How to Read a Natural Stone Shop Drawing: A Guide for Designers

A shop drawing is the point where design intent becomes instructions for a saw. Approving one without reading it closely is one of the most common causes of expensive mistakes in stone projects.

What a shop drawing is

Architectural drawings describe what the finished space should look like. A shop drawing, prepared by or for the fabricator, describes every stone piece that has to be produced: its exact size, thickness, edges, openings and how it meets the pieces around it. The factory cuts from the shop drawing, not from the architectural set.

Start with the title block

The title block tells you what you are looking at and whether it is current. Check:

• Drawing number and revision. Make sure you are approving the latest revision and that changes since the previous one are clouded or listed.
• Scale, and whether the drawing is to scale at all.
• Material name, thickness and finish.
• Project and location reference.

Dimensions

Check overall dimensions against the architectural drawings and, where relevant, against site measurements. For countertops and vanity tops, confirm whether dimensions were taken from site templates after cabinets were installed. Look for the dimensions that locate openings, such as the distance from the end of a vanity top to the centre of the sink.

Edge profiles and details

Each exposed edge should have a defined profile: eased, bevelled, bullnose or mitred. For thick-looking edges made from thinner slabs, the drawing should show a mitred apron detail with the apron height and the mitre angle, usually 45°. Check which edges are exposed and which sit against a wall, because unfinished edges are cheaper and should not be polished by mistake.

Cut-outs

Sink, hob and tap openings are where fabrication errors most often happen. For each cut-out, confirm:

1. Type: undermount, flush-mounted or top-mounted.
2. Size and corner radius, taken from the actual appliance or sink template.
3. Position, dimensioned from a fixed edge.
4. Tap hole diameter and position, for example Ø35 mm.
5. Minimum stone width left around the opening, which affects strength.

Always use the manufacturer's template for the exact model being installed. Two sinks with the same nominal size can have different cut-out requirements.

Joints and vein direction

Stone is limited by slab size, so long runs need joints. The shop drawing should show where joints fall and how they are formed. Ask whether joint positions have been placed with the veining in mind, and whether a slab layout exists showing which part of which slab each piece is cut from. For directional stones, such as vein cut travertine or strongly veined marble, every piece should carry a vein direction arrow.

Tolerances

A drawing without tolerances leaves the acceptable result open to interpretation. Typical items to agree are length and width tolerance, thickness tolerance and flatness. These should match what the inspection will later check against.

Fixing and installation details

For wall cladding, façades and heavy pieces, the shop drawing or a separate installation drawing should show anchors, supports and movement joints. The structural design of fixings is the responsibility of the project's engineer, but the stone drawing must show where fixings go so kerfs and holes can be cut in the factory.

Before you approve

1. Is this the latest revision, and are all previous comments closed?
2. Do overall dimensions match the site or the architectural drawings?
3. Is every exposed edge profiled, and every hidden edge left plain?
4. Are all cut-outs dimensioned from the correct templates?
5. Are joints and vein direction acceptable to the design team?
6. Are thickness, finish and tolerances stated?

Marble Technic reviews and prepares shop drawings for stone produced in Turkey, and checks them against slab sizes, veining and factory capability before cutting.