Getting ready to cut a cast iron vent stack to put in a new vent, now I know
that I must support the weight of the stack and brace it from side movement
I will be renting one of those chain type tools for snapping the pipe. I am
concerned since I never did this, what is going to happen since the weight
of the stack is still there all though supported from dropping how is it
going react, I really dont want this pipe to crack the wrong way. Any one
who has done this and can let me know what to expect would be appreciated.
I'm with Joe on this. And it can be risky.
Whatever the weight/height, you need to "preload"
the support system so that when the cut is made,
the stack doesn't drop at all. That's especially
critical in the case where there are connections
above where you are cutting (likely) since movement
of any joints (or the roof terminal) will lead to failures later.
5" diameter pipe, about 10' above cut no branches to roof, supported by
using existing framing and building a clamping device off of the framing
about two and three feet above the cut (hub about three feet above cut), and
about 15' below cut to concrete floor several branches comming off.(tub,
That will be 4" trade size pipe.
Probably looking at around 100 Lbs weight above you.
Wedge a brace at an angle under the support you have
so you can pretension it. You will need to lift that
weight in any event after you make the cut.
If the current framing doesn't support the lower
part of the stack from moving sideways, nail some
blocking down to keep it from shifting.
When the job is done, keep an eye out for roof leaks
where the penetration is.
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