Galvanized RePipe- Tight Squeeze on Risers.

Progressing on re pipe of 1943 two fam... this is why I need PEX as opposed to copper for the risers. It is starting to get a little scarey. Check out stack in first pick. Very tight squeeze in there..... what to do about heating ducts???

From what I can see, sweating copper risers should not be an impossible job. Certainly care would have to be taken to protect against fire by having a spray bottle of water within reach and flame guards to keep flame away from the joists. Guess you might have figured out that I'm not fan of PEX.

I hope you do not think you can make a "square corner" by bending the PEX.

Nothing says you have to follow the route of the old pipes.

Although not a pro, I'm not a fan of PEX either.

One thing to consider -- even though fewer joints is less to go wrong, you can always prefabricate sections before installation to get the in-place joints where you want them. For example, if you can get the riser out by undoing the union (background pipe in second picture) then you can get a copper section in just like it...

Also, they make those fabric heat shields. If you can't afford that, even a couple layers of aluminum foil behind the joint can help some, with the added benefit that it will warn you by a noisy crinkling sound and melting just before the wood catches on fire. Have a good bucket of water and extinguisher handy.

I have had good result soldering in tight quarters using a opened and flattened #10 can. Usually I cut a notch on one edge so I can slip it around a pipe and bend it a bit to get better coverage when needed. Not as fancy as the story bought fabric heat shield, but works fine.