Combination mortgage: How does the combination of different mortgage types work?

Staggering the maturities is central. Instead of choosing a single large fixed-rate mortgage, several tranches with different end dates are created. When one tranche matures, it can be renewed at the then-current conditions without the entire financing being affected at once. This spreads interest-rate risk over time. At the same time, amortization can be deliberately assigned to a specific tranche, usually the more expensive or riskier part. Reducing a second mortgage more quickly improves loan-to-value and affordability metrics and creates room for future negotiations.

The combination requires clear rules in the contract. Important are the margin per tranche, the length of the interest periods for the SARON tranche, any switching rights into a fixed-rate mortgage, and the possibilities for prepayments, especially at the end of a fixed term. Coordination of the maturities also matters. If several tranches mature on the same day, the desired risk diversification can be lost. It makes sense to schedule maturities so that decisions are staggered and the market does not determine the entire financing on a single date.

Costs and benefits should be tested with simple scenarios. If interest rates rise sharply, the fixed tranche provides protection, while the SARON part becomes noticeably more expensive. If rates fall, the fixed tranche remains stable and the SARON part benefits. The right allocation depends on income, liquidity reserves, planning horizon and personal risk tolerance. Those who want to avoid every fluctuation will choose a higher fixed portion. Those with reserves who can take advantage of interest opportunities will allocate more to the money-market–based part.

In practice, the added value of independent advice becomes apparent. Brokers and intermediaries with a market overview compare offers from banks, insurers and pension funds, negotiate margins and clauses, and ensure that tranches, maturities and the amortization schedule fit together. Especially in sale scenarios, planned renovations or uncertain timelines, a combination structure helps avoid being forced into decisions while keeping affordability stable.

In the end, the combination mortgage is a toolbox. Properly assembled, it combines stability with room to act and makes the financing more robust across different interest-rate environments. The decisive point is not to leave the mix static, but to review at each renewal whether the allocation, maturities and repayment still fit your life plans, the property and the market.