Thread: How many screws in boards and joists?

Originally Posted by pawnhead

Not unless you climb under your deck to look at it.

Aw har hae har har har harrrr, Arrr that was good

Originally Posted by UteMad

The impact driver is definately the go.... we use 3 when doing large decks so as to rotate them and save burning them out as we screw off the whole deck in one go generally....
The board shouldn't stand up if your pilot hole in the board is 1/8 inch for a 10g screw and the tip is a type 17 point to cut into the joist....

cheers utemad

Hey Utemad,
I'm gonna be using the square drive Type 17 point to go into F17 120 x 45 joists. I assume they need pre-drilling all the way down? Or can I get away with only drilling and counter sinking the merbau board.
Also, what do I need to do when coming to joins. I'm reading all this 20mm from the edge stuff. Your thoughts on 140 x 22 merbau decking joins on 120 x 45 F17 joists would be greatly appreciated. Oh, and I'll be driving them in with my Pana 14.4v Li-Ion Impact Driver.

Awaiting your reply,
Cheers,
Akilas.

You dont predrill all the way into the joist. The screw will go into the joist without any trouble, but you just want to predrill and countersink the merbau. You want the screw to grab the joist and thread its own patterin int the joist, hence the need to not predrill in joist.

The 20mm in from the edge really has nothing to do with the joist, its all about the merbau. The further in from the edge you are the less likely your board will crack at the edge. 20mm is a safe distance, just make sure you hit the joist!

I used a makita 14.4v impact driver. I gave it a rest every 45mins or so coz I didnt want to kill it. Had a battery on charge and a battery on the go at all times. You'll find you get better results if you blip the impact driver as the screw goes down.

I found some boards lifting a little, it may have been becuase my pilot hole was too small, but I was using 3mm. I just sat or kneeled ont he boards when screwing them in, and letting the impact driver spin the screw 1 or 2 more times once the screw is flush with the board to pull it down a little if need be.

Some of my countersinking was too deep, so keep an eye on that. I used a sperate drill for a countersink, I should have tapped it so i knew where to stop but i was lazy.

Good luck. Cheers.