Finance⏱ 5 min read
How to Calculate the Rebuild Cost for Buildings Insurance
Buildings insurance should cover the rebuild cost — not the market value. Most homes are either over- or under-insured because people confuse these two very different numbers.
Insuring your home for its market value is almost certainly wrong. Market value includes land and location premium — which can't burn down. Buildings insurance should cover only the rebuild cost.
Market Value vs Rebuild Cost
Market value = Rebuild cost + Land value + Location premium
In an expensive area:
Market value: £600,000
Land value: £250,000
Rebuild cost: £350,000
If insured at market value (£600,000):
Overpaying on premium by ~71%
If insured at rebuild cost (£350,000):
Premium is appropriate — land cannot burn down or flood
In a cheap area:
Market value: £150,000
Rebuild cost: £200,000 (labour, materials, planning)
If insured at market value: UNDERINSURED by £50,000
Estimating Rebuild Cost: BCIS Calculator
The Building Cost Information Service (BCIS) House Rebuilding
Cost Calculator (free at abi.org.uk) is the standard method.
Inputs required:
- Property type (detached, semi, terraced, flat)
- Number of bedrooms
- Gross external floor area (if known)
- Location (affects labour costs)
Approximate rebuild costs by property type (2024, England):
1-bed flat: £130,000-£180,000
2-bed terraced: £170,000-£250,000
3-bed semi-detached: £220,000-£320,000
4-bed detached: £300,000-£500,000
5-bed detached: £420,000-£700,000+
Rebuild cost per m2: approximately £1,800-£2,800 for standard spec
Premium finish: £2,800-£4,000+/m2
What Buildings Insurance Covers
Standard buildings insurance should include:
- Structural rebuild: walls, roof, foundations
- Fixtures: bathroom suites, fitted kitchen, built-in wardrobes
- Outbuildings: garage, garden walls, fences (check limits)
- Service pipes and cables within property boundary
- Demolition and debris removal (often adds 10-15% to rebuild cost)
- Professional fees: architect, surveyor (add ~15% to rebuild)
Total sum insured should account for:
Rebuild cost + demolition (10%) + professional fees (15%)
= Rebuild cost x 1.25 approximately
If rebuild cost £300,000:
Buildings insurance sum insured: £300,000 x 1.25 = £375,000
The Underinsurance Problem
If a claim is submitted and the property is underinsured,
insurers apply the "average clause":
Claim paid = Actual loss x (Sum insured / True rebuild cost)
Example: £80,000 kitchen fire damage
True rebuild cost: £400,000
Sum insured: £240,000 (60% of rebuild cost)
Claim paid: £80,000 x (240,000/400,000) = £80,000 x 0.6 = £48,000
The insurer pays only 60% of the claim — despite an apparently
adequate £80,000 loss vs £240,000 coverage.
This is a poorly understood provision that leaves many
homeowners significantly out of pocket after major claims.