The PTC Index fell to 258 points in September, a notable decline from August’s 294 points, but not an entirely surprising one. Borrowing costs increased significantly during the month, with mortgage rates surpassing seven percent and reaching their highest level in roughly 20 months. Pair that with the start of the Treasure Valley’s traditionally quieter fall season, and September faced some considerable headwinds.
As we head deeper into the fourth quarter, expectations should be tempered by seasonality and the interest-rate environment. The bigger question now is whether September represents the beginning of a more pronounced slowdown or simply the market settling into its typical fall and winter rhythm after an unusually soft summer..
New Home Sales…
After posting a modest rebound in August, new home sales fell 16.5 percent in September compared with the previous month. They were also 10.6 percent below September 2025 levels. Higher mortgage rates did little to help affordability during the month, and with the peak summer buying season now firmly behind us, September’s decline underscores the challenges facing the new-construction market heading into the final quarter of the year.
Existing Home Sales…
The resale market also lost additional ground. Existing home sales declined nearly eight percent from August, marking the fifth consecutive month of month-over-month declines. However, sales were still 16.6 percent higher than September 2025, suggesting that while activity has steadily cooled since spring, the market continues to outperform where it stood at this point last year.
Building Permits…
For the third consecutive month, building permit filings declined, falling 16.7 percent from August. Compared with September 2025, filings were down an even more substantial 35 percent.
Average Treasure Valley Sales Price…
After five consecutive months of month-over-month gains, the average Treasure Valley sales price finally dipped—but just barely. Average sales prices declined a paltry half percent from August. More noteworthy is the year-over-year comparison: the average sales price remained 5.6 percent higher than September 2025.
The PTC Index is a monthly measurement of the vibrancy of the Treasure Valley real estate market. Based on a custom-weighted algorithm, it combines nine critical measurements of the real estate market into a single, useful number: the PTC Index.