Some membranes fail quickly within 5 to 10 years.

Spent $70,000 replacing a full roof (took everything off and all new joists, plywood, membrane, etc), building out a one bedroom one bath apartment with a full kitchen.

To be safe with anything except a fairly new house, you’d really need to excavate around the house, parge the outside of the foundation with an asphalt/tar product, install a dimpled plastic membrane over that, and then on the inside, fastidiously install rigid foam on the floor and walls, spray foam/tape all seams, etc… Then frame, then drywall.Seems ungodly expensive.

Often times a good (not acrylic) liquid applied membrane can salvage a flat roof and even have a warranty of up to 20 years included.

Due to the wood subfloor, the bathroom floors have a little give to them and one of the small tiles is cracked. not a big enough deal to replace (2 inch tile) but knowing how difficult it is to stabilize old wood floors with the seasonal temperature/humidity changes in our area...we'll be doing allure in the future.Thats one reason to install a crack isolation membrane before tiling.