A buyer who saw "Castro Valley sales down sharply" this month and wrote an offer at asking price would probably have lost the house. According to the Bay East Association of REALTORS September 2026 report for Castro Valley detached homes, buyers paid an average of 105% of list price in September, and homes went under contract in about 24 days on average. A year earlier, in September 2025, the sale-to-list ratio was 100% and average days on market was 33.
The headline figures say the market went quiet. Sales fell 31.8%, from 44 homes in September 2025 to 30 in September 2026, and the median sale price slipped 4.64% to $1,154,250. Bay East's October 2026 video market update listed Castro Valley with Alameda, Newark and San Lorenzo as the 880-corridor communities with "big drops" in sales.
Both numbers are accurate. Neither one shows a market where buyers have gained leverage. Last fall was an unusually busy stretch to measure against, and the mix of homes closing this year has changed. Once you account for both, Castro Valley in September 2026 looks tighter at the offer table than it did a year ago.
The offer math, three Septembers side by side
Bay East's report covers three Septembers, and the middle one is the outlier.
| Castro Valley detached homes | Sept. 2024 | Sept. 2025 | Sept. 2026 |
|---|---|---|---|
| Homes sold | 25 | 44 | 30 |
| Median sale price | $1,185,000 | $1,210,444 | $1,154,250 |
| Average days on market | 20 | 33 | 24 |
| Sale price to list price | 104% | 100% | 105% |
September 2025's 44 sales were up 76% from September 2024. That month was also the softest of the three for sellers. Homes took longer to sell, and buyers paid list price on average with no premium. A comparison against that month makes 2026 look like a collapse in volume. This September actually closed more sales than September 2024, and bidding was a little stronger than in either earlier year.
The year-to-date totals tell the same story. Through September, 258 detached homes sold in Castro Valley in 2026, compared with 297 in 2025, 224 in 2024 and 242 in 2023. That is about 13% below last year and above the two years before it. A 32% monthly drop is real arithmetic, but it measures how strong the 2025 baseline was more than it measures any weakening this year.
Supply held steady while sales fell
At the end of September 2026, 41 detached homes were actively listed in Castro Valley. September 2025 ended with the same count, 41. Fewer sales on the same inventory raised months of supply from 1.0 to about 1.3. Even at 1.3 months, a buyer still has very few choices at any given moment.
Sellers didn't change their asking prices. The average list price of homes that sold in September was $1,209,747, down 0.01% from September 2025. List prices stayed flat, and the share buyers paid above them rose by about five points. In 2026, that premium arrives sooner after listing than it did a year ago.
Every month of 2026 in the Bay East table shows an average sale-to-list ratio between 102% and 108%. No month this year averaged at or below list price.
The median fell while price per square foot rose
The September median dropped 4.64%. Over the same period, the average sold price per square foot rose from $670 to $707, about 5.5%. Those two measures moving in opposite directions suggest the set of homes that closed in September differed from last year's, rather than a broad drop in what comparable homes bring.
The year-to-date price bands show a modest shift away from the upper middle of the market:
- Under $800,000: 25 sales in 2026, up from 13 in 2025
- $800,000 to $999,999: 47, down from 70
- $1 million to $1.299 million: 77, down from 80
- $1.3 million to $1.699 million: 76, down from 98
- $1.7 million to $1.999 million: 26, up from 23
- $2 million and above: 7, down from 13
The $1.3 million to $1.699 million band lost the most sales of any group, 22 homes year over year. The band under $800,000 nearly doubled. Average sale price fell only 1.97% in September, less than half the median's decline. By average sold price per square foot, Castro Valley's September 2026 sales came in higher than September 2025's.
Higher rates thin out both sides of the deal
Mortgage rates help explain why fewer homes changed hands without any slack showing up at the offer table. Freddie Mac's Primary Mortgage Market Survey put the national 30-year fixed average at 7.40% as of October 8, 2026, up from 6.30% at the same point a year earlier. On a Castro Valley price, more than a full percentage point changes the monthly payment enough to push some buyers into a lower price band. That fits the drop in the $1.3 million to $1.699 million range.
Rates also affect sellers. In a September 23, 2026 speech on housing, Federal Reserve Governor Michael Barr said that "about half of all mortgages still carry rates of 4 percent or lower, and nearly 80 percent have a rate below 6 percent." He said this lock-in effect "reduces both demand and supply," and that "in tight housing markets, the lock-in effect can raise home prices because the reduction in housing supply associated with fewer homeowners selling can outweigh the corresponding reduction in demand."
Castro Valley's September fits that description. Sales fell, inventory held at 41, and the buyers who stayed bid against each other with no more homes to choose from. Fewer transactions happen, and each one is still competitive.
What October's numbers are likely to show
October will probably look weak in the year-over-year headlines too. At the end of September 2026, Castro Valley had 22 pending sales, compared with 33 a year earlier. Pending sales usually close in the following weeks. October 2025 also had 49 closed sales, the highest monthly count in Bay East's 13-month table. When October 2026 is compared against that, another large percentage drop is likely regardless of how competitive the month actually is. For sellers and buyers, the numbers to watch are sale-to-list ratio and days on market, not the sales count.
A few cautions apply to all of these figures. A month with about 30 sales is a small sample, and a handful of unusual homes can move the median a lot. Data publishers also differ. Another Alameda County data series agrees with Bay East on September 2025's 44 sales and $1,210,444 median, but it reports 60 days on market and a 102.6% sale-to-list ratio for that month, compared with Bay East's 33 days and 100%. The same series shows August 2026 at a $1,250,000 median, up 3.3% year over year, on 30 sales, which was also down 31.8%. The two sources agree on direction: fewer sales and steady or rising pricing per home.
FAQ
Is now a good time to make a below-asking offer in Castro Valley? The September 2026 data doesn't support it as a general strategy. Buyers paid an average of 105% of list price that month, and no month in 2026 averaged below 102%. Individual homes vary. A home that has been listed well past the roughly 24-day average is a different negotiation.
Did Castro Valley home values go down this year? The median sale price for September 2026 was 4.64% below September 2025. The average price per square foot was about 5.5% higher. When the two measures move in opposite directions, it points to a change in which homes sold rather than a broad decline in value.
Why are fewer homes selling if buyers are still competing? Higher borrowing costs reduce both the number of owners willing to sell and the number of buyers who can afford a given price, as Governor Barr described in his September 2026 speech. Castro Valley's inventory stayed flat while sales fell. That points to a smaller market overall, not a weaker one.
For a Castro Valley seller, list price is only part of the pricing question. The other part is which band your home competes in, and how buyers in that band have behaved since rates rose. The Kristy Peixoto Team reads each month's Bay East figures one price range at a time, so your list price reflects what comparable square footage is actually bringing this fall. Schedule Your White-Glove Consultation.
