Oakmasters US : FAQ : Types of Oak
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Do you use only English oak?
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Do you use reclaimed oak?
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Doesn't green oak shrink and crack?
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Do you use Kiln Dried Oak?
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Q: Do you use only English oak?
A: Oakmasters uses mixed sources from the UK and northern europe. We never ship Oak trees from the eastern block or from indescriminate random individuals and always select carefully sustainable forestry managed sources. Should there be a preference for a particular type of oak, then we will endevour to adhere to the customer's choice.
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Q: Do you use reclaimed oak?
A: Oakmasters rarely deal in reclaimed oak. Architectural salvage yards can supply original oak beams in a range of sizes. Beams can be cut to a length but the consumer will foot the bill for the entire beam.
However structural engineers regard reclaimed Oak as notoriously difficult to work with as it often contains old, hidden nails which damage machinery, and is extremely difficult to get hold of.
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Q: Doesn't green oak shrink and crack?
A: The simple answer to this question is yes - the oak will shrink.
Most shrinkage arises when wood is subject to fast drying. When fresh timber meets hot sun the outer surface dries first and therefore shrinks faster than the inside. The fibres separate causing cracks.
Wood can be kiln dried, which controls this process and helps prevent cracks caused by uneven drying. Wood can be air dried but it takes much longer -a year for every inch of thickness. Oak sections larger than 3-4" in thickness cannot be fully dried (down to ~ 12% moisture) by any conventional kiln methods. In addition the process of kiln drying is very space and energy intensive and so greatly increases the cost of the oak to the consumer.
Dry oak is therefore only usually used in the manufacture of joinery products such as windows, doors and tables.
This means that ANY building made of green or semi-seasoned oak will dry out during its first few years in a central heated environment. This drying period will see the moisture content of oak change from around 60% to around 16%. This is a huge change, and so it's not surprising that the oak shrinks a little and that cracks occur. However, it is generally agreed that it is these very cracks and splits which add to the character and charm of the finished product.
Oak is likely to shrink by approximately 2.5% across its grain, however there is virtually no shrinkage at all along the grain.
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Q: Do you use Kiln Dried Oak?
A: Kiln Dried Oak is wood that has been dried in a controlled environment that can prevent cracks appearing that are caused by uneven drying. It takes a year for every inch of thickness to dry and Oak sections larger than 3-4" in thickness cannot be fully dried (down to ~ 12% moisture) by any conventional kiln methods. The process of kiln drying is very space and energy intensive and greatly increases the cost of the oak to the consumer.
Because of this Dry Oak is usually only used in the manufacture of joinery products such as windows, doors, tables and specialist Beam Casings.
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