September 12, 2026

How to Write a Marble Specification: A Consultant’s Guide

A marble specification fails in one of two ways. Either it is so loose that any supplier can satisfy it with material the design team would never have approved, or it is so tightly written around one product that the tender returns a single compliant bid at whatever price that supplier chooses. Both failures come from the same root: a specification that describes a look instead of describing a test.

This is a working guide for consultants and engineering offices writing the stone section for a project in the Kingdom. It sets out what each clause has to contain to be enforceable at the delivery gate — because a specification that cannot be tested at delivery is a preference, not a requirement.

The principle: every clause must be checkable by someone holding a caliper

Before writing anything, apply one test to each sentence: could an inspector, standing at a supplier’s yard with a caliper, a moisture meter and the approved sample, decide objectively whether this clause is met? If not, the clause will not survive a dispute.

“High-quality white marble with elegant veining” fails that test. “Marble to the approved sample range, water absorption not exceeding the stated limit tested to the referenced standard, 20 mm nominal thickness with a stated tolerance, honed finish” passes it. The second version also allows more than one supplier to compete, which is the point of a specification rather than a purchase instruction.

The ten clauses a project stone specification needs

1. Material identification

Commercial name, geological classification, country and quarry of origin. Name the origin, because two quarries producing a similar-looking stone can produce materially different technical results. Where competition matters, specify by performance plus an approved reference sample and allow equivalents to be proposed with full test data.

2. Technical performance

State the property, the limit, and the standard it is tested to. At minimum:

Water absorption
Bulk density
Flexural or modulus of rupture strength
Abrasion resistance for floors
Slip resistance for wet and circulation areas
Freeze-thaw and colour stability for external cladding

Require test reports on the material actually offered, not a generic certificate for the stone family. A certificate that names the stone type but not the block tells you nothing about what will be delivered.

3. Dimensions and tolerances

Nominal thickness per application, with an explicit plus and minus tolerance. Length, width, squareness and flatness tolerances. Edge condition. Without a stated tolerance, “20 mm” is an aspiration that arrives at 18 mm.

4. Finish

Specify the finish per area, not per project. Polished in a lobby and honed in a wet area is a normal, deliberate combination. State how the finish will be verified — gloss level by measurement where it matters, otherwise against the approved sample.

5. Appearance and the approved sample range

This is the clause that prevents most disputes and is most often written badly. Do not write “colour variation to be commercially acceptable”. Instead, require the supplier to submit slabs representing the full acceptable range, have the design team approve the two extremes, photograph and reference them, and make that record the acceptance criterion. Anything outside the two approved extremes is rejectable; anything between them is not.

6. Submittals

List exactly what has to be submitted and in what order: technical data and test reports, full slab photographs with block references, physical samples, the cutting plan and shop drawings, and the mock-up. State which submittals are hold points — that is, which ones stop the works until approved.

7. Mock-up requirements

Area, location, lighting conditions under which it will be reviewed, and what it establishes. A mock-up that is reviewed under site floodlights and then judged in a finished lobby has established nothing. State explicitly that the approved mock-up becomes the workmanship standard for the area.

8. Delivery, handling and storage

Packing and pallet marking convention, batch traceability on the packing list, site storage conditions, and protection after installation. Assign responsibility for protection to a named party — when protection is everyone’s duty it becomes nobody’s.

9. Attic stock and maintenance

Quantity, batch, storage condition and handover format. Add a requirement for written cleaning and maintenance instructions naming permitted and prohibited products, to be handed to the operations team at completion. This single clause prevents a large share of post-handover surface damage.

10. Conformity to the Saudi technical regulation

Dimension stone is a regulated product in the Kingdom. The SASO Technical Regulation for Building Materials, Part 4 covers granite, marble, limestone, slate and travertine dimension stone under HS headings 6801, 6802 and 6803, and requires a Certificate of Conformity issued by a SASO-approved notified body, with the obligation falling on whoever places the product on the market.

Write this into the specification as a submittal, not an assumption: require the supplier to provide the Product Certificate of Conformity and, for each consignment, the SABER Shipment Certificate of Conformity — a shipment without one does not clear into the market. Name the party responsible in the same clause. This is the one requirement in the stone section that can stop material at a port rather than at a submittal review.

Writing tolerances that are enforceable

A tolerance needs three parts to work: the property, the limit, and the measurement method. Leave out the method and two parties will measure differently and both will be right.

Property	What to state	How it is verified at the gate
Thickness	Nominal plus explicit ± tolerance	Caliper, several points per piece, random pieces from several pallets
Length and width	Nominal plus ± tolerance	Tape or gauge against the piece list
Squareness	Maximum deviation over the diagonal	Set square and feeler gauge
Flatness	Maximum deviation under a stated straightedge length	Straightedge and feeler gauge
Appearance	Within the two approved sample extremes	Daylight comparison with the physical range present
Finish	Named finish, gloss level where critical	Gloss meter or approved sample

Specifying for competition without losing control

Naming a single product guarantees the appearance and eliminates the tender. A performance specification alone invites substitutions that meet the numbers and miss the intent. The workable middle is a three-part clause:

The reference product, named, with its origin and an approved sample — this fixes the intent.
The performance requirements, stated as testable limits — this defines the floor.
The equivalence procedure — what a supplier must submit to propose an alternative, who approves it, and by when. Without a deadline, equivalence proposals arrive after the programme has committed.

Five clauses that cause the most arguments

“Commercially acceptable variation.” Undefined, and therefore decided by whoever has more leverage. Replace with the approved sample range.
Thickness without tolerance. Invites material at the bottom of the manufacturing spread.
“As per approved sample” where no sample record exists. The clause references a document that was never created.
Silence on batch continuity. Permits a second phase from a different block, which will be visible.
Protection assigned to “the contractor” on a project with several contractors. Name the party.

A pre-issue checklist for the stone section

Can every clause be verified by measurement or by comparison with a physical reference?
Is SASO conformity certification required as a submittal, with a named responsible party?
Is a tolerance stated for every dimension?
Is the finish specified per area rather than per project?
Is the approved sample range defined as two physical extremes, recorded and referenced?
Are submittals listed, sequenced, and marked as hold points where appropriate?
Is batch continuity required for the full contracted quantity?
Is attic stock specified by quantity, batch and storage condition?
Is the equivalence procedure defined, with a deadline?
Is responsibility for protection assigned to a named party?
Are written maintenance instructions a deliverable at handover?

Frequently Asked Questions

Should the specification name a single supplier?

Naming a reference product is normal and useful; naming a single permitted supplier usually is not, because it removes the commercial tension that keeps the price honest. The stronger approach is a named reference plus a clear equivalence procedure — you keep the design intent and still receive competing offers.

How do you specify appearance for a natural material objectively?

By range, not by adjective. Approve two physical slabs that define the acceptable extremes, photograph them with their block references, and make that record the acceptance criterion. Natural variation between the extremes is accepted by definition; anything beyond them is rejectable on a documented basis.

What if a supplier proposes an equivalent that meets every number but looks wrong?

Then the specification was incomplete, because appearance was never fixed. This is exactly why the approved sample range sits alongside the performance limits rather than instead of them. An equivalent must satisfy both.

Does a mock-up replace the sample approval?

No — they answer different questions. The sample approval fixes the material. The mock-up fixes the workmanship: joint widths, layout, levels and finish quality in the actual space under the actual lighting. Specify both, and state that the approved mock-up becomes the standard the area is measured against.

Also available in Arabic: كيف تكتب مواصفة رخام محكمة

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