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close this bookMaking of Roof Flashing - Course: Timberwork techniques. Trainees' handbook of lessons (Institut für Berufliche Entwicklung, 15 p.)
View the document(introduction...)
View the document1. Purpose of Roof Flashings
View the document2. Types of Roof Flashings
View the document3. The Eaves Flashing of Couple Roofs
View the document4. The Eaves Flashing of Purlin Roofs
View the document5. Structural Design of Purlin Roof Eaves Flashings
View the document6. The Suspended Gutter

3. The Eaves Flashing of Couple Roofs

An eaves flashing of a couple roof can only be made with a roof structure to be newly built which is supported by a wooden beam ceiling.


Figure 8

1 wooden beam, 2 roof rafter, 3 chantlate, 4 beam bearing, 5 eaves board, 6 roof boards

The wooden beams projecting over the outside walls can be designed with a profiled beam head or be faced by a roof base facing.


Figure 9

(1) profiled beam head, (2) roof base facing
1 wooden beam, 2 roof rafter, 3 chantlate, 4 beam bearing, 5 eaves board, 6 roof boards

The profile of the beam head is manually sawn out with a frame saw with fret saw blade or with a hand chain saw. If a hand chain saw is used, the wooden beam must be safely supported by the saw horse so that it cannot tilt when the saw is applied.

Why must the wooden beam tilt not or cant when the saw is applied?
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If the beam heads are faced by a roof base facing, it is recommended to let the beam project by 300 mm and to provide the cross-grain end with a 50 mm back-off.


Figure 10

1 roof rafter, 2 wooden beam, 3 chantlate, 4 beam bearing

By backing off the cross-grain ends, the front face of the roof base facing can be inclined so as to make the roof base facing look more elegant.

Tongued and grooved boards of 130 mm width should be used for the roof base facing.


Figure 11

Structural design of roof base facing
1 roof rafter, 2 wooden beam, 3 chantlate, 4 beam bearing, 5 chamfer at the longitudinal sides of the boards, 6 chamfer at both sides of the narrow face of the board, 7 outside edge of outside wall, 8 plasterwork strip

Why should no wider boards be used for the roof base facing?
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The roof base facing boards should not be forced together to allow the wood to contract and expand.

The longitudinal sides of the joined boards should be slightly chamfered to make the joint between the facing boards look better when the wood contracts or expands. The tongues of the first bottom board and face board are to be cut off to achieve a good contact with the eaves board and the face board (see. Figure 11).

The lower face board should extend 15 mm below the bottom board. The groove of this board is to be cut off and the narrow face of the board to be provided with a chamfer at both sides. The nails used for fixing the roof base facing boards are to be driven in.

An air gap of about 10 mm is to be left between the outside plasterwork and the bottom board of the roof base facing.

This air gap is covered by a plasterwork strip which is adapted to the existing unevenness of the plaster surface (see Fig. 11).

Why shall the nails be driven in?
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If the couple roof is supported by a solid ceiling, the eaves flashing is achieved by a cornice connected to the solid ceiling.


Figure 12

Cornice at solid ceiling
1 solid ceiling, 2 main reinforcement, 3 cross reinforcement, 4 cornice, 5 ceiling bearing, 6 roof rafter, 7 chantlate, 8 sleeper, 9 steel angle, 10 eaves board, 11 roof boards