Our Timber Specifications

It is essential that timber is properly specified, inspected and graded before being used in oak frame construction to ensure the structural integrity of the building.

knot in oak

Knots, grain and other natural characteristics of timber all add to the beauty and charm of an oak frame building. However, there are too few manufacturers who fully understand when one of these natural characteristics on an individual piece of timber can actually impact upon the structural integrity of the oak frame.

It is not acceptable for manufacturers to pass off a piece of timber within your building as “charming” and “beautiful” without understanding the structural impact and being able to confirm to you that the combination of all of its natural characteristics fall within the tolerances of the engineer’s strength grading within the frames structural calculations!

In order to ensure that your oak frame is structurally sound, it is essential that all timbers are properly specified and the manufacturer fully understands the requirements to meet the engineers’ specified strength grading levels for each individual piece of timber within the oak frame. To achieve this, the manufacturer’s timber graders must be able to identify and understand the individual characteristics of each piece of timber and the impact upon strength grading of various features such as:

  • Amount of sapwood
  • Size and position of knots
  • Angle of grain
  • Amount of distortion and bow

These items are all natural characteristics of timber which must be measured within specified tolerances to ensure that the oak frame meets structural calculations and will stand the test of time when assembled. The timber graders at English Heritage Buildings are all TRADA qualified graders to ensure that we fully understand when a piece of timber does not meet the required structural standards and must be rejected before being allowed to pass through to the manufacturing process however “charming” and “beautiful” it may look! In this way, we can maintain the charm and beauty of a piece of timber with these natural characteristics whilst knowing when it cannot be used if it falls outside certain strength grading parameters.

In addition to strength grading, English Heritage Buildings also have aesthetic standards for timbers to make sure that the visual impact of your frame is not spoilt by an unsightly natural feature within the timber even though it may fall within strength grading tolerances.