Stonework practice — choose the correct statements regarding the placement of natural beds (bedding planes) of sedimentary stones in arches, cornices, and walls for structural performance and durability.

Introduction / Context:
For sedimentary stones such as sandstone and limestone, the natural bed (stratification plane) is the plane along which the stone was originally deposited. Correct orientation of this bed in construction affects load-carrying capacity, weathering resistance, and crack control in arches, cornices, and walls.

Given Data / Assumptions:

• Sedimentary stones exhibit different strengths parallel and perpendicular to bedding.
• Arches, cornices, and walls impose distinct stress and weathering conditions.
• Traditional stonemasonry rules of thumb apply.

Concept / Approach:

Arches: Voussoirs work largely in compression along radial lines; placing natural beds radially keeps layers in compression and reduces delamination. Cornices: These project outward; placing the natural bed vertical minimizes shearing along bedding due to the cantilever action and improves weathering resistance of exposed horizontal surfaces. Walls: For stacked masonry under vertical loads, stones should generally be laid with the natural bed horizontal (as they were in nature) to ensure maximum stability and reduce the risk of spalling along bedding planes.

Step-by-Step Solution:

Verification / Alternative check:

Historical stonemasonry texts and building conservation guidance echo these orientations to maximize durability and structural reliability of sedimentary stones.

Why Other Options Are Wrong:

Choosing only one orientation ignores the different load cases; all three are context-correct.

Common Pitfalls:

Using a single rule for all elements; disregarding that igneous/metamorphic stones may behave more isotropically than sedimentary stones.

Final Answer:

All the above