Me, I hope never to see the underside of a sink ever again.

I have heard comments that homes in TX or GA need a major rehab after 10 years, builders use MDF for trim, pressboard under siding instead of OSB sheeting etc As an investor we buy 1960s homes, they have good bones and are worth an update.

A "sure repair" may require removing ceiling drywall and locating the leak on the underside of the roof sheathing.

The home has been occupied by tenants for the last several years.I would plan to have the underside of the roof painted in the attic to cover up the black coloring.

They accused me of being a bad landlord and that they were treated as "lowest on the totem pole" When I asked for an example they cited the dishwasher steam getting on the underside of the formica!!!!

I'm not a plumber, but trying to seal a leak at the bottom (underside) of the sink is a losing battle.

One suggested using spray foam on the underside of the attic walls (roof) and the other suggested blowing in cellulose over the floorboards of the attic.

The entire under side was gone both times.

This is taken from the height of the existing grade in the front yard to the underside of the first-floor joist. 

N1102.2.8 (R402.2.8) Floors Floor framing-cavity insulation shall be installed to maintain permanent contact with the underside of the subfloor decking.