[ilyt]

>Those systems must be new. The classic solution is to install drain pipes before pouring the slab, so one can imagine how difficult it would be using 1980's construction techniques to retroactively add piping below a finished house.

They didn't had diggers and drills in the 80's ?

[iudqnolq]

It's easy to make a hole. Making a hole underground without making a hole aboveground is harder.

[hinkley]

For instance, the first subway systems in London were installed via cut and cover. Dig a trench, build a roof. Usually those trenches were in the street, or a former canal, not under a building.

Using modern tunnel boring equipment, Seattle's attempt to move the downtown section of 99 into a tunnel ended up stalled for a year because the ground shifted and pinched the boring machine in place. Oopsie.

And of course if you're worried about gasses, puncturing a solid piece of concrete is just going to make that problem worse.