With so many choices when it comes to timber cladding it’s difficult to know what is best for you. Today we’ll run through boarding – be it horizontal, vertical or diagonal, giving you the low-down so you can decide what to use in your build.

The type of cladding you use on your build can be determined by factors such as cost and appearance, as well as which is the best practical application for your project. Cladding can vary in pattern, texture and colour due to it being a natural product. These panels, made from shingles to shakes and logs, or as close boarded panels are laid horizontally or diagonally with flush or overlapping faces. Add in board width variation, an extensive colour range and surface finish as well as profile shape design and you have the utmost in versatility for your project.

When considering board cladding, it’s important to consider factors such as the species available and their different sizes and lengths of boards to judge which would be best for your needs. Weather protection is also something to consider, as some boards may be more resilient than others. For some, the consideration will be more a case of logistics. Some boards have a more time-consuming fixing method which can hinder the speed of the erection, and some boards have finishes that would not compliment certain building designs so easily. For others, the robustness of a material is more important than appearance. Choosing carefully can ensure your cladding achieves a good level of durability and performance, with minimum maintenance and fuss. For those concerned about appearance, it’s worth noting that some cladding also changes its appearance over time such as red cedar which weathers from an attractive red shade as the name suggests, to a subtle silver colour.

Boarding

Boarding can be fitted horizontally, vertically or diagonally, and choosing the design is probably the first job that needs completing when considering the aesthetics of your project. When it comes to boards, they all follow similar design aspects to each other, depending on the category in which they fall. BS 1186-3 timber is mostly known for its use in joinery. Wood trim is used for internal use rather than external. Profiles included in BS EN 15146 are suited for softwood panelling and cladding, whereas machined profiles that do not have tongue and groove are also more suitable for internal than external use.

Specialist board profiles can often be machined to order, providing you require a reasonable quantity. But as with all profiles, it is important to consider the principles of weatherproof design as all wood is prone to move due to the changes in moisture content. Another thing worth considering is the practicality of obtaining lengths and widths in the species chosen, particularly if you opt for machined to order wood. The strength of these sections during installation and handling could make them difficult to erect, especially on high-level installations or larger, repetitive installations as well as potentially increasing costs. To avoid some of these issues on larger builds, it’s a good idea to design as much prefabrication as possible and discuss your options with installation contractors and suppliers to minimise costly damage.

Horizontal boards

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Horizontal boarding is easily the most common form of board cladding and is nailed to battens mounted vertically on a timber frame or masonry walls. A choice of fitting designs are possible, including a simple overlap, feathered or square edged designs. If you require a flush surface, it is possible to use rebated feather edge or shiplap. Tongue and grooved boards with a rebated profile and limited face width also give a good finish.

You can also use horizontal boards in an ‘open jointed’ form, where the top and bottom edges of the board are chamfered providing overlap, rather than square cut which allows water to drain to the outside. The gap between these boards if they’re used ‘green’ allows you to hide any shrinkage or distortion of the boards. Remember to take into account the UV light reaching the breather membrane behind the open jointed boards, as this could spoil the effect you are attempting.

Extra battens may be needed at butt joints between the ends of boards when fixing horizontal cladding, so it’s important to consider this in your design, opting for standard lengths of boards rather than random lengths. Opting for standardised boards allows the joints to occur in line, giving a panelled effect to the wall, enabling you to save time by prefabricating the panels.

If choosing ‘random’ board lengths for a different effect, their lengths should be in multiples of the batten spacing, allowing for the possibility of an additional short length to be nailed to the side of the existing batten to give the extra width required at end joints.

Diagonal boards

Red Grandis

Red Grandis

Diagonal layouts usually have boards angled at 45 degrees and fixed to vertical battens which coincide with battens or studs fixed to the masonry walls. It’s possible a thicker board may be required to close up the centres of the battens behind, as these span a bigger distance than if used horizontally or vertically. One of the great benefits of using diagonal layouts is that you can reduce the amount of water that penetrates the boarding and battens by running the battens diagonally instead of the usual horizontal positioning. You may also be able to avoid the use of counter battening if there is sufficient space for ventilation and drainage at the base of the wall and the end of the battens. Ensure that you don’t run the boards into a V-pattern because it will stop water from draining correctly, causing it to collect at the junction. When boards are butt jointed at the corners of walls, a vertical board should be used to cover the edges to prevent water penetration. It’s also not advised to use two pieces to make up one length of a diagonal board as the join will allow water to rot the joint, and water may seep in against the masonry wall.

Vertical boards

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The same issues that apply to the joints on diagonal boards can also cause problems on vertical boards. Therefore it’s important not to make your vertical length out of more than one board butted together, as water ingress will occur on the bottom board. This is likely to be less than diagonal boards but worse than open-jointed horizontal boards. A way around this issue, particularly with multi-storey buildings is to limit the use of boards to storey lengths and put a horizontal lead flashing at floor level on each floor to allow for drainage.

If you are to use open jointed horizontal boards, you should contact the breather membrane manufacturer to check the potential effect of UV light on its durability, as more daylight will penetrate than horizontal boards. Tongue and groove boards are most frequently used for vertical cladding, but care should be taken to ensure that the board widths are limited to prevent movement if the board tongues. Some prefer the use of rebated board to give a flush surface and has been overlapped to allow for possible shrinkage as a viable alternative to tongue and groove vertical boards.

The simplest way of vertically cladding is to use ‘board-on-board’ cladding which is made up of an inner layer of spaced apart boards with a layer of outer boards fixed to cover any gaps. This method can be used for surface modelling by adjusting the widths of the boards of battens in each layer. The bonus of using this cladding method is that it can be done with simple rectangular boards of similar or different profiles for the outer layer boards to create a unique effect. It’s also useful for properties with dimensional variation thanks to its tolerance for fluctuations and curves. Using narrow boards helps to clad around a tight radius too, but please bear in mind the importance of board shrinkage, so allow for additional overlap. Vertical boards fitted in a board-on-board way also benefit from sufficient ventilation without providing counter-battens, saving time and effort with the installation.

That’s the low-down on the vertical, horizontal and diagonal cladding types. Check out part two of our cladding articles series to learn about shingles and shakes and panel cladding.