While discussing oak timber, your framer may assert that they exclusively use Quercus robur. Usually, this statement is accurate.
Nonetheless, it’s vital to inquire about the timber grade that the structural engineer has specified for your unique building, considering factors like elevation, orientation, and wind loadings. Confirming that the purchased grades match your requirements is critical. Equally important is ensuring that certified timber graders participate in the manufacturing process to maintain compliance with the appropriate standards.
You might also encounter the term “English-sawn oak,” which describes trees sourced from Europe, transported to the UK, and subsequently cut.
This guide covers how to ensure you are getting the best oak grade for your project.
When buying an oak framed garage, you should aim to understand the varying oak grades available:
- QPA and QP1: These are appearance classes (EN957-1) that correspond to Strength Classes (EN 338) used by structural engineers to specify oak strength requirements.
- QPA corresponds to D30, which is a standard strength grade.
- QP1 corresponds to D24, and while some engineers may use this grade, it requires larger timber sections to meet the same calculations.
When ordering from Europe, the following classifications are commonly used:
- QP1: Sawn timber with sharp arrises, allowing wane less than 10% of the face width across no more than 30% of the length. Additional specifications apply to sections above 250 x 250mm.
- QPA: Sawn timber with sharp arrises, permitting wane less than 10% of the face width across no more than 25% of the length for pieces longer than 3m.
- Additional specifications apply to sound sapwood, knots, boxed heart, slope of grain, and more.
At The Garage Specialist, our standards for Fresh Green Oak Beams include:
- Sawn timber with sharp edges
- Tolerance for small quantities of sound sapwood on two edges, covering less than 30% of the width of faces and edges
- Acceptance of sound knots based on diameter limits related to timber cross-section size
- Compliance with specified grain angle limits for different timber cross-section sizes
- Certain defects, such as woodworm, bug holes, heart shaking, soft knots, inner bark, wane, and others, are not accepted
To maintain the integrity of oak beams, proper packing requirements must be followed, including:
- The identification of packs
- Use of identifying colours
- Clear packing lists
- Weight limits
- Stacking guidelines
- Banding practices
Structural Integrity and Our Grading Process
It’s important to note that using unsatisfactory oak beams in your structure poses a risk of beam failure. Having qualified oak timber graders involved in grading the beams for your building is crucial. At The Garage Specialist, we reject approximately 35% to 40% of standard-grade beams through our rigorous four-stage quality grading process. Our oak timber graders are trained and recertified annually to ensure adherence to our high standards.
The chain of custody involves the structural engineer using Eurocodes to design the frame, considering factors like building positioning, elevation, orientation, and wind loadings in their calculations.
While there are many oak mills in Europe, only a few consistently produce the quality of oak we demand for our buildings. The standard grades from these mills may be available at a lower cost, but we prioritise maintaining the quality and viability of our beams. It’s important to recognise that when manufacturers mention using the same oak, they are referring to the botanical group and not the specific quality and grading of beams used in your frame.
By understanding the significance of oak grades, timber grading, and adherence to quality standards, you can make an informed decision when choosing oak frame components for your project with The Garage Specialist.