First of all I don't recommend this for over a real solid wood floor whether nailed or glued. This is for standard floor boards / plywood / chipboard etc. 1- You need to plywood over existing floor using flooring grade / exterior graded plywood. This should be nailed / stapled at approx 6 inch centers and 2 inch centers around the edge (the more the better). YOU MUST USE RING SHANK NAILS OR DIVERGENT staples! Do not use panel pins. 2- Next caulk all joints and edges and gaps. Do not use silicon. 3- Prime plywood with f-ball 131 neoprene primer (neat) 4- Next you need to screed floor using f-ball 700 flex. This is a fibre-reinforced smoothing and leveling compound designed to flex. You could also use Uzin 175. Same product different manufacturer 5- Make sure you mix correct as on bag and put on at minimum 3mm. This stuff is really runny and you cant go wrong getting level. You can practically tip it in and let it level it self. As for where to buy products from you will have to try to source for yourselves, but most flooring wholesalers stock. Hope you all find this useful. If part of the sub floor is wood and the other half is concrete/screed etc, follow the instructions above on the wooden side and just prime, fill in cracks etc on the concrete side. Next poor compound out and flow between the two different sub floors. Read the instructions on how to use leveling compound for concrete For a bit more detail on the concrete side of things. Also you must use the flex compound over the whole floor and not a mix of different types of compound. ie acrylic then flex! If the wooden side is flat and smooth already then you need to just plywood then part screed onto it with gentle ramp between compound and the plywood.