A crossing in construction is the point or line where two structural elements intersect or meet. In roof construction, a crossing is the point where two ridges or roof lines meet. The term is also used for timber joints where two beams pass over or through each other.
Types of crossings in construction
| Type | Description |
|---|---|
| Ridge crossing | Point where two ridge lines of a cross roof converge |
| Beam crossing | Two beams that pass over or through each other |
| Cross halving joint | Timber joint where two beams are notched into each other |
| Service crossing | Point where pipes or cables pass each other |
Crossings in roof construction
In a cross roof or compound roof, crossings occur at the points where:
- Two ridge lines meet
- Valley rafters and hip rafters converge
- A cross gable intersects the main roof
These points require extra attention for:
- Weathertightness: proper lead flashings or sealing tape
- Structural strength: sufficient fixings and connectors
- Drainage: water must be able to flow away freely
Cross joints in timber
- Half-lap cross joint: both beams are notched halfway and slotted together
- Full housing joint: one beam passes through fully, the other is cut around it
- Bearing crossing: one beam rests on top of the other, connected with a bolt or nail
Tips for the DIY enthusiast
- At a ridge crossing: use a ridge piece or tie plate for extra strength
- Always weatherproof roof crossings with lead flashing or EPDM
- For timber crossings: avoid weakening the timber by more than half with notches
Related terms
- Cross roof
- Valley rafter
- Hip rafter
- Ridge beam
- Compound roof