ARM Caps

Adjustable rate mortgages (ARMs) come with built-in protections called caps that limit how much your interest rate and payment can change. Understanding these caps helps you assess the risk of an ARM and plan for potential payment changes. While ARMs can offer lower initial rates, the caps ensure payments don't increase without limit.

Types of ARM Caps

ARMs have several types of caps that protect borrowers. Periodic caps limit how much the rate can change at each adjustment period. For example, a 2/6 ARM might have a 2% periodic cap, meaning the rate can increase no more than 2% at each adjustment. This prevents dramatic payment jumps from one period to the next.

Lifetime caps limit how much the rate can increase over the life of the loan. Typically, lifetime caps are around 5-6% above the initial rate. If your initial rate is 4%, a 5% lifetime cap means your rate can never exceed 9%. This provides certainty about maximum rate and payment levels.

Adjustment Periods

The adjustment period determines how often your rate can change. Common adjustment periods include 1-year ARMs (rate adjusts annually), 3-year ARMs (rate adjusts every 3 years), 5-year ARMs (rate adjusts every 5 years), and 7/10 ARMs (fixed for 7 years, then adjusts annually). Longer initial fixed periods provide more payment stability but come with slightly higher initial rates.

More frequent adjustments mean more uncertainty about future payments but potentially more benefit from falling rates. Less frequent adjustments provide stability but may lag behind market changes. Consider how long you plan to keep the loan when choosing an adjustment period.

Index and Margin

ARM rates are determined by adding a margin to an index. Common indexes include the London Interbank Offered Rate (LIBOR), the Constant Maturity Treasury (CMT) rate, and the Prime Rate. The margin is set by the lender and doesn't change—for example, your margin might be 2.75% regardless of index movements.

When your ARM adjusts, your new rate equals the current index value plus your margin. If the index is 3% and your margin is 2.75%, your new rate would be 5.75%. Understanding which index your ARM uses and its historical behavior helps you predict potential rate changes.

Payment Caps

Some ARMs have payment caps that limit how much your monthly payment can change, even if the rate changes more. These caps prevent payment shock but can result in negative amortization—when payments don't cover interest, the unpaid interest gets added to your balance. This can cause your loan balance to grow rather than shrink.

Payment-capped ARMs may have recasting periods where the payment is recalculated to fully amortize the loan. This can result in significantly higher payments later. Understand how payment caps work and whether negative amortization is possible before choosing this type of ARM.

Planning for ARM Changes

If you have an ARM, plan for potential payment changes. Budget for the maximum possible payment based on lifetime caps. Understand what happens when your ARM adjusts—contact your servicer before adjustment periods to understand upcoming changes. Consider whether you'll have options to refinance before adjustments if rates rise significantly.

Keep an eye on market conditions and index values. If rates have risen significantly, you might want to explore refinancing into a fixed-rate loan. Some borrowers prefer to sell or refinance before the first adjustment to avoid uncertain payments. Understanding your ARM's terms helps you make informed decisions.