Decking joists - which screws?

[Douglas2]

I am making a decking subframe for a ground deck and am looking for advice on which size of screws I should use for the joists (rather than joist hangers).

I was thinking 100mm and thought that the timberlok screws that I used for some of the sleeper work would do?

Joists are 100x50, so the screw would penetrate 50mm into the joists (after travelling 50mm through the right angle joist).

 

[adders21]

I used Wickes own brand timberlock screws and they did the job fine on my decking project. I used them as you intend, fixing the joist to posts and joist to joist. Easy to use, I skew screwed them in.