A few flooring questions.

Hello all.

I'm wanting to lay a new floor in my front room. The current sub-floor is 22mm T&G chipboard flooring, the floor seems flat and is currently creak free so I'm loathed to pull the whole thing up.

The floor I've settled on is engineer wood T&G.

Right in the doorway there is a lintel which protrudes about 9mm, it always made quite a pronounced line in the old carpet.

I'm considering overboarding the chipboard with some 9mm plywood, so it sorts out the lintel level problem and also tidies up the subfloor (it's covered in paint and plaster etc).

Questions are;

What's the best method of fixing the ply to the chipboard? Do I need to make sure I fix right through to the joists or can I just use something like spax or even just ring nails to fix directly to the chipboard. (I really want to avoid a creaky floor!) What kind of length screws / nails should I use and what maximum distances apart from each other?

Secondly am I just been really over the top here? Because the chipboard seems flat and level would some good underlay just do the trick and maybe I'd be better just flooring up to the lintel and creating a little step up on top of it.

I've attached a picture of the lintel in case anyone has any other ideas.

Thanks a lot

Mathew

The ply is the best idea, screw it every 4 inches accross the width and length ( LOTS of screws) into the chipboard, leaving a slight gap between each board. Then lay an underlay like Duralay Duratex and then the Engineered floors, just be aware of the door height, and the fact that you may need to featheredge the ply/lintel area to keep everything smooth and level in this area.