Do you have a clever home construction/engineering solution for my problem?

To clarify a bit, it sounds like. Trying to imagine it to come up with a solution.

( ) (your heating system)
| === | (baseboards/sheetrock/ductwork that presumably connects to something)
______ (platform that needs to be replaced)
===== (some sort of pipe/duct)
______ (concrete immovable slab)

With all that in there, he probably gave you a “I don’t want to mess with it” bid to account for the fact that if me breaks any of that pipe/ductwork he has to replace it and pay for the damage it will cause.

If I were you, I’d look specifically where the duct work meets the next connector. If it’s insulated, you might have to pull the insulation off to find out. It got in there in pieces, so you might be able to remove it in pieces easily. Barring that, I’d take measurements and head to the hardware store to see what kind of connections are available, then probably cut it out with the hopes of putting a piece back in with connectors on each side, then reinsulating. (sawzalls are magic, powerful magic that must be respected)

The baseboards can be pulled off usually with a crowbar. Depending on how successful you are, you may not need to buy new ones.

The sheetrock, I would score with a utility knife and break off at a point above where I will be working (if possible). Maybe 18 inches or two feet above the floor? Basically score it, hammer a hole, and then pull it off in the biggest chunks you can manage. You don’t want to cut it directly with a saw because of the studs/pipes/electrical that are probably behind it. Once you’re done you can cut a sheet to fit and “patch” the bottom 1–2’ of those walls along the line you scored, so spend some time making sure it breaks along that line.

So that leaves the thing that was leaking and sits on the floor you want to replace. I think that really depends on how heavy, how mobile it is while connected, etc. The right way to do it is no doubt to disconnect it, get it out of there, replace the floor, and then put it back in. Sometimes with a friend or a jack, you can raise it, hold it with a crossbeam or something to the walls (you’ll have exposed studs if you remove the sheetrock) and then remove your old floor, slide and position your new floor, and get it all connected.

That’s the thing though, you run the same risk the professional did of breaking something unintended and it ends up costing much more than expected. It’s also a lot of work in a closet that you presumably don’t really have enough room to move around like you’d like to.

Interested to know how it goes and good luck.

Photos?

Yes photos, It sounds like the furnace is “trapped” in the closet. So they have to remove the furnace to get to the old platform. For that price it sounds like the furnace is being replaced.
Did you get an itemized quote? I would get two or three more quotes.

Right. From bottom to top, it’s slab, 3” gap, rotted platform, sheet metal ducting, heating unit, other ducting.

Installing a new unit adds $3,000 and includes a warranty.

@funkdaddy, I see where you’re going. It would be complex since it’s also attached to the refrigerated cooling on the roof, and the refrigerant would have to be drained and refilled. I guess what I’m aiming at is can I somehow replace the platform without moving the system?

Need a picture

Am I understanding right that you want to remove a floor with a load on it, without moving the load?

That sounds like the tablecloth trick would be your only option ;)

just joking around, what am I missing?

They replace huge highway bridge supports without interrupting traffic by building new supports, and then removing the old.

Kind of the tablecloth trick.

When they raised the street level in Chicago, they famously jacked up whole hotels and replaced the foundations without closing for business.

So it’s possible, but of course the question is whether it’s time- and cost-effective.

How is there a 3” gap between the slab and platform?

Are you certain that there’s not damage to the ductwork resting on the rotted platform?

You’re asking one question but raising others that you seem to not want to address, but which the contractor has apparently not ignored.

You said that the platform has rotted because of a leaking water pipe, and you want to replace only that platform.

What about the leaking pipe? Has that already been corrected and / or replaced? What about damaged insulation caused by the leak? Is there any more damage in the closet area behind and beneath the platform, and which you have either not noticed or not cared to look too closely for? Finally, what about the heater itself? It’s not clear to me from your reply up-thread whether the quoted costs include replacement of the heater, too. If they do, then it sounds on its face like it might be a pretty reasonable cost, depending on the replacement heater and the overall quality of the job to be performed, and the time to perform it.

Replacing that 3” platform may be pretty simple: bricks turned on their sides could do that. But you need more than that for a proper job. And depending on the heater and the damage that has already been caused, if it involves combustion and has any kind of corrosion of the combustion chamber, you could put the entire structure at high fire risk, as well as possible / likely CO poisoning for inhabitants. Heaters have to be gotten right.

Something akin to removing and adding support (or a tablecloth trick) is what I am wondering about.

@ibstubro, the plumbing company rep inspected the ducting and said it looks fine.

@CWOTUS, it’s a hydronic system, so there is no combustion. Just hot water in a radiator and an electric blower.

The pipe leak will need to be fixed. The leak is in a pipe that sits halfway up the closet space, but the location of the leak is completely external to the heating system (i.e. exposed and easy to fix without moving any other parts.) Currently, a bucket is catching the drip.

Ripping everything out and replacing with a new system is $7,300. Putting the existing system back is $4,300.

Amazingly, it does not appear that there is noteworthy damage to the surrounding drywall, but I’m sure there is at least a little.

“Right. From bottom to top, it’s slab, 3” gap, rotted platform, sheet metal ducting, heating unit, other ducting.”

How is there a 3” gap between the slab and the platform?
Yeah, we really need a picture if we’re going to be of much help. Honestly, I think we can do this, but verbalizing isn’t detailed enough.

Maybe start here and find one similar if you can’t post pix of yours?

If you post a pic this will probably be easy

Possibly, @ARE_you_kidding_me.

Well, I found an awesome plumber who did it. He suspended the heating unit with straps and removed the plenum (the ductwork I refer to above), which gave him 16 inches of elbow room to knock out the old OSB (oriented strand board) platform. Then he did a bang up job putting in new board, fixing the leak and restoring everything. Saved me at least $3,300 vs my previous estimate. I was happy to say the least.

Thanks for giving us the outcome, @kevbo