PHILADELPHIA | THE LAUREL @ 1911 Walnut | 604 FT | 48 FLOORS

[Jayfar]

Originally Posted by summersm343

They are indeed called caissons:
https://weinsteinconstruction.com/caissons/
https://www.mckinneydrilling.com/solutions/techniques/drilled-shafts-caissons

I stand corrected. I see in the reference I gave they sharply differentiate between Pier Foundation, Caisson and Pile Foundation, but also confusingly "The types of pier foundations are masonry or concrete piers and drilled caissons."

[Marcos]

Originally Posted by GtownFriend

Thanks for the shots. Helps give the depth to things that is hard to guage from the contruction webcam. Also shows how tight this site is.
In particular the last shot shows how far down they are going to underpin the house to the west. Slow and delicate work here.

I'm never 100% sure how this works & what I'm looking at (re: underpinning), it often looks like it's constructed out of horizontal wood beams & I'm wondering if that's just a form? Is there concrete behind it & if not & it's buried as-is how does it not rot & give way, or is it just temporary while the adjacent construction is completed then becomes moot when the soil is compacted back down around it between the foundations? What I'm looking at in these photos looks like part concrete & part wood, a little different?

[hammersklavier]

Underpinning is slow and delicate work. Basically you're trying to pull one over on the buildings next door and switch what they're standing on à la what Indy did in Raiders with the idol and bag of sand. And the deeper the hole, the more underpinning is needed too.

Once the neighboring properties are fully underpinned I rather expect the hole will be fully excavated, caissons installed, and the foundation mat poured before work belowdecks gets going in force. Once the basement levels are fully built up, then the superstructure will start going up. Point being, it'll take a while before this thing pops out of the ground.

[Kfmcshan]

The penthouse hit the market 4 days ago for $25M

[iheartphilly]

Originally Posted by Kfmcshan

The penthouse hit the market 4 days ago for $25M

That's gotta be up there if not more than what Roberts paid for each condo in CTC.

[City Wide]

Originally Posted by hammersklavier

Underpinning is slow and delicate work. Basically you're trying to pull one over on the buildings next door and switch what they're standing on à la what Indy did in Raiders with the idol and bag of sand. And the deeper the hole, the more underpinning is needed too.

Once the neighboring properties are fully underpinned I rather expect the hole will be fully excavated, caissons installed, and the foundation mat poured before work belowdecks gets going in force. Once the basement levels are fully built up, then the superstructure will start going up. Point being, it'll take a while before this thing pops out of the ground.

Since the 'basement' doesn't include parking I doubt that they will have a very big pit to dig. I'll put my $1 on 20' max. If the reinforced piles on the east side are any indication there might not be any basement to speak of.

[kool-ski]

Originally Posted by hammersklavier

Underpinning is slow and delicate work. Basically you're trying to pull one over on the buildings next door and switch what they're standing on à la what Indy did in Raiders with the idol and bag of sand. And the deeper the hole, the more underpinning is needed too.

Once the neighboring properties are fully underpinned I rather expect the hole will be fully excavated, caissons installed, and the foundation mat poured before work belowdecks gets going in force. Once the basement levels are fully built up, then the superstructure will start going up. Point being, it'll take a while before this thing pops out of the ground.

Worst case scenario, hypothetically speaking, if this underpinning is not done, what potential disaster/damages would happen?

[RET48]

Originally Posted by Marcos

I'm never 100% sure how this works & what I'm looking at (re: underpinning), it often looks like it's constructed out of horizontal wood beams & I'm wondering if that's just a form? Is there concrete behind it & if not & it's buried as-is how does it not rot & give way, or is it just temporary while the adjacent construction is completed then becomes moot when the soil is compacted back down around it between the foundations? What I'm looking at in these photos looks like part concrete & part wood, a little different?

I had wondered about that too until I saw retaining-wall installation and removal at a large project across the street from my office. As foundation work began, steel piles were driven into the soil about 4 feet beyond the foundation perimeter. As soil was extracted, timbers were placed between the piles from the top down. The steel and timber retaining wall was secured to the soil by steel rods as needed. After the basement walls were poured and the building's superstructure took shape, the retaining walls were disassembled and removed, and crushed stone was poured in to fill the gap.

[cardeza]

Originally Posted by kool-ski

Worst case scenario, hypothetically speaking, if this underpinning is not done, what potential disaster/damages would happen?

The wood is part of the shoring system that keeps the dirt from caving in on the excavation. Without that, the bearing pressure of the soil adjacent to the hole would cause a landslide. When there is a building next door to the pit, you shouldn't need it if that building is modern and sitting on steel and concrete foundation- but on old rowhouses there are sometimes issues with adjacent construction- likely due to old houses sitting on rubble foundations that are susceptible to deterioration over time due to water or vibration- which is how you end up with old home collapsing next to new construction at times without proper temporary shoring measures taken. The steel beams are the vertical anchors for the lagging that runs horizonatally. Even when doing utility work this becomes necessary once you get below a certain depth. Often they drop in a steel box that can be lifted out once the repair is done.

[jsbrook]

Originally Posted by Kfmcshan

The penthouse hit the market 4 days ago for $25M

Awfully steep for Philly. Around $8 million more than what the 500 Walnut penthouse sold for. But what is the size? That could be the difference. Is it bilevel, full floor?

[Redddog]

Originally Posted by jsbrook

Awfully steep for Philly. Around $8 million more than what the 500 Walnut penthouse sold for. But what is the size? That could be the difference. Is it bilevel, full floor?

gotta be Yuuuuuge.

[allovertown]

Originally Posted by jsbrook

Awfully steep for Philly. Around $8 million more than what the 500 Walnut penthouse sold for. But what is the size? That could be the difference. Is it bilevel, full floor?

500 Walnut is pretty narrow. A full floor, single floor penthouse at the Laurel seems like it would be larger than two full floors at 500 walnut, maybe even considerably so, but not sure where I'd find the numbers to confirm that.

Even if the condos were the same size, being on Rittenhouse is still considerably more attractive to most buyers than Independence square.

[phishtown]

https://www.zillow.com/homedetails/1911-Walnut-St-4801-Philadelphia-PA-19103/2082756498_zpid/

8,666 sq ft!

[iheartphilly]

^^^
New record of over $2800 per square foot. Blows the past record at 500 walnut and the Robert’s condos at CTC out of the water.

[cardeza]

Originally Posted by iheartphilly

^^^
New record of over $2800 per square foot. Blows the past record at 500 walnut and the Robert’s condos at CTC out of the water.

Let's just see if they can sell it. Listing it is one thing- getting a buyer is another.

[Jawnadelphia]

^Wow! I heard Joel Embiid bought one in 500 Walnut.
Has Bryce Harper bought a pad in Philly yet??

How does one become a realtor for big-time properties like this--looking for a career change!?

[iheartphilly]

Originally Posted by cardeza

Let's just see if they can sell it. Listing it is one thing- getting a buyer is another.

True. There's big money around this town and the tony suburbs. And maybe a wealthy executive or investment banker outside of PA. Even if they sell above the $2000 but under the $2800, it's still a new record.

[iheartphilly]

Originally Posted by Jawnadelphia

^Wow! I heard Joel Embiid bought one in 500 Walnut.
Has Bryce Harper bought a pad in Philly yet??

How does one become a realtor for big-time properties like this--looking for a career change!?

Track record to sell high-end properties. These realtors have preferred wealthy client lists that get first dibs on prime real estate and the finances to back it up. Kind of like an club where money talks.

[iamrobk]

Originally Posted by iheartphilly

^^^
New record of over $2800 per square foot. Blows the past record at 500 walnut and the Robert’s condos at CTC out of the water.

Eh, given the scale of that project and the uniqueness of those units, I'm not sure we should look to them for a sense of the market one way or the other. Who knows what their 'true' value is. That said, I am very curious to see what this penthouse ends up going for...

[kool-ski]

Originally Posted by cardeza

The wood is part of the shoring system that keeps the dirt from caving in on the excavation. Without that, the bearing pressure of the soil adjacent to the hole would cause a landslide. When there is a building next door to the pit, you shouldn't need it if that building is modern and sitting on steel and concrete foundation- but on old rowhouses there are sometimes issues with adjacent construction- likely due to old houses sitting on rubble foundations that are susceptible to deterioration over time due to water or vibration- which is how you end up with old home collapsing next to new construction at times without proper temporary shoring measures taken. The steel beams are the vertical anchors for the lagging that runs horizonatally. Even when doing utility work this becomes necessary once you get below a certain depth. Often they drop in a steel box that can be lifted out once the repair is done.

I understand. Thank you for the explanation.