Flooring – Patches of drywall mud on subfloor. Do I need to remove before installing flooring

Prescriptive nailing schedules are part and parcel of flooring or wall exteriors. In both above grade situations, the goal is to create a unitized structure. Wall panels properly attached become stressed members that resist lateral racking forces.

In the basement, over a poured concrete slab, no structure enhancement is necessary. Therefore any fastening that produces a secure, trip free (smooth)surface is the goal.

It somewhat depends on what the final surface will be. Floating laminate floors would work over floated ply. Heavy cabinets or a workshop might work better over a more secured surface.

One comment on the advice you read is that I don't see a thing in there about deflection - evidently Mike Holmes is sure that if he merely has 1-1/4" of subfloor, all is good. Real tile specs tend to involve a concept called deflection, and that's the distance part of the floor system moves when loaded, relative to the span you measure over. L/360 is a typical spec - L/180 is twice as bad. (It's usually a lowercase L, but on the computer I'm using a capital to be clear that it's an L.) I happen to have a 3/4" subfloor that's L/587, so it really doesn't need another half-inch on that basis.

Consider what a tile manufacturer has to say... (I'm not going to cut and paste their extensive text here, or rewrite it all) but for one thing they specifically mention setting the backer board in a mortar bed, not "gluing" it down. I'd also venture to sneak in that if you really want "the best" (and will you pay for it these days) look at the "old fashoned mortar bed" (TCNA (Method F145-02)) mentioned at the end of their article. That, of course, means you need to establish an adequately rigid base 3/4" or 1-1/4" + tile thickness below the surrounding floor level, which is why it's not popular these days. But it was a VERY good method, as a lot of old houses demonstrate.

Kinsman Tile