What screws to fix OSB to joists

[toomuchworknotenoughtime]

I'm planning to fit 18mm OSB3 (smartply3) structural boards (2.4 x 1.2m) onto joists (spaced 35cm) before floating a solid timber floor above.

Any advice please on what screws to use to fix the boards to the joists and the recommended spacing.

Many thanks

 

[big-all]

your not talking attic are you!!

what floor is there already!!!

 

[toomuchworknotenoughtime]

No. Not the attic. This is bedroom in an Edwardian house.

I can see why my question raises more questions.

Currently very sawn cracked and split floorboards. I want replace with some nice oak flooring laid in the same direction as the existing boards. BUT I also want to introduce some soundproofing from the floor below. So best solution seems to be acoustic mineral wool in floor void, panels (in this case OSB), acoustic underlay, then solid floating floor. I was worried that simply laying the boards on the joists would not give sufficient sound insulation.

Why OSB and not ply? Because I want zero added formaldehyde and the only product I could find is SmartPly3 (which in fact is an OSB).

 

[big-all]

personaly i would go for 8x2/2.25"
or 4.5mm x50/60mm

plus the thickness off the accoustic underlay iff its more than 3mm

 

[speed]

some 2" 8's will be spot on

x5 screws across the 1.2m in every joist

what about using 2400x600 t&g chipboard flooring sheets?

 

[toomuchworknotenoughtime]

Thanks very much for the replies. Screws sorted.

Re the chipboard question, I only really saw reference to it being used for light use in lofts and was a bit worried about using it in a bedroom. Too late now anyway, spent an age trying to find smartply and have ordered it now!

 

[Deluks]

OSB over chip any day of the week.

 

[toomuchworknotenoughtime]

OSB over chip any day of the week.

I'm so excited! 20 boards of 18mm 1200 x 2400 OSB arriving at 8.00am with just me to get them to the first floor. I've pre-booked the hernia clinic!

 

[Deluks]

You'll be kicking yourself when I tell you that osb t&groove flooring can be purchased in 8x2 sheets. They do work out more expensive though so it's not all bad news.

 

[geraint]

whatever thickness of floor you are fitting. times it by 2.5 to give you the screw length.