How Fuel Prices Affect Home-Building Costs: Update the BOQ by Cost Code

A change in fuel prices can affect construction costs, but it does not automatically justify changing the entire house price per square metre by the same percentage. The defensible method is to trace the change through the project’s BOQ, supplier quotations and cost codes.

As of 23 September 2026, Thailand was considering targeted fuel-excise relief for E20 and B20. Reuters reported the proposal on 21 September, but no final tax-reduction rate or effective date had been announced. The policy event is therefore a monitoring signal, not a confirmed saving that should be inserted into every quotation.

1. Which construction costs are exposed to fuel?

Direct costs may include delivery charges, earthmoving equipment, generators, cranes and other machinery billed by fuel use or operating hours. Indirect costs may include supplier production and distribution costs for concrete products, asphalt, aggregates and energy-intensive finishes.

Exposure is not uniform. TPSO’s August 2026 data illustrates the point: the overall Construction Materials Price Index was 113.1, up 6.1% year on year, yet concrete products rose 9.6%, electrical and plumbing materials rose 12.7%, while cement and steel categories declined. Different drivers—including oil, gas, copper, competition and global oversupply—move categories differently.

2. Separate direct and indirect impacts

Cost area	Typical evidence	Update method
Material transport	Haulage quote, distance, load size, fuel surcharge	Update delivery cost code
Site machinery	Equipment rate, fuel consumption, operating hours	Update plant/equipment cost code
Ready-mix concrete and aggregates	Supplier quotation and delivery zone	Update the specific material and transport lines
Energy-intensive materials	Supplier price list with effective date	Update only confirmed SKUs/specifications

3. Identify affected cost codes

Tag each BOQ item by exposure: transport, diesel machinery, production energy, commodity input or no material exposure. This prevents a policy headline from becoming a blanket markup or discount.

4. Update the Price Book with dates and evidence

• Record supplier, product/specification, region and delivery basis.
• Store the quoted price, effective date and expiry date.
• Separate base material price from freight and fuel surcharge where possible.
• Do not replace the prior price; retain history for audit and comparison.

5. Recalculate only the affected BOQ sections

Run the revised quantities and unit rates only through the relevant sections. Compare Budget, Committed and Actual Cost where the project has progressed beyond estimating. A market index is useful as a reasonableness check, but it is not a substitute for quantities and supplier quotations.

6. Compare with the previous cost per square metre

After recalculating the BOQ, divide the total change by the same area definition used in the original estimate. The area basis must remain consistent—usable area, gross floor area or another defined construction area—otherwise the comparison is misleading.

7. Set an approval threshold before changing the selling price

• Define the minimum verified cost change that triggers review.
• Require current quotations and a traceable BOQ variance.
• Check contract clauses, quotation validity and agreed specifications.
• Document who approved the change and when it becomes effective.

A simple example

Suppose a 300 sq.m. house has a verified THB 90,000 increase across delivery and machinery cost codes. The measured effect is THB 300 per sq.m.—not the percentage movement in a national index and not a guess applied to every BOQ line. The same logic applies if verified costs fall.

GDC analysis: BOQ, Cost Code, Price Book and Budget–Committed–Actual practices in this article are Greenery Design & Construction’s management framework. Reuters, TPSO and the Thai Government do not prescribe this internal workflow. Actual project costs depend on the design, specifications, location, delivery distance, procurement terms and timing.

Frequently asked questions

Should a fuel-price change alter every BOQ line?

No. Update only cost codes with verified transport, machinery, production-energy or supplier-price exposure.

Can a national construction-material index replace supplier quotations?

No. Use the index as a market benchmark; project pricing still requires quantities, specifications, delivery terms and dated quotations.

When should the cost per square metre be recalculated?

After the affected BOQ sections have been updated, using the same area definition as the original estimate.

Sources

• Reuters report republished by CNA: Thailand considering oil tax cut (published 21 September 2026; accessed 23 September 2026)
• Royal Thai Government: 2026 diesel price-support measures (published 21 September 2026; accessed 23 September 2026)
• TPSO: Construction Materials Price Index, August 2026 (accessed 23 September 2026)
• TPSO: Full August 2026 economic price-index documents (accessed 23 September 2026)