Chipboard - plywood - solid oak?!

I've tried to have look over relevant posts and info available re laying a solid oak floor but have a couple of remaining questions which I'm hoping you can assist with;

I've a recently installed chipboard sub-floor which is solid, level and sound. I've a variety of lengths of solid oak t&g flooring to lay on top (120mm x 18mm). I've pretty much settled on nailing as the installation method (considered floating or elastilon underlay but not totally comfortable with either - prob just a weird personal thing!).

Appreciate the need for ply to be screwed down on top of the chipboard but not sure what thickness would be required. Not happy to go to 18mm ply (+ 18mm oak) as the difference in adjoining floor levels would be excessive, so would 6mm ply screwed onto the chipboard be sufficient?

The other point I was curious about was whether any additional membrane needs to be fitted between any of the layers (chipboard to play or ply to oak) - did read somewhere (don't believe it was on here) that wax paper should sit beneath the oak flooring?! Couldn't see any particular benefit myself but I was considering an underlay with good insulating properties possibly between the chipboard and ply (integral garage conversion and not convinced the volume of insulation fitted beneath the chipboard is totally sufficient for the winters up here). Would there be any issues in installing the flooring this way? Got quite a few sq.mtr of the silver coloured foam/dpm underlay from B&Q from laying laminate a few years back (thankfully, I've seen the light and have converted to real wood)!

Appreciate any thoughts advice.

Thanks.

If you want to secret nail your solid Oak floor your nails should be at least 50 - 60mm long. Any which way you turn this, 6mm nor 18mm ply wood will give it sufficient body on the chipboard, the nail would still 'explode' the chipboard rendering the nailing useless.

If you manage to screw down 6mm plywood onto the chipboard you can fully bond the Solid Oak floor with flexible adhesive like Mapei P990 - no need for extra membranes in any case.

If you have the "standard" offer 1200 x 18mm which has many very short lengths you cannot install this floor floating, it will too unstable due to the many hinges all joints will create.

Thanks for the prompt response WYL.

Gutted tho - had finally thought I'd got this installation straight in my mind but you're effectivly saying I'd need to install something in the region of 40mm ply on top of the chipboard to be able to secret nail? Can this be right? Surely as long as the ply is suitably bonded to the chipboard (plan was to pre-drill and screw) that even if a portion of the 'secret nail' extended through the flooring, the ply and then into the chipboard that the ply itself would offer enough resistance to the nails to prevent any problems/movement?!

(I've not had a proper look at the packs yet so not sure of the %age of smaller pieces - as I suspect may often be the case I only found you're website after I'd already purchased the flooring unfortunately - however from a purely personal point of view, floating wouldn't be my preferred installation method anyway.)

However, if secret nailing is not viable, then from a cost perspective it would presumably make more sense to reconsider Elastilon?

Your 50 - 60mm nails need a firm body to do the trick, chipboard is not a firm body I'm afraid. Effectively your nails would only grip the plywood and 6mm wouldn't be enough to keep the floor down this way.

Glueing directly onto chipboard is not recommended too, most modern chipboard does not bond well with the adhesives.
Options for you IMHO: elastilon on chipboard or plywood and fully bond - glue down - the boards.
Sorry

How about using tongue-tite screws instead of nails?

http://www.screwfix.com/cats/A454312/Screws/Interior-Wood-Screws/Screw-Tite/Tongue-Tite-Screws

Would they hold in the chipboard?

Can't comment on screws I'm afraid. Know they exist, never used them - don't like them.
Chipboard is just plain rubbish and a horrible underfloor.

Thanks guys.

Beginning to agree re the chipboard - frustrating thing is I'd have had ply installed instead of the chipboard had I known of these issues (didn't know what the floor covering was going to be either mind!). Could always rip the chipboard out but if Elastilon is as good as some people suggest then seems a bit of an extravagant expense!

So looks like Elastilon will be the most cost effective solution - area is approx 15 sq.mtr (roughly 3m x 5m room) so the cost of ply and the required amount of adhesive a good bit more than the underlay.

One question tho - when using elastilon is it adviseable to glue the t&g as well (on the short side at least)?

You could, especially if your floor turns out to have many short lengths. Doesn't hurt, will help