25mm WBP Ply Floor

[richburgan]

Hi All.

Have purchased 2 boards 25mm ply and was wondering what are the best screws to fasten to joists? Also what way round is it best to lay the boards...lengthwise along joists or across joists?

Rich

 

[White Room]

Right angles to the joists for the ply, screwfix do a good range of screws

 

[Stan001]

... agree - right angles to the joists - as for screws, i find Spax are easily superior to most of the screws out there, they grip the wood, they pull in tight and stay tight, the heads are formed really nice so you dont slip with your drivers, not the cheapest, but if i have Spax and other stuff, the other stuff just stays in my screw box.

 

[White Room]

Screwfix do them stan, I think

 

[Stan001]

Rich - before you start the job make sure you have spare nogins to insert additional nogins on the overhanging edge of boards! i.e. do this as you go, board by board. There is an NHBC recommended minimum overhang spec but i cant remember it right now, cos i just insert those extra nogins anyway!

 

[richburgan]

Thanks all for your replies....what size spax would you recommend? and what size timber for the noggins please?

 

[Stan001]

If using flat head nails for overboarding onto joists you would use nails 2.5 x thickness of joist. But I cant find a defined length for screws! Minimum I would say into joist would be 2 x thickness of overboard, but in reality see the hyperlink below which lists the standard lengths. I would use screws as this is a small job and they will jack the boards down firmer and better for eventual tiling. Leave 10mm clear at edge of board to wall min for expansion, and you should leave 1.5~2mm gap between boards for expansion. All ply ends to occur over joists and noggins according to NHBC, and they should be minimum of 38mm (so there’s the answer for your noggin size ref NHBC – but tell your local wood dealer what you want to use and he can sometimes sell you bundles cheap just for noggins, and you can also use any spare wood you have around too remember). I know you already purchased you board but fyi the min board thickness for 450mm joist ctrs is 12mm and for 600 ctrs its 16mm. A cheap addition we don’t talk about here on the forum is sound insulation! Think about it now as you are putting floor boards down … (cheap bonus offer job for the prof tillers here!) The current mass required for floor decking in England and Wales is 15kg/m sq! I can tell you any house over 10 years old probably wont be meeting this. The wood specs above don’t necessarily meet that, so now’s the opportunity to buy (especially because its cheap this time of the year at all the sheds) sound insulation material and pack out your floor cavity gap (especially around soil vent pipes!).
Here’s the hyperlink to Spax screws at Screwfix (as recommended by others here, I also agree, they are very competitive), look for the hyperlink for choosing the right screw for your style options (you are looking at softwood joists I think – but the guys in Screwfix stores have forgotten more than we know about screws, they will help you at the counter ref style and length.
Spax Countersunk - Buy quality Spax Countersunk at Screwfix.com

 

[Stan001]

ooops - forgot to add - important ... screw fixings are 150mm max between ctrs around permimeter of your board and 300mm between ctrs on intermediate supports.

 

[richburgan]

Thanks Stan....one more thing, would you drill pilot holes in the ply?

 

[Stan001]

well i do, but my chippies dont - if you have a plain shank where the screw goes through ply then the screw will jack the board down tight - so if you are using plain shank then i guess they are right! ... I just found it dead easy to wizz pilot holes thro the ply as it makes the electronic driver job easy just bashing into the joists and not struggling thro the ply (some ply can be tough ... Im a little hairy builder not a big hairy builder:lol.

 

[Stan001]

If using flat head nails for overboarding onto joists you would use nails 2.5 x thickness of joist.http://www.screwfix.com/cats/A432527/Screws/Interior-Wood-Screws/Spax/Spax-Countersunk#

crazy typo - should have read 'not less than 32mm penetration into joist' - my sentance above just doesnt make sense - sorry

 

[Olz]

Id use 35mm screws for 25mm ply.

 

[diamondtiling]

get a drill bit with a countersink attached to it, quick and easy

:8:

 

[richburgan]

Thanks all.

Stan I'm big and hairy but no builder...still think drilling pilot holes wil save me from puffing. Liked the typo, made me laugh! :lol:

Oli, 10mm penetration into joists doesn't seem a lot but you must have done a few more floors than I have.

Diamond, I have seen those for drywalling, good tip thanks.

Rich.

 

[richburgan]

Thanks all.

Job done...plenty noggins and spax floor screws 60mm (brilliant screws, don't even need to pilot drill) really pleased with the results.

Regards Rich.