Thin structural flooring boards needed.

[ProDave]

This is the floor surface for the mezanine floor above bedroom 3, that will be accessible from bedroom 2 (daughters bedroom) which will be open to the vaulted ceiling.

 

The mezanine comes out to just beyond the centreline of the main room, and even at this point, there is barely room to stand up. So I am doing everything possible to reduce the overall make up of the mezanine deck to preserve as much headroom as possible.

 

Originally she wanted carpet up there. With this in mind I have spaced the joists a lot closer than normal at 250mm centres, planning something like 15mm plywood as an adequate thin floor to span that small gap between joists.  I currently have a temporary sheet of 11mm OSB up there which seems fine.

 

Now she tells me she wants a "wooden" floor up there.

 

I thought about laminates, but they are not normally regarded as structural. I strongly suspect they would be okay spanning 250mm centres but no manufacturer is going to state that.  i guess at a worst case laminate onto my 11mm OSB?

 

Does anyone know a "thin" and "Wooden" floor that will span 250mm centres?

 

It's not like it's going to take heavy traffic, have heavy furniture on it. As I say you can walk on one bit at the edge, anywhere else you will be crawling, it really is more of a storage space than a "room"
 

[Crofter]

What about some sort of v lining or shiplap? Should gain strength through the interlocking.

[Nickfromwales]

Why not infill between the 'joists' with battens and 18mm ply, finished flush. Then put a 12mm V grooved engineered floor down. 

Bingo. 

[ProDave]

9 hours ago, Nickfromwales said:

Why not infill between the 'joists' with battens and 18mm ply, finished flush. Then put a 12mm V grooved engineered floor down.

Bingo.

Too much work and fiddle to infill flush. I'm looking for something that will just go down as a thin floor.

 

the trouble is I put my joists at 250 centres deliberately to allow a thin floor, but nobody else works to less than 400mm so nobody specifies what will "do" with 250mm centres.

 

I will probably look at the ply in the merchants next time I am there and see if any is good enough to sand and varnish as a finished floor.

 

[Barney12]

18mm is going to give you a structural board. Are you really going to notice 7mm?

 

(by the way I would be the same as you but I'm just trying to save you another job )

[ProDave]

Yes, but 18mm would give you a structural board at 400mm centres, so logic says at 250 centres you need less.  Looks like I am not going to find any official guidance here as nobody does it.

 

I am just trying to maximise the headroom in a tight space, so yes half an inch may be the difference between hitting your head or not.
 

[Onoff]

How about 9mm Buffalo board and she can just live with the pseudo industrial finish? 

 

Or 6mm ali chequer plate?

[PeterW]

Ok - from the Australian building codes (useful for stuff like the actual strengths and spans of far eastern ply ....) then you get this :

 

 

I would suggest that a normal person reading that would say you won't have an issue with 12mm ply (with 5 plies) but that would need an SE to confirm - just did the deflection calc and 12mm is the square root of naff all at normal domestic loading.

 

If you were really worried then taking Nicks idea you could glue and screw thickening ribs down the middle of  each panel / joist pair before you glued and screwed the panel to the joists. 

 

 

[ProDave]

On that basis I think I will go with 12mm ply, providing I can find some that has a decent surface finish.
 

[Temp]

Is there a potential issue with Part E (Sound) in that if you don't build to a "robust standard detail drawing" you may have to get a sound transmission test done?

[ProDave]

That's a good point. I don't think so or rather hope not.

 

The mezanine is a storage platform, nothing more, nothing less that happens to be open to one of the bedrooms. If the issue is raised I will be arguing that it should be treated like any other bit of loft space and noise transmission is not an issue as there is normally nobody there to create noise.

 

I will be filling the gap between the floor and the ceiling with some form of insulation (probably whatever is left over or can be bought exceedingly cheap)

 

I will admit it is a deviation to the plans.  The plans showed two adjacent bedrooms, each with half a vaulted ceiling (i.e the dividing wall going right up to the apex)  But we had a think about it and decided it might look a bit odd so we hatched the idea to put a ceiling over one room creating a mezanine accessed from the other.  It saved having to build a 4 metre high partition wall.
 

[ProDave]

Sorted.

 

Jewsons had some 12mm ply with a decent finish that felt really solid.  It will end up being sanded and varnished.

 

Still a work in progress.