What screws to use?

[Mr Punter]

We are fixing some 18mm ply down onto 22mm chipboard in bathrooms so we can finish with 2.5mm Luxury Vinyl Tile and the finished level will match the oak floor on the adjacent landing.

 

I was thinking of screwing this down, but we can't get many fixings into the underlying joists, so I would like to just screw into the chipboard using 38mm screws.  Can I get these threaded half way, so the ply does not get jacked up by the screw?  I will be needing a fair few.

[RichS]

http://www.screwfix.com/c/screws-nails-fixings/woodscrews/cat840066#category=cat840066&productlength=38_mm

[Mr Punter]

Do you know which ones are threaded half way?  Screwfix tend to show the same pic for all lengths and mostly the shorter ones are fully threaded.

[Construction Channel]

what is stopping you from aiming at the joists? 

you don't often see anything below 45mm with some bare shank, Reiser for example are fully threaded until they get to 60mm IIrc

[Ferdinand]

10 minutes ago, Mr Punter said:

Do you know which ones are threaded half way?  Screwfix tend to show the same pic for all lengths and mostly the shorter ones are fully threaded.

 

On occasion I have gone into Screwfix and asked to look at about 8-10 similar items before buying one sort. You could do that.

 

They have always been amenable.

 

The only one which ever raised eyebrows was when I looked at about 6 different sorts of security safe, and they were still tolerant despite the weight.

[PeterW]

Glue it and 35mm staple to hold while it's drying. 

[MikeSharp01]

Just drill a clearance hole in the boards then screw it down, jacking won't be a problem. If its floor boards then glue is also a must to prevent squeaking You can set a depth stop on the drill using a short length of suitable diameter pipe round it.

[Barney12]

As @MikeSharp01 says above just pre-drill the top board. You could save even more time by using a countersunk pilot drill.

Something like: Linky 

And glue too!