When I bought my third rental property nine years ago, the wood-frame apartment building I was looking at showed a cap rate of 8.9%, while a steel-frame building two blocks away, same neighborhood, similar rent roll, showed 6.4%. That 2.5-point gap looked like free money at first glance. It took me two vacancy cycles and one very expensive roof repair to understand why the market prices them so differently, and which one actually made me more money over time.
I now own 9 properties across both structure types, so this is not a theory exercise for me. Here is what I have learned about reading cap rates on wood-frame versus steel-frame buildings, and where the headline number can mislead you.
What Cap Rate Actually Tells You (and What It Hides)
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Cap rate is just net operating income divided by purchase price, so on paper a higher number always looks better. The problem is that cap rate says nothing about how much of that net operating income you will actually get to keep once you account for the building’s remaining useful life. A wood-frame building depreciates over roughly 22 years for tax and lending purposes in Japan, while steel-frame runs closer to 34 years. That difference shapes financing terms, resale value, and how conservative you need to be about the capital reserve you set aside every month.
I also learned to check whether a listed cap rate is calculated on gross rent or on rent after a realistic vacancy allowance. Two agents showed me nearly identical wood-frame listings last year, one quoting 9.1% and one quoting 7.8%, and the only difference was that the higher number assumed zero vacancy across 12 months. Once I ran both at my own historical vacancy rate of about 6%, the gap almost disappeared.
Why Wood-Frame Buildings Post Higher Cap Rates
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Wood-frame buildings are cheaper to construct, so purchase prices are lower relative to rent, which pushes the cap rate up. On my two wood-frame fourplexes, average purchase price per unit was around 6.8 million yen versus 11.2 million yen per unit on my steel-frame buildings. Lenders also treat wood-frame as higher risk once the structure passes 20 years old, so loan terms shorten and interest rates creep up by 0.3 to 0.5 percentage points in my experience, which investors price into the purchase by demanding a fatter cap rate up front.
Where Steel-Frame Earns Its Keep
Steel-frame buildings cost more to buy, but they hold rent levels better over a 20 to 30 year horizon because tenants perceive them as sturdier and quieter. My steel-frame six-unit building has kept average monthly rent within 4% of its original asking rent for 11 years running, while a comparable wood-frame unit I own has dropped rent twice, a total of 9%, just to stay competitive against newer builds nearby. Steel-frame also qualifies for longer bank loans, sometimes 35 years, which lowers monthly debt service and can make the actual cash-on-cash return closer to the wood-frame number than the raw cap rate suggests.
Running the Numbers on Two of My Own Buildings
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Here is a simplified side-by-side from my own portfolio, both bought within an 18-month window:
- Wood-frame fourplex: purchase price 27.2 million yen, cap rate 8.9%, annual maintenance reserve I budget at 3.5% of rent roll
- Steel-frame sixplex: purchase price 67.5 million yen, cap rate 6.4%, annual maintenance reserve budgeted at 2% of rent roll
- Wood-frame roof and exterior repaint at year 15: 2.1 million yen out of pocket
- Steel-frame exterior repaint at year 15: 1.4 million yen, no structural work needed
- Effective 10-year average yield after maintenance and vacancy: wood-frame 7.1%, steel-frame 6.0%
The wood-frame building still won on raw return, but the gap narrowed from 2.5 points to about 1.1 points once real repair costs and two extra weeks of average vacancy per turnover were factored in.
Maintenance Costs I Did Not Expect Going In
The line item that surprised me most was termite and moisture inspection. On wood-frame buildings I now budget for a professional inspection every 5 years at roughly 80,000 yen per building, and I have had to treat active termite damage twice in nine years at a combined cost of about 650,000 yen. Steel-frame buildings do not carry that risk, but they come with their own surprise: rust at weld joints and balcony railings, which showed up on one of my buildings at year 12 and cost 480,000 yen to address properly. Neither structure type is maintenance-free, they just fail in different places on different timelines, and your cap rate assumptions should build in a repair curve, not just year-one numbers.
My Rule of Thumb When Comparing Listings
When I am evaluating a new listing now, I discount a wood-frame cap rate by roughly 1 to 1.5 percentage points to make it comparable to a steel-frame listing, to account for the shorter loan term, faster rent decay, and higher probability of a mid-life structural repair. If a wood-frame building is only offering a 7% cap rate against a steel-frame building at 6.5%, I usually pass on the wood-frame deal unless the location or tenant demand is clearly stronger. The headline cap rate is a starting point for negotiation, not a final answer about which building will make you more money by the time you sell it.
That is the framework I use every time I look at a new deal across all 9 of my properties, and it has saved me from a couple of purchases I would have regretted by year 10. I would rather close on a building with a slightly lower cap rate and a repair history I understand than chase the highest number on the listing sheet.
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