Punching 300 window openings in a post-tensioned slab building

The unit mix answer I've seen most often isn't light wells at all, it's just accepting a lot of studios and turning the dark middle into storage, laundry and mail. But that only works if your rent per foot on a small unit is high enough to carry the wasted core. In a $1.80 a foot market a 500 sf studio is $900 and you've spent conversion money to build a closet with a bed in it. Does your submarket support studio pricing that runs above your one-bedroom on a per-foot basis? That's the number I'd want before arguing about tendons.

Your structural guy gave you $18 to $24 and you called it the structural scope alone. That's the number that grows. Every penetration you scan and then have to move six inches drags MEP coordination with it, and the drywall and fireproofing patch behind it never shows up in the original line item.

I'd also push on the light well idea for a different reason. Cutting a court through 11 floors takes leasable area out of every single floor, not just the ones with dark units. You're paying $20 a foot to remove revenue. Run the version where you keep the plate whole, eat the deep units, and spend the same money on unit finishes and amenity instead. Sometimes the dumb plan wins on paper.

What's your floor to floor? If it's 12 feet you have room to drop new drain lines in a ceiling and the deep units get easier. Under 11 and the depth problem becomes a ceiling height problem too.

Numbers first. 6,700 leasable on 22,000 gross is a 30 percent efficiency. Ground-up multifamily lands somewhere around 80 to 85. So your $270 comparison is meaningless until you restate it per leasable foot. If your conversion is $200 a gross foot at 30 percent efficiency you're at roughly $660 a leasable foot, and ground-up at $270 gross and 82 percent is about $330. That gap is enormous and no amount of structural cleverness closes it.

So either the 8,500 sf core number is wrong, or you're not counting corridor-adjacent area you can actually rent, or the deal only works because acquisition is close to free.

Which is it? I'd want the core broken down. Elevators, stairs and shafts you keep. Old telecom rooms, oversized electrical closets and a lobby sized for a 1978 tenant roster you might reclaim. I've seen 8,500 turn into 5,200 with a real space audit, and 3,300 sf a floor across 11 floors is the whole deal.

The other thing I'd stress test is what happens to your absorption if 40 percent of units are dark studios. Girder, your renewal worry is the right one, but it shows up in your model as a turnover cost and a concession line, not as a vibe. Model 55 percent renewal instead of 70 and see if the deal still clears.