Attaching rafters to timber

[SaudisLoveAudis]

I have a patio structure done and now I want to attach the rafters.

The timber is about 4.7cm wide.
How long screws should I use to attach the rafters?
The rafter (birds mouth bit) is about 8.5cm thick.
The underlying timber is twice as thick so I think 16cm long screw would be enough.

Should I use 18cm long screws that are of 6mm diameter?
What drill size should I use for pre-drilling 5mm?

Or should I use brackets?
Are these soft brackets strong enough or should I get some sturdy ones?

On top I put EZ Glaze 3mn thick transparent polycarbonate.
The whole structure is rather strong 6x6 posts etc but of course I don't want the rafters to be lifted by wind one day.

 

[noseall]

I have a patio structure done and now I want to attach the rafters.

The timber is about 4.7cm wide.
How long screws should I use to attach the rafters?
The rafter (birds mouth bit) is about 8.5cm thick.
The underlying timber is twice as thick so I think 16cm long screw would be enough.

Should I use 18cm long screws that are of 6mm diameter?
What drill size should I use for pre-drilling 5mm?

Or should I use brackets?
Are these soft brackets strong enough or should I get some sturdy ones?

On top I put EZ Glaze 3mn thick transparent polycarbonate.
The whole structure is rather strong 6x6 posts etc but of course I don't want the rafters to be lifted by wind one day.

We skew screw using 100mm 5's and then add truss clips (for uplift prevention) if needed.

 

[catlad]

On top I put EZ Glaze 3mn thick transparent polycarbonate

Why not just use normal multi wall poly carb?