I just finished an ICF foundation for an addition that is tied to an old but solid brick foundation of a 1923 home. I do not know how o waterproof the cold joint where the ICF meets the brick. Any thoughts? And should I use a flexible or rigid weeping tile pipe? Thanks everyone.

I would use a good concrete caulk or sealant, troweling it on the irregular joint, let it cure and then cover with a patch of whatever waterproofing membrane you used over the ICF.

I like rigid "triple wall" footing drains because it is hard to get the flexible stuff straight and level. I have also excavated drains with the single wall flexible pipe that are collapsed.