Seasoning Categories and Shrinkage
Oak is particularly prone to shrinkage as it dries out. This can result in dimensional change, splitting, twisting, bending or other deformation from its green(unseasoned) state.
At The Oak Frame Carpentry Co we store beam oak for sale and for inclusion in our frames. The moisture content of the timber is monitored as we dry it in carefully controlled conditions.
We can offer oak in the following states of seasoning:
Green oak:
- Preperation
- Fresh sawn oak to any given dimension
- Analysis:
- >30% moisture content at .25 minimum radius*
- Characteristics
- Fairly uniform appearance; easily worked; prone to significant shrinkage and deformation;
- Applications
- Internal framing; structural framing; roof trusses; outside structures; fully clad frames. External framing requires weatherseal design or cladding
Part-steady beam oak
- Preperation
- Air dried for an initial period, dependent upon sectional area
- Analysis:
- <30% moisture content at .25 minimum radius*
- Characteristics
- Grey surface colouration; surface shaking; end checking; some open heart shake; some discolouration of sapwood; reduction in future shrinkage.
- Applications
- As for green oak, but with superior selection of orientation and use according to visible defect. lintels where some future shrinkage is tolerable; applications where reduced shrinkage and deformation is preferable.
Stable beam oak
- Preperation
- Air dried for a longer initial period, dependent upon sectional area
- Analysis:
- < 30% moisture content at .5 minmum radius
- Characteristic
- Grey surface colouration, surface shaking, end checking, some heart shake; sapwood discolouration; significant shrinkage has already occured
- Applications
- Exterior framing where shrinkage may cause weathersealing problems; direct glazed framing; lintels; applications where significant shrinkage and deformation can not be allowed; repairs and replacements of large section beams.
Seasoned/ Air dry oak
- Preperation
- Usually smaller section as slabs and curves.
- Analysis
- <25% ,moisture content core value
- Characteristics
- Essentially dry timber; harder texture that takes a polished surface. No appreciable future shrinkage or deformation.
- Applications
- Detailed framing work; carving; repairs to old timbers;
- For fine joinery or cabinet work, kiln dried timber cut as planks is available elsewhere to around 10% core moisture content. Although some of our smaller beam or slab stock may achieve this level, we do not recommend its use for extremely exacting applications.
*Minimum radius is defined as the shortest distance from the external faceof a given timber, to its centre