The Hidden Costs of Each Path
🏗️ Extending
- • Construction quote
- • Planning & architect fees
- • Contingency (10-20% overrun)
- • Temporary accommodation
- • Disruption to daily life
- • Value added to property (varies)
🚚 Moving
- • Agent fees (2-6% of sale price)
- • Legal/conveyancing fees
- • Stamp duty / transfer taxes
- • Moving costs
- • New mortgage arrangement fees
- • Higher mortgage (if trading up)
Transaction Costs: The Moving Tax
The biggest surprise for people considering a move is the sheer scale of transaction costs. Selling your current home and buying a new one typically costs 5-10% of the home value in fees, taxes, and related expenses.
On a $400,000 home, that's $20,000-$40,000 in transaction costs alone — money that buys no additional square footage, no improvements, and no equity. It simply evaporates in the process of moving. This "moving tax" is often larger than the contingency budget for an extension.
Cost Per Square Foot: The Equalizer
The most useful metric for comparing extend vs. move is cost per additional square foot. This normalizes the comparison:
Extension cost per sqft
(Construction + Architect + Contingency + Temp Accommodation) ÷ Extension Square Footage
Moving cost per sqft
(Price Difference + Transaction Costs + Moving Costs) ÷ Additional Square Footage Gained
When adding transaction costs to the price premium of a larger home, the moving cost per square foot is often 2-3x the extension cost per square foot. This is why extensions frequently come out ahead in purely financial terms.
The Mortgage Impact
Moving to a more expensive home typically means a larger mortgage. The monthly payment increase needs to be considered over the life of the loan. An additional $100,000 in mortgage at 5% over 25 years costs roughly $585/month — or $175,500 in total payments.
An extension might be financed through a remortgage or home improvement loan, but the borrowed amount is usually smaller (since you're only paying for the construction, not buying an entire new property). This difference in ongoing monthly costs is a major factor in the long-term comparison.
When Moving Makes Sense Anyway
Despite the financial case for extending, there are scenarios where moving is the better choice:
- • You need to change location (schools, commute, lifestyle)
- • Your home's layout can't accommodate what you need (e.g., need more bedrooms, not just more space)
- • Planning permission is unlikely for the extension you want
- • The extension cost per sqft exceeds the local purchase price per sqft (diminishing returns)
- • You can't tolerate the disruption of living in a construction zone
Compare Your Options
Our Extend vs. Move calculator compares total costs, cost-per-square-foot, mortgage impact, and uses a weighted scoring system covering financial, space, lifestyle, and disruption factors.
Try Extend vs. Move