12 hidden costs of building a house that aren't in the BOQ

A contractor's price covers the "house itself", but a livable house always costs more. Here are 12 items usually not in the BOQ, in order from before to after, with rough price ranges for a typical house (provincial/suburban — inner Bangkok may be higher)

Before building

• Land filling + compaction — Depends on fill height and local soil prices: tens of thousands to several hundred thousand baht; low-lying land costs more
• Boundary survey — A few thousand baht
• Construction drawings — Ready-made plans cost thousands to tens of thousands; hiring an architect for a new design usually costs 3–8% of construction
• Permit fees — Hundreds to a few thousand baht
• Temporary electricity and water during construction — Temporary meter fees + monthly usage, totaling tens of thousands

During and after building

• Permanent electricity and water meters — Fees + installation, from thousands to over ten thousand baht, depending on meter size and distance for poles and cables
• Water pump + tank — A standard set for a typical house: 15,000–40,000 baht
• Window grilles, insect screens, curtains — Usually 30,000–100,000 baht for the whole house
• Air conditioners with installation — 12,000–40,000 per unit, times the number of rooms
• Furniture + appliances — The biggest lump after the house is done; budget a separate 10–20% of the house cost
• Fence + gate + house number sign — Fencing is priced per meter; a whole plot usually runs into hundreds of thousands
• Garden/parking area paving — From tens of thousands

A safe budgeting formula

Real total budget = BOQ construction cost × 1.25 to 1.35 — this multiplier covers the 12 items above plus a buffer for the unexpected. If the number is too much, shrink the house at the design stage rather than running out of money midway and ending up with a house with no fence and no AC that you can't actually live in