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Wood | Technical Area & Advice

Wood Info | What is wood?

Which wood to choose

We are timber specialists and below we briefly cover some topics that may assist you with your choice of timber, installation and on-going care/maintenance;

Areas covered;

1)      About wood

2)      Moisture content - read more

3)      Choice of species - click for more about specific wood

4)      Installation

5)      Maintenance/moisture Content

6)      Other useful tips and advice 

1. Wood | What is wood?

Wood is a natural product and is one of the most versatile and beautiful materials available to us providing a long term sustainable solution to endless applications.

Wood has the best thermal insulation properties of any mainstream construction material. When sourced from sustainably managed forests it can actually be better than carbon neutral.

As a natural product and every piece, regardless of species, is completely unique. This means that it can vary dramatically in appearance (even form the same tree/board). This adds to the character, diversity and beauty of the material – but is also something to consider if you are expecting all pieces to look alike.

Wood is a hard, fibrous structural tissue found in the stems and roots of trees and other woody plants. It has been used for thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibres (which are strong in tension) embedded in a matrix of lignin which resists compression.

The chemical composition of wood varies from species to species, but is approximately 50% carbon, 42% oxygen, 6% hydrogen, 1% nitrogen, and 1% other elements (mainly calcium, potassium, sodium, magnesium, iron, and manganese) by weight. Wood also contains sulphur, chlorine, silicon, phosphorus, and other elements in small quantity.

In chemical terms, the difference between hardwood and softwood is reflected in the composition of the constituent lignin. Hardwood lignin is primarily derived from sinapyl alcohol and coniferyl alcohol. Softwood lignin is mainly derived from coniferyl alcohol.

Woods are categorised into hardwoods and softwoods. These terms actually relate to the tree’s botanical classification and not the properties of the wood, which can cause some confusion! The definitions below are thus just basic pointers;

What is the difference between hardwood and softwood? We explore what separates these timber types and what they have in common 

Hardwood - What is hardwood?

Hardwoods come from trees with fruits or seeds.

Hardwood tends to come from slow-growing, deciduous trees with broad leaves. The wood is usually heavy, tough, and (unsurprisingly) hard. But there are exceptions to the rule: cork oak and balsa wood are both light hardwoods; birches and willows are fast-growing hardwoods; and tropical hardwoods are not deciduous.

Hardwoods often have additional channels for transporting sap, known as vessels or pores. These may be visible to the naked eye, or under magnification, as tiny pinholes when the wood is cross cut.

Softwood - What is softwood?

Softwoods come from conifers (cone bearing trees). Pines, spruces, larches are familiar examples.

Softwoods normally come from coniferous or needle-leafed trees, which are fast-growing, producing soft and light wood. The exception to the rule is yew, which is both slow-growing and very dense.

Confusingly, some softwoods are harder than hardwoods!

Softwoods don’t normally have visible pores. Rays also may be narrow or virtually invisible. Softwoods can sometimes be identified by the presence of resin, or a ‘turpentine’ smell, particularly when freshly cut.

2. Moisture content in wood - what you need to know

The moisture content level within timber ultimately dictates the subsequent movement and potential distortion when in service.

For guidance please see the table below for the recommended moisture content levels for timber in any given situation;

Wood moisture content

To download this handy illustration please click here.

Illustration explained;

Category

Sub-category based on intended   in-service climates

Moisture Content range in %

External joinery

 

12-19%

Internal joinery

For unheated buildings

12-16%

Internal joinery

For buildings with heating providing   room temperatures of 12 deg C to 21 degrees C

9-13%

Internal joinery

For buildings with heating providing   room temperatures in excess of 21 degrees C

6-10%

Our manufacturers monitor the moisture content of their timbers and all are kiln dried (with the exception of some structural timbers and green oak). The moisture content normally falls between 12-18% but this does vary between species. Please see the specific materials for an indication of the moisture content at the point of supply. If you have a specific moisture level requirement please indicate this on your order (special instructions). Please note however that the cost and timescales may vary if your requirement is different to the projected moisture content levels shown. Once you receive your timber product, it is important to protect it and maintain the moisture levels to ensure that are at the desired level at time of install/positioning - for more information on protection click to go to finishing (care and handling).

If you purchase timber regularly or have concerns over moisture content levels in timber (this especially applies to building contractors, architects and other trade related professionals) we recommend that you invest in an accurate, quality moisture meter. It is important to obtain the correct type of meter – we strongly recommend the Wagner MMC220 (we have used one for years with great success). Having outstanding accuracy, another key advantage of these meters is that they provide measurement deep into the wood without the downside of unsightly holes that you get when using a pin-type meter.  Wagner's technology allows quick scanning of your wood, and Wagner meters provide INTELLISENSETM technology with virtually ignores absorbed surface moisture that can negatively affect other meters’ accuracy. For more information click here 

If you are interested in purchasing a Wagner meter please contact us - info@wooduchoose.com.

3. Choice of Wood Species

The choice of species can depend on many factors;

i.            Appearance - read more about figure of wood

ii.           Colour

iii.          Durability

iv.          Workability

v.           Price

vi.          Moisture Content

vii.         Environment impact

… To name a few!

Our wood section describes the properties of each of the of wood species along with lots more information to help you make an informed choice. You can sort by wood durability, price and other factors plus view the colours and learn more about where the timber is from and how it is sourced. Click here to go to timbers.

See our unique comparison tables for more information on which wood to choose - DurabilityWorkabilitySustainability.

4. Installation of wood or joinery products

We recommend that you employ a professional carpenter or joinery to carry out the installation of any timber products. You may find a suitable installer in your area on our database of related services.

The method of installation will be determined by product type and what it is being fixed to. Careful consideration as to the type and number of fixings is also needed. As a general rule; use non-ferrous metals or stainless steel for external timbers. Some timbers do react with metals leaving stains – notes on the specific materials will identify potential conflicts. For internal products you may wish to use ferrous metals or adhesives. But the internal environment still needs to be considered- an area of high humidity may cause similar problems to that of external exposure.

To reduce the visual impact of a fixing we recommend the use of a timber pellet (in the same species as the timber being fixed) these can be extracted from an off cut of the timber using a specific pellet cutter with a corresponding drill bit to form the hole (for the fixing). Better still; secret fixings could be used either with clips/brackets or fixed through faces that are not ultimately seen. There are also suitable adhesives but caution is needed when using this method; if there is movement and the timber is adhered to a surface, splitting can occur.

When fixing cladding, decking or flooring (or any timber boarding that is covering a large surface area) it is important to introduce expansion gaps. This will depend on exposure and moisture content. It is also important to allow the boards to move in these situations. As the timber takes on moisture it will expand forcing against adjacent boards if gaps are insufficient. By the same affect; if boards are already very wet and then exposed to dry, hot conditions they will shrink - increasing the gaps between the boards.

Linear Boards - For wide boards being fixed to a wall or flat substrate – consider the use of more than one fixing across the board width to reduce ‘cupping’. The number of fixings along the run of timber can vary but 400-600mm centres is a common spacing.

5. Maintenance of Wood

Our timber products are designed and engineered to meet the requirements and expectations of modern living and construction. Any product - whether it is a boiler, washing machine, car, window, and door (of any material) – will need some form of maintenance in order to ensure a long service life. Failure to keep to a planned maintenance schedule may at best ruin the products appearance and, at worst, lead to the early deterioration of the components.

Most of our products are solid timber products and therefore relatively easy to look after – but they still need care. This will depend on their intended use and location (exposure to the elements). You may have already made your timber selection (see above for more help on this) and you will have an intended use for the product. You may also have decided how to install (see above) you now need to plan maintenance/monitoring schedule and the following needs to be considered to help determine this;

Location of product – it is external? Is in a south facing position? Is it exposed to sunlight? Is it in a room with high humidity?

If the answer is yes to any of these questions the chances are your maintenance should be fairly regular.

The type and level of maintenance required will depend on the item’s location and exposure to the weather. An external joinery item in a south facing position in a coastal area will deteriorate far quicker than one that is north facing and sheltered from the wind and rain.

It is important to remember that regular, minimal maintenance will make re-decorating a far easier job.

Mould and algae - All external items can suffer from mould and algae caused by airborne spores, which settle on the surface (which is why exterior plastic products go grey over time).

To remove mould and algae, wash with a solution of one part bleach to two parts water, and leave for 20 minutes to work. Then rinse. If the blemish is stubborn, scrub with a stiff nylon bristle (not metallic) brush.

Cleaning and washing - Wash external, decorated products with hot water and liquid detergent every 6 months. Rinse with clean water. During this process it is advisable to inspect for defects and take action if necessary.

Damage - If any part of the items coating system is damaged to the point of showing bare timber you should consult the coating manufacturer’s guidelines, determine the appropriate coating material to use and apply their practical instructions on how to maintain/reinstate the coating. Click for more about wood care and decoration.

6. Tips, Advice and further info

We recommend that you spend time to explore our website and use our links to make an informed choice in a timber product and species. Choosing the wrong wood or product for your intended use can lead to on-going, costly problems. We have designed this site to help you through this process and we hope you will find some useful information. We are confident that you will find a product that suits your requirements. If you have any queries, or, in the unlikely event that you cannot find what you need, please do not hesitate to contact us info@wooduchoose.com

Glossary of Wood Terms

Defects in Wood

Toxic Wood

Our Only Renewable Resource - Wood