What diameter threaded rod to brace crotch of tree with two 12″ codominant stems

I had similar concerns with my home purchase in the U.S. about 7 years ago. It was noted on my home inspection that A tree had been recently removed (long enough ago for grass to re-grow over the area but there was still a depression) from the front yard where the main lines go.

I had a plumber run a scope down the lines starting at a basement cleanout/drain and inspect the lines all the way to the street to determine if there is any current damage from roots (or anything else). Cost me an extra $125 but most of that was simply the service call fee (compared to the estimated 10K repairs would have cost, I was happy to pay it).

Of course, this only checks for existing damage. There is the slimmest of chances that a tree root could be just on the verge of busting through which would have been undetectable but in my case where the tree had already been removed that chance is diminished since tree roots eventually stop growing after the tree is removed. In your case (with live trees), it would be a higher chance but still unlikely and there really isn't anything else you could do to prevent it that would be cost effective.

I would have to agree with Ed, with the added suggestion that a SawzAll might be used on the fencing if nails are an issue, or if you don't have a chain saw. The smaller size might also work better if the clearances between objects that are being cut are such that a chain saw might be unwieldy.

But, yeah, chain saw rules otherwise.

Be safe, Bill