the timber species chosen for shingles are well known for their natural resistance to decay, vacuum/pressure impregnation with CCA preservative in accordance with AS 1604,and the requirements of statutory authorities in NSW and QLD will significantly increase the service life of timber exposed to extreme conditions.
Such treatment will be effective in resisting decay and discouraging the growth of fungi, moulds, and other surface vegetation.
Australian experience has shown that under certain circumstances the treatment of all types of timber shingles with a long lasting water repellent preservative prior to installation will improve their overall performance and increase life expectancy.
Australian Local Government regulations may restrict the use of shingles and shakes on the roofs and walls of commercial buildings even when treated with fire retardant chemical. Intending users should check with their local building authority or local Timber Advisory Service before specifying.
Specifiers requiring pre-treatment with preservative or fire retardant chemical are referred to their shingle supplier. The use of such treatments may affect the suitability of "roof water" for drinking.
Manufacturers specifications give full details of the fixing procedures. It is essential that these procedures be carefully followed.
Shingles should be stored on-site prior to fixing under cover clear of the ground.
If outside storage is unavoidable, shingles and shakes should be covered with waterproof materials to prevent staining.
The most common use of timber shakes and shingles is as a roof cladding. Although they are usually applied in straight single courses, their application may be varied to achieve other decorative effects. Whatever the style chosen, there are certain basic details that must be followed to achieve a weatherproof and durable result. Detailed information about the construction of shingle clad roofs is available from all shingle and shake suppliers.
On walls, shingles and shakes are generally fixed over solid or spaced sheathing. Solid sheathing is preferred and 9 mm or thicker exterior grade plywood provides a smooth, even base for fixing. Plywood also offers the added benefit of giving increased structural rigidity to the building. Spaced sheathing is usually 100 x 25 mm or 150 x 25 mm softwood boarding spaced at centres appropriate to shingle/shake size.
If plywood sheathing is chosen to back shingles, it should be designed to gain the structural and economic advantages of bracing and roof hold-down.
Before fixing either plywood or spaced sheathing, flashing material should be fixed to the frame in accordance with good building practice at all vertical joins, window sills, heads and other openings.
After the sheathing is fixed a vapour permeable fire retardant building paper must be fixed over the sheathing directly under the the shingles or shakes. If reflective insulation or non-permeable vapour barrier is required, it is generally fixed to the inside face of the wall frame directly under the interior lining. Shingles are fixed over the sheathing by either the single coursing or double coursing method.
Single coursed walls provide a weather tight exterior wall cladding with two layers of shingles at every point. In single coursing each row of shingles covers slightly more than half the previous row.
Double course fixing of shingles gives an attractive wall characterised by wide exposures and deep shadow lines. This method offers economy because of the wide exposures of the outer shingle and the opportunity to use a utility grade shingle for the concealed under layer.
Plywood/Shingle Wall Construction
This method gives a wall with identical appearance to a conventional double coursed wall. However prior sheathing is not required, and strips of exterior plywood are used instead of shingles for the concealed under layer. This system offers economy of materials, increased strength, speed of erection and design flexibility.
Shingles and shakes should be fixed with either hot dipped galvanised, or silicon bronze nails. Mild steel, brass or copper fixings should NEVER be used with western red cedar. For general use a 30 x 2.0 mm hot dipped galvanised flat head nail is satisfactory. Where special applications or re-roofing is being undertaken, the shingle supplier should be consulted.
Finishing and Maintenance
Shingles and shakes can be dipped in a water repellent preservative before installation. On roofs they are often given no further treatment and weather to a soft silver-gray tone. On walls, where access for maintenance may be easier, pigmented stains may be used to retain a natural looking timber colour.