Opinions sought regarding subfloor

Hi All,

This is my first post, so firstly I would like to say hi to everybody. This looks like a a fantastic forum with a wealth of information!

Some background info - I have just secured 130sqm of Boral Karri solid timber flooring (19 x 80), which I will be installing on both levels of a double storey house, which is currently carpeted in the rooms where I will be laying floorboards.

The ground floor has a good particle board subfloor, which I don't believe will present any issues.

The second storey has, what looks like, a treated pine floorboard subfloor. I have been told that my new floorboards cannot be installed in the same direction as the floorboards of the subfloor, and that they will either need to be laid in the opposite direction to the existing subfloor (not an option for us), removed, or have plyboard layed over them.

However, I have also read (in the Boral installation guide) that our new floorboards can be layed over the existing floorboards, in the same direction.

I would be happy to lay a plyboard overlay over the existing boards, but it would have to be a thin board (~4mm), so that the floor does not sit too high when finished.

Other than this, the subfloor is solid. There are a few squeaky boards and uneven joins that I will correct before laying the new boards.

I was innitially planning to glue and secret nail the new boards directly to the subfloor

So I would love to hear any opinions on:

1. laying the new boards directly onto the existing boards (in the same direction), and any pro's and con's
2. Using a relatively thin plyboard overlay (~4mm) between the existing boards and new boards, i.e. should I be using a thicker ply?

Many thanks,
Jonty

Without going into details, on further investigation, the whole subfloor where I was intending to lay the new floorboards is pine floorboards.

I now realise after reading svereal posts that these could probably be sanded and polished, instead of laying the hardwood floorboards over it.

Please view this thread if you have an opinion/comments on the whether to go with the hardwood or the existing pine floorboards

Thanks
JG