Last edited 25 Sep 2020

Weatherboarding

1 Introduction
2 Timber weatherboarding
3 Fibre cement weatherboarding
4 uPVC weatherboarding
5 Related articles on Designing Buildings Wiki

[edit] Introduction

Weatherboarding is a form of external cladding. Traditionally, weatherboarding has been made from timber, although other materials have also become popular such as uPVC and fibre cement. There are numerous types of profile and finish available depending on aesthetic requirements. It is designed to be laid with an overlap, as opposed to flush cladding where boards are fitted together with no overlap.

Weatherboarding is particularly effective in damp climates or in close proximity to the sea where there is a risk from high salt-content spray.

[edit] Timber weatherboarding

[edit] Types of wood

Many different species of wood can be used for weatherboarding, suitable because of their natural resistance to decay. Traditional British timbers such as oak, elm, sweet chestnut, western red cedar, and larch have been used for centuries. Imported timbers such as Siberian larch and Canadian western red cedar are becoming more popular for achieving a more modern aesthetic.

The most durable (and therefore most expensive) types tend to be oak and cedar, although the board’s thickness has a large influence on its cost, as well as how long it will last and how well the detailing holds its integrity.

Fresh sawn boards are cheaper than machined, and provide a simple, classic finish. The variations in section and width, provided by rough sawn boards, give a rustic and informal aesthetic. Machined boards are generally more expensive but require no drying and so can be installed straight away. As the sections are consistent, it gives a crisper aesthetic and can allow for easier fitting and detailing.

Untreated weatherboarding will gradually ‘silver down’ under exposure to sunlight, meaning that the oxidation process ultimately brings most timbers to a similar appearance.

[edit] Installation

It is preferable that weatherboarding planks are fixed horizontally. In this way rain can flow down the front face of one plank onto the one beneath. Vertical fixing is not generally advised, as water flowing down can also flow along and through joints. If vertical boards are required, the plank overlaps should be arranged away from the prevailing wind.

Planks are usually fixed to vertical timber battens, with a damp proof membrane fitted between the battens and the building structure if the building is timber frame. A gap of at least 25 mm (1 inch) is required behind the boards to allow air circulation and prevent moisture build-up.

The first boards should be installed to a starter trim, ensuring that they are level as this will affect all the boards that follow. Boards should be screw-fixed or nailed at every batten, with the fixing screw or nail flush so that it doesn’t interfere with the next board. Stainless fixings are advisable wherever possible as they offer the best durability. Where required, a cover strip or drip trim should be fixed to prevent moisture from entering the cavity at the top.

[edit] Advantages

There are several advantages to timber weatherboarding, including:

It is lightweight and quick to install.
Its lightness reduces the size and cost of the building structure required to support it.
It has excellent thermal and acoustic properties.
It is easy to maintain and repair.
It can have attractive aesthetic qualities.
It has a low carbon footprint and is a sustainable material.

[edit] Fibre cement weatherboarding

Fibre cement weatherboarding is typically square-edged and has a timber-like surface finish, which means that it can be used as an aesthetic substitute for timber if required. It can also be worked and fixed like timber but has the benefit of several additional properties, including:

It is available in a large range of colours.
It is low maintenance and easy to install.
It is resistant to damp, fire and infestation.
It does not warp, shrink or rot.
It has good weather-resistance.
It can be installed vertically or horizontally.

For more information, see Fibre cement.

[edit] uPVC weatherboarding

uPVC weatherboarding is a versatile form of cladding that combines the texture and natural aesthetic of timber with the maintenance-free durability of fibre cement. It can be fixed vertically, horizontally or even diagonally on any kind of building frame.

It usually has a thinner section than timber and can be easily moulded to certain specifications, such as giving it increased strength for installation at low level where impact is more likely.

uPVC planks can be manufactured to tight tolerances, and they do not twist, warp or split; meaning they can be easier to work with than timber. Different makes of uPVC planks will have their own fixing method, but they can usually be mounted onto wooden battens.

uPVC is available in a range of different colours, and is generally quite low maintenance. However, scrapes or surface damage can reveal the white uPVC underneath the sometimes thin coating of colour application.

Other advantages of uPVC include the following: