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close this bookAttic Completion Work - Course: Timberwork Techniques. Instruction Examples for Practical Vocational Training
View the document(introduction...)
View the documentPreliminary Remarks
View the documentInstruction Example 2.1.: Making Openings for Roof Superstructures in Existing Roofing
View the documentInstruction Example 2.2.: Making a Rafter Trimming
View the documentInstruction Example 2.3.: Making the Opening for the Roof Window to be Built in
View the documentInstruction Example 2.4.: Joining of the Parapet Transom
View the documentInstruction Example 2.5.: Joining of the Window Posts
View the documentInstruction Example 2.6.: Joining of the Lintel Transom
View the documentInstruction Example 2.7.: Joining of the String Transoms and Roof Rafters

Instruction Example 2.4.: Joining of the Parapet Transom

This instruction example teaches how to join the parapet transom for an upright roof window with lean-to dormer roof.

Constructional details

- The opening in the roofing has already been made.
- Window posts are to be joined with a corner tenon.
- Cross sections of timbers are shown in the workshop drawing on page 7.
- Parapet transom is just cut to the length of 950 mm.


Hand tools

Hammer, engineer's square

Measuring and testing means

Folding rule

Auxiliary accessories

Trestles (one ell), pencil, marking gauge, workshop drawing

Necessary previous knowledge

Measuring, scribing, angling, use of marking-out marks, reading of drawings

Explanations to the working drawing

(D sectional view A-A, (2) upright roof window - front view.
The figures 1 to 12 represent the steps as per sequence of operations.

Sequence of operations


1. Manufacture a marking gauge.

See working drawing point VII.
Make sure that the recess sizes (35 mm, 70 mm) are sawn out at right angles!

2. Erect the trestles and prepare the working place.

Ensure firm standing and stability of the trestles!
Store timbers, which are not required, outside the working area!

3. Put the parapet transom on the trestles, decide on the joining side and mark it.

Joining side III shall have a flat face!
If the timber is slightly cambered, take that camber on top (VI)!

4. Scribe the section line at the left end of the parapet transom and mark with marking-out mark.

Go only as far to the right as to permit a right-angle section to be produced!
Use engineer's square and scribe a thin line!

5. Measure-in and scribe parapet transom length, starting from the section line and measuring to the right, mark with marking-out mark.

Use engineer's square and scribe a thin line!

6. Measure-in and scribe at left and right section the window post width towards the centre.

Use engineer's square.

7. Measure-in and scribe the comer tenon width from the two scribed lines towards the two ends of the parapet transom.

Use engineer's square and don't scribe over the total timber width!

8. Scribe the tenon thickness.

Use marking gauge and scribe with sharp pencil exactly at marking gauge end face (VIII)!
Do not cant marking gauge when scribing!

9. Scribe section line on all four sides at the two ends of the parapet transom and mark with marking-out mark.

Use engineer's square. The scribed section lines of all timber sides must be congruent!
If section lines are not congruent, find out the reasons:
- Engineer's square not correctly placed.
- Faulty square.

10. Scribe roof rafter inclination of main roof and mark with marking-out mark.

Place square legs for scribing and exactly scribe the diagonal.

11. Measure-in, scribe and mark with marking-out mark the rafter width of the main roof on the side (V) opposite the joining side.

Use engineer's square and place it exactly!

12. Transfer rafter width line to bottom side (IV) and mark with marking-out mark.

Place engineer's square exactly.

13. Work parapet transom accordingly, take it off the trestles and store it outside the working area.

Joining of the parapet transom