When to Order Materials: A Worked Example of Lead Time and Cost

Ordering too late stops the site; ordering too early ties up cash and risks damage. A calculation that finds the useful middle.

Material ordering is usually handled by instinct: order when the previous trade is nearly finished. That works until one item has a long lead time, at which point the entire programme waits for it. The example below shows how to identify which items deserve attention.

The situation

A villa project is approaching the finishing stage. The owner wants to know when to order the main finishing items so the site does not stop, without paying for materials months before they are needed.

Assumptions (illustrative)

• Planned start of tiling: week 26 of the programme.
• Assumed lead time for imported floor tiles: 10 weeks.
• Assumed lead time for locally available tiles: 2 weeks.
• Assumed lead time for bespoke joinery: 12 weeks from approved drawings.
• Assumed sample approval and drawing period for joinery: 3 weeks.
• Assumed site overhead if work stops: SAR 1,100 per day.

Step 1: Imported tiles order date

Week 26 minus 10 weeks lead time equals week 16.

The decision on imported tiles must be final by week 16, which is usually long before owners feel ready to choose finishes.

Step 2: Adding an approval buffer

Adding a 2 week buffer for sample approval moves the decision to week 14.

Sample approval is not instant, and shipping schedules do not accommodate indecision. The buffer is what absorbs the ordinary friction of choosing.

Step 3: Joinery critical path

Week 26 minus 12 weeks production minus 3 weeks drawings and approval equals week 11.

Joinery, not tiling, is the earliest decision on the list. Items with design plus production cycles almost always govern.

Step 4: Cost of getting it wrong

A two week stoppage at SAR 1,100 per day across 10 working days equals SAR 11,000 of site overhead for one late decision.

This cost buys nothing. It is the price of a decision made three weeks later than the programme required.

Step 5: The alternative comparison

If locally available tiles cost SAR 30 per square metre more across 300 square metres, the premium is SAR 9,000, against a 10 week shorter lead time.

Once the delay cost is quantified, a more expensive but faster material can be the cheaper decision overall. Without the calculation, only the unit price is visible.

What changes the answer

• Shipping disruption extends imported lead times unpredictably, which strengthens the case for local alternatives on critical path items.
• Storing materials on site early risks damage and theft, and consumes space needed for work.
• Paying early for materials reduces your leverage and exposes you if the supplier or contractor fails.
• Batching several imported items into one order can reduce shipping cost but couples their delivery dates together.

What the numbers tell you

• Identify long lead items at the start of finishing, not when the trade is about to begin.
• Add explicit approval time to every lead time, because approval is part of the duration.
• Compare material options on delivered cost including the delay they imply, not on unit price alone.
• Accept delivery to site close to installation, and pay against delivery rather than against order where possible.

Limits of this example

Every figure above is an illustrative assumption used to show the method, not a quote, valuation or market rate. Costs, rates, fees and regulations change and must be confirmed with the relevant authority, lender or supplier before you commit.

If you are preparing to build, Domira can review your drawings, scope and contractor offers before you commit, and supervise delivery against the programme and specification you agreed.