3. How Treasury yields reach the housing market

Official sources checked September 6, 2026. Unless stated otherwise, numbers and scenarios are hypothetical, not current rates or product returns.

The same house and loan amount can become affordable or unaffordable when the interest rate changes. That is why Treasury yields appear so often in housing coverage. But the ten-year Treasury yield is not the mortgage rate.

What two percentage points do to a payment

Take a hypothetical $300,000, thirty-year fixed-rate mortgage with equal monthly payments. Exclude property taxes, insurance, and fees; calculate principal and interest only.

The same principal costs about $367 more each month. The formula is principal × monthly rate / (1 − (1 + monthly rate)^(-number of months)). It translates a market-rate discussion into a household budget.

An existing 4% fixed-rate contract does not automatically become a 6% contract when market rates rise. New borrowers, floating-rate borrowers, and existing fixed-rate borrowers face different changes.

What sits between Treasuries and mortgages?

Research published by the Boston Fed examines differences in cash flows, guarantees and intermediation costs, and borrowers’ prepayment option. The mortgage–Treasury spread is therefore not constant.¹

When rates fall, refinancing can return principal to mortgage-backed securities investors earlier than expected. When rates rise, refinancing may slow, leaving those investors with lower coupons for longer. This asymmetry helps explain why MBS cannot be treated like otherwise identical long Treasuries.¹

Also distinguish owning a rental building, buying a REIT’s shares, and investing in mortgage payments. Investor.gov describes REITs that own or finance real estate. A REIT holding should not be mistaken for a bond contract promising repayment of face value at maturity.²

Higher rates do not mechanically produce lower home prices

An owner with a cheap fixed mortgage may avoid moving if a new mortgage would be much more expensive. Freddie Mac analyzes this mortgage-rate lock-in effect.³

Weaker demand can therefore coincide with fewer homes offered for sale. Transaction volumes and prices may respond differently. Local incomes, construction, and migration matter as well.

Applying the example to Korean property requires checking the actual loan contract: fixed, floating, or mixed rates; reset dates; maturity; and repayment structure. A U.S. thirty-year fixed mortgage is an illustration of transmission, not a universal template.

Separate rental income from financing costs

Suppose a building generates annual net operating income of KRW 50 million. Here that means income after operating expenses but before financing costs and the owner’s income tax. Holding that income constant gives this simplified capitalization calculation:

This is an illustration, not an appraisal or transaction forecast. A one-percentage-point Treasury move does not force an equal capitalization-rate move. Rental growth expectations and property-specific risk compensation differ.

Now assume debt of KRW 600 million refinances from 4% to 6%. Simple annual interest rises from KRW 24 million to KRW 36 million. Operating income less interest falls from KRW 26 million to KRW 14 million. Principal repayments and major capital works would reduce available cash further.

Why this belongs in a bond plan

Adding long bonds beside a property does not automatically diversify every risk. Persistently high long rates could hurt long-bond prices and refinancing conditions together. In a severe slowdown, Treasuries might help while rents or occupancy deteriorate. These are scenarios, not fixed correlations.

Freddie Mac’s PMMS is a starting point for U.S. mortgage-rate data. A survey rate is not your personal loan quote; retain the observation date and survey conditions.⁴ Add your property’s next rate reset and refinancing date to the same calendar as your bond maturities. Those dates can be more useful than another rate headline.

Read the series

1. Why a Treasury investment can lose money
2. Why long yields can rise when the Fed cuts
3. How Treasury yields reach the housing market
4. What to read before buying a Treasury
5. Choosing between bond ETFs, TIPS, and currency exposure
6. Build the bond plan before the rate forecast

Footnotes

1. Paul S. Willen · Federal Reserve Bank of Boston, Why Mortgage Rates Exceed Treasury Yields. Accessed September 6, 2026. ↩ ↩²

2. U.S. Securities and Exchange Commission · Investor.gov, Real Estate Investment Trusts (REITs). Accessed September 6, 2026. ↩

3. Freddie Mac, Mortgage Rate Lock-In and the Housing Market. Accessed September 6, 2026. ↩

4. Freddie Mac, Primary Mortgage Market Survey. Accessed September 6, 2026. ↩