Here’s the concluding part of our two-part feature on timber cladding, and today we’re going to discuss shingles and shakes and panel cladding. Whether using hardwoods, or even plywood, these types of cladding with brighten up your buildings and give a unique look with a relatively simple erection.
Shingles and shakes
Many of the oldest buildings in the world are clad with shingles or shakes, which are tapered wooden pieces, made from solid wood, and many are choosing to go back to this traditional material either through necessity to renovate their listed building, or to embrace a natural look. While they are most often found in Canada and North America, they are becoming increasingly popular in the UK thanks to their ability to shed water readily and their durability. Hardwood varieties such as oak or sweet chestnut are commonly used, as is softwood European larch wood or Western red cedar, which fades to an attractive silvery hue.
Fans of the material have lauded the benefits of using these smaller sized shingles to accommodate tight curves through the use of short lengths and closely spaced battens, much to the delight of architects and installers worldwide. Bending shingles into a curved form may also be achieved through boiling, but this can be time-consuming.
It should be noted that sourcing stock of shingles or shakes is not as easy in the UK as other parts of Europe, with many designers having to import their stock from North America. UK woods are available, but they are not usually treated with a preservative, which can cause issues should they be required for roofing on low-pitched roofs as they will not drain as readily. Therefore, many builders in the UK will either use the pre-preserved North American shingles of 405mm, 455mm or 610mm in length, or European shingles which have been treated to enhance durability.
While the standard sizes of shingles and shakes apply to their length, the width of individual shingles can vary in width, which can make it difficult to apply if you are looking for a uniform appearance. Another downside is that not more than 40% of the shingle should be exposed in vertical cladding, again causing design boundaries. In older properties, though, this lack of uniformity can give a rustic appearance which is difficult to imitate with any other type of cladding.
Shingles and shakes are fitted across three horizontal battens using annular ring shank nails. The overlapping layer is then nailed through the layer below at the next batten up, much in the way roofing tiles would be fitted.
As with most cladding installations, shingles and shakes require a well-ventilated cavity behind them to prevent the build-up of moisture. A weatherproof membrane must be fitted behind which also allows air to penetrate between the shingles. Vertical counter battens should be used to allow a clear airflow. It’s not essential to coat shingles or shakes, but some prefer to. In Europe, it is often left to bleach, but paints are often used in America so the choice is up to the homeowner which route they choose.
While they are more commonly used for temporary buildings, plywood panels can be used for permanent builds too, often fitted into window frames or curtain walls. These are most commonly seen in sheds and outbuildings. Great care should be taken when choosing external plywood, which should be Class 3 to BS EN 314-2 standard and made with suitable glues. Any plywood with veneers should be a Class 2 (durable) or Class 3 standard wood. If budget allows, a possible choice would be marine plywood, which has hardwood veneers that make it exceptionally durable. It is, however, worth considering that these are generally only Class 3 (moderately durable) which means that they may suffer from end grain swelling. A good compromise would be pressure treated softwood sheathed plywood, which has the same quality glue lines but stops moisture from being trapped in the veneers. Sheets should be cut down to size before treated with a preservative or edge sealer on the edges of the sheet.
Glazing is not recommended, as this will increase the potential of moisture beading at the bottom of the panel, however, if an infill panel in a glazed wall is required you should leave 6mm minimum between the edges of the plywood and framing for ventilation and movement. Omit the glazing bead at the bottom for maximum ventilation, and seal only the inner and outer faces of the panels. The same process applies for plywood panels fitted without a visible framework. The top of the sheet must be protected too, and the bottom stopped short of a sill or flashing by 12mm minimum. Sadly, in this case, all fixings will be visible. These can be made more attractive by using rubber washers.
One of the simpler methods is to add cover battens of treated soft or hardwood over vertical joints between panels to avoid water damage by sealing the edges. This negates the need for lipping and additional edge sealer. The plywood sheets are then nailed or screwed over the supports, and fixings are concealed. Machining deep grooves on the inner face of the cover battens also allows water to drain behind the batten and to prevent it from running onto the vertical joints. Horizontal joints between sheets may need continuous metal flashings to protect the sheet below.
Plywood sheets also have a high vapour resistance compared to wood boarding, which can cause condensation as vapour refuses to diffuse away. Keeping a ventilated cavity can help this situation, helping to maintain the wood for longer. It is important to install plywood sheets that are thick enough to span the supports without bending under the wind. Larger sheets such as 1200mm wide sheets will require vertical central battens at the front and rear of the board and fixings if they are quite thin. If the panels are half this size, intermediate fixings will not be required, and a cover batten can conceal all fixings. Should you leave your plywood exposed, it is important to consider the visual aspects of the plywood.
When it comes to aesthetics, you can choose to colour external plywood. However, it’s important to use low-build penetrating finishes or high solid coating systems as these give colour to the top veneer, but don’t penetrate to the lower levels, preventing moisture damage. Choosing a hardwood plywood may give a less textured appearance, but if you choose hardwoods such as birch or tropical hardwoods, these may look more exotic, but you balance that against durability, which is lower on these types of plywood, so they will require pre-treating with a preservative. You could also opt to veneer your plywood for a better appearance, which can be used on the whole face or only to conceal the lippings around the edge of the panels. Applying the veneers to interior panelling gives the best results, as it can be prone to damage on external panels due to exposure. Bear in mind that if you apply veneers to thick sheets of plywood, it will not cause bowing, but on thin sheets, it will be necessary to apply a balancing veneer to the other side.
Pre-finished resin-coated plywood panels can also be used as cladding. Usually intended for concrete formwork, these can extend the service life of the plywood, but are only available in a limited range of colours which may or may not fade over time due to UV light. Another thing to consider when utilising these is that cutting panels into smaller sizes breaks the resin coated finish of the plywood, meaning it will need additional sealing and add to cost. A possible alternative could be laminated veneer lumber (LVL) which can be made of softwood or birch veneers and offers fewer issues with water ingress.
That’s it! You’ve now learned all you need to know about the various types of cladding you can use on your building erection. Time to put your new-found knowledge to the test.