Scribing timbers for structural timber frames


Overview
This intermediate level standard provides the learner with the information and skills to accurately scribe the timbers for a simple oak frame structure.

CITB has developed this standard in discussion with industry

Duration

Minimum 3 days of 6 learning hours

Purpose/Scope

This training module, ‘Scribing timbers for structural timber frames’ will provide the attendee with the information and skills to accurately scribe the timbers for a simple oak frame structure.

The scope of this standard covers:

  • personal protective equipment (PPE)
  • respiratory protective equipment (RPE)
  • scribing techniques
  • move & position timbers
  • prepare timbers for scribing
  • stack/lofted scribing
  • plumb scribe
  • box scribing
  • scarf joints
  • remote scribing & copying
  • square rule scribing
  • housings
  • ‘two foot rule’
  • second fit scribing

Occupational relevance

Training delivered against this standard would be relevant to the following occupational groups:

  • operative and craft

Candidate pre-requisites

It is expected that the candidate will be employed within the oak frame industry or have significant relevant carpentry experience.

Instruction/Supervision

As a minimum, course instructors must be able to demonstrate that, in relation to this standard, they have:

  • a train the trainer or instructional techniques course certificate
  • successfully completed training to this standard
  • at least 10 years relevant industrial experience
  • a verifiable CV

Delivery

Delivery may be in an on or off the job environment.

All materials and equipment must be of a suitable quality and quantity for candidates to achieve learning outcomes, and must comply with relevant legislation.

The class size and candidate/instructor ratio must allow training to be delivered in a safe manner and enable candidates to achieve the learning outcomes.

The following delivery methods may/may not be used in the delivery of this standard:

  • classroom
  • workshop

This standard is considered to contain 51% or more practical learning.

This standard is considered to be set at an intermediate level.

Assessment

For the successful completion of training, candidates must complete an end of course practical assessment and knowledge test that measures the learning outcomes and has a pass or fail criteria.

Quality assurance

Quality assurance against this standard will require initial approval of the training organisation and their content mapped to the standard. 

CITB will also conduct an approval intervention, either desk-based or centre visit, to ensure the training organisation can meet the requirements of the Training Standard. 

Approved training organisations will be required to present information on records of training and assessment upon request to CITB for desk based analysis. They will also be visited annually by the CITB quality assurance team.

Renewal/refresher

There is no mandatory renewal or recommended refreshment requirements for this standard.

Approval date

April 2019

Review cycle

Either on request or in 3 year(s) from approval date.

Learning outcomes

The candidate will be able to: Additional guidance to support learning outcome

Select, fit and use the appropriate Personal Protective Equipment (PPE), store, maintain and report defects in training and work equipment.

Will be able to Identify the correct PPE and understand storage, maintenance and employer damage reporting procedures for:

  • safety footwear
  • safety gloves
  • safety eyewear
  • RPE/dust masks
  • knee protectors
  • hearing protectors
  • hard hats
  • high visibility clothing

Be familiar with Provision and Use of Work Equipment Regulations (PUWER) regulations, workshop hazard identification, safe working conditions.

Select the most appropriate scribing technique

Take into account the context to decide which method is most suitable for the task including:

  • plumb scribe
  • square rule
  • distance scribe
  • boxing

Safely lift, move, position and secure timbers as required

Explain the health and safety requirements for safe manual handling

Prepare timbers in readiness for scribing

Describe how to assess twist, flatness and condition of timbers at joint location and how to rectify or prepare timber as required for the chosen scribing process

Demonstrate stack/lofted scribing, mark out and loft a lay-up in readiness for plumb scribing

Explain the following techniques and principles

  • laying out over full size marks on workshop floor
  • use of stools and bearers
  • use of setting out lines on timbers
  • levelling techniques
  • precise location of datum points on reference lines and on timbers
  • principles of lofting or stacking timbers
  • use of wedges and packers to accommodate varying thicknesses and twists in the timbers

Demonstrate plumb scribe timbers

Explain the following techniques and principles

  • referencing horizontal and vertical planes in lofted timbers using levels and plumbobs
  • the use of dividers and rules to establish vertical displacement between timbers to be scribed together
  • the use of scratch awls and other marking equipment
  • aligning a reference plane to remote marks by eye and by using a straight edge
  • significance of eye position when referencing plumb and level planes
  • the procedures for referencing/adjusting the square end of a brace or strut tenon to the square end of the mortise to be cut

Demonstrate box scribing, box a timber and mark up scarf joints

  • Describe the method to establish chalk/ink lines on a timber to produce two perpendicular intersecting reference planes
  • Explain choosing datum points to form boxing/reference lines at appropriate length.
  • Describe marking out joints using a roofing square with reference only to boxing lines.

Demonstrate remote scribing, establish position and angle of the joint to be cut using remote scribing techniques and copy an existing timber

  • Explain how to establish a reference level to ascertain the relative pitch of the joint surface
  • Describe how to establish a reference line to ascertain the deviation of the true shoulder of the timber to be jointed ie to calculate the true length of the jointed timber
  • Explain how an existing timber can be reproduced from another such that its contact points within a frame are identical.

Demonstrate square rule scribing, establish a reference line on timber, create housings of standard length, depth and width with reference to marked lines and positions

  • Explain how fixed reference lines on principal timbers can be used to standardise the length of intermediate timbers
  • Describe how the width and depth of the intermediate timbers can be standardised at the joint position making all such timbers interchangeable.

Demonstrate the “two foot rule” scribing and use second-fit scribing techniques to fit a timber to an existing mortise

Explain how a fixed reference line can be used to re-fit a joint by scribing an approximated joint for a second time in situ.

Additional information

Recommended reading:

OAK FRAMED BUILDINGS – Rupert Newman

FRAMING ROOFS – The best of Fine Homebuilding

BARNS OF RURAL BRITAIN –Graham Hughes ISBN 0-906969-36-0

TIMBER FRAME – Ted Benson ISBN 1-56158-281-6

TIMBER FRAMED BUILDINGS – John Bailey Bed Bucks and Cam Historic Building Research Group

CONSERVATION OF TIMBER BUILDINGS – F. W. B. Charles ISBN 0-7487-0376-4

Share