Laying Solid Oak Directly On Joists - Possible?

[EViS]

The floor boards in every room of our house have been in excellent shape to date and once sanded have all come out looking fantastic... The final room however is a different story. The tongue&groove floor boards have very large gaps between them and many are damaged beyond repair (although structually sound!).

My question is: Can I rip the current boards out and lay a new solid oak floor directly onto the current joists? If so, are 20mm thickness boards sufficient for this?

The room in question is on the 1st floor of the house.

 

[WoodYouLike]

20mm thick is good, minimum is 18mm to make your floorboards load-bearing. All new boards should at least connect (nailed onto) 3 joists.

Another important issue is the space between the joists: not further apart than 35 - 40mm is fine, wider and you'll have a problem.

 

[EViS]

Is there any benefit at all in laying directly onto the old floor boards? Other than maybe some extra sound insulation?

Also, how large should the gap be between the boards closest to the wall and the wall itself (to allow for expansion)?

 

[WoodYouLike]

No extra benefits.
And expansion gap: rule of thumb with solid Oak floorboards: 3-4mm per meter width of the room, minimum of 10mm.
Say your room is 3 meter wide = 12 mm gap.

 

[EViS]

But that 12mm gap is only between the wall and first board. All other T&G boards can be pushed flush together and nailed down? Will the boards not expand between each other too and result in creeking?

 

[WoodYouLike]

Oh, if you like you can create a bicycle parking (what we call gaps between all boards )

But to be honest: you only need an expansion gap (where the wood can expand to) around the perimeter of the whole floor. wood will work during the normal changes of the seasons but not to the extend you are imagining.

 

[Reynardine]

How large should the gap be between the boards closest to the wall and the wall itself (to allow for expansion)?

If you are concerned about the 12mm / 15mm gap left around the edge of your room you can always consider filling the gap with some proprietary expanding, sound sealing material i.e. something like this

http://www.soundreduction.co.uk/images/file/Soundseal 05.pdf

( I have no connection with this firm )

 

[WoodYouLike]

Filling an expansion gap will render the EXPANSION GAP useless.
Where should the expanding wood go to then? Up in smoke?

ALWAYS leave expansion gaps empty, it is there for one and only one reason: if the wood expands during the normal changes of the seasons it has space to move instead of buckling and cupping!